Valvular Heart Disease



Valvular Heart Disease






General considerations


Development

Cardiac valves develop from the mesodermal germ layer between the 4th and 7th week of gestation. Any factors affecting embryogenesis during this time can affect development of valves and include infection (German measles/rubella), drugs, etc.





Acute rheumatic fever


Epidemiology



  • <1:1000 in developed countries; 10:1000 schoolchildren in developing countries. It is rarer, but still accounts for half of cardiac disease in the developing world.


  • Declining incidence is due to improved economic standards and housing, decreased crowding, and access to medical care and antimicrobials.


  • Typically affects children aged 5-15 years from lower socio-economic class living in crowded conditions; 20% of cases are in adults. Incidence is higher in native Hawaiians and Maoris despite antibiotic prophylaxis.


  • No sex difference but chorea and mitral stenosis (MS) are more common in females.


Pathology



  • Typically occurs several weeks after a streptococcal pharyngitis. Usually group A beta haemolytic streptococci: Streptococcus pyogenes serotype M. Antigenic mimicry is implicated—antibodies to carbohydrate in cell wall (anti-M antibodies) of group A Streptococcus cross-react with protein in cardiac valves.


  • Delay from acute infection to onset of rheumatic fever (RF) is usually 3-4 weeks. RF is thought to complicate up to 3% of untreated streptococcal sore throats. Previous episodes of RF predispose to further events (up to 50% of streptococcal sore throat is complicated by RF if there has been a previous episode). Other areas of crossreactivity may explain other signs (e.g. involvement of connective tissue in joints—arthritis, caudate nucleus in brain—Sydenham’s chorea).


  • Commonly causes a pancarditis. Pericarditis can cause haemodynamic instability or constriction. Myocarditis may cause acute heart failure and arrhythmias. Endocarditis affects the mitral valve (65-70%), aortic valve (25%), and tricuspid valve (10%, never in isolation) causing acute regurgitation and heart failure, and eventually chronic stenosis.


  • Pericardium, perivascular regions of myocardium, and endocardium develop perivascular foci of eosinophilic collagen surrounded by lymphocytes, plasma cells, and macrophages called Aschoff bodies.


Clinical features



  • Sore throat 1-5 weeks earlier is reported in two-thirds of cases.


  • Fever, abdominal pain, and epistaxis.


  • Migratory large-joint polyarthritis starting in the lower limbs in 75% of cases. Duration less than 4 weeks at each site. Severe pain and tenderness in contrast to degree of joint swelling.


  • Pancarditis in 50% of cases with features of acute heart failure, mitral and aortic regurgitation, an apical, mid-diastolic flow murmur (Carey Coombs murmur), and pericarditis.


  • Chorea in 10-30%, usually 1-6 months after the index pharyngitis. Difficulty writing and speaking, generalized weakness, choreiform movements, and emotional lability. Joints hyperextended with hypotonia, diminished tendon reflexes, tongue fasciculation, and a
    relapsing grip (alternate increases/decreases in tension). Recovery 2-3 months.


  • Erythema marginatum is an evanescent rash with serpiginous outlines and central clearings on the trunk and proximal limbs. Seen in 5-13% of cases. Begins as erythematous, non-pruritic papules or macules that spread outwards. Fades and reappears in hours and persists.


  • Subcutaneous nodules in 0-8% of cases several weeks after the onset of severe pancarditis. Mainly over bony surfaces or prominences and tendons. Commonly involves the elbows, knees, wrists, ankles, Achilles tendons, occiput, and vertebral spinous processes. Duration 1-2 weeks.


  • There is a danger of overdiagnosing RF in children admitted with fever, soft murmurs, and arthralgia, all of which are common in childhood.




Prognosis



  • Determined by level of cardiac involvement and antibiotic prophylaxis (5 years or until 21 years old if no carditis, 10 years or well into adulthood if carditis but no valve disease, 10 years or until 40 years old if valves affected and for all dental and surgical procedures).


  • Acute phase duration about 3 months in 80% of cases. Mortality 1-10% in developing countries.


  • Recurrence rates are high. Chronic valve disease occurs in one-third without and two-thirds with recurrent infections.


  • Murmurs resolve in 50% of cases up to 5 years after index infection.





Mitral stenosis: clinical features


Causes

Mitral stenosis (MS) is most commonly due to rheumatic fever. Other causes are rare. They include congenital (isolated lesion or in association with an atrial septal defect (ASD)—Lutembacher’s syndrome), mitral annular calcification, carcinoid heart disease, valvulitis (systemic lupus erythematosis), mucopolysaccharidoses (e.g. Hurler’s syndrome), and endocardial fibroelastosis. Stenosis occurs at three levels: the chordae (fuse, thicken, then shorten), cusps (initially rolled under edges, then thicken and eventually calcify), and commissures (progressive fusion).




Mitral stenosis: investigations


Investigations



  • Electrocardiography (ECG): P mitrale—bifid P wave (if in sinus rhythm) due to LA enlargement most prominent in lead II. Tall and peaked P waves in pulmonary hypertension. AF is frequent. Right-axis deviation and RV hypertrophy.


  • Chest X-ray (CXR): Straightening of the left heart border, prominent upper lobe veins, pulmonary artery enlargement, Kerley B lines—interstitial oedema. Large LA visible as a double shadow.








