SECTION 1
CLINICAL CASE PRESENTATION
The patient is an 82-year-old man with a longstanding history of a heart murmur. He was initially seen in consultation at the request of his primary care physician 11 years ago for an evaluation of a heart murmur. At that time, he was completely asymptomatic and categorically denied any angina, dyspnea, heart failure symptoms, or syncope. An echocardiogram was obtained which demonstrated severe aortic stenosis. In view of his lack of symptoms, the patient was managed expectantly. Over the ensuing 11 years, he was seen frequently for follow-up and underwent periodic echocardiography (Figures 3-1-1 to 3-1-5). He continued to deny any symptoms and was quite physically active, frequently working out at his local fitness center with no limitations. His echocardiogram (Table 3-1-1) demonstrated progressive worsening of his aortic stenosis with significant increases in the calculated aortic valve gradients. His physical examination was consistent with severe aortic stenosis. He demonstrated delayed carotid upstrokes with diminished volume, a harsh, late peaking systolic ejection murmur that radiated to the carotids and across the precordium, and an absent aortic component of the second heart sound. His lungs were clear, and he had no lower extremity edema. A brain naturetic peptide (BNP) was obtained, which was elevated at 306. In order to further risk stratify him, he underwent a stress test during which time he remained asymptomatic; however, he developed significant ST depression and ventricular ectopy (Figure 3-1-6). His blood pressure response was hypotensive. Given the findings on his stress test, surgery was recommended, but the patient declined, stating that he felt fine. Shortly thereafter, however, he began to notice a questionable decrease in his functional capacity. Whether or not he truly developed new symptoms, or simply began to recognize symptoms that he had ignored or not recognized but which became evident after the concerns raised on the stress test, is not clear. He contacted his physician. Further diagnostic testing, including cardiac catheterization, was undertaken, and he subsequently underwent aortic valve replacement with a 27 mm pericardial valve. He had an uneventful surgical course. Postoperatively, in retrospect, he stated that he was somewhat limited and in fact felt that his exercise capacity had improved.
FIGURE 3-1-1 Parasternal long axis view demonstrating LVH, a heavily calcified, immobile AV as well as mitral valve thickening and annular calcification.
FIGURE 3-1-2 Parasternal short axis view of the heavily calcified aortic valve.
FIGURE 3-1-3 Apical 4 chamber view demonstrating LVH and preserved LV ejection fraction.
FIGURE 3-1-4 Parasternal long axis view with color Doppler demonstrating mild aortic regurgitation as well as mitral insufficiency.
FIGURE 3-1-5 Continuous-wave Doppler demonstrating markedly elevated peak and mean aortic valve gradients. These velocity measurements were obtained from the right parasternal window.
TABLE 3-1-1 Serial Echocardiographic Data Over an 11-year Period
FIGURE 3-1-6 Baseline ECG from the patient described in the case presentation.
FIGURE 3-1-6 Rhythm strip (upper panel) and peak stress ECG (bottom panel) from the case presentation.
CLINICAL FEATURES AND NATURAL HISTORY1
• Most patients with mild to moderate aortic stenosis (AS) are asymptomatic.
• As the severity of the stenosis progresses, patients may experience angina, syncope, or congestive heart failure. Once symptoms develop, the prognosis is poor. After the onset of symptoms, average survival is 5 years (angina), 3 years (syncope), and 2 years after the onset of congestive heart failure.6
• The most feared complication of aortic stenosis is sudden cardiac death. Patients with symptomatic AS are at high risk for sudden cardiac death, while sudden death occurs quite rarely and infrequently in patients with asymptomatic aortic stenosis.
• The rate of progression varies among individuals. Thus, careful monitoring of the patient is warranted.
EPIDEMIOLOGY
• Aortic stenosis is the most common form of valvular heart disease in adults, with a reported prevalence of 2% to 9% in the elderly.1,7,8
• The precursor of AS, aortic sclerosis, was detected in 29% of subjects over the age of 65 in an echocardiographic study.10
PATHOPHYSIOLOGY AND ETIOLOGY
• Obstruction to left ventricular outflow and the resultant increase in LV pressure leads to LVH and potentially LV systolic dysfunction.
• Increased oxygen demand can lead to angina.
• Systolic and diastolic dysfunction may result in symptoms of congestive heart failure.
• Fixed cardiac output and dysrhythmias can lead to syncope and sudden cardiac death.
• The most common causes of AS include calcification of a congenitally bicuspid AV (~50% of surgically replaced valves in the US and Europe), calcification of a trileaflet valve and rheumatic valve disease.1,10,11
• The underlying etiology of aortic stenosis is a function of age.1,11 Congenital abnormalities of the aortic valve predominate in children, adolescents, and young adults.
• Acquired AS, due to calcification of a congenitally abnormal valve an initially normal trileaflet AV, predominates in older patients.
• The calcification process is an active disease process (rather than a “wear and tear” process). It is characterized by active inflammation, lipid accumulation, and calcification.1
• Rheumatic valvular aortic stenosis is becoming much less frequent in the developed world. Most patients have concomitant mitral valve disease.
ECHOCARDIOGRAPHY
Echocardiography remains the standard diagnostic tool to assess for the presence and severity of aortic stenosis (Figures 3-1-7 to 3-1-11). A transthoracic echo with a comprehensive Doppler examination is appropriate.1,3 Echocardiography can evaluate left ventricular size, structure, and function, including evidence of left ventricular hypertrophy and systolic and diastolic function. In addition to evaluating the aortic valve (including determination of peak and mean gradient as well as calculated valve area) and the presence of aortic regurgitation, concomitant valvular heart disease can also be detected. The proximal portion of the aorta can frequently be imaged quite well.
• There are many potential measures of AS that can be obtained by echocardiography.10 They all have potential limitations and advantages (Table 3-1-2). Current standards recommend that several measures be obtained in all patients (A), with other parameters reasonable (R) if additional data is needed. Many other parameters that can be assessed are not currently recommended for clinical use.
AS jet velocity (A). It is critical to interrogate the Doppler signal from multiple windows, using data from highest velocities measured.
Peak velocity.
Character of the continuous-wave Doppler signal, including its shape, acceleration time.
Calculation of mean gradient from the Doppler signal (A).
Calculation of the AV area using the continuity equation (A).
Careful attention to accurately measuring the LVOT diameter and sample volume placement for the LVOT velocity.
The preferred method is to use the LVOT and AV time velocity integrals; however, it is acceptable to substitute the respective peak velocities.
Calculation of the dimensionless index, the ratio of the LVOT velocity and the AV velocity (R). A ratio ≤0.25 suggests severe AS.
