Hypertrophic Obstructive CardioMyopathy (Diastolic dysfunction)

AKA idiopathic hypertrophic subaortic stenosis

HOCM/IHSS is hypertrophy not caused by other cardiac/systemic dz

PATHO

  • Genetic: Family hx of heart problem "my dad died from sudden cardiac arrest during intense physical activity"

  • Asymmetrical septal overgrowth ➔

    • Impaired relaxation ➔ poor filling (diastolic dysfunction)

      • Less blood goes in means less blood goes out ➔ ↓ output ➔ ↓ perfusion (periphery and heart)

    • Left Ventricular Outflow Obstruction ➔ ↓ stroke volume that worsens with ↓ preload or ↑ HR/contractility:

      • Valsalva

      • Dehydration/Diuretics

      • Exercise

      • ACEi/ARBs, digoxin

  • Arrhythmias, bundle branch blocks

  • It is autosomal dominant with varying degrees of penetrance (not sex linked and might skip some generations)

  • This is not left ventricular hypertrophy from HTN

  • Interventricular septum grows larger than wall

    • Makes it harder to get blood out during contraction (systole)

    • Also creates a "wind tunnel" that sucks anterior leaflet of mitral valve into septum and further closes off outflow tract (Systolic Anterior Motion)

  • Arrhythmia/BBB could be from altered conduction pathways

  • Increased cardiac cells require more oxygen (that it doesn't get) ➔ ischemia ➔ tachy-arrhythmias and sudden death

SSX

  • This is the kid/adolescent that dies while playing basketball

  • Presents in early adulthood with dyspnea, syncope/pre-syncope (I get dizzy when I exercise), chest pain

  • S4 (late diastole) Lalub-dub

  • Systolic ejection/crescendo decrescendo murmur (louder then softer) that changes because of the outlet obstruction

    • ↓ murmur with squat or hand grip (the murmur squats down and you grip a kettlebell)

    • ↑ murmur with valsalva or standing (the murmur stands up)

  • ± Bifid pulse

  • Mitral regurgitation (secondary to SAM) - pansystolic

  • How is a dead kid showing up in a question? They aren't... Probably something along the lines of "AED shocked vfib... what's the patho?"

    • Maybe asks about how the outflow is a problem or how ischemia irritated some foci ➔ vfib

  • S4 from active filling (atria squeezing those last drops into ventricle) during late diastole into stiff wall

  • Squat or hand grip ➔ lessens obstruction ➔ ↓ murmur

    • ↑ vascular restisance ➔ ↑afterload

    • more blood stays in heart (↑preload) ➔ stretches chamber (pushes fat septum out of the way)

  • Valsalva or stand ➔ worsens obstruction ➔ ↑ murmur

    • ↓ venous return ➔ ↓ preload

    • less blood gets to heart ➔ less stretch on chamber (more fat septum in the way)

  • Bifid/pulsus bisferiens (double pulse) from mitral valve slapping the septum mid systole

DX

  • ECHO shows asymmetric (septal) thickness with Systolic Anterior Motion of mitral valve

  • EKG has deep Q waves in inferior leads, LVH, ± atrial enlargement

  • Transthoracic echo with doppler (to see blood moving)

  • Early detection with exercise testing because there may only be sx on exertion

TX

  • Tell them not to get dehydrated (which should be easy because you're telling them not to exercise)

  • β-blockers or CCB (verapamil & diltiazem)

  • AICD (automated implantable cardioverter/defib) for sustained v-tach/v-fib or after their cardiac arrest

  • Surgical myomectomy if refractory (maybe etOH ablation)

AVOID

  • Digoxin, diuretics, ACEi, nitrates

  • You should not be handling this pt's meds without an adult (a cardiologist) because meds can worsen obstruction

  • β-blockers ➔ ↓ HR ➔ ↓ diastolic filling pressure and ↑ time to fill ventricle and stretch it out

    • CCB have to be non-dihydropyridine (verapamil & diltiazem)

      • dihydropyridines (amlodipine) ➔ way more vasodilation ➔ ↓ preload/afterload ➔ less stretch and worse obstruction

    • Digoxin (inotrope) and other meds that ↓ preload/afterload are the exact opposite of what you want to do

  • Septal myectomy via Morrow procedure or etOH ablation if surgery too risky