Episodic syncope in hypertrophic cardiomyopathy: evidence for inappropriate vasodilation

K Prasad, L Williams, R Campbell, P M Elliott, W J McKenna, M Frenneaux

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Symptoms of impaired consciousness (syncope and pre-syncope) occur in 15-25% of patients with hypertrophic cardiomyopathy (HCM).1 In young patients a history of recurrent syncope is associated with an increased risk of sudden death.2(-)5 Syncope usually occurs without warning or symptoms suggestive of the cause. Detailed investigations identify a probable mechanism in a minority, usually paroxysmal atrial fibrillation or ventricular tachycardia. In the majority however no likely mechanism is found despite repeated 24-hour ambulatory echocardiography (ECG) or patient-activated monitoring, exercise testing and invasive electrophysiological studies.1 6 Empirical treatment with amiodarone, a pacemaker or an implantable cardioverter-defibrillator is commonly employed, but is often unsuccessful in relieving the symptoms. We have previously observed that approximately 30% of patients with HCM have abnormal blood pressure response during maximal upright exercise.7 8 This was due in the majority of patients to an exaggerated fall in systemic vascular resistance, possibly arising from abnormal activation of stretch-sensitive left ventricular mechanoreceptors,9 10 by a mechanism similar to that described in aortic stenosis.11 However, in some patients an inadequate cardiac output response to exercise may be responsible.12 We hypothesised that abnormal vasodepressor-mediated hypotension may also occur during daily life in patients with HCM, and that this may be an important mechanism of syncope when conventional investigations fail to reveal a cause.
Original languageEnglish
Pages (from-to)1312-7
Number of pages6
Issue number10
Publication statusPublished - Oct 2008


  • Adolescent
  • Adult
  • Blood Pressure
  • Cardiomyopathy, Hypertrophic
  • Dilatation, Pathologic
  • Exercise
  • Humans
  • Hypotension
  • Pressoreceptors
  • Syncope
  • Tilt-Table Test

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