Planimetry of the AV orifice (R).
• The frequency of serial echocardiograms depends upon the initial study data, the severity of the AS, and the patient’s symptoms.1
For patients with mild aortic stenosis, an echocardiogram is recommended every 3 to 5 years.
For patients with moderate aortic stenosis, the recommendation is for echocardiography every 1 to 2 years.
For patients with severe aortic stenosis, an annual echocardiogram is appropriate.
• New or changing symptoms or a significant change in physical exam findings should prompt an echocardiogram.
• Transesophageal echocardiography plays a limited role in the diagnosis and management of patients with aortic stenosis. In selected patients with discordant clinical, echocardiographic, and catheterization data, TEE may be useful to better define the AV anatomy.
TEE is used for intraprocedural monitoring of patients undergoing aortic valve replacement (AVR), both surgical and with transcatheter AVR. It also has a role in the management of patients with suspected AV endocarditis and prosthetic valve dysfunction.
FIGURE 3-1-7 Parasternal long axis view of a different patient demonstrating a heavily calcified, restricted AV. Figures 3-1-8 to 3-1-10 demonstrate the measurements obtained in this patient to calculate the AVA by the continuity equation.
FIGURE 3-1-8 Parasternal long axis image demonstrating the LVOTd measurement.
FIGURE 3-1-9 Pulsed wave Doppler of the LVOT velocity (V1) and VTI.
FIGURE 3-1-10 Continuous-wave Doppler of the peak AV velocity (V2). In this patient, using the continuity equation, the calculated AVA is 0.51 cm sq using the VTI method and 0.58 using the Vmax data.
FIGURE 3-1-11 Intraoperative TEE prior to a TAVR demonstrating severe AS.
TABLE 3-1-2 Selected Echocardiographic Parameters for the Evaluation of Aortic Stenosis
OTHER DIAGNOSTIC TESTING AND PROCEDURES1,10
• Cardiac catheterization should be performed in most cases only to evaluate the patient for concomitant coronary artery disease in anticipation of surgery. In patients with equivocal echocardiographic findings or discrepancies between clinical examination findings and the echocardiogram, cardiac catheterization with hemodynamic assessment to determine aortic valve gradient and valve area may be warranted.
• In patients with congenital aortic valve pathology (eg, bicuspid valves) or in patients with suspected aortopathy, further imaging of the aorta may be warranted using either cardiac magnetic resonance angiography or CT scanning.
• Exercise testing in asymptomatic patients may be useful to identify symptoms and risk stratify the patient. The identification of a limited functional capacity, the development of symptoms, an abnormal blood pressure response, or significant dysrhythmias may prompt more serious consideration for AVR in the asymptomatic patient. Stress testing (other than a dobutamine stress test to assess low gradient AS) is contraindicated in the patient with symptomatic AS.
DIFFERENTIAL DIAGNOSIS
• While the symptoms of aortic stenosis may be caused by a variety of cardiac diseases, including ischemic heart disease (angina), cardiomyopathies of a variety of etiologies (dyspnea/CHF), and syncope (dysrhythmias, HCM), once the diagnosis of AS is made, symptoms are usually attributed to the aortic valve disease.
• In patients with concomitant cardiac diseases such as coronary artery disease, other valvular heart disease, or other co-morbidities (eg, COPD), it may be difficult to ascribe symptoms entirely to the valve.
• On rare occasions, it may be difficult to determine the exact location of a stenosis (eg, a subaortic membrane, hypertrophic cardiomyopathy, supravalvar AS). Careful echocardiographic assessment, along with data from other imaging modalities, is warranted.
DIAGNOSIS
• The diagnosis of AS is made by a combination history, physical examination, and echocardiography.
• The severity of AS is based primarily on echocardiographic data (Table 3-1-3).
• Patients with a low cardiac output may have severe AS with a lower mean gradient (low-output or low-gradient AS). Dobutamine echocardiography may be used to better define the AV pathology and assess for contractile reserve in the patient with a low EF.
• On rare occasions, cardiac catheterization with hemodynamic assessment is needed to determine the severity of AS.
• Cardiac MRI and cardiac CT play a limited role in the diagnostic assessment of AS.
• All patients should have an ECG and chest x-ray as part of the initial diagnostic evaluation.
TABLE 3-1-3 Classification of the Severity of Aortic Stenosis
MANAGEMENT1
• The management of patients with severe symptomatic aortic stenosis is relatively straightforward. Assuming a patient is a candidate for surgery, surgical replacement of the aortic valve is warranted expeditiously. For patients who are felt to be either high risk or in whom surgery is contraindicated, percutaneous aortic valve replacement is becoming an option. At the present time, two transcatheter valves are available for clinical use in the United States for inoperable (“extreme risk”) and high risk patients with severe symptomatic AS. Both the Medtronic CoreValve and the Edwards SAPIEN Valve have received FDA approval in the United States for use in selected individuals. Transcatheter valve technology is rapidly developing and newer devices, as well as expanded indications for current valves, are undergoing active clinical investigation.
• The management of patients with asymptomatic aortic stenosis remains somewhat controversial. Some authors advocate elective aortic valve replacement to prevent sudden cardiac death. Others recommend a watchful waiting approach. The role of BNP testing and stress testing remains somewhat controversial as well, though stress testing is being utilized more frequently. Annual echocardiography is warranted, as is careful clinical observation and follow-up.
• The only effective treatment for AS is valve replacement surgery (or for selected individuals, transcatheter-based AV replacement).
AVR should be recommended in symptomatic patients, patients undergoing other cardiac surgical procedures such as coronary artery bypass grafting, and asymptomatic patients with an LV ejection fraction <50%.
AVR should be considered in the asymptomatic patient with an abnormal stress test, patients with severe valve calcification, and in individuals who demonstrate rapid progression of the valve stenosis, as well as individuals who may experience a delay between symptom onset and surgery.
• There currently is no role for “medical therapy” in the management of patients with AS, other than to manage symptoms in patients who are not candidates or who refuse surgery.
• While there was some initial data suggesting that statin therapy could delay the progression of AS, current evidence suggests that statins do not prevent progression of AS.12,13
• Antibiotic prophylaxis to prevent infective endocarditis is no longer recommended for patients with native valve AS.1,14
Patients with rheumatic valve disease should be given appropriate prophylaxis to prevent recurrent rheumatic fever.
FOLLOW-UP1
• In patients with severe, asymptomatic aortic stenosis and in whom surgery is deferred, very careful clinical follow-up is warranted. Such patients should be seen frequently and extensively questioned as to the development of symptoms including angina, dyspnea, or heart failure and syncope. Careful attention to subtle changes in their functional capacity should be elicited as well. The development of any symptoms related to their valvular heart disease is an indication for proceeding to valve replacement.
