61Case 13 Restrictive Cardiomyopathy

Table 13.2: Differences between constrictive pericarditis and restrictive cardiomyopathy

LV function Normal Mildly impaired

MV and TV Normal Regurgitation

MV inflow Abrupt halt Slow relaxation

Table 13.1: Causes of restrictive cardiomyopathy Endomyocardial

Endomyocardial fibrosis Hypereosinophilic syndrome

involvement may lead to nephrotic syndrome, which exacerbates the pedal edema of heart failure.

It is often challenging to differentiate restrictive cardiomyopathy from constric tive pericarditis and cardiac catheterization may be required for their distinc tion. The diagnosis of pericardial constriction is suggested if there is past history of tuberculosis, cardiac surgery or radiotherapy. Also, the X-ray chest shows linear pericardial calcification and ECHO may reveal pericardial thickening with multiple parallel lines, casting a bright reflection. Computed tomography (CT) or magnetic resonance imaging (MRI) may be required to demonstrate pericardiac thickening. Moreover, in constrictive pericarditis, the cardiac chamber size, myocardial thickness, valve structure and ejection fraction are all normal (Table 13.2). Clinically speaking, constrictive pericarditis presents with sole or predominant right heart failure while restrictive cardiomyopathy often presents with biventricular failure.

62 Section 4 The Cardiomyopathies

MANAGEMENT ISSUES

Diuretics reduce dyspnea and edema and they are the mainstay of the medical management of restrictive cardiomyopathy. However, vigorous diuresis should be avoided since it would compromise ventricular filling, reduce cardiac output and even cause syncope. It is crucial to maintain sinus rhythm and to cardiovert atrial fibrillation by electrical (DC shock) or pharmacological (amiodarone) means. This is because atrial fibrillation leads to loss of atrial contribution to ventri cular filling and shortens the diastolic filling time. Digoxin is best avoided for rate control and heart failure treatment, due to the high risk of ventricular arrhythmias in the presence of myocardial disease. Beta blockers and verapamil improve diastolic dystunction and control tachyarrhythmias. Specific therapies for restrictive cardiomyopathy are steroids for sarcoidosis and scleroderma as well as iron chelation therapy with desferrioxamine for hemochromatosis.

RECENT ADVANCES

The diagnosis of cardiac amyloidosis can now be confirmed by tissue biopsy.

Amyloid shows birefringence when stained with Congo red and viewed under polarized light. Biopsy material can be obtained either from abdominal fat pad or from rectal and gingival sites. Endomyocardial biopsy is only performed if the above tissue biopsies are inconclusive and yet the clinical suspicion is strong.

Of late, cardiac MRI imaging with gadolinium enhancement has shown high sensitivity and specificity for amyloidosis. Recently, chemotherapy targeted against clonal plasma cells, that produce monoclonal light chains, has been tried as a treatment modality in cardiac amyloidosis. Also, sequential cardiac and stem cell transplant has been optimistically attempted.

C A S E

14 Hypertrophic

Cardiomyopathy

CASE PRESENTATION

A 48-year old man was brought to the emergency room by his office colleagues, because he had fainted while climbing stairs. There was no history of tonic-clonic jerks, frothing at the mouth or tongue bite. On regaining consciousness, the patient admitted having had two such episodes in the past, one while playing cricket with his son and the other while changing a flat-tyre of his car. There was no sensation of palpitation before these syncopal episodes. There was no past history of exertional chest pain or breathlessness, although at times he did feel light-headed at the end of the day. He did not suffer from hypertension or diabetes but he did smoke occasionally and took alcohol over the weekends. His father had passed away due to sudden cardiac death at the age of 42 and one of his elder cousin brothers was on treatment for heart disease.

On examination, the patient was not tachypneic and there was no sweating. The pulse rate was 88 beats/min. and regular, but two distinct peaks were felt in systole.

Vigorous pulsations were seen over the carotid arteries. The BP was 118/78 mm Hg in the right arm. There was no anemia, cyanosis or sign of congestive heart failure. The apex beat was forceful and normal in location but two separate impulses were felt on palpation. The S₁ and S₂ were normal with a prominent S₄ audible in late diastole.

A short systolic murmur was appreciated at the upper left sternal border that peaked in mid-systole and ended abruptly. There was no ejection click or palpable thrill and the murmur did not radiate to the neck. The lung fields were clear.

CLINICAL DISCUSSION

From the history and physical examination, this patient had syncope due to left ventricular outflow tract (LVOT) obstruction. The cause of obstruction possibly had a familial basis. ECG showed tall R waves with T wave inversion, in the lateral precordial leads, but there was no S-T segment shift or presence of Q waves. The rhythm was sinus and the Q-T interval was not prolonged. The X-ray chest did not reveal any cardiomegaly or sign of pulmonary edema.

On ECHO, the left ventricle cavity was small in size with a normal ejection fraction. There was significant hypertrophy of the left ventricular walls, with hypertrophy of the interventricular septum (IVS) exceeding that of the LV posterior wall (LVPW). The anterior mitral leaflet (AML) impinged on the

64 Section 4 The Cardiomyopathies

hypertrophied septum during systole (Fig. 14.1). The aortic valve was structurally normal. On Doppler, an LV outflow tract gradient was demonstrated, proximal to the aortic valve. The high velocity jet had a typical concave appearance. On colour flow mapping, a mitral regurgitation jet was seen entering the left atrium. These ECHO findings are typical of hypertrophic obstructive cardiomyopathy (HOCM).

In retrospect, there were several pointers towards the diagnosis of HOCM, in the patient’s history and physical examination. History of syncope with an ejection systolic murmur raised the possibility of aortic stenosis, but there was no ejection click, palpable thrill or radiation of murmur to the neck. Moreover on ECHO, the aortic valve leaflets were structurally normal and the outflow tract gradient was located proximal to the aortic valve. A positive family history of sudden cardiac death may be due to congenital channelopathies that cause ventricular tachyarrhythmias but the patient denied palpitation and the ECG showed sinus rhythm with a normal Q-T interval and no evidence of WPW syndrome. Moreover in most channelopathies, the heart is structurally normal.

Atherosclerotic coronary artery disease is a prominent cause of premature sudden cardiac death which may run in families. However, coronary artery disease is rarely if ever associated with left ventricular hypertrophy, unless there is severe hypertension. Syncopal episodes are also uncommon, unless there is severe calcific aortic stenosis.

A double-peaked radial pulse that consists of a percussion wave and a tidal wave, is known as pulsus bisferiens. It indicates rapid early ejection of the left ventricle, followed by slow delayed emptying, after recoil of the vascular bed.

Pulsus bisferiens is typical of HOCM but also occurs in combined aortic valve disease (stenosis plus regurgitation). The strong and bifid apex beat indicates forceful atrial contraction preceding ventricular systole. A prominent S₄ sound in presystole also carries the same significance. These are both clinical signs of reduced left ventricular compliance due to myocardial hypertrophy.

Figure 14.1: ECHO showing asymmetrical septal hypertrophy impinging on the left ventricular outflow tract

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