Hypertrophic Cardiomyopathy (HCM)

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Pathophysiology
➤Defined as unexplained ventricular hypertrophy (no due to systemic HTN or AS). Histopathologic features are myocardial fiber disarray, myocyte hypertrophy, and interstitial fibrosis.
➤ Cause is felt to be a genetic defect involving of the cardiac sarcomatic proteins (>100 mutations associated with development of autosomal dominant inheritance)
➤ Clinical manifestations
     ⤱ Asymptomatic
     ⤱ Dyspnea
     ⤱ Angina
     ⤱ Presyncope/syncope-LV outflow obstruction or arrythemia
     ⤱ CHF
     ⤱ Arrythemias
     ⤱ Sudden death (may be first manifestation) 

 Henodynamic Classification
➤ Hypertrophic obstructive cardiomyopathy (HOCM): dynamic outflow tract LVOT obstruction.
     ⤱ Either resting or provocable LVOT obstruction
➤ Non-obstructive hypertrophic cardiomyopathy decreased compliance and diastolic dysfunction (imparied filling)
➤ Complications; obstruction, arrythemia, diastolic dysfunction
Hallmark Signs of HOCM
➤Pulses
    ⤱ Rapid upstroke pulse
    ⤱ Bifid pulse
➤Precordial palpation
    ⤱ PMI: localized, sustained, double impulse, 'triple ripple' (triple apical impulse)
➤Precordial ascultation
    ⤱ Normal or paradoxically split S2 
    ⤱ S4 
    ⤱ Harsh, systolic, diamond shaped mumur at LISB or apex, enhanced by squat to standing or valsalva (mumur secondary to LVOT obstruction mitral regurgitation)
Investigations
➤ 12 lead ECG
     ⤱ LVH
     ⤱ Prominent Q waves septal or tall r wave in V1 
➤ Echocardiography
     ⤱ LVH - asymmetric septal hypertrophy (most common presentation)
     ⤱ Systolic anterior motion (SAM) of anterior MV leaflet
     ⤱ Resting or dynamic ventricular outflow tract obstruction
     ⤱ MR (due to SAM and associated with LVOT obstruction)
     ⤱ Diastolic dysfunction
     ⤱ LAE
➤ Cardiac catheterization
     ⤱ Increased LV end-diastolic pressure
     ⤱ Variable systolic gradient across LV tract
Natural History
➤ Variable
➤ Potential complications: A fib, VT, CHF, sudden death
➤ Risk factors for sudden death
     ⤱ Most reliable
         ⤱ History of survival cardiac arrest/sustained VT
         ⤱ Family history of multiple sudden deaths
     ⤱ Other factors associated with increased risk of sudden cardiac death (SCD)
          ⤱ Syncope
          ⤱ VT on ambulatory monitoring 
          ⤱ Marked ventricular hypertrophy
      ⤱ Prevention of sudden death in high risk patients
          = amoidarone or implantable cardioverter defibrillator (ICD)
Management
➤ Avoid extremes of excertion
➤ Avoid factors which increase obstruction
➤ Infective endocarditis prophylaxis for patients with obstructive HCM
➤ Treatment of obstructive HCM
     ⤱ Medical agents
         ⤱ β blockers
          ⤱ Dysopyramide
     ⤱ CCB only used in patient with no resting/provocable obstruction
     ⤱ Patient with drug-refractory sypmptoms
         ⤱ Options
             1- Surgical myectomy
             2- Septal ethanol ablation
             3- Dual chamber pacing
➤ Treatment of ventricular arrhythmias - AMIO or ICD
➤ Adult first degree relatives of patients with HCM be screened (physical exam, ECG, 2D-ECHO) serially every 5 years.

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