Hypertrophic Obstructive Cardiomyopathy

Hypertrophic obstructive cardiomyopathy is the most common inherited cardiac disease (autosomal dominant, ~1 in 500), characterized by asymmetric left ventricular hypertrophy with dynamic left ventricular outflow tract obstruction (LVOTO), and is a leading cause of sudden cardiac death (SCD) in young adults. [1-2] Two-thirds of HCM patients have LVOT obstruction at rest or with provocation. [3]

• Exertional symptoms: dyspnea, chest pain, fatigue, presyncope/syncope — all typically provoked by exertion, dehydration, or postprandial states [4-5]
• Characterize timing: onset with activity, relieved by rest or recumbency; worsened by standing, Valsalva, or heat
• Palpitations — may indicate atrial fibrillation (present in >50% paroxysmal) or ventricular arrhythmia [4-5]
• Orthopnea and PND if congestive symptoms develop
• Ask about prior cardiac arrest, ICD shocks, or documented arrhythmias
• Important negatives: absence of pleuritic pain, positional pain, fever, cough (helps exclude other causes of dyspnea/chest pain)

• Syncope — especially exertional or without prodrome; recent syncope (within 6 months) is a major SCD risk marker [6]
• Cardiac arrest or sustained ventricular tachycardia [2][6]
• Acute hemodynamic collapse/hypotension — a medical urgency in obstructive HCM; can be precipitated by vasodilators, dehydration, or tachyarrhythmia [6]
• New-onset atrial fibrillation with rapid ventricular response — can cause acute decompensation and carries high stroke risk [1][7]
• Progressive dyspnea at rest or NYHA class III–IV symptoms
• Family history of SCD in a first-degree relative <50 years old [6]

First-line treatments (per 2024 AHA/ACC Guidelines): [6]

• Nonvasodilating beta-blockers (e.g., metoprolol, propranolol, nadolol) — titrate to resting HR 50–60 bpm [2][5]
• Nondihydropyridine calcium channel blockers (verapamil, diltiazem) — substitute if beta-blockers ineffective or not tolerated; avoid combining with beta-blockers for HCM-directed therapy [6][8]

Second-line / add-on: [6]

• Disopyramide — potent negative inotrope; must be combined with an AV nodal blocker to prevent rapid AF conduction [6][8]
• Cardiac myosin inhibitors: mavacamten (Camzyos, FDA-approved 2022) and aficamten (Myqorzo, FDA-approved 2025) — reduce hypercontractility and LVOT gradients [6][9-10]

Contraindicated / to avoid: [6][8]

• Pure vasodilators: dihydropyridine CCBs (amlodipine, nifedipine), nitrates, ACE inhibitors, ARBs
• Positive inotropes: dobutamine, dopamine, digoxin
• High-dose diuretics (reduce preload → worsen obstruction)
• ADHD stimulant medications
• Excessive caffeine and alcohol

• Adequate hydration is critical — dehydration reduces preload and worsens LVOTO [8]
• Avoid large, heavy meals (postprandial splanchnic vasodilation can provoke symptoms)
• Limit excessive caffeine and alcohol intake [8]
• Maintain healthy body weight [8]
• No specific long-term dietary restrictions beyond the above

• Cardiovascular: chest pain, dyspnea, palpitations, syncope/presyncope, orthopnea, edema
• Neurologic: lightheadedness, transient loss of consciousness, focal deficits (embolic stroke from AF)
• Respiratory: exercise intolerance, paroxysmal nocturnal dyspnea
• GI: postprandial worsening of symptoms
• Psychiatric: anxiety, depression (common with chronic disease and activity restriction)
• Screen for sleep-disordered breathing (comorbidity that worsens HCM) [11]

• Three-generation family history is recommended at initial evaluation [4][12]
• Ask specifically about SCD, unexplained drowning, single-vehicle accidents, or unexplained death in relatives <50 years [6]
• Family members with known HCM, ICDs, or heart failure
• Autosomal dominant inheritance — pathogenic sarcomere gene variants found in 30–60% of cases [1][4]
• First-degree relatives require screening with ECG and echocardiography [4]
• Genetic counseling by a counselor versed in cardiac genetics is strongly recommended [4]

