Introduction:
Cardiomyopathy refers to a group of diseases that affect the heart muscle, leading to structural and functional abnormalities. It is a significant cause of heart failure and sudden cardiac death worldwide. Depending on the type, cardiomyopathy can impair the heart’s ability to pump blood effectively, cause arrhythmias, or lead to other life-threatening complications.
Classification:
Dilated Cardiomyopathy (DCM):
Also known as congestive cardiomyopathy, it is the most common form of cardiomyopathy.
Pathophysiology:
Due to various underlying causes, the heart chambers become dilated and weakened, leading to impaired systolic contraction. This systolic dysfunction reduces ejection fraction and increases pressure in both ventricles, resulting in systemic and pulmonary complications such as congestion and heart failure.
Causes:
• Idiopathic
• Genetic mutations
• Alcohol abuse
• Nutritional deficiency (beriberi)
• Cocaine use
• Viral infections (e.g., Coxsackie virus)
• Chagas disease
• Chemotherapy (e.g., doxorubicin)
• Hemochromatosis
• Peripartum cardiomyopathy (pregnancy-related)
Clinical Findings:
• Symptoms of heart failure: dyspnea, fatigue, orthopnea, edema
• S3 heart sound (due to volume overload)
• Regurgitant murmurs (mitral or tricuspid regurgitation from annular dilation)
• Arrhythmias and risk of sudden death
Investigations:
• Echocardiography: dilated chambers with reduced ejection fraction
• Chest X-ray: enlarged, “balloon-like” heart
• ECG: arrhythmias or conduction delays
Hypertrophic Cardiomyopathy (HCM):
Hypertrophic cardiomyopathy is the most common cause of sudden cardiac death in young athletes.
Pathophysiology:
There is asymmetric hypertrophy of the left ventricle, most prominently involving the interventricular septum. This hypertrophy narrows the left ventricular outflow tract, producing a functional obstruction similar to aortic stenosis. The stiffened ventricle also impairs diastolic filling, leading to decreased cardiac output. Death often results from ventricular arrhythmias.
Causes:
• Familial cases are common.
• Most are due to autosomal dominant mutations in genes encoding sarcomere proteins (e.g., β-myosin heavy chain, myosin-binding protein C).
Clinical Features:
• Syncope, particularly during or after exertion
• Dyspnea, chest pain, palpitations
• Harsh systolic murmur, best heard along the left sternal border
o Murmur increases with Valsalva or standing (due to decreased preload)
o Murmur decreases with squatting (due to increased preload/afterload)
• S4 heart sound (due to stiff ventricle)
• Mitral regurgitation may occur due to systolic anterior motion of the mitral valve
Histopathology:
• Myofiber hypertrophy with disarray is the characteristic biopsy finding.
Complications:
• Sudden cardiac death, especially in young athletes
• Progressive heart failure
• Atrial fibrillation with risk of thromboembolism
• Ventricular arrhythmias
Restrictive Cardiomyopathy (RCM):
Restrictive cardiomyopathy is the least common form of cardiomyopathy, characterized by impaired ventricular filling due to stiff ventricular walls, while systolic function is usually preserved in the early stages.
Pathophysiology:
The ventricles become rigid and noncompliant, leading to impaired diastolic filling. This raises ventricular filling pressures, which in turn causes pulmonary and systemic venous congestion. Eventually, reduced cardiac output may occur.
Causes:
• Infiltrative diseases: Amyloidosis, sarcoidosis
• Storage disorders: Hemochromatosis, glycogen storage diseases
• Fibrosis/Scarring: Post-radiation, endomyocardial fibrosis
• Other: Post-surgical or idiopathic cases
Clinical Features:
• Symptoms of right and left heart failure: dyspnea, fatigue, peripheral edema, ascites, hepatomegaly
• Exercise intolerance due to reduced cardiac output
• S4 heart sound (due to stiff ventricle)
• May mimic constrictive pericarditis clinically
Investigations:
• Echocardiography: Normal or slightly thickened ventricles with biatrial enlargement, preserved ejection fraction
• Cardiac MRI: Identifies infiltrative disease (e.g., amyloid)
• Endomyocardial biopsy: May confirm infiltrative or fibrotic process
Complications:
• Progressive biventricular heart failure
• Arrhythmias (atrial fibrillation, conduction abnormalities)
• Thromboembolic events
• Poor prognosis without treatment of the underlying cause
Conclusion:
Cardiomyopathies represent a diverse group of myocardial disorders that can lead to significant morbidity and mortality through heart failure, arrhythmias, and sudden cardiac death. Dilated cardiomyopathy is the most common type, hypertrophic cardiomyopathy is a leading cause of sudden death in young athletes, and restrictive cardiomyopathy is often linked to infiltrative or fibrotic conditions. Early recognition, appropriate diagnostic evaluation, and timely management—including pharmacological therapy, device implantation, surgical options, and genetic counseling—are crucial in improving patient outcomes. A multidisciplinary approach with long-term follow-up is essential to reduce complications and enhance the quality of life in affected individuals.