RHEUMATIC FEVER

This acute febrile illness is due to a cross-reaction following a group A β-haemolytic streptococci pharyngitis, which causes inflammatory lesions involving the joints, heart and subcutaneous tissues. It presents with polyarthritis, carditis, subcutaneous nodules, rash (erythema marginatum) and chorea. Carditis consists of:

Chronic rheumatic heart disease occurs in about 40% of those with apical and basal diastolic murmurs, and 70% with heart failure or pericarditis during the acute attacks. It is still common in the Middle East, India, Africa and South America, and causes 20–40% of all cardiovascular disease in the Third World.² It is now rare in North America, western Europe, Australasia and parts of Asia.

MITRAL STENOSIS

Rheumatic fever is the main cause of mitral stenosis; rarer causes are:

Scarring or fibrosis of the valves, especially at the edges and sometimes involving the subvalvular apparatus, causes narrowing and hence increased left atrial pressure, pulmonary venous hypertension and pulmonary arterial hypertension. Thus the lungs and right ventricle suffer the most burden. Main symptoms are breathlessness on exertion, recurrent bronchitis, fatigue, palpitations due to paroxysmal atrial fibrillation (AF), haemoptysis and stroke. The onset of AF is usually associated with marked symptomatic deterioration and significantly increases the risk for left atrial thrombus formation and embolism.

Classic signs of mitral stenosis are:

The first clue to the diagnosis is often the loud first heart sound, which should prompt a careful search for the diastolic rumble which may be soft, low-pitched and localised to the apex. An opening snap is present if the valve is not calcified and this occurs 0.04–0.10 s after S₂.

An electrocardiogram (ECG) shows a broad P-wave in lead 2 due to left atrial hypertrophy. Chest X-ray shows an enlarged left atrium and appendage, prominent upper-lobe pulmonary veins, but heart size is usually within normal limits. The diagnosis can readily be confirmed by echocardiography, which allows assessment of the valve anatomy, and estimation of valve area and gradient. Severe stenosis is considered to be present if the valve area is < 1 cm² (Figure 21.1).

Figure 21.1 Mitral stenosis. Thickened and calcified anterior and posterior mitral valve leaflets with reduced opening. LV, left ventricle; LA, left atrium.

Treatment is the use of β-blockers to slow the heart rate and increase diastolic filling time diuretics, and digoxin is given if the patient is in AF. Anticoagulation is essential if there is significant mitral stenosis and AF. Mitral balloon valvuloplasty has been shown to be very successful therapy with excellent long-term outcome, and compares well with surgical treatment.⁵ The main contraindications to balloon valvuloplasty are significant mitral regurgitation and heavy calcification when mutual valve replacement should be done.

MITRAL REGURGITATION

There is a considerable difference between acute and chronic mitral regurgitation (Table 21.1). In chronic mitral regurgitation, there is time for the left ventricle and left atrium to adapt to the increasing regurgitation, leading to their gradual enlargement. In acute mitral regurgitation, the sudden pressure overload of the left atrium and pulmonary veins leads to severe pulmonary oedema. The treatment for acute mitral regurgitation is urgent surgery. The management of chronic mitral regurgitation is more difficult. Initially, medical therapy can be helpful, but the probability of postoperative death or persistent severe heart failure after valve replacement increases abruptly when the left ventricular (LV) end-systolic diameter exceeds 45 mm on echocardiography, or ejection fraction falls below 60%.⁶ In patients without mitral stenosis, mitral valve repair is preferable to replacement, and evidence suggests that preservation of the chordae improves postoperative LV function.⁷

Table 21.1 Mitral regurgitation

MI, myocardial infarction; LV, left ventricle/ventricular; IHD, ischaemic heart disease; IE, infective endocarditis; LA, left atrium/atrial; ACE, angiotensin-converting enzyme.

MITRAL VALVE PROLAPSE⁸

This is a common condition affecting 5% of the adult population – more women than men. It has a number of synonyms, such as Barlow and click–murmur syndrome. It is due to myxomatous degeneration of the valve, with redundancy of the leaflets, which may affect both the anterior and posterior valves. At the end of diastole, the valve closes normally, but as LV pressure rises during systole, a portion of the valve leaflet prolapses in the left atrium, with associated regurgitation. It is usually mild, but can progress and become more severe, and, rarely, the chordae may rupture to produce severe acute regurgitation.

Mitral valve prolapse is usually asymptomatic, but a wide variety of symptoms have been associated, including odd chest pains, palpitations and fatigue. On examination, typical findings are a mid-systolic click and a late systolic murmur, which are separated from the first heart sound, but usually reaching the second heart sound. The murmur may have a crescendo/decrescendo quality. It is usually louder with the Valsalva manoeuvre and on standing. As the prolapse worsens with age the murmur becomes more pansystolic. Echocardiography is diagnostic, and can accurately assess the degree of severity of mitral valve prolapse (Figure 21.2). In most patients, mitral prolapse is a benign condition with a good prognosis. It poses a risk for infective endocarditis, which then leads to a substantial risk of death and need for mitral valve surgery.⁹ There is a very small increased incidence of embolic neurological ischaemic events.

Figure 21.2 Mitral valve prolapse with bowing of the anterior mitral valve leaflet with enlargement of the left atrium but normal left ventricle size.

AORTIC STENOSIS

The commonest cause of aortic stenosis is degeneration of a bicuspid aortic valve. Valve stenosis leads to increased LV systolic pressure, LV hypertrophy and reduced LV compliance. The increased LV work may induce subendocardial ischaemia, arrhythmias and sudden death.

The main symptoms are angina, syncope and breathlessness. Typical findings on examination are a slowly rising small-volume pulse, evidence of LV hypertrophy without an enlarged heart, and a harsh ejection systolic murmur radiating into the neck. If the valve is calcified, there is no click and the A₂ is soft.

An ECG confirms LV hypertrophy. The chest X-ray may show:

Echocardiography is diagnostic, and allows the measurement of the aortic valve area, gradient and the degree of aortic incompetence (Figure 21.3).

Figure 21.3 Aortic stenosis. A calcified thickened valve with reduced opening and the presence of left ventricular hypertrophy.

Medical treatment is not effective. Valve replacement should be performed as soon as the patient is symptomatic, if asymptomatic with LV systolic dysfunction, or if the jet velocity is > 4 m/s in patients undergoing coronary artery bypass surgery.¹⁰

AORTIC REGURGITATION