Mitral Valve Diseases

A 23-year old woman of low socio-economic status came to a general hospital with
shortness of breath, fatigue and palpitations since 2 years and fever with productive
cough for the last 1 week. She denied any chest pain, wheezing or hemoptysis. At the
age of 12, she had a prolonged febrile illness with joint pains and ever since, she had
been receiving monthly injections of penicillin.
On examination she was tachypneic with pallor but there was no cyanosis
or icterus. Pulse rate was 96 beats/min. regular, with a BP of 100/70 mm Hg. Her
temperature was 1000 F. The JVP was not raised, thyroid gland was not enlarged and
there were no palpable lymph nodes. There was no evidence of pharyngo-tonsillitis,
swollen joints or petechial spots over the skin, eyes or finger-tips. The apex beat
was tapping in nature with a left parasternal heave. The S1 was loud and the P2 was
also accentuated. A low-pitched mid-diastolic rumbling murmur was heard over the
cardiac apex. The murmur was preceded by an opening snap and accentuated just
before systole. There were scattered rhonchi and crepts over the lung fields.
From the history and physical examination, this young woman in all probability
had rheumatic heart disease with mitral valve stenosis . The S1 is loud since the mitral valve leaflets are distant from each other at the end of diastole
and snap together loudly. Other reasons for a loud S1 are sinus tachycardia and a
short P-R interval, where the diastole is short. The mid-diastolic murmur of mitral
stenosis (MS) is best heard with the patient in the left lateral decubitus position,
using the stethoscope bell.
The length of the murmur correlates with the severity of stenosis. The murmur
undergoes presystolic accentuation due to atrial contribution to ventricular
filling. In mild MS, the murmur may be only presystolic. If MS is associated
with atrial fibrillation the S1 is variable in intensity due to variable duration of
diastole. Also, presystolic accentuation is lost due to lack of atrial contribution to
ventricular filling. Presystolic accentuation is also absent in a calcified valve and
after commissurotomy. Severe mitral stenosis may be silent due to low cardiac
output and the fact that the right ventricle underlies most of the precordium
because of clockwise cardiac rotation.
The opening snap heralds the onset of ventricular diastolic filling and the
end of isovolumic relaxation. It indicates pliability of the valve, suitability for
valvotomy and is absent in a heavily calcified valve or after commissurotomy.
An early opening snap after A2 (short 2A-OS interval), indicates higher left atrial
pressure and more severe MS. Besides mitral stenosis, other reasons for a middiastolic murmur are acute rheumatic valvulitis (Carey-Coomb murmur), aortic
regurgitation (Austin-Flint murmur), left atrial myxoma (prolapse into mitral
orifice) and left-to-right shunt (increased transmitral inflow).
ECG showed sinus rhythm, P mitrale, right ventricular hypertrophy with a
rightward QRS axis. X-ray chest findings were straightening of the left heart border
with pulmonary congestion. On M-mode ECHO, excursion of the anterior leaflet
was reduced with paradoxical excursion of the posterior leaflet (Fig. 6.2). On 2-D
ECHO, the left atrium and right ventricle were dilated. The mitral valve leaflets
were thickened with limited excursion and restricted valve opening. The anterior
mitral leaflet showed diastolic doming (Fig. 6.3). There was no abnormality of the
aortic valve and the estimated pulmonary artery pressure was elevated.
The severity of mitral stenosis can be gauged and classified, according
to several calculated indices from echocardiography. These are the pressure
gradient across the valve (PG), the time taken for the PG to fall to half (P½t;
pressure half-time), the pulmonary artery pressure (PAP) estimated from the
peak tricuspid velocity (TR Vmax) and the mitral valve area (MVA) calculated by
planimetry (Table 6.1). However, there are some fallacies associated with these calculations. The peak velocity and pressure gradient depend on the heart rate
and stroke volume. Measurement of mitral valve area may be fallacious due to
heavily calcified leaflets, subvalvular pathology and prior commissurotomy.
Rheumatic heart disease is the predominant cause of mitral stenosis. 80% of
cases are women in the 2nd or 3rd decade of life, from the developing countries. Rare
causes are congenital MS (parachute valve), mucopolysaccharidosis (Hurler’s
syndrome), severe annular calcification and connective tissue disorders (Table
6.2). Complications of MS are pulmonary congestion, respiratory infections,
hemoptysis, right heart failure and systemic thrombo-embolism due to atrial
fibrillation associated with left atrial thrombus PERTINENT INVESTIGATIONS
Since rheumatic heart disease is the predominant cause of mitral stenosis, all
patients who are febrile should be investigated for rheumatic fever, infective
endocarditis and respiratory tract infection. Relevant investigations are Hb, TLC,
DLC, ESR, urine R/E, CRP value and ASLO titre. Throat-swab culture for betahemolytic Streptococcus and bacterial blood cultures may be included.
Transthoracic ECHO is central to the diagnosis and assessment of mitral
stenosis. Besides determining the severity of MS, it can assess left atrial size, left
ventricular function and estimate pulmonary artery pressure. Transesophageal
echocardiography (TEE) allows better assessment of the subvalvular and
commissural architecture and improves the detection of a left atrial thrombus.
All patients of mitral stenosis should be offered penicillin prophylaxis against
rheumatic fever, until they attain the age of 40 years. A broad-spectrum antimicrobial agent should be administered prior to any invasive dental or surgical procedure, to guard against infective endocarditis. Diuretics reduce pulmonary
congestion, especially in patients with associated mitral or aortic regurgitation.
Rate control with digoxin, beta-blocker or verapamil improves left ventricular
diastolic filling, in patients who are in sinus rhythm and controls the ventricular
response, in whom the rhythm is atrial fibrillation. Since atrial fibrillation in
patients with mitral stenosis is associated with a high risk of thrombo-embolism,
these patients should also be on a long-term oral anticoagulant agent like warfarin.
Percutaneous balloon mitral valvuloplasty (BMV) is the procedure of choice
in symptomatic severe mitral stenosis, provided a transesophageal echocardiography (TEE) does not reveal subvalvular fusion, commissural calcification,
atrial thrombus or more than mild MR (Table 6.3). Recurrence of symptoms
after valvotomy is more often due to induced mitral regurgitation rather than
restenosis. If valvotomy cannot be performed because of the aforementioned
reasons, mitral valve replacement (MVR) is undertaken. During MVR, if atrial
fibrillation is present, left atrial radiofrequency ablation (RFA) and appendage
ligation are also performed.