Hypertrophic obstructive cardiomyopathy (HOCM) is one of those Step classics that rewards pattern recognition: a young patient, exertional symptoms, a crescendo–decrescendo systolic murmur, and the “weird” maneuver behavior (gets louder when the LV gets smaller). A memory palace helps you recall the whole package fast—path, murmur, maneuvers, complications, and management—in one mental walkthrough.
The Memory Palace: “The Crowded Gym With the Bouncing Door”
Picture a high school gym hosting a charity sprint. At the entrance is a narrow door into the gym, and the doorway is being blocked by an overgrown wall and a floppy curtain that keeps getting sucked into the opening.
Station 1: The Overgrown Wall = Asymmetric Septal Hypertrophy
- The gym’s septal wall is too thick, especially near the doorway.
- High-yield associations:
- Autosomal dominant mutations in sarcomere proteins (classically β-myosin heavy chain, myosin-binding protein C)
- Often in young athletes or those with a family history of sudden cardiac death
One-liner: HOCM = AD sarcomere mutation → asymmetric septal hypertrophy → dynamic LV outflow obstruction.
Station 2: The Floppy Curtain = Systolic Anterior Motion (SAM) of the Mitral Valve
- The “curtain” (mitral valve leaflet) gets pulled into the doorway during systole, worsening the blockage.
- This can cause mitral regurgitation because the valve can’t close normally.
Step trigger: SAM + asymmetric septal hypertrophy is the hallmark of obstructive physiology.
Station 3: The Bouncing Door Sound = Systolic Ejection Murmur
At the doorway you hear a harsh crescendo–decrescendo systolic murmur (LV outflow tract obstruction).
Where/how it’s heard:
- Best at left sternal border
- Often with an S4 (stiff hypertrophied ventricle → atrial kick into a noncompliant LV)
Maneuvers: “Make the Room Smaller → Louder; Make it Bigger → Softer”
In the memory palace, the key is what changes the size of the gym (LV volume).
Maneuver Table (High Yield)
| Maneuver | LV volume effect | HOCM murmur | Why |
|---|---|---|---|
| Standing up | preload | Louder | Smaller LV → more obstruction |
| Valsalva (strain) | preload | Louder | Less filling → worsens LVOT obstruction |
| Squatting | preload & afterload | Softer | Bigger LV + higher SVR → reduces obstruction |
| Handgrip | afterload | Usually softer | Higher LV pressure can reduce dynamic obstruction (and increases MR murmur instead) |
High-yield contrast:
- Aortic stenosis murmur typically gets louder with squatting (more flow) and softer with Valsalva—the opposite pattern from HOCM.
“Why They Pass Out”: Symptoms and Complications (USMLE Favorites)
Walking through the crowded gym, runners start to stumble.
Symptoms
- Exertional dyspnea (diastolic dysfunction: stiff LV → high filling pressures)
- Chest pain/angina (increased O demand + reduced supply)
- Syncope/presyncope, especially on exertion (dynamic obstruction + arrhythmias)
- Palpitations
Big complications to remember
- Sudden cardiac death (ventricular arrhythmias), classically in young athletes
- Atrial fibrillation (from LA enlargement due to impaired filling)
- Heart failure with preserved EF (HFpEF) physiology due to diastolic dysfunction
Diagnosis: What You “See in the Gym”
Echocardiogram (most tested)
- Asymmetric septal hypertrophy
- SAM of the mitral valve
- Dynamic LV outflow tract gradient (worsens with decreased preload)
ECG (common but not specific)
- LV hypertrophy patterns, deep narrow Q waves (septal), repolarization abnormalities
Treatment: “Slow the Runners and Open the Door”
You want to reduce obstruction by improving filling and decreasing contractility.
First-line medical therapy
- β-blockers (most classic)
- Non-dihydropyridine CCBs (e.g., verapamil) if needed
If refractory symptoms
- Disopyramide (negative inotrope; antiarrhythmic) as an add-on in selected patients
- Septal reduction therapy: surgical myectomy or alcohol septal ablation (specialist-driven)
ICD (prevention of sudden death)
Consider in high-risk features (Step-relevant concept): prior VT/VF, strong family history of SCD, massive hypertrophy, unexplained syncope, etc.
The “Don’t Make It Worse” List (Very Testable)
In the memory palace, these are the things that shrink the room (lower preload) or increase contractility—they worsen obstruction.
Avoid/Use caution:
- Nitrates, diuretics, dehydration (↓ preload)
- Dihydropyridine CCBs (vasodilation → ↓ preload/afterload in a way that can worsen obstruction)
- Inotropes (↑ contractility)
Shareable Quick Mnemonic: “HOCM = HOT Gym, CROWDED Door, Moves Like This”
- Hypertrophic Obstructive Cardiomyopathy
- Crowded door = asymmetric septal hypertrophy
- Curtain sucked in = SAM
- Moves:
- Valsalva/Standing → louder
- Squat/Handgrip → softer (and handgrip boosts MR)
The One-Liner You Should Be Able to Say Cold
HOCM is an AD sarcomere mutation causing asymmetric septal hypertrophy and SAM of the mitral valve → dynamic LV outflow obstruction with a systolic murmur that gets louder with Valsalva/standing and softer with squatting.