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hocm

hypertrophic cardiomyopathy (HCM or HOCM)

see also:

introduction

  • idiopathic hypertrophy of the myocardium resulting in left ventricular hypertrophy (LVH) which is usually assymetric involving the interventricular septum in 2/3rds of cases
  • 25% have obstructed outflow at rest, while 70% have obstructed outflow under certain conditions (“dynamic outflow obstruction”)
    • the obstructive variant of HCM, hypertrophic obstructive cardiomyopathy (HOCM) has also historically been known as idiopathic hypertrophic subaortic stenosis (IHSS) and asymmetric septal hypertrophy (ASH).
  • 30% have abnormal vascular responses and inability to increase systolic blood pressure during exercise
  • one of the commonest causes of sudden death in young athletes and is often asymptomatic prior
  • arrhythmias are common especially atrial fibrillation and supraventricular tachycardias.
    • ventricular dysrhythmias also occur and may be a cause of sudden death.
  • 50-60% are due to a mutation in one of 9 sarcomeric genes, usually inherited as autosomal dominant or arise de novo
    • 45% of these mutations occur in the β myosin heavy chain gene on chromosome 14 q11.2-3
    • 35% involve the cardiac myosin binding protein C gene
    • an insertion/deletion polymorphism in the gene encoding for angiotensin converting enzyme (ACE) alters the clinical phenotype of the disease
    • troponin T mutations are particularly dangerous and are associated with a 50% mortality before the age of 40
  • prevalence is 0.2% - 0.5% of the general population
  • a non-obstructive variant of HCM is apical hypertrophic cardiomyopathy, also called Yamaguchi Syndrome or Yamaguchi Hypertrophy, first described in individuals of Japanese descent

diagnosis

  • ECG may show:
      • >40 mm S wave in V2
      • +/- flattened or inverted T waves in inf-lat leads
      • +/- ST-T changes although left ventricular hypertrophy (LVH) may be absent in pre-pubescent children
      • +/- increased precordial voltages
      • +/- P ‘mitrale may be seen due to left atrial hypertrophy, which occurs when there is left ventricular diastolic dysfunction
    • LAD or RAD
    • BBB or prolonged PR interval
    • Sinus bradycardia with ectopic atrial rhythm
    • abnormal and prominent Q wave in the anterior precordial and lateral limb leads, short P-R interval with QRS suggestive of preexcitation
      • deep narrow (‘dagger like’) Q waves in the lateral (V5-6, I and AVL) and inferior (II, III and AVF) leads, due to asymmetrical septal hypertrophy.
      • these Q waves are distinct from those of previous myocardial infarction, in that they are typically < 40ms duration whereas infarction Q waves are typically > 40 ms duration
    • giant T wave inversion in apical HCM (mainly in Japanese)
  • HOCM can be detected on echo in over 80% of cases

DDx

athlete's heart

  • highly trained athletes can also develop cardiac hypertrophy (‘athlete's heart’).
  • ECG changes seen as part of cardiovascular adaptation in an endurance athlete include:
    • sinus bradycardia
    • increased QRS voltage
    • tall peaked T wave
    • J point elevation
    • U waves
  • in contrast, the presence of pathological Q waves, left axis deviation, and T wave inversion are indicators of HCM as opposed to the athlete’s heart

Brugada syndrome

congenital long QT syndrome

pre-excitation syndromes

Mx of suspected HCM

  • patients should be advised not to undergo any exertional stress which could put them at risk of sudden cardiac death
  • urgent echocardiogram and cardiology review

AVOID

consider

references

hocm.txt · Last modified: 2017/09/01 21:39 (external edit)