Left Atrial and Right Atrial Size, Function, and Pathology

Left Atrial and Right Atrial Size, Function, and Pathology

Bryan Simmons

1. A 67-year-old gentleman presents to the hospital with chest pain and is ultimately diagnosed with a non-ST-elevation myocardial infarction (NSTEMI). Cardiac catheterization reveals multivessel coronary artery disease and he is scheduled to undergo coronary artery bypass grafting. A preoperative transthoracic echocardiogram (TTE) demonstrates normal biventricular function as well as the following imaging shown in Figure 30.1 and image Video 30.1.

Based on the imaging, the patient is most likely to have which of the following?

A. Positive blood cultures

B. A patent foramen ovale (PFO)

C. A defect in the septum secundum

D. A cleft mitral valve leaflet

View Answer

1. Correct Answer: B. A patent foramen ovale (PFO)

Rationale: image Video 30.1 demonstrates an atrial septal aneurysm (ASA), which is a redundant, mobile atrial septal tissue present in approximately 2% of the general population. Although most patients with ASAs are asymptomatic, the presence of an ASA is associated with a PFO, Chiari network, and stroke. Echocardiographic diagnosis of an ASA requires a total septal excursion (right and left) of at least 15 mm or an excursion of at least 10 mm into either chamber (right or left atrium). M-mode can be particularly useful in obtaining these measurements.

There is no clinical or echocardiographic suggestion of endocarditis that would put the patient at risk for having positive blood cultures. When the atrioventricular valves are involved, vegetations usually involve the atrial side of the valve. Vegetations are also associated with regurgitation and move in tandem with the valve leaflet. The septum secundum is the thicker portion of the interatrial septum. Primum ASDs are associated with a cleft mitral valve leaflet, an invagination of mitral valve leaflet, resulting in mitral regurgitation.

Selected References

1. Agmon Y, Khandheria BK, Meissner I, et al. Frequency of atrial septal aneurysms in patients with cerebral ischemic events. Circulation. 1999;99(15):1942-1944.

2. Cabanes L, Mas JL, Cohen A, et al. Atrial septal aneurysm and patent foramen ovale as risk factors for cryptogenic stroke in patients less than 55 years of age. A study using transesophageal echocardiography. Stroke. 1993;24(12):1865-1873.

3. Pearson AC, Nagelhout D, Castello R, Gomez CR, Labovitz AJ. Atrial septal aneurysm and stroke: a transesophageal echocardiographic study. J Am Coll Cardiol. 1991;18(5):1223-1229.

2. A 58-year-old female with hypertension and hyperlipidemia presents to the Emergency Department with a 2-hour history of word-finding difficulty. The patient is diagnosed with a stroke and administered tissue plasminogen activator (tPA) with resolution of her symptoms. She undergoes a TTE for evaluation of a cardioembolic etiology of her stroke. image Video 30.2 is obtained.

Based on image Video 30.2, the patient most likely has which of the following?


B. A ventricular septal defect

C. A transpulmonary shunt

D. An atrial septal defect (ASD)

View Answer

2. Correct Answer: C. A transpulmonary shunt

Rationale: image Video 30.2 is a bubble study. While TEE is considered the gold standard in detection of intracardiac shunts at the atrial level, bubble studies obtained with TTE are typically the initial imaging modality given the less invasive nature and acceptable sensitivity and specificity. A bubble study is commonly performed with 10 mL of agitated saline (or 8-10 mL of saline mixed with 0.5 mL of air) rapidly injected through a peripheral IV catheter. When interrogating the interatrial septum, provocative maneuvers, such as Valsalva maneuver or abdominal pressure, are provided to transiently increase right atrial pressures and elicit a right-to-left shunt. These maneuvers are released once the contrast opacifies the right atrium. The apical four-chamber view is the preferred imaging plane when a bubble study is performed. It is recommended to record at least 20 consecutive heart beats to ensure detection of transpulmonary shunts. A bubble study is positive for an intracardiac shunt if bubbles are seen in the left atrium or left ventricle within four cardiac cycles following opacification of the right atrium. Appearance of bubbles in the left-sided chambers beyond six cardiac cycles is most consistent with a transpulmonary shunt, which can be seen with pulmonary arteriovenous (AV) malformations and hepatopulmonary syndrome. With transpulmonary shunting, the contrast may be seen originating from the pulmonary veins.