• Family history of HCM or HCM-related SCD [6]
• Sarcomere gene mutations (8 genes identified; most common: MYH7, MYBPC3) [4]
• Young age — SCD risk is highest in younger patients and inversely related to age [2][6]
• Massive LV hypertrophy (wall thickness ≥30 mm) [6]
• LV apical aneurysm [6]
• Extensive late gadolinium enhancement (≥15% LV mass) on CMR [6]
• LVEF <50% (end-stage phase) [6]
• Nonsustained ventricular tachycardia on Holter [6]
• Comorbidities: hypertension, obesity, obstructive sleep apnea, atrial fibrillation [11]

• Hypertensive heart disease — can produce LVH but rarely >20 mm wall thickness; requires uncontrolled hypertension [13]
• Athlete's heart — physiologic LVH typically concentric, ≤13 mm, with normal diastolic function; regresses with detraining [14]
• Cardiac amyloidosis — consider if LVH with low voltage on ECG, diastolic dysfunction, apical sparing on strain imaging [11][13]
• Fabry disease — X-linked, concentric LVH, renal/dermatologic features; check alpha-galactosidase A [11][13]
• Aortic stenosis — fixed obstruction; crescendo-decrescendo murmur radiating to carotids; murmur decreases with Valsalva (opposite of HOCM)
• Mitochondrial cardiomyopathy — consider in pediatric patients with multisystem disease [11]
• Glycogen storage diseases (Pompe, Danon) — especially in young patients with massive hypertrophy

• Prior episodes of syncope, cardiac arrest, or documented arrhythmias
• Known ICD or pacemaker
• Prior septal reduction therapy (myectomy or alcohol septal ablation)
• Atrial fibrillation history and anticoagulation status
• Comorbid hypertension, coronary artery disease, valvular disease
• Obstructive sleep apnea
• Pregnancy history (hemodynamic changes can exacerbate LVOTO)

• Harsh crescendo-decrescendo systolic murmur at left lower sternal border/apex [1][5]
  • Increases with Valsalva, standing, dehydration (decreased preload/afterload)
  • Decreases with squatting, leg elevation, hand grip (increased preload/afterload)
• Separate murmur of mitral regurgitation — holosystolic at apex, radiating to axilla [5]
• Brisk, bifid (bisferiens) carotid pulse
• Prominent apical impulse; may have S4 gallop
• Jugular venous distension and peripheral edema if decompensated
• Vital signs: assess for hypotension (medical urgency), tachycardia, irregular rhythm (AF)

• BNP/NT-proBNP — elevated with heart failure symptoms; useful for monitoring [7]
• Troponin — may be mildly elevated chronically; rule out acute coronary syndrome in chest pain presentations
• BMP — assess renal function (relevant for medication dosing and diuretic use)
• TSH — thyrotoxicosis can exacerbate symptoms
• CBC — rule out anemia as contributor to symptoms
• Genetic testing — sarcomere gene panel after genetic counseling; identifies pathogenic variants in 30–60% [4]
• Alpha-galactosidase A (if Fabry suspected), serum/urine protein electrophoresis (if amyloid suspected) [11][13]

First-line: Transthoracic echocardiography [6][13]

• Diagnostic criterion: maximal LV end-diastolic wall thickness ≥15 mm (≥13 mm with family history or positive genetic test) [1][4][13]
• Assess LVOT gradient at rest and with provocation (Valsalva, exercise)
• LVOT gradient ≥30 mm Hg defines obstruction; ≥50 mm Hg is the threshold for intervention [13]
• Evaluate mitral valve anatomy, systolic anterior motion (SAM), mitral regurgitation, EF, LA size

Exercise stress echocardiography — preferred method to provoke latent LVOTO when resting gradient is <30 mm Hg [6][12]

Cardiac MRI (CMR): [2][12-13]

• Gold standard for wall thickness measurement and tissue characterization
• Identifies LV apical aneurysm, extent of late gadolinium enhancement (LGE ≥15% LV mass = high SCD risk)
• Differentiates HCM from phenocopies (amyloid, Fabry)
• Repeat every 3–5 years for surveillance [12]

Cardiac CT — alternative when CMR is contraindicated; evaluates coronary anatomy and myocardial bridging [2]