    Radiographic features of mitral stenosis





















    PA film


    Lateral film


    • Straight or convex L heart border


    LA or RV enlargement


    • Double shadow of LA behind RA


    • Valvular calcification frequent


    • Splaying of carina (>90°)—rare


    • Dilated upper lobe veins


    LA calcification seen rarely (McCallum’s patch)


    • Prominent pulmonary conus


    • Oesophageal indentation on barium swallow


    • Pulmonary haemosiderosis




  • Transthoracic ECHO (TTE): Parasternal long-axis view (LAX) shows enlarged LA and doming of the valve leaflets due to commissural fusion. In short-axis view (SAX), the mitral valve orifice can be calculated by planimetry. Calcification can be visualized. M-mode imaging—restricted valve leaflet separation due to commissural fusion. Continuous wave (CW) Doppler can be used to estimate the valve area and transvalvular gradient (see image p. 15). Valve ECHO score can be calculated (based on leaflet mobility, leaflet thickening, subvalvular thickening, and calcification).


  • Transoesophageal echocardiography (TOE): Provides better anatomic detail, can visualize small vegetations and thrombi in the LA.


  • Cardiac catheterization: Increased pulmonary capillary wedge pressure (PCWP). Increased PCWP to LV end-diastolic pressure gradient. If the mean mitral gradient is low at rest, get the patient to perform exercise on the cath-lab table (e.g. straight-leg raising) to calculate gradient again. Assessment of co-existing coronary and valvular lesions.


Classification










Table 3.2 Classification of mitral stenosis

























Severity


Mean gradient (mmHg)


PA systolic (mmHg)


Valve area (cm2)


Mild MS


<5


<30


>1.5


Moderate MS


5-10


30-50


1-1.5


Severe MS


>10


>50


<1


PA = pulmonary artery.



Management


Medical management



  • Mild symptoms: salt intake restriction and oral diuretics (cautious).


  • In AF: digoxin, β-blocker, or calcium-channel blocker for rate control. Restoration of sinus rhythm may be attempted if appropriate.


  • Anticoagulation: recommended for those with AF, prior thromboembolism, or LA thrombus. Patients with low-output states, right heart failure, or LA dimension ≥55 mm by echocardiography should also be anticoagulated. There is no proven benefit if the patient is in sinus rhythm.


  • Endocarditis prophylaxis is no longer recommended.1


Balloon valvotomy



  • Suitable for patients with pliable valves with minimal MR, no subvalvular distortion, and without heavy calcification (ideal if valve score ≤8).


  • Contraindicated in moderate or severe MR or atrial thrombus.


  • A guide wire is placed in the LA after trans-septal puncture, and a balloon (Inoue balloon) is directed across the valve and inflated at the orifice.


Indications for surgery



  • Not indicated in asymptomatic patients


  • In New York Heart Association (NYHA) III-IV patients:



    • mitral valve area (MVA) ≤1.5 cm2 if valve not suitable for percutanaous mitral balloon valvuloplasty (PMBV)


    • MVA >1.5 but with pulmonary artery systolic pressure (PASP)>60 mmHg, PCWP≥25 mmHg, or MV gradient>15 mmHg during exercise


  • In NYHA I-II patients for MVA≤1.5 cm2 AND pulmonary artery systolic pressure (PASP)>60-80 mmHg if percutaneous mitral balloon valvotomy (PMBV) contraindicated.








Mitral regurgitation


Causes

Acute: Infective endocarditis, acute myocardial infarction (MI), trauma.

Chronic: Most common—myxomatous degeneration (mitral valve prolapse), chronic rheumatic heart disease, left ventricular or annular dilatation of any cause (e.g. chronic ischaemia, cardiomyopathy, annular calcification), degeneration of valve cusps, collagen vascular disease, hypertrophic cardiomyopathy.


Nomenclature



  • Essentially there is a spectrum of myxomatous degenerative disease from single-segment prolapse in small valves (fibroelastic deficiency) to multisegment prolapse in large valves (Barlow’s disease).


  • Mitral regurgitation (MR) can be classified by mechanism according to Carpentier’s classification:



    • type I—normal leaflet motion, e.g. dilated annulus from dilated cardiomyopathy, leaflet perforation due to endocarditis


    • type II—leaflet prolapse, e.g. myxomatous degeneration


    • type IIIa—restricted leaflet opening, e.g. rheumatic disease


    • type IIIb—restricted leaflet closing, e.g. ischaemic dilated cardiomyopathy (functional).



Clinical features

In acute severe MR—pulmonary oedema is common, hypotension, cardiogenic shock. This is a medical emergency. See image p. 728.





Investigations



  • ECG: LA enlargement, left ventricular hypertrophy (LVH), RA enlargement in pulmonary hypertension. AF common in chronic MR.


  • CXR: Cardiomegaly, LA and LV enlargement, and pulmonary venous congestion. Calcified mitral annulus may be seen.


  • TTE: Demonstrates MV anatomy (lesion and type of MR). Colour Doppler to detect and quantify the MR (Table 3.3). Assessment of LV function from EF, end-systolic dimension and end-diastolic dimension (Note: In compensated MR, EF is always overestimated because of the low-resistance retrograde pathway).


  • TOE: Shows the anatomy in greater detail and allows accurate assessment of the feasibility of valve repair. Should be performed pre- or intra-operatively.


  • Cardiac catheterization: Not always required. Ventriculogram can quantify MR severity and EF. Detection of co-existing valve lesions and coronary artery disease.

Jul 22, 2016 | Posted by in CARDIOLOGY | Comments Off on Valvular Heart Disease

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