The bubble study provided in the vignette illustrates a transpulmonary shunt. Contrast appears in the left atrium, but not until the tenth cardiac cycle following opacification of the right atrium.

Selected References

1. Mitchell C, Rahko PS, Blauwet LA, et al. Guidelines for performing a comprehensive transthoracic echocardiographic examination in adults: recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr. 2019;32(1):1-64.

2. Silvestry FE, Cohen MS, Armsby LB, et al. Guidelines for the echocardiographic assessment of atrial septal defect and patent foramen ovale: from the American Society of Echocardiography and Society of Cardiac Angiography and Interventions. J Am Soc Echocardiogr. 2015;28(8):910-958.

3. A 56-year-old gentleman with a history of hypertension and obesity is admitted to the intensive care unit (ICU) with fever, hypotension, and hypoxemia. He remains hypotensive despite 30 mL/kg of intravenous (IV) fluids and IV antibiotics. He is intubated and a transesophageal echocardiogram (TEE) is performed. Interrogation of the interatrial septum is shown in Figure 30.2.

Which of the following would the patient most likely benefit from?

A. Inhaled pulmonary vasodilators

B. Vasopressors

C. Percutaneous placement of a septal occlusion device

D. Cardiac surgery consult for resection of an intracardiac mass

View Answer

3. Correct Answer: B. Vasopressors

Rationale: There are a number of benign anatomic variants involving the atria that the astute echocardiographer must know. Figure 30.2 illustrates lipomatous hypertrophy of the atrial septum (LHAS), a condition caused by adipose infiltration of the interatrial septum. The incidence of LHAS has been quoted to be as high as 7%. Echocardiographically, LHAS appears as a circumscribed, dumbbell-like structure involving the superior and inferior portions of the interatrial septum. Typically, the fossa ovalis is spared. This condition is nearly always benign and of no hemodynamic significance.

In the setting of suspected sepsis, initiation of vasopressor therapy for persistent hypotension is the most appropriate next step following source control, antibiotics, and fluid resuscitation. Percutaneous septal occlusion devices are Food and Drug Administration (FDA)-approved for transcatheter closure of a PFO to prevent recurrent stroke in patients with a history of cryptogenic stroke. There is no evidence of a PFO on the image provided, nor is there a history of cryptogenic stroke.

Selected Reference

1. Pochis WT, Saeian K, Sagar KB. Usefulness of transesophageal echocardiography in diagnosing lipomatous hypertrophy of the atrial septum with comparison to transthoracic echocardiography. Am J Cardiol. 1992;70(3):396-398.

4. A 64-year-old female presents to the Emergency Department with a 3-week history of palpitations and a 2-day history of presyncopal episodes. Electrocardiography (ECG) reveals atrial fibrillation with rapid ventricular response. Despite attempts at rate control, the patient remains in atrial fibrillation with intermittent presyncopal episodes. She is ultimately scheduled for TEE and synchronized cardioversion. Based upon the TEE images obtained as shown in Figure 30.3, image Videos 30.3, and 30.4, which of the following is most accurate?

A. There is no clot visualized in the left atrial appendage (LAA); however, LAA exiting velocities are low and the patient may still be at risk for cardioembolic stroke following cardioversion.

B. There is a clot in the LAA. No cardioversion should be attempted.

C. There is no clot visualized in the LAA. Exiting velocities are normal. Cardioversion should be attempted.

D. TEE is not an appropriate test to evaluate LAA thrombus.

View Answer

4. Correct Answer: A. There is no clot visualized in the LAA; however, LAA exiting velocities are low and the patient may still be at risk for cardioembolic stroke following cardioversion.

