Myocardial disease; categorized as dilated, hypertrophic, or restrictive Cardiomyopathy
1. Dilated Cardiomyopathy
The most common cardiomyopathy. Left ventricular dilation and ↓ EF must be present for diagnosis. Most cases are idiopathic, but known 2° causes include alcohol, post-viral myocarditis, postpartum status, drugs (doxorubicin, AZT, cocaine), radiation, endocrinopathies (thyrotoxicosis, acromegaly, pheochromocytoma), infection (coxsackievirus, HIV, Chagas disease, parasites), genetic factors, and nutritional disorders (wet beriberi). The most common causes of 2° dilated cardiomyopathy are ischemia and longstanding hypertension.
- Often presents with gradual development of CHF symptoms such as dyspnea on exertion, and diffuse edema of the ankles, feet, legs, and abdomen.
- Exam often reveals displacement of the left ventricular impulse, JVD, rales, an S3/S4 gallop, or mitral/tricuspid regurgitation.
- Echocardiography is diagnostic.
- CXR shows an enlarged, “balloon-like” heart and pulmonary congestion.
- Address the underlying etiology (eg, alcohol use, endocrine disorders, infection).
- Treat CHF as noted in above section with lifestyle changes, and pharmacologic and advanced treatments.
An S3 gallop signifies rapid ventricular filling in the setting of fluid overload and is associated with dilated cardiomyopathy. A S3 gallop sounds similar to the word “KEN-tuc-ky.”
An S4 gallop signifies a stiff, noncompliant ventricle and ↑ “atrial kick,” and may be associated with hypertrophic cardiomyopathy. A S4 gallop sounds similar to the word “Tenn-es-SEE.”
S3 Heart Sound
S4 Heart Sound
2. Hypertrophic Cardiomyopathy
HOCM is the most common cause of sudden death in young, healthy athletes in the United States.
- Impaired left ventricular relaxation and filling (diastolic dysfunction) due to thickened ventricular walls secondary to stressors on the myocardium, such as HTN (most common cause) and aortic stenosis.
- Hypertrophy may also involve the interventricular septum, leading to left ventricular outflow tract obstruction and impaired ejection of blood due to asymmetric septal hypertrophy.
- The congenital form, hypertrophic obstructive cardiomyopathy (HOCM), is inherited as an autosomal dominant trait in 50% of HOCM patients and is the most common cause of sudden death in young, healthy athletes in the United States.
- Patients are often asymptomatic but may also present with syncope, lightheadedness, dyspnea, palpitations, angina, or sudden cardiac death.
- Key finding is a harsh systolic ejection crescendo-decrescendo murmur in the lower left sternal edge that ↑ with ↓ preload (eg, Valsalva maneuver, standing) and ↓ with ↑ preload (eg, passive leg raise).
- Symptoms worsen with exercise, diuretics, dehydration, ACEIs/ARBs, digoxin, and hydralazine.
- Exam also often reveals a sustained apical impulse, an S4 gallop, paradoxical S2, and an abnormal bifid or bisferiens pulse (sudden quick rise followed by a slower longer rise due to LV outflow tract obstruction).
- Best initial test: Echocardiography is diagnostic and shows an asymmetrically hypertrophied interventricular septum and dynamic obstruction of blood flow (due to systolic anterior motion of the mitral valve against hypertrophied septum).
- ECG may be normal or show signs of LVH and nonspecific ST- and T-wave changes. Septal Q waves are common in HOCM (inferior and lateral leads).
- CXR may reveal left atrial enlargement (LAE) 2° to mitral regurgitation.
- Best initial treatment: β-blockers are the best initial therapy for symptomatic relief in both HCM and HOCM; non-dihydropyridine CCBs (negative inotropic effect) and ventricular pacemakers are second-line agents.
- Digoxin and spironolactone are contraindicated. Diuretics may help in HCM but are contraindicated in HOCM.
- Implantable defibrillators should be used in symptomatic HOCM patients.
- Patients should avoid intense athletic competition and training.
- Surgical options for HOCM with persistent symptoms include partial excision or alcohol ablation of the myocardial septum.
- Surgical septal myomectomy is reserved for patients when medical and catheter procedures fail.
3. Restrictive Cardiomyopathy
Decreased elasticity of myocardium leading to impaired diastolic filling without significant systolic dysfunction (a normal or near-normal EF). It is caused by infiltrative disease (eg, amyloidosis, sarcoidosis, hemochromatosis), scleroderma, Loeffler eosinophilic endocarditis, endomyocardial fibrosis, or by scarring and fibrosis (2° to radiation).
Signs and symptoms of right-sided heart failure (JVD, peripheral edema, ascites, hepatomegaly) often predominate over left-sided failure, but dyspnea is the most common complaint.
- Echocardiography is key for diagnosis, with rapid early filling and a near normal or elevated EF. CXR, MRI, and cardiac catheterization are helpful for characterization (eg, sarcoid, amyloidosis).
- Cardiac biopsy may reveal fibrosis or evidence of infiltration.
- ECG frequently shows LBBB; low voltages are seen in amyloidosis.
Treat the underlying cause. Therapeutic options are limited and are generally palliative only. Medical treatment includes cautious use of diuretics for fluid overload and vasodilators to ↓ filling pressure.