• Patients with severe AS should undergo an echocardiogram on an annual basis to define changes in left ventricular function as well as progression of their aortic valve disease. Echocardiographic findings that should prompt consideration of valve replacement (even with no symptoms) include rapid progression of the valvular stenosis and deterioration of LV function.
• Postoperatively, patients who have undergone aortic valve replacement warrant continued clinical follow-up on an annual basis, surveillance for symptoms, management of anticoagulation, and endocarditis prophylaxis for dental procedures in accordance with the recently revised AHA guidelines.1,14
• All patients should undergo a baseline echocardiogram post AVR. This serves to establish the normal (expected) parameters for the individual patient’s valve as well as the baseline LV function and concomitant cardiac abnormalities.
Routine serial or annual echocardiography is not warranted in the absence of symptoms.1,3
In patients with a biological valve, annual echocardiograms may be considered after 10 years.1
In selected patients with a mechanical or bioprosthetic valve, earlier echocardiography (≥3 years) may be appropriate.3
In patients with a prosthetic valve, more frequent echocardiography may be appropriate if the patient has other cardiac disease that would warrant more frequent assessment by echocardiography.
• Echocardiography should be performed if patients develop symptoms possibly related to their prosthetic valve or changes in their physical examination.
REFERENCES
1. Nishimura RA, Otto CM, Bonow RO, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease:executive summary; a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014;63:2348-2388.
2. Cheitlin MD, Armstrong WF, Aurigemma GP, et al. ACC/AHA/ASE 2003 guideline update for the clinical application of echocardiography- summary article A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines. (ACC/AHA/ASE 2003 Committee to Update the 1997 Guidelines for the Clinical Application of Echocardiography). J Am Coll Cardiol. 2003;42:954-970.
3. Douglas PS, Garcia MJ, Haines DE, et al. ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 appropriate US criteria for echocardiography: a report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, American Society of Echocardiography, American Heart Association, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society of Cardiovascular Angiography and Interventions, Society of Critical Care Medicine, Society of Cardiovascular Computed Tomography, and Society of Cardiovascular Magnetic Resonance. J Am Coll Cardiol. 2011;57(9):1126-1166. doi: 10.1016/j.jacc.2010.11.002.
4. Holen J, Simonsen S. Determination of pressure gradient in mitral stenosis with Doppler echocardiography. Br Heart J. 1979;41:529-535.
5. Hatle L, Angelsen B, Tromsdal A. Noninvasive assessment of aortic stenosis by Doppler ultrasound. Br Heart J. 1979;43:284-292.
6. Ross J Jr, Braunwald E. Aortic stenosis. Circulation. 1968;38:61-67.
7. Freeman RV, Otto CM. Spectrum of calcific aortic valve disease: pathogenesis, disease progression, and treatment strategies. Circulation. 2005;111:3316-3326.
8. Lindroos M, Kupari M, Heikkila, Tilvis R. Prevalence of aortic valve abnormalities in the elderly: an echocardiographic study of a random population sample. J Am Coll Cardiol. 1993;21:1220-1225.
9. Otto CM, Lind BK, Kitzman DW, Gersh BJ, Siscovick DS. Association of aortic-valve sclerosis with cardiovascular mortality and morbidity in the elderly. N Engl J Med. 1999;341:142-147.
10. Baumgartner H, Hung J, Bermejo J, et al. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice. J Am Soc Echocardiogr. 2009;22:1-23.
11. Roberts WC, Ko JM. Frequency by decades of unicuspid, bicuspid, and tricuspid aortic valves in adults having isolated aortic valve replacement for aortic stenosis, with or without associated aortic regurgitation. Circulation. 2005;111:920-925.
12. Rosenhek R, Rader F, Loho N, et al. Statins but not angiotensin-converting enzyme inhibitors delay progression of aortic stenosis. Circulation. 2004;110:1291-1295.
13. Chan KL, Teo K, Dumesnil JG, Ni A, Tam J, ASTRONOMER Investigators. Effect of lipid lowering with rosuvastatin on progression of aortic stenosis: results of the aortic stenosis progression observation: measuring effects of rosuvastatin (ASTRONOMER) trial. Circulation. 2010;121:306-314.
14. Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: Guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. 2007;116:1736-1754.
SECTION 2
PATIENT STORY (CLINICAL CASE PRESENTATION)
A 53-year-old white male with a history of hypertension and obesity presented with a chief complaint of dyspnea on exertion and leg swelling. His symptoms began two years ago. He has had no medication changes. He reported a history of a heart murmur but had not sought medical attention or follow-up in several years.
His physical examination demonstrates jugular venous distension, a normal S1, with a soft A2 component of S2, an S3 gallop, and a faint 2/6 late-peaking systolic murmur heard best at the right upper sternal border. There were bilateral crackles at the bases of the lungs, a distended abdomen, and 2+ bilateral pitting edema below the knees. His electrocardiogram demonstrated normal sinus rhythm and an isolated premature atrial contraction. An echocardiogram revealed a severely dilated left ventricle, with severe global left ventricular dysfunction, a left ventricular ejection fraction of 10%, and a calcified, restricted aortic valve with a mean aortic gradient of 22 mm Hg (Figures 3-2-1 to 3-2-6). He underwent cardiac catheterization, which demonstrated no obstructive coronary artery disease, a mean aortic gradient of 26 mm Hg, and a calculated aortic valve area of 1.0 cm2.
FIGURE 3-2-1 Parasternal long axis view demonstrating a calcified, restricted AV and a dilated LV with severely depressed LV function.
FIGURE 3-2-2 Parasternal long axis, focused on the aortic valve, demonstrating a calcified, restricted aortic valve. Color Doppler demonstrates no aortic regurgitation.
FIGURE 3-2-3 Parasternal short axis of the aortic valve, demonstrating calcified, restricted leaflets.
3-2-4 Apical 4 chamber view demonstrating severely decreased LV function as well as RV dysfunction.
FIGURE 3-2-5 Continuous-wave Doppler across the aortic valve demonstrating a mean gradient of 22 mm Hg.
FIGURE 3-2-6 Pulse wave Doppler at the LVOT, measuring the LVOT TVI, used in determining the dimensionless index and calculating the AV area. In this patient, the LVOT VTI is quite low, consistent with low stroke volume.
