Hypertrophic cardiomyopathy

TTE in apical view with color-flow Doppler with turbulent flow in the left ventricular outflow tract (white arrow) and mitral regurgitation (yellow arrow) because of mitral valve systolic anterior motion.

TTE in apical view with color-flow Doppler with turbulent flow in the left ventricular outflow tract (white arrow) and mitral regurgitation (yellow arrow) because of mitral valve systolic anterior motion.

Today, we discussed an interesting case of episodes of transient right-sided weakness (UE and LE) with going from the lying/sitting position to standing in a patient with diffuse nonobstructive intracerebral atherosclerosis and new diagnosis of left ventricular outflow tract (LVOT) obstruction. The thought was that weakness was secondary to focal cerebral hypoperfusion, basically TIAs in the anterior circulation, from hypovolemia leading to decreased preload and worsening LVOT obstruction (and decreased perfusion in stenotic areas of territories of the left MCA and ACA). Some learning points:

1) Sorting out unilateral weakness: can be divided into central and peripheral causes.

  • Clues to central causes include associated cortical findings (apraxia, aphasia, hemineglect, etc), facial involvement (think brainstem if contralateral to the extremities involved), cranial nerve deficits, or suspicion for lacunar lesions.
  • Peripheral causes include radiculopathies (often with myotomal weakness and pain), plexopathies (brachial or lumbar), or peripheral nerve entrapment syndromes.

2)  There are two murmurs associated with hypertrophic cardiomyopathy :

  • Systolic anterior motion (SAM) of the mitral valve leading to poor leaflet coaptation and mitral regurgitation; this is a midsystolic murmur best heard at the apex and radiating to the axilla.
  • Turbulent flow through the outflow tract; presents as as a mid-systolic, crescendo-decrescendo murmur, often loudest at the LLSB  which can mimic the murmur of aortic stenosis. Maneuvers may enable the differentiation between the two entities: murmur of LVOTO worsens with reduced preload (eg, Valsalva, squat-to-stand, dehydration). Alternatively, maneuvers that increase preload (stand-to-squat or passive leg raise) or increase afterload (handgrip) will lead to a reduction in murmur intensity in HCM.

3) Complications of hypertrophic cardiomyopathy: syncope, sudden cardiac death, mitral regurgitaiton, arrhythmias (afib in 20% of patients, also can be ventricular), anginal chest pain (often from microvascular ischemia from supply/demand mismatch), progressive heart failure (diastolic with impaired ventricular filling and late-stage with reduced systolic function).

4) Therapy for hypertrophic cardiomyopathy:

  • Pharmacologic therapy:  Focused on maintaining adequate preload (avoiding diuretics, hypovolemia, etc) and decreasing ionotropy (leading to decreased heart rate and therefore increased diastolic filling time). Be the first to list two of the common pharmacologic categories below that do the latter and win a STARBUCKS gift card!
  • Other therapies include septal myomectomy, alcohol ablation (risk of conduction system damage), and biventricular pacing.