• Ambulatory ECG monitoring (24–48 hr Holter or ≥2-week wireless patch) — detect NSVT, AF [6][12-13]
• Cardiopulmonary exercise testing (CPET) — objective assessment of functional capacity; useful when symptom severity is uncertain [8][12]
• Exercise stress echocardiography — provoke latent LVOT gradients [12]
• Genetic testing with pre-test counseling — 8 sarcomere genes associated with HCM [4]
• SCD risk calculators — HCM Risk-SCD (ESC) and AHA/ACC individual risk marker strategy to guide ICD decisions [6][13]

The following algorithm from the AHA/ACC guidelines outlines the ICD decision-making framework:

ECG is abnormal in ~90–95% of HCM patients: [1][4-5][14]

• LV hypertrophy voltage criteria
• Prominent Q waves — especially in inferior and lateral leads (septal depolarization)
• ST-segment depression and T-wave inversions — particularly in lateral/anterolateral leads
• Left axis deviation
• P-wave abnormalities (left atrial enlargement)
• Giant negative T waves in precordial leads — suggest apical variant HCM [5][15]
• A normal ECG does not exclude HCM but is present in only 5–10% of cases [5][13]

Dangerous patterns to recognize:

• Sustained or nonsustained ventricular tachycardia
• Atrial fibrillation with rapid ventricular response
• Pre-excitation (WPW) — associated with some HCM subtypes

• HOCM is a chronic, progressive genetic cardiomyopathy with dynamic LVOTO that is highly variable throughout daily life [6]
• Severity stratification is based on: NYHA functional class, resting/provoked LVOT gradient, LV wall thickness, EF, presence of SCD risk markers [6][12]
• Most patients achieve normal longevity with appropriate management; annual SCD rate ~1% before ICD era [2]
• Atypical presentations include isolated AF, embolic stroke, or incidental murmur/ECG finding [4-5]
• Complications: SCD, progressive heart failure, atrial fibrillation with stroke, infective endocarditis (rare), end-stage (burned-out) phase with EF <50% [2][7]

The following figure from Braunwald's 2025 NEJM review illustrates the stepwise treatment algorithm:

Initial stabilization (ED setting): [6]

• Acute hypotension is a medical urgency: IV fluids for volume resuscitation, IV phenylephrine (pure alpha-agonist to increase afterload), IV beta-blocker to reduce contractility and HR
• Avoid vasodilators, inotropes, and aggressive diuresis
• Trendelenburg positioning; passive leg raise

Chronic pharmacologic management (per 2024 AHA/ACC): [6]

• Nonvasodilating beta-blockers — first-line; titrate to resting HR 50–60 bpm
• Verapamil or diltiazem — if beta-blockers fail or are not tolerated
• Escalation if persistent symptoms: add disopyramide (with AV nodal blocker), or cardiac myosin inhibitor (mavacamten or aficamten), or refer for septal reduction therapy (SRT)

Septal reduction therapy (at experienced HCM centers): [6]

• Surgical myectomy — gold standard; preferred when concomitant cardiac surgery needed
• Alcohol septal ablation — alternative for non-surgical candidates

SCD prevention: [2][6]

• ICD for secondary prevention (prior cardiac arrest/sustained VT)
• ICD for primary prevention based on individual risk marker assessment (≥1 major risk factor)
• Reassess SCD risk every 1–2 years

Atrial fibrillation management: [1][7]

• Anticoagulation is strongly recommended for all HCM patients with AF regardless of CHA₂DS₂-VASc score
• Rhythm control preferred for symptomatic AF

Admit for

• Acute hemodynamic instability / hypotension
• Syncope with suspected arrhythmic etiology
• New sustained ventricular arrhythmia or cardiac arrest
• Acute decompensated heart failure (NYHA III–IV)
• New-onset rapid atrial fibrillation with hemodynamic compromise
• Post-septal reduction therapy

Observation for

• Presyncope with borderline hemodynamics
• New AF with controlled rate but uncertain stability

Discharge with close follow-up if

• Stable, known HOCM with mild symptom exacerbation attributable to identifiable trigger (dehydration, medication non-adherence)
• No syncope, no hemodynamic instability, no new arrhythmia
• Adequate oral intake and stable vital signs

Specialist consultation triggers: All patients with HCM should be managed in conjunction with a comprehensive HCM center — these centers have better outcomes. [4][12] Urgent cardiology consultation for new diagnosis, syncope, arrhythmia, or refractory symptoms.