To further clarify the severity of the aortic stenosis (AS) in the setting of low cardiac output and to test for contractile reserve, the patient underwent dobutamine stress echocardiography. With dobutamine infusion (Table 3-2-1), the calculated aortic valve area remained essentially unchanged, the mean gradient increased to 36 mm Hg, and contractile reserve was present, as demonstrated by an increase in the LVOT VTI and an improvement in EF. The patient was referred for surgery and had successful mechanical aortic valve replacement. Postoperatively, he reported an improvement in his symptoms. Postoperative echocardiogram demonstrated improved left ventricular function (Figure 3-2-7).
TABLE 3-2-1 Dobutamine Stress Echo Results
FIGURE 3-2-7 Postoperative parasternal long axis, demonstrating improvement in LV function and the presence of a bio-prosthetic AV.
PATHOPHYSIOLOGY AND ETIOLOGY
• Severe AS is defined as an aortic valve area less than or equal to 1.0 cm2, mean aortic gradient greater than or equal to 40 mm Hg, or a jet velocity greater than or equal to 4.0 M per second.1
• Severe AS may be present with a lower transvalvular gradient and velocity if the cardiac output is low.1
• The most common causes of AS are calcification of a normal trileaflet aortic valve or a congenital bicuspid valve.1 The obstruction generally develops gradually, and the left ventricle adapts with increasing hypertrophy.2 If the hypertrophy is inadequate to compensate for the increasing pressure, a decrease in ejection fraction occurs.3
• Alternatively, a depressed ejection fraction may represent a cardiomyopathy. It can be difficult to determine whether the low ejection fraction is secondary to the cardiomyopathy or due to the valve stenosis.4 In either situation, the low cardiac output and low gradient contribute to a calculated effective valve area that can meet criteria for severe AS.1
• Aortic valve replacement for severe AS in the setting of a normal ejection fraction carries a risk of mortality of less than 1%.5 The risk increases in the setting of a low ejection fraction.5 If the low ejection fraction is caused by a depressed contractility (primary myopathic process) as opposed to severe AS, surgery will be less beneficial.6
EPIDEMIOLOGY
• AS is the most common valvular abnormality in the United States. However, of those patients with AS, only 5% are comprised of the subset of patients with low ejection fraction and a low aortic valve gradient.5
ECHOCARDIOGRAPHY
• Echocardiography, including Doppler echocardiography, is employed to assess the presence/severity of AS (see Section I: Asymptomatic Severe Aortic Stenosis).
• A complete transthoracic echocardiogram should be performed in patients with low-gradient, low-output AS, similar to those with AS and a normal ejection fraction. The extent of valve calcification and the status of the other valves should be assessed.
• In cases of low-gradient, low-output AS in the setting of impaired ejection fraction, Dobutamine echocardiography can be utilized. It is a class IIa indication in the ACC/AHA Guidelines for the Management of Patients with Valvular Heart Disease.1
• Dobutamine echocardiography may distinguish between truly severely stenotic AS and resultant low ejection fraction from only mild to moderate AS with a concurrently depressed ejection fraction (due to a cardiomyopathy).
Dobutamine echocardiography can determine whether contractile reserve, defined as the appearance of increased contractility with dobutamine infusion, is present. The presence or absence of contractile reserve provides important prognostic information with regard to operative mortality.
Baseline echocardiographic images are obtained, and include the left ventricular outflow tract (LVOT) diameter, the LVOT time velocity integral (TVI), the LVOT velocity, the aortic valve (AV) TVI, the AV velocity, and the AV mean gradient.
The left ventricular ejection fraction (LVEF) is obtained at baseline.
Dobutamine infusion is begun at 2.5 to 5 micrograms/kg/min and is sequentially increased in 5 micrograms/kg/min increments (every 3-5 minutes) to a maximum of 20 micrograms/kg/min. The hemodynamic information and reassessment of the LVEF are obtained at each stage.
If, with dobutamine infusion, the aortic valve area increases, the gradient remains the same, and there is an increase in stroke volume, then severe AS is unlikely.1,5 If, however, with dobutamine infusion, the aortic valve area remains the same, with increased gradient and an increase in stroke volume, then severe AS is likely.
In those patients with severe AS, dobutamine infusion will increase the LVOT velocity and the AV velocity proportionally; therefore, the ratio between LVOT velocity and the AV velocity will remain stable throughout the infusion. In those patients with milder AS, the LVOT velocity will increase more with dobutamine than the aortic valve velocity (due to the increase in the aortic valve area). Therefore the ratio between the LVOT velocity and the AV velocity will increase.
If the stroke volume increases by more than 20%, then contractile reserve is present. Patients who fail to demonstrate contractile reserve have a very poor prognosis with surgery as compared to those patients with contractile reserve (32%-33% versus 5%-8%).7–10
OTHER DIAGNOSTIC TESTING AND PROCEDURES
• Echocardiography without dobutamine and cardiac catheterization hemodynamic assessments without dobutamine are often performed in the patient with low-gradient, low-output AS. Both have inherent flaws in their ability to define the severity of AS in the setting of low cardiac output.
• In echocardiography, the continuity equation is used to estimate aortic valve area; however, it relies on the LVOT TVI and AV TVI, both of which are based on the cardiac output.
• In cardiac catheterization hemodynamic assessments, the calculated valve area is proportional to the stroke volume. Furthermore, the constant in the Gorlin formula varies with transvalvular flow.11,12
• As an alternative to dobutamine echocardiography, a dobutamine challenge may be performed in the cardiac catheterization laboratory, and a similar assessment of the aortic valve area, gradient, and the cardiac output may be obtained.1,8
• Prior to undergoing open-heart surgery, coronary angiography should be performed to assess for the presence of concomitant coronary artery disease and the need for coronary bypass grafting at the time of surgery.
MANAGEMENT
• Aortic valve replacement is (either surgical AVR or transcatheter aortic valve replacement [TAVR], depending on surgical risk) indicated for symptomatic patients with severe AS and for patients with severe AS and an ejection fraction less than 50%.1
• Those patients with low output severe AS and contractile reserve have a better outcome with aortic valve replacement than medical therapy and should undergo replacement.1,5
• In those patients with low output severe AS and no evidence of contractile reserve, the choice is a difficult one; either face an operative mortality of 32% to 33% or an abysmal prognosis without surgery.13
FOLLOW-UP AND PATIENT EDUCATION
• In patients who are not candidates for surgery, careful clinical follow-up and treatment of congestive heart failure is appropriate. Their prognosis is poor.
• Patients who undergo AVR should be followed clinically and undergo follow-up echocardiography as detailed elsewhere in this chapter. Endocarditis prophylaxis is indicated in patients post-AVR.
SUMMARY
• In patients with severe symptomatic AS, AVR is the preferred treatment. In the setting of severe AS and a low ejection fraction, AVR is also recommended.
