Cardiology > Hypertrophic Cardiomyopathy

Background 

Hypertrophic cardiomyopathy (HCM) is a genetic cardiac disorder characterized by asymmetric left ventricular hypertrophy, most commonly involving the interventricular septum, without an identifiable secondary cause (e.g., hypertension or aortic stenosis). It often results in dynamic left ventricular outflow tract (LVOT) obstruction, diastolic dysfunction, myocardial ischemia, and an increased risk of sudden cardiac death (SCD). 

II) Classification/Types 

By Anatomy: 

• • Asymmetric Septal Hypertrophy (most common) 

• • Concentric Hypertrophy 

• • Apical Hypertrophy 

• • Midventricular or Mass-like Hypertrophy 

By Obstruction: 

• • Obstructive HCM (HOCM): Involves dynamic LVOT obstruction, often due to systolic anterior motion (SAM) of the mitral valve. 

• • Non-obstructive HCM: No significant LVOT gradient at rest or with provocation. 

By Genetics: 

• • Familial (Autosomal Dominant): Mutations in sarcomere protein genes (e.g., MYH7, MYBPC3). 

• • Sporadic Cases: Without identifiable family history. 

III) Pathophysiology 

HCM arises from mutations in sarcomere proteins, leading to myocardial fiber disarray, hypertrophy, and fibrosis. LVOT obstruction results from septal thickening and systolic anterior motion of the mitral valve, which contributes to mitral regurgitation and increased intraventricular pressures. Diastolic dysfunction impairs ventricular filling and raises left atrial and pulmonary pressures. Myocardial ischemia may occur despite normal coronary arteries. 

IV) Epidemiology 

• • Sex: Affects both sexes; obstructive forms more commonly symptomatic in women. 

• • Age: Can present at any age; often diagnosed in adolescence or early adulthood. 

• • Prevalence: ~1 in 500 in the general population. 

• • Comorbidities: Can be associated with atrial fibrillation, syncope, or heart failure. 

Etiology

I) Causes 

• • Genetic mutations in sarcomere proteins (MYH7, MYBPC3) 

• • Sporadic mutations 

• • Rarely secondary to metabolic or syndromic disorders (e.g., Fabry disease, Noonan syndrome) 

II) Risk Factors 

• • Family history of HCM or sudden cardiac death 

• • Known sarcomeric gene mutations 

• • History of syncope or ventricular arrhythmias 

• • High-intensity athletic activity in adolescents with undiagnosed HCM 

Clinical Presentation

I) History (Symptoms) 

• • Dyspnea on exertion 

• • Chest pain (angina) 

• • Palpitations 

• • Presyncope or syncope (often exertional) 

• • Sudden cardiac arrest (especially in adolescents and athletes) 

• • Fatigue and exercise intolerance 

II) Physical Exam (Signs) 

Vital Signs: 

• • Normal or elevated BP 

• • Tachycardia (if in atrial fibrillation) 

Cardiac Exam: 

• • Harsh crescendo-decrescendo systolic murmur at the left lower sternal border (increases with Valsalva or standing; decreases with squatting) 

• • S4 gallop (stiff ventricle) 

• • Bifid carotid pulse (pulsus bisferiens) 

Pulmonary/Peripheral: 

• • Pulmonary congestion in advanced cases 

• • Peripheral edema (rare; in advanced heart failure) 

Differential Diagnosis (DDx)

• • Aortic stenosis 

• • Mitral valve prolapse 

• • Dilated cardiomyopathy 

• • Restrictive cardiomyopathy 

• • Coronary artery disease 

• • Arrhythmogenic right ventricular cardiomyopathy 

• • Athlete’s heart 

Diagnostic Tests

Initial Tests: 

• • Transthoracic Echocardiogram (TTE): 
    Confirms diagnosis 
    Measures septal thickness (>15 mm is diagnostic) 
    Assesses LVOT gradient and systolic anterior motion (SAM) 
    Detects mitral regurgitation 

• • Electrocardiogram (ECG): 
    LV hypertrophy 
    Deep Q waves in lateral/inferior leads 
    Atrial enlargement 
    Ventricular arrhythmias 

• • Cardiac MRI: 
    Superior for assessing myocardial fibrosis and apical hypertrophy 

• • Holter Monitor (24–48 hours): 
    Detects arrhythmias or nonsustained VT 

• • Exercise Stress Test: 
    Risk stratification and symptom assessment 

• • Genetic Testing: 
    For probands and family screening 

• • Cardiac Catheterization/Coronary Angiography: 
    If CAD is suspected or prior to septal reduction therapy 

Treatment

I) Medical Management 

• • Beta-blockers: First-line for symptomatic patients; reduce heart rate and improve diastolic filling 

• • Non-dihydropyridine calcium channel blockers (e.g., verapamil): Alternative if beta-blockers not tolerated 

• • Disopyramide: Negative inotrope used in obstructive HCM 

• • Diuretics: For volume overload (use cautiously in obstructive HCM) 

• • Anticoagulation: For atrial fibrillation or left atrial thrombus 

• • Avoid: ACE inhibitors, ARBs, nitrates, and digoxin in obstructive HCM due to risk of worsening obstruction 

II) Interventional/Surgical 

• • Implantable Cardioverter-Defibrillator (ICD): 
    For primary or secondary prevention of sudden cardiac death in high-risk patients 

• • Septal Reduction Therapy: 
    Surgical myectomy (gold standard) for symptomatic obstructive HCM 
    Alcohol septal ablation for patients unfit for surgery 

• • Heart Transplantation: 
    In end-stage HCM with refractory heart failure 

Patient Education, Screening, Vaccines

• • Educate about symptoms of worsening obstruction (e.g., syncope, exertional chest pain) 

• • Avoid dehydration and excessive exertion 

• • Avoid medications that reduce preload or afterload 

• • Family screening with echocardiogram and/or genetic testing 

• • Weight and BP control 

• • Vaccinations: 

• • Annual Influenza 

• • Pneumococcal 

• • COVID-19 

Consults

• • Cardiology: All patients with confirmed or suspected HCM 

• • Electrophysiology: For ICD evaluation or arrhythmia management 

• • Genetic Counseling: For patients and at-risk family members 

• • Cardiothoracic Surgery: For surgical myectomy 

• • Primary Care/Internal Medicine: For chronic disease optimization 

Follow-Up

• • Echocardiogram: 
    Every 1–2 years for stable patients 
    Annually for symptomatic or high-risk patients 

• • Holter Monitoring: 
    Periodic to screen for arrhythmias 

• • ICD Interrogation: 
    If implanted 

• • Lifestyle Modification: 
    Avoid intense sports or competitive athletics 
    Monitor for symptom progression and new arrhythmias 
    Assess risk for SCD regularly