Cardiovascular · Year 1 · from Cardiovascular

Case 3: Hypertrophic Cardiomyopathy with Dynamic Outflow Obstruction

Patient Presentation

Demographics: 28-year-old male

Chief Complaint: Exertional dyspnea and near-syncope

History of Present Illness: A 28-year-old male athlete presents with exertional shortness of breath and two episodes of near-syncope during basketball games over the past 6 months. He describes lightheadedness and "graying out" of vision during intense exertion. He has also noticed occasional palpitations. His father died suddenly at age 42 while jogging. No prior cardiac history.

Physical Examination:

  • Vital Signs: BP 125/78 mmHg, HR 70 bpm, RR 14/min, SpO2 99% on room air
  • General: Muscular, athletic male in no acute distress
  • Cardiovascular:
  • Carotid pulse: Brisk, bifid (spike and dome)
  • PMI: Sustained, double impulse
  • Auscultation: Harsh crescendo-decrescendo systolic murmur at left lower sternal border
  • Murmur increases with Valsalva and standing (decreased preload)
  • Murmur decreases with squatting and passive leg raise (increased preload)
  • S4 gallop present

Workup

  • ECG: LVH with deep, narrow Q waves in lateral leads (septal hypertrophy), T-wave inversions
  • Echocardiogram:
  • Asymmetric septal hypertrophy (septal wall 24 mm, posterior wall 11 mm)
  • Systolic anterior motion (SAM) of mitral valve
  • LVOT gradient: 65 mmHg at rest, 110 mmHg with Valsalva
  • Hyperdynamic LV function (EF 75%)
  • Mild mitral regurgitation
  • Genetic testing: MYH7 mutation (beta-myosin heavy chain)

Diagnosis

Hypertrophic obstructive cardiomyopathy (HOCM) with dynamic left ventricular outflow tract obstruction

Cardiac Cycle Correlation:

  • Dynamic obstruction: LVOT obstruction worsens during systole as the hypertrophied septum and SAM of mitral valve narrow the outflow tract
  • Murmur characteristics:
  • Increased with Valsalva/standing: Decreased preload → smaller LV cavity → more obstruction → louder murmur
  • Decreased with squatting: Increased preload → larger LV cavity → less obstruction → softer murmur
  • Bifid carotid pulse: Initial rapid ejection (spike) followed by obstruction then continued ejection (dome)
  • S4 gallop: Atrial contraction against stiff, hypertrophied LV
  • PV loop: Shows mid-systolic obstruction with pressure spike after initial ejection

Treatment

  1. Avoid strenuous competitive athletics (risk of sudden cardiac death)
  2. Beta-blockers (first-line therapy to reduce obstruction)
  3. Disopyramide (negative inotrope, reduces SAM)
  4. Avoid dehydration, vasodilators, high-dose diuretics
  5. ICD implantation indicated for high-risk features (family history of sudden death, massive LVH, unexplained syncope)
  6. Consider septal myectomy or alcohol septal ablation if refractory

Clinical Image

Image Description: Echocardiogram demonstrating hypertrophic cardiomyopathy with asymmetric septal hypertrophy and systolic anterior motion (SAM) of the mitral valve causing left ventricular outflow tract obstruction.

Source: Radiopaedia - Hypertrophic cardiomyopathy License: CC BY-NC-SA 3.0 URL: https://radiopaedia.org/cases/hypertrophic-cardiomyopathy-hcm

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