• In those patients with low-gradient, low-output AS, further investigation is required. Dobutamine echocardiography can differentiate those patients with truly severely stenotic AS from those with a cardiomyopathy and only mild to moderate AS. Additionally, assessment of contractile reserve can be performed with dobutamine echocardiography, further risk-stratifying patients for surgery.
REFERENCES
1. Nishimura RA, Otto CM, Bonow RO, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease:executive summary; a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014;63:2348-2388.
2. Spann JF, Bove AA, Natarajan G, Kreulen T. Ventricular performance, pump function and compensatory mechanisms in patients with aortic stenosis. Circulation. 1980;62:576-582.
3. Krayenbuehl HP, Hess OM, Ritter M, Monrad ES, Hoppeler H. Left ventricular systolic function in aortic stenosis. Eur Heart J. 1988;9 Suppl E:19-23.
4. Huber D, Grimm J, Koch R, Krayenbuehl HP. Determinants of ejection performance in aortic stenosis. Circulation. 1981;64: 126-134.
5. Martinez MW, Nishimura RA. Approach to the patient with aortic stenosis and low ejection fraction. Curr Cardiol Rep. 2006;8:90-95.
6. Carabello BA, Green LH, Grossman W, Cohn LH, Koster JK, Collins JJ Jr. Hemodynamic determinants of prognosis of aortic valve replacement in critical aortic stenosis and advanced congestive heart failure. Circulation. 1980;62:42-48.
7. Monin JL, Monchi M, Gest V, Duval-Moulin AM, Dubois-Rande JL, Gueret P. Aortic stenosis with severe left ventricular dysfunction and low transvalvular pressure gradients: risk stratification by low-dose dobutamine echocardiography. J Am Coll Cardiol. 2001;37:2101-2107.
8. Nishimura RA, Grantham JA, Connolly HM, Schaff HV, Higano ST, Holmes DR Jr. Low-output, low-gradient aortic stenosis in patients with depressed left ventricular systolic function: the clinical utility of the dobutamine challenge in the catheterization laboratory. Circulation. 2002;106:809-813.
9. Monin JL, Quere JP, Monchi M, et al. Low-gradient aortic stenosis: operative risk stratification and predictors for long-term outcome: a multicenter study using dobutamine stress hemodynamics. Circulation. 2003;108:319-324.
10. Quere JP, Monin JL, Levy F, et al. Influence of preoperative left ventricular contractile reserve on postoperative ejection fraction in low-gradient aortic stenosis. Circulation. 2006;113:1738-1744.
11. Burwash IG, Thomas DD, Sadahiro M, et al. Dependence of Gorlin formula and continuity equation valve areas on transvalvular volume flow rate in valvular aortic stenosis. Circulation. 1994;89:827-835.
12. Cannon SR, Richards KL, Crawford M. Hydraulic estimation of stenotic orifice area: a correction of the Gorlin formula. Circulation. 1985;71:1170-1178.
13. Lange RA, Hillis LD. Dobutamine stress echocardiography in patients with low-gradient aortic stenosis. Circulation. 2006;113:1718-1720.
SECTION 3
CLINICAL CASE PRESENTATION
A 31-year-old man with a history of hypertension and obesity presented to an outpatient clinic appointment at The Ohio State University’s Wexner Medical Center with complaints of chest heaviness upon exercise and dizziness going up three flights of stairs. He denied any episodes of syncope. He has noticed this over the past 3 months and limited his exercise routine. He denies orthopnea, lower extremity edema, or paroxysmal nocturnal dyspnea (PND). He has been told during his high school physical exam that he had a heart murmur but did not have any further follow-up or cardiac evaluation.
On exam, he was an overweight man. His blood pressure (BP) was 160/100 mm Hg. His cardiac exam revealed an early medium-pitched, systolic ejection click and a 3/6 systolic ejection murmur in the upper right sternal border. In addition, a faint, high-pitched early diastolic decrescendo murmur was heard along the left sternal border. Simultaneous palpation of his radial and femoral arteries demonstrated a delay in the femoral arterial pulse. His exam was felt to be consistent with a bicuspid aortic valve (AV) with aortic stenosis (AS) and aortic regurgitation (AR) as well as coarctation of the aorta. This was confirmed with echocardiography (Figures 3-3-1 to 3-3-4). He also underwent an MRA of his aorta (Figure 3-3-5), which demonstrated a mildly dilated ascending aorta as well as evidence of aortic coarctation. He was felt to have mild to moderate AS. He underwent percutaneous treatment of his coarctation with a stent with an improvement in his BP as well as his symptoms. He will be followed with serial examinations and echocardiography for his AV disease, as well as serial MRA of his aorta.
FIGURE 3-3-1 Parasternal long axis view demonstrates a mildly thickened AV with mild aortic root dilation.
FIGURE 3-3-2 Zoomed parasternal short axis view of the bicuspid AV.
FIGURE 3-3-3 M-mode of the AV demonstrates an eccentric diastolic closure line of the AV leaflets consistent with a bicuspid AV.
FIGURE 3-3-4 Continuous-wave Doppler demonstrating the peak and mean gradients across the AV in our patient. The average peak (46 mm Hg) and mean (29 mm Hg) gradients as well as the calculated AVA (1.26 cm sq) are noted.
FIGURE 3-3-5 MRA of the aorta in the patient with a bicuspid valve, demonstrating a dilated ascending aorta and coarctation of the aorta.
CLINICAL FEATURES OF AORTIC STENOSIS
• Most patients are asymptomatic until the stenosis becomes severe. They are often detected when a murmur is appreciated on physical examination.
In asymptomatic patients, confirmation of the etiology of the murmur and the severity of the valvular heart disease with echocardiography is warranted.
In athletes (as was the case in our patient), when a murmur is detected on examination for sports participation, further investigation is warranted.
• Dyspnea on exertion is the most prevalent presenting feature.
• Approximately 50% of patients develop symptoms of heart failure (HF), including dyspnea, orthopnea, paroxysmal nocturnal dyspnea, fatigue, cough, and weight gain.
• Around 35% develop angina pectoris, especially with exertion.
• Although more rare, 15% develop exertional dizziness or syncope that can be quite limiting.
• Features of heart failure including elevated jugular venous distention (JVD), hepatomegaly, and an S3 gallop that may be appreciated on physical examination.
• Physical exam may demonstrate a pulsus parvus et tardus, crescendo-decrescendo harsh, systolic ejection murmur at the upper right sternal border that radiates into carotids bilaterally and may be associated with an early systolic ejection click.