Routine follow-up: [4][12]

• Cardiology re-evaluation every 12 months (or up to 24 months if stable)
• Annual: echocardiogram + 12-lead ECG
• Every 1–3 years: ambulatory ECG monitoring (Holter or wireless patch)
• Every 3–5 years: contrast CMR (or sooner if clinical concern)
• SCD risk reassessment every 1–2 years [6]
• First-degree family member screening: ECG + echocardiography every 1–3 years (pediatric relatives) or 3–5 years (adult relatives) [4]

Return precautions — instruct patients to seek immediate care for:

• Syncope or near-syncope
• Sustained palpitations or irregular heartbeat
• Worsening dyspnea at rest or with minimal exertion
• Chest pain not relieved by rest
• ICD shocks

Patient counseling

• Maintain adequate hydration at all times; avoid dehydration [8][11]
• Avoid sudden intense exertion; individualized exercise guidance per shared decision-making with cardiologist [7]
• Avoid vasodilators, stimulants, and excessive alcohol/caffeine [8]
• Educate on medication adherence and side effects
• Reassure that most patients with HCM achieve normal longevity with appropriate management [12]

1. Cardiomyopathy: A Guide for Primary Care. — Coppiano J, Carrasco M, Asif I. American Family Physician. 2026.

2. Hypertrophic Cardiomyopathy. — Braunwald E. The New England Journal of Medicine. 2025.

3. Randomized Trial of Metoprolol in Patients With Obstructive Hypertrophic Cardiomyopathy. — Dybro AM, Rasmussen TB, Nielsen RR, et al. Journal of the American College of Cardiology. 2021.

4. Diagnosis and Management of Hypertrophic Cardiomyopathy: Updated Guidelines From the ACC/­AHA. — Leggit JC, Whitaker D. American Family Physician. 2022.

5. Hypertrophic Obstructive Cardiomyopathy. — Veselka J, Anavekar NS, Charron P. Lancet. 2017.

6. 2024 AHA/­ACC/­AMSSM/­HRS/­PACES/­SCMR Guideline for the Management of Hypertrophic Cardiomyopathy: A Report of the American Heart Association/­American College of Cardiology Joint Committee on Clinical Practice Guidelines. — Ommen SR, Ho CY, Asif IM, et al. Journal of the American College of Cardiology. 2024.

7. Current Management of Hypertrophic Cardiomyopathy. — Sikand N, Stendahl J, Sen S, Lampert R, Day S. BMJ. 2025.

8. Management of Hypertrophic Cardiomyopathy: JACC State-of-the-Art Review. — Maron BJ, Desai MY, Nishimura RA, et al. Journal of the American College of Cardiology. 2022.

9. FDA Orange Book. — FDA Orange Book. 2026.

10. Aficamten or Metoprolol Monotherapy for Obstructive Hypertrophic Cardiomyopathy. — Garcia-Pavia P, Maron MS, Masri A, et al. The New England Journal of Medicine. 2025.

11. Comprehensive Evaluation of Hypertrophic Cardiomyopathy: European Journal of Heart Failure Expert Consensus Document. — Martens P, Olivotto I, Garcia-Pavia P, et al. European Journal of Heart Failure. 2026.

12. Diagnosis and Evaluation of Hypertrophic Cardiomyopathy: JACC State-of-the-Art Review. — Maron BJ, Desai MY, Nishimura RA, et al. Journal of the American College of Cardiology. 2022.

13. Hypertrophic Cardiomyopathy: A Practical Approach to Guideline Directed Management. — Ommen SR, Semsarian C. Lancet. 2021.

14. The Adolescent Athlete and the Team Physician: A Consensus Statement. 2025 Update. — Putukian M, Leclere LE, Herring SA, et al. Medicine and Science in Sports and Exercise. 2026.

15. Advanced Imaging Insights in Apical Hypertrophic Cardiomyopathy. — Hughes RK, Knott KD, Malcolmson J, et al. JACC. Cardiovascular Imaging. 2020.

16. Inherited Heart Diseases. — Antoni Bayés De Luna, Miquel Fiol‐Sala, Antoni Bayés‐Genís, et al. Clinical Electrocardiography. 2021.