HYPERTROPHIC CARDIOMYOPATHY

Hypertrophic cardiomyopathy is characterized by marked hypertrophy of the left and/or right ventricle particularly the interventricular septum in the absence of a cardiac or systemic cause (asymmetrical septal hypertrophy).

The hypertrophied septum and the anterior movement of the mitral valve across the outflow tract making contact with the ventricular septum in mid systole result in mechanical obstruction to left ventricular ejection. Some degree of mitral regurgitation may develop. The left ventricular outflow tract is narrowed during systole between the bulging septum and systolic anterior motion (SAM) of the anterior mitral leaflet causing obstruction to left ventricular emptying, therefore, called obstructive cardiomyopathy. The obstruction is worsened by factors that increase myocardial contractility (sympathetic stimulations, digoxin) or that decrease left ventricular filling (Valsalva’s manoeuvre, peripheral vasodilators).

It is the most common genetically transmitted cardiac disorder. Incidence is 1 in 500 of the general population.

This type of hypertrophy usually manifests in adolescents and young adults, most of the patients are identified during the screening of relatives of patients with hypertrophic cardiomyopathy. It may manifest in the 4^th  or 5^th  decade and sometimes in the elderly.

The physiological characteristic of HOCM is diastolic dysfunction (while systolic dysfunction in dilated cardiomyopathy) resulting in abnormal stiffness of the left ventricle with resultant impaired ventricular filling. Left ventricular end-diastolic pressure increases resulting in pulmonary congestion and dyspnea.

Associations

Noonan syndrome

Friedreich’s ataxia.

Glycogen storage disease

Mitochondrial myopathies.

Symptoms

The patient may be asymptomatic, diagnosed on echo during screening.

Dyspnea: — It is due to pulmonary congestion resulting from elevations in pulmonary venous and left atrial pressure because of the stiffness of hypertrophic ventricles (diastolic dysfunction).

Chest pain:– This occurs on exertion or at rest due to compression of intramyocardial coronary arteries and increased oxygen requirement due to increased myocardial contraction and muscle mass. Chest pain usually does not respond to sublingual nitroglycerine.

Syncope:–  Especially post-exertional due to inadequate cardiac output with exertion or from cardiac arrhythmia.

Palpitation —  It is due to arrhythmias. Atrial fibrillation is common and a poor prognostic sign. Ventricular arrhythmias are also common and sudden death may occur.

Sudden death: — This can occur at any age but the highest rates occur in adolescents and young adults.

Congestive heart failure

Signs

On CVS Examination

Palpation:

Apex’ beat is displaced laterally, forceful and diffuse. A double apical pulsation (forceful atrial contraction produces a palpable fourth heart sound).

Auscultation:

SI is normal, often preceded by S4, normal S2.

Late systolic murmur beast heard between the apex and left sternal border radiating to lower sternal border, axilla, and base of heart but not into the neck vessel (that differentiates it from the murmur of aortic stenosis). It is produced due to left ventricular outflow obstruction in late systole. This murmur is increased by the Valsalva manoeuvre and by standing while decreased by squatting.

A pansystolic murmur at the apex may be heard due to mitral regurgitation as a result of the systolic anterior motion of the anterior leaflet of the mitral valve).

Reversed splitting of second heart sound,

Pulse: A jerky carotid pulse with a sharp upstroke (because of rapid ejection and sudden obstruction to left ventricular outflow during systole).

JVP; prominent a wave due to forceful atrial contraction.

INVESTIGATIONS

X-ray chest: — The heart is usually not greatly enlarged

ECG: — ECG demonstrates left ventricular hypertrophy Occasionally LBBB or RBBB, APCs, PVCs, short PR may be present.

Echocardiography. It is diagnostic showing:

• Asymmetric left ventricular hypertrophy.
• The systolic anterior motion of the anterior leaflet of the mitral valve.
• Small left ventricular cavity size.
• Dilated left atrium.

Cardiac catheterization

• The small hypercontractile left ventricle
• Dynamic left ventricular outflow obstruction
• Diastolic dysfunction.

MANAGEMENT

No specific treatment.

Strenuous exercise should not be allowed.

Beta-blockers help in relieving syncope, dyspnea, and anginal pain. Calcium channel blocker especially verapamil is also effective in the symptomatic patient.

Anticoagulation if needed

Diuretics: Cautious use of diuretics may help reduce symptoms of pulmonary congestion.

Vasodilators and digoxin should be avoided because they may aggravate left ventricular outflow obstruction.

Dual-chamber pacemaker insertion is advised in patients with severe symptoms and significant outflow obstruction, especially in elderly patients.

Surgical treatment: Surgical options are used when there is severe outflow’ obstruction in severely symptomatic patients not responding to medical treatment.

Mitral valve replacement: It abolishes obstruction by preventing systolic anterior motion of the mitral valve.