EPIDEMIOLOGY
• Bicuspid AV is present in as many as 1% to 2% of the population, but it is often underestimated and undetected as it can remain silent during infancy, childhood, and adolescence. In many cases, it is an incidental finding unless significant stenosis is present or infective endocarditis occurs. It is most commonly found in men age 50 or younger and affects males in a 2:1 or greater preponderance.
• In developed countries, a bicuspid AV is the etiology of severe AS in approximately 50% of young adults with AS.
• Most cases are sporadic with familial clusters identified in 10% to 17% in first-degree relatives of probands. Bicuspid AV is associated with aortopathy (see Chapter 7, Section V: Aortopathy in Bicuspid Aortic Valve Disease). First degree relatives of probands should be screened for AV and aortic pathology. Recent evidence suggests autosomal dominant inheritance with variable penetrance.1
PATHOPHYSIOLOGY AND ETIOLOGY
• It is related to abnormal embryologic development and associated with syndromes such as coarctation of the aorta (>50% with a bicuspid AV), Williams syndrome (11.6% with supravalvular aortic stenosis), and Turner syndrome (30% have bicuspid AV).2–4
• Findings are typically one complete line of coaptation. Most have a fusion of the raphe between the right and left coronary cusps (86%) and of the raphe between the left and non-coronary cusps (3%).5
• With aging, the valve can have sclerosis, calcification, and degeneration with symptoms of critical AS and heart failure. One-third of patients over the age of 20 have complications including aortic regurgitation (AR) if they present with AS symptoms at a younger age.6
ECHOCARDIOGRAPHY
A complete echocardiographic evaluation is suggested as a class I recommendation by the American College of Cardiology and American Heart Association (ACC/AHA).7 This assessment utilizes a combination of short-axis (SAX) and long-axis (LAX) images to identify the number of leaflets as well as leaflet mobility, thickness, and calcification. Two-dimensional imaging and Doppler echocardiography are utilized to determine the level of obstruction, left ventricular (LV) function, and associated lesions.
Using transthoracic echocardiogram (TTE), the following structural parameters are assessed:
• Diagnosis is most often reliable in the parasternal SAX when the two cusps are seen in systole with only two commissures framing an elliptical systolic orifice (Figure 3-3-2).
• Parasternal long-axis (PLAX) demonstrates a thickened AV with systolic doming of the leaflets. In some cases, dilatation of the ascending aorta may be seen. There may be associated aortic regurgitation as well.
• M-mode in the parasternal long axis view demonstrates an eccentric diastolic closure line of the AV leaflets (Figure 3-3-3).
• Standard hemodynamic valvular measurements include AS jet velocity, mean transaortic gradient, and valve area by the continuity equation.8
• Evaluate LV size, function, and wall thickness.
• Evaluate for coexisting lesions such as AR, coarctation of the aorta, ventricular septal defect (VSD), patent ductus arteriosus, aortic aneurysm, aortic dissection, infective endocarditis, and Shone’s complex.
• 3-D echocardiography may enhance visualization.
Transesophageal Echocardiogram (TEE)
• TEE can be used when improved visualization/clarification of valve anatomy is needed (Figures 3-3-6 and 3-3-7).
• TEE may also provide a better assessment of the aortic anatomy, though CT angiography or MRA of the aorta is more often employed as these modalities can provide an assessment of the entire aorta.
• TEE is indicated in cases of suspected endocarditis if the TTE images do not provide adequate information.
FIGURE 3-3-6 TEE short axis view of a bicuspid AV.
FIGURE 3-3-7 Three-dimensional TEE from a different patient demonstrating fusion of the right and left AV cusps.
OTHER DIAGNOSTIC TESTING AND PROCEDURES
• Common ECG findings include left ventricular hypertrophy, left atrial enlargement, and atrial fibrillation.
• Computed tomography (CT), Magnetic Resonance Imaging (MRI), and Angiography (MRA) can be utilized for improved visualization of the valve (Figure 3-3-8) and, more importantly, the aorta.
• Invasive cardiac catheterization is recommended if echocardiography is nondiagnostic or discrepant with clinical findings to define the hemodynamic severity of the AS.
FIGURE 3-3-8 MRI of a bicuspid valve in a short axis view.
FIGURE 3-3-9 TEE X-plane view of a bicuspid AV in another patient demonstrating prolapse of the fused right and left cusps. The patient had severe, eccentric AR.
DIAGNOSIS
• The presence of a congenital bicuspid AV is determined from clinical examination and history as well as direct visualization by echocardiography of the fused raphe on short axis imaging of the valve and the M-mode appearance.
• The classification of aortic stenosis severity is described in detail in Section 1 of this chapter.
Current European and US guidelines summarize these features in more detail for the interested reader.7,9,10
DIFFERENTIAL DIAGNOSIS
The differential diagnosis includes calcific aortic stenosis of a trileaflet valve, rheumatic heart disease, subaortic or supravalvular aortic stenosis, mitral valve prolapse, ventricular septal defect, and Ebstein anomaly.
MANAGEMENT
Medical Therapy
• Asymptomatic patients should be monitored for symptoms and progression of the underlying valve stenosis and aortic pathology.
• It is reasonable to give a β-adrenergic blocking agent to patients with bicuspid valves and dilated aortic roots (diameter greater than 40 mm) who are not candidates for surgical correction and who do not have moderate to severe AR.7
Imaging Surveillance
• Patients with bicuspid AV, jet velocity greater than 4.0 m/sec, or severe AR should have an annual TTE. For a jet velocity of 3.0 to 4.0 m/sec, or moderate AR, TTE should be done every 1 to 2 years. For a jet velocity of less than 3.0 m/sec and mild AR, surveillance with TTE should be done every 3 to 5 years.
• Patients with dilatation of the aortic root or ascending aorta (diameter greater than 4.0 cm) should undergo serial evaluation of aortic root/ascending aorta size and morphology by TTE, MRI, or CT on a yearly basis, or if symptoms suggest a clinical change.7
• Evaluation for aortopathy including coarctation should be done by CT or MRI (Figures 3-3-8).
Surgical Intervention
• AV replacement and/or aortic root repair or replacement is warranted based on the hemodynamic severity of the valve disease and the presence of significant aortic pathology.
• Criteria for bicuspid AV replacement are similar to those for other causes of severe AS. Patients with severe AS and symptoms (angina, syncope, CHF) warrant AV replacement (AVR).
• In the asymptomatic patient with severe AS due to a bicuspid AV, consider valve replacement if one or more of the following features is present: LVEF less than 50%, moderate-to-severe AR, abnormal exercise test shows poor functional capacity, abnormal blood pressure response, or symptoms of chest pain.7 Please see Section I: Asymptomatic Severe Aortic Stenosis for further discussion.
