Hypertrophic Cardiomyopathy

Patient: 48M with exertional dyspnea and near-syncope when climbing stairs. Systolic murmur that increases with Valsalva. Echo: septal thickness 24 mm, LVOT gradient 72 mmHg at rest, SAM of MV with moderate MR. EF 70%.

Key findings: Obstructive HCM (resting gradient > 30 mmHg) with NYHA II-III symptoms. SAM causes dynamic LVOT obstruction + MR. Gradient worsens with decreased preload (Valsalva, dehydration, standing).

Management:

• Metoprolol succinate 50 mg → titrate to 200 mg daily (first-line, slows HR, increases filling time, reduces gradient)
• If beta-blocker inadequate: add disopyramide 100 mg QID (negative inotrope, reduces LVOT gradient)
• Mavacamten 5 mg daily if refractory to above EXPLORER-HCM, 2020
• AVOID: vasodilators (ACEi, nitrates), diuretics (reduce preload → worsen obstruction), digoxin (positive inotrope)
• If refractory to all medical therapy: septal myectomy (surgical, gold standard) or alcohol septal ablation

Teaching point: In HCM, everything that reduces preload or increases contractility worsens obstruction. The hemodynamic goal is the opposite of HFrEF, increase preload, decrease contractility, slow HR.

Patient: 22M diagnosed with HCM on screening echo after his brother died suddenly during basketball at age 19. Septal thickness 30 mm, no resting LVOT obstruction, EF 65%. Asymptomatic. Holter: 3-beat run of NSVT.

Key findings: Multiple SCD risk factors: family history of SCD, massive LVH (≥ 30 mm), NSVT on Holter. HCM is the #1 cause of SCD in young athletes.

Management:

• ICD implantation recommended, ≥ 1 major risk factor for SCD in HCM warrants primary prevention ICD
• SCD risk factors: family hx SCD, syncope, NSVT, max wall thickness ≥ 30 mm, abnormal BP response to exercise
• No competitive sports (AHA/ACC Class III recommendation for HCM with any risk factor)
• Cardiac MRI with LGE, extent of fibrosis is an emerging risk predictor
• Screen all first-degree relatives with echo + ECG (genetic counseling, consider genetic testing)

Teaching point: The decision to place an ICD in HCM requires only ONE major risk factor. This is different from HFrEF (where EF ≤ 35% is the threshold). A 22-year-old with massive LVH + family SCD + NSVT has a very high SCD risk.

Patient: 56F with known HCM, presents with palpitations and dyspnea. HR 148 irregularly irregular, BP 88/60. Echo: LVOT gradient now 95 mmHg (was 35 at baseline). New moderate MR.

Key findings: Afib with rapid ventricular response in HCM, hemodynamic emergency. Loss of atrial kick + fast HR → decreased filling time → dramatically increased LVOT gradient → hypotension.

Management:

• IV phenylephrine for hypotension (pure alpha agonist, increases afterload without increasing contractility, reduces gradient)
• IV metoprolol for rate control (do NOT use diltiazem or verapamil acutely if hypotensive)
• If hemodynamically unstable: emergent synchronized cardioversion
• Long-term anticoagulation, ALL HCM patients with Afib need anticoagulation regardless of CHA₂DS₂-VASc score
• Consider amiodarone or catheter ablation for rhythm control (Afib recurrence is poorly tolerated in HCM)

Teaching point: Afib in HCM is a medical emergency. Unlike the general population, ALL HCM patients with Afib require anticoagulation, the stroke risk is markedly elevated regardless of CHA₂DS₂-VASc score.