Rationale: For patients in whom maintenance of normal sinus rhythm is desirable and conventional anticoagulation (consisting of 3-4 weeks of therapeutic anticoagulation) prior to cardioversion is not feasible, TEE can be utilized to evaluate the atria for the presence of clot. TEE is superior to TTE in this regard given the closer proximity of the TEE transducer to the atria and the higher frequency (better resolution).

Thrombus responsible for cardioembolic events most frequently arises from the LAA. In evaluating for thrombus, the LAA should be imaged in multiple planes with 2D imaging. Color flow Doppler (CFD) should be utilized to ensure the entire LAA fills with color, employing a lower Nyquist limit. Pulse-wave Doppler (PWD) is useful in measuring LAA flow velocities. As peak LAA exiting velocities fall below 40 cm/s, one must become increasingly suspicious of LAA thrombus risk. Peak LAA exiting velocities less than 20 cm/s have been clearly associated with LAA thrombus and stroke. To obtain LAA flow velocities, the PWD sample cursor should be placed 1 cm into the LAA. Note that when using TEE, LAA exiting velocities obtained with PWD travel toward the transducer and by convention are displayed above the baseline.

A common pitfall is mistaking the ligament of Marshall, or artifacts arising from this structure, as LAA thrombus. The ligament of Marshall, also known as the coumadin ridge or warfarin ridge, is the atrial tissue that separates the LAA from the left upper pulmonary vein. Imaging the LAA from multiple different planes will help avoid this problem.

In this vignette, there is no clot present in the LAA on TEE imaging. The LAA fills completely with color Doppler; however, LAA exiting velocities seen on the PWD image provided are less than 20 cm/s. As mentioned earlier, LAA exiting velocities less than 20 cm/s are associated with both clot formation and stroke.

Selected References

1. Goldman ME, Pearce LA, Hart RG, et al. Pathophysiologic correlates of thromboembolism in nonvalvular atrial fibrillation: I. Reduced flow velocity in the left atrial appendage (The Stroke Prevention in Atrial Fibrillation [SPAF-III] study). J Am Soc Echocardiogr. 1999;12(12):1080-1087.

2. Klein AL, Grimm RA, Murray RD, et al. Use of transesophageal echocardiography to guide cardioversion in patients with atrial fibrillation. N Engl J Med. 2001;344(19):1411-1420.

5. A 75-year-old female with a history of hypertension, obesity, and nonobstructive coronary artery disease is admitted to the ICU on postoperative day 2 following a left hip arthroplasty with new-onset atrial fibrillation and an increase in oxygen requirement. Her ECG is without significant ST changes, troponins are negative, and brain natriuretic peptide is elevated. Diastolic dysfunction is suspected and a TTE is performed. In assessing this patient’s diastolic function, which of the following views and measurement methods are most appropriate in assessing left atrial (LA) size?

A. Biplane method of discs, apical four-chamber and apical two-chamber views

B. Anteroposterior (AP) linear measurement, parasternal long-axis view

C. Area-length technique, apical four-chamber and apical two-chamber views

D. Area via planimetry, apical four-chamber view

View Answer

5. Correct Answer: A. Biplane method of discs, apical four-chamber and apical two-chamber views

Rationale: LA enlargement is associated with a number of adverse outcomes including stroke, atrial fibrillation, diastolic dysfunction, and congestive heart failure. As mentioned in the vignette, LA size is important in assessing diastolic dysfunction with LA enlargement being one diagnostic criteria. The clinical significance of diastolic dysfunction in the ICU patient population is becoming increasingly recognized. The presence of diastolic dysfunction has been associated with failure to wean from mechanical ventilation and even mortality.