• Average survival after onset of symptoms in patients with severe AS is 2 to 3 years with a high risk of sudden death; therefore, surgery to replace the AV is recommended if symptoms are present.
• In patients with bicuspid AV undergoing AVR due to severe AS or AR, repair of the aortic root or replacement of the ascending aorta is indicated if the diameter of the aortic root or ascending aorta is greater than 4.5 cm.7,10
• Surgery to repair the aortic root or replace the ascending aorta is recommended in patients with bicuspid AV if the diameter of the aortic root or ascending aorta is greater than 5.0 or 5.5 cm or if the rate of increase in diameter is 0.5 cm per year or more.7,10 The presence of significant aortic pathology in patients without hemodynamically significant valve pathology can make decision making complicated in terms of whether or not to pursue valve replacement (in a patient who otherwise would not warrant AVR) at the time of aortic surgery. This decision is made on a case-by-case basis with input from the surgeon, cardiologist, and patient.
TABLE 3-3-1 Classification of Aortic Stenosis (AS) Severity in Those with Normal LV Function as Determined by the ESC and AHA/ACC Guidelines 8–10
PATIENT EDUCATION
• First-degree family members (especially males) should be screened by their physician, including a thorough physical examination, an ECG, and an echo to assess the AV and aorta.
• Prophylactic antibiotics for dental, gastrointestinal, and gynecologic procedures are no longer indicated. The risk of endocarditis is 10% to 30% over a lifetime. If a previous history of endocarditis exists, then prophylactic antibiotics are recommended.10
• Anomalous coronary arteries such as a left dominant coronary arterial system are commonly associated with a bicuspid AV. In rare cases, the left coronary artery may arise from the pulmonary artery.5
• Screen for familial hypercholesterolemia or early CAD. A cardiac diet and more aggressive primary prevention for cardiovascular events are recommended to delay sclerosis and calcification.
• There are no activity limitations for patients with a normally functioning bicuspid AV with normal aorta dimensions after thorough clinical evaluation. With AV insufficiency and aortic root diameter greater than 45 mm, patients should avoid strenuous isometric activity, such as weight lifting, rope climbing, and pull-ups and can participate only in low-intensity competitive sports.
• Risk of aortic root dissection is 5%, unless the individual has Marfan syndrome, then the risk is 40%.11
FOLLOW-UP
The patient was found to have a bicuspid aortic valve and aortic coarctation. Following repair of the coarctation, he will need periodic3 surveillance of his aorta with MRA (or CTA). He will also require serial follow-up of his aortic valve with echocardiography.
REFERENCES
1. Cripe L, Andelfinger G, Martin LJ, Shooner K, Benson DW. Bicuspid aortic valve is heritable. J Am Coll Cardiol. 2004;44(1):138-143.
2. Duran AC, Frescura C, Sans-Coma V, Angelini A, Basso C, Thiene G. Bicuspid aortic valves in hearts with other congenital heart disease. J Heart Valve Dis. 1995;4(6):581-590.
3. Hallidie-Smith KA, Karas S. Cardiac anomalies in Williams-Beuren syndrome. Arch Dis Child. 1988;63(7):809-813.
4. Sachdev V, Matura LA, Sidenko S, et al. Aortic valve disease in turner syndrome. J Am Coll Cardiol. 2008;51(19):1904-1909.
5. Libby P, Bonow RO, Mann DL, Zipes DP, Braunwald E, eds. Braunwald’s Heart Disease: A Ttextbook of Cardiovascular Medicine. Eighth 8th ed. Philadelphia, PA: Saunders Elsevier; 2008; No. 1-2.
6. Ward C. Clinical significance of the bicuspid aortic valve. Heart. 2000;83(1):81-85.
7. Bonow RO. Bicuspid aortic valves and dilated aortas: A critical review of the ACC/AHA practice guidelines recommendations. Am J Cardiol. 2008;102(1):111-114.
8. Baumgartner H, Hung J, Bermejo J, et al. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice. Eur J Echocardiogr. 2009;10(1):1-25.
9. Vahanian A, Baumgartner H, Bax J, et al. Guidelines on the management of valvular heart disease: The task force on the management of valvular heart disease of the European Society of Cardiology. Eur Heart J. 2007;28(2):230-268.
10. Nishimura RA, Carabello BA, Faxon DP, et al. ACC/AHA 2008 guideline update on valvular heart disease: Focused update on infective endocarditis: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. J Am Coll Cardiol. 2008;52(8):676-685.
11. Michelena HI, Khanna AD, Mahoney D, et al. Incidence of aortic complications in patients with bicuspid aortic valves. JAMA. 2011;306(10):1104-1112.
SECTION 4
CLINICAL CASE PRESENTATION
A 48-year-old man with a history of hypertension underwent the Ross Procedure in 1998 (autograft of his pulmonary valve to the aortic valve, with allograft of his pulmonic valve) for treatment of aortic insufficiency of unclear etiology. He had done well postoperatively, working as a construction worker. For 3 weeks prior to presentation, however, he developed progressive weakness and shortness of breath. On the day prior to admission, his breathing worsened to the point that he was having labored breathing at rest. He had mild chest pressure, orthopnea, and a 5-pound weight gain.
On presentation to the emergency department, his blood pressure was 135/62 mm Hg, his heart rate was 105 beats/min, and his oxygen saturations were adequate but required 2 L nasal cannula. His cardiac and pulmonary exam exhibited a short decrescendo diastolic murmur heard best over the left sternal border. He had bibasilar crackles and elevated jugular venous pressures to the angle of the jaw at 45°. He had bilateral lower extremity edema.
A chest x-ray showed pulmonary edema. Transthoracic echocardiogram demonstrated a moderately enlarged left ventricle, with an EF of 50%. He had moderate pulmonic stenosis (homograft) and severe aortic regurgitation (Figures 3-4-1 to 3-4-5).
FIGURE 3-4-1 Parasternal long axis view with color Doppler demonstrating severe AR. MR is also noted.
FIGURE 3-4-2 Apical 4 chamber with color Doppler demonstrating the color Doppler jet in the LV and a hyperdynamic LV.
FIGURE 3-4-3 Parasternal long axis view demonstrating a dilated LV.
FIGURE 3-4-4 Continuous-wave Doppler demonstrating a pressure half-time of 195 msec consistent with severe AR.
FIGURE 3-4-5 Spectral Doppler of the descending aorta demonstrating holosystolic flow reversal.
He went to the operating room and underwent aortic valve replacement (AVR) with a Capentier-Edwards Perimount Magna valve. He also had a pericardial patch enlargement of the pulmonary valve annulus and right ventricular outflow tract with a pulmonary valve replacement with a Carpentier-Edwards Perimount Magna valve. He has done well postoperatively and has returned to work.
CLINICAL FEATURES
• Patients with acute severe aortic regurgitation (AR) present with signs of CHF, including shortness of breath, orthopnea, paroxysmal nocturnal dyspnea, and edema.1
• Patients can have myocardial ischemia and chest pain secondary to supply demand mismatch, as well as decreased coronary perfusion pressure from the low aortic diastolic pressure.
• Findings associated with the underlying cause of the acute AR can often be elicited.
EPIDEMIOLOGY
• Trace aortic regurgitation (AR) or greater was seen in 13.0% of men and 8.5% of women in the Framingham Heart Study.1 Severe aortic regurgitation is much less common.
PATHOPHYSIOLOGY AND ETIOLOGY
• Acute AR can be caused by abnormalities of the aortic valve leaflets, or secondary to the problems with the aortic root/ascending aorta.1,2
• The most common causes of acute AR are infective endocarditis, aortic dissection, trauma, and acute dysfunction of a prosthetic valve.1
• In acute, severe AR there is a sudden, large regurgitant volume into a normal sized ventricle. The ventricle is not able to compensate, and there is an abrupt increase in LVEDP and left atrial pressure.3
• There is a decrease in effective forward stroke volume. Although tachycardia develops, it is often insufficient to maintain forward cardiac output, and cardiogenic shock and pulmonary edema ensue.2
• The LVEDP increases, and with rapidly decreasing aortic diastolic pressure the coronary perfusion pressure drops. With the increased demand secondary to tachycardia, signs and symptoms of myocardial ischemia can develop.2
ECHOCARDIOGRAPHY (SEE TABLE 3-4-1)
• Echocardiography, using 2-D echocardiography with color flow and comprehensive spectral Doppler evaluation, is essential in the assessment of aortic regurgitation.4
• Echocardiography is indicated to confirm the diagnosis based on physical exam, to assess the cause of AR, to assess the severity of AR, and assess (and follow over time) LV dimension, mass, and LV function (all Class I, LOE B recommendations).1,5
• Two-dimensional echo is used to assess the valve anatomy (eg, bicuspid valve, presence of vegetations) and structural deformities. The aortic root and proximal ascending aorta can be well visualized, and the diagnosis of an ascending thoracic aortic aneurysm as the cause of the AR can often be made. Additionally, the adaptive changes of the ventricle can be measured and followed. This becomes important in the decision and the timing of surgery in chronic AR patients.
• The severity of AR is assessed using color flow and spectral Doppler.
• Using color flow Doppler imaging, a regurgitant jet that is 65% of the LV outflow tract diameter is considered severe aortic regurgitation.4
• The rate of deceleration of the regurgitant diastolic flow reflects the rate of equalization of pressure between the aortic and the LV diastolic pressures (Figure 3-4-4). This can be measured with Doppler as the “pressure half time.” In general, the more severe the AR, the more rapid the deceleration of the regurgitant jet and the shorter the “pressure half time.” A pressure half time of <200 ms is suggestive of severe AR.4
• It is normal to have a small amount of early diastolic blood flow reversal in the descending and abdominal aorta. As AR progresses, however, the duration and the velocity of that flow increases. In severe AR, holodiastolic flow reversal can be seen using spectral Doppler (Figure 3-4-5).
• Echocardiography can quantify the regurgitant volume, regurgitant fraction, and the regurgitant orifice area. While this can be time consuming, it is helpful in differentiating degrees of moderate AR (2 plus to 3 plus), and in borderline cases.
• Transesphageal echocardiography (TEE) is particularly useful in assessing the anatomy of the valve and the aorta.4
TABLE 3-4-1 Selected Echocardiographic Parameters for the Evaluation of Aortic Regurgitation
OTHER DIAGNOSTIC MODALITIES
• If aortic dissection is suspected TEE, MRA (limited in unstable patients) and CTA are extremely valuable.1
• Cardiac catheterization is rarely needed in acute, severe AR and can delay surgery unnecessarily.1
MANAGEMENT
• Medical therapy for acute, severe AR is supportive only, and death without urgent surgical intervention is common.1
• β-blockers with aortic dissection should be used with caution.
• While awaiting surgery, medical therapy with vasodilators, such as nitroprusside, and inotropes can be used as temporizing measures to bridge to surgery.3
• Invasive hemodynamic monitoring may be useful to guide therapy (Figure 3-4-6).
• Intra-aortic balloon pumps are contraindicated, as they can worsen the AR.1
FIGURE 3-4-6 Arterial line tracing from a different patient with acute AR due to endocarditis demonstrating tachycardia and a wide pulse pressure.
FIGURE 3-4-7 Parasternal long axis view from a different patient demonstrating a large aortic valve vegetation that resulted in severe acute AR.
FIGURE 3-4-8 Parasternal long axis view with color Doppler from the patient seen in Figure 3-4-7 demonstrating severe acute AR.
FIGURE 3-4-9 Pulsed Doppler of the descending aorta from the patient in Figures 3-4-7 and 3-4-8 with severe acute AR demonstrating impressive holodiastolic flow reversal. The antegrade (systolic) VTI was 26 cm. The retrograde (diastolic) VTI was 18 cm, consistent with a regurgitant fraction well over 60%.
FOLLOW-UP
• Patients with acute aortic regurgitation require urgent surgical attention.
SUMMARY
• The most common causes of acute AR are infective endocarditis, aortic dissection, trauma, and acute dysfunction of a prosthetic valve.
• Echocardiography is valuable in the diagnosis.
• Surgery is essential to patient survival in acute severe aortic regurgitation.
PATIENT EDUCATION AND MANAGEMENT
• Following AVR, patient follow-up and serial echocardiography is warranted as detailed in other sections of this chapter1,5.
REFERENCES
1. Bonow RO, Carabello BA, Chatterjee K, et al. 2008 focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to revise the 1998 guidelines for the management of patients with valvular heart disease). Endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. J Am Coll Cardiol. 2008;52:e1-142.
2. Roberts WC, Ko JM, Jones WH 3rd. Causes of pure aortic regurgitation in patients having isolated aortic valve replacement at a single US tertiary hospital (1993 to 2005). Circulation. 2006;114:422-429.
3. Stout KK, Verrier ED. Acute valvular regurgitation. Circulation. 2009;119(25):3232-3241.
4. Zoghbi WA, Enriquez-Sarano M, Foster E, et al. Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and Doppler echocardiography. J Am Soc Echocardiogr. 2003;16:777-802.
5. Nishimura RA, Otto CM, Bonow RO, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease:executive summary; a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014;63:2348-2388.
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