In patients with restrictive cardiomyopathies and restrictive filling patterns, LA enlargement can be quite remarkable and atrial size can approach the size of the left ventricle. Measurements of the left atrium can be obtained from a multitude of views; however, LA volume measurements are recommended by guidelines. Volume measurements more accurately reflect LA remodeling and enlargement, which can occur in all directions. The recommended technique to measure LA volume is the disc summation method (or biplane method of discs, Figure 30.9A) in which LA volume is approximated with a series of discs. After the volume of each disc is estimated, the discs are summed to yield a total LA volume. Note that the LAA and pulmonary veins are not included in the measurement. Also, measurements of LA size should always be obtained at the end of left ventricular (LV) systole, when the left atrium is largest. LA volume is indexed to body surface area (BSA) with LA enlargement defined as >34 mL/m2. As mentioned previously, an LA indexed volume of >34 mL/m2 is one of the diagnostic criteria for diastolic dysfunction.

Other methods for LA quantification are commonly obtained. The most commonly reported linear measurement (Figure 30.9B) is the LA AP diameter obtained from the parasternal long-axis view. With the aortic root in long axis, the LA is measured with a perpendicular line drawn at the level of the aortic sinus. Normal values for women are 2.7 to 3.8 cm and for men are 3.0 to 4.0 cm. Three-dimensional echocardiography has shown promise in the evaluation of LA size, but currently lacks robust standardization of normal values and is not a recommended standard at this time.

Selected References

1. Barnes ME, Miyasaka Y, Seward JB, et al. Left atrial volume in the prediction of first ischemic stroke in an elderly cohort without atrial fibrillation. Mayo Clin Proc. 2004;79(8):1008-1014.

2. Benjamin EJ, D’Agostino RB, Belanger AJ, Wolf PA, Levy D. Left atrial size and the risk of stroke and death. The Framingham Heart Study. Circulation. 1995;92(4):835-841.

3. Gonzalez C, Begot E, Dalmay F, et al. Prognostic impact of left ventricular diastolic function in patients with septic shock. Ann Intensive Care. 2016:6(1):36.

4. Lang RM, Badano LP, Mor-Avi V, et al. Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr. 2015;28(1):1-39.

5. Mourad M, Chow-Chine L, Faucher M, et al. Early diastolic dysfunction is associated with intensive care unit mortality in cancer patients presenting with septic shock. Br J Anaesth. 2014;112(1):102-109.

6. Nagueh SF, Smiseth OA, Appleton CP, et al. Recommendations for the evaluation of left ventricular diastolic function by echocardiography: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr. 2016;29(4):277-314.

7. Papanikolaou J, Makris D, Saranteas T, et al. New insights into weaning from mechanical ventilation: left ventricular diastolic dysfunction is a key player. Intensive Care Med. 2011;37(12):1976-1985.

8. Simek CL, Feldman MD, Haber HL, et al. Relationship between left ventricular wall thickness and left atrial size: comparison with other measures of diastolic function. J Am Soc Echocardiogr. 1995;8(1):37-47.

9. Tsang TS, Barnes ME, Bailey KR, et al. Left atrial volume: important risk marker of incident atrial fibrillation in 1655 older men and women. Mayo Clin Proc. 2001;76(5):467-475.

10. Tsang TS, Barnes ME, Gersh BJ, et al. Risks for atrial fibrillation and congestive heart failure in patient >/=65 years of age with abnormal left ventricular diastolic relaxation. Am J Cardiol. 2004;93(1):54-58.

6. A 50-year-old female with a 2-month history of worsening dyspnea on exertion is intubated and sedated in the ICU after being admitted for a stroke. A transthoracic echocardiogram (TTE) is attempted but results in poor image quality. A transesophageal echocardiogram (TEE) is obtained (Figure 30.4 and image Video 30.5).

Which of the following is most likely true of the anatomic abnormality shown in Figure 30.4 and image Video 30.5?

A. The defect is associated with partial anomalous pulmonary venous return (PAPVR)

B. There is a defect in the septum secundum

C. The defect is associated with Scimitar syndrome

D. There is a defect in the septum primum

View Answer

6. Correct Answer: D. There is a defect in the septum primum

Rationale: There are a number of abnormal atrial septal communications that can go undiagnosed long into adulthood. These defects can predispose patients to paradoxical emboli and, if large enough, eventually lead to pulmonary hypertension and right heart failure. Although many abnormal atrial septal communications can be diagnosed with TTE, TEE is superior in characterization of atrial septal abnormalities given its higher resolution.

The most common atrial septal abnormality is a PFO. A PFO is not a true ASD, but instead is a potential communication between the atria that occurs due to incomplete fusion of the septum primum and septum secundum. It is a remnant of fetal circulation that allows shunting of oxygenated blood from the inferior vena cava (IVC) to the left atrium. A PFO is present in up to 25% of the population. A PFO can be diagnosed with TTE or TEE utilizing CFD or a bubble study. Contrast or CFD can often be seen traversing the interatrial septum between the thin septum primum and thicker septum secundum. The flow of contrast or color Doppler is typically parallel to the septum, distinguishing it from a secundum ASD.

A secundum ASD, or ostium secundum ASD, is the most common ASD. It is important to remember that a secundum ASD is actually a defect in the septum primum, the thin membranous portion of the interatrial septum. The defect can vary from small fenestrations to complete absence of the septum primum. Unlike a PFO, the direction of CFD or contrast across the interatrial septum is usually perpendicular to the septum. Secundum ASDs are amenable to percutaneous closure and associated with mitral valve prolapse, mitral regurgitation, and anomalous pulmonary venous return.

A primum ASD, or ostium primum ASD, is the second most common ASD. It is a defect in the inferior portion of the interatrial septum and falls within the spectrum of endocardial cushion defects. A primum ASD may also be referred to as a partial AV canal defect. Primum ASDs are associated with cleft mitral valves, trisomy 21, and conduction abnormalities. Complete and transitional AV canal defects consist of a primum ASD and inlet-type ventricular septal defect.

Other rare atrial communication abnormalities include sinus venosus defects and coronary sinus defects, although these are not true ASDs. Sinus venosus defects are abnormal communications between superior (SVC) or IVC and the pulmonary veins. With SVC-type sinus venosus defects, the right upper pulmonary vein drains anomalously into the SVC, resulting in PAPVR. This can be identified with TEE in the bicaval view appearing as a defect in the interatrial septum that occurs superior to the crista terminalis. IVC-type sinus venosus defects involve communication between the IVC and either the right lower or middle pulmonary vein (Scimitar syndrome). Coronary sinus defects are characterized as direct communication between the coronary sinus and the left atrium, commonly referred to as “unroofing” of the coronary sinus. This allows a communication between the left and right atria via the coronary sinus. Coronary sinus defects are associated with a persistent left superior vena cava (PLSVC).

Selected References

1. Allan LD, Sharland GK. The echocardiographic diagnosis of totally anomalous pulmonary venous connection in the fetus. Heart. 2001;85(4):433-437.

2. Ari ME, Dogan V, Özgür S, et al. Persistent left superior vena cava accompanying congenital heart disease in children: experience of a tertiary care center. Echocardiography. 2017;34(3):436-440.

3. Craig RJ, Selzer A. Natural history and prognosis of atrial septal defect. Circulation. 1968;37(5):805-815.

4. Leachman RD, Cokkinos DV, Cooley DA. Association of ostium secundum atrial septal defects with mitral valve prolapse. Am J Cardiol. 1976;38(2):167-169.

5. Schneider B, Zienkiewicz T, Jansen V, Hofmann T, Noltenius H, Meinertz T. Diagnosis of patent foramen ovale by transesophageal echocardiography and correlation with autopsy findings. Am J Cardiol. 1996;77(14):1202-1209.

6. Silvestry FE, Cohen MS, Armsby LB, et al. Guidelines for the echocardiographic assessment of atrial septal defect and patent foramen ovale: from the American Society of Echocardiography and Society of Cardiac Angiography and Interventions. J Am Soc Echocardiogr. 2015;28(8):910-958.

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Jun 9, 2022 | Posted by in CARDIOLOGY | Comments Off on Left Atrial and Right Atrial Size, Function, and Pathology
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