PT - JOURNAL ARTICLE AU - Prasad, K AU - Williams, L AU - Campbell, R AU - Elliott, P M AU - McKenna, W J AU - Frenneaux, M TI - Episodic syncope in hypertrophic cardiomyopathy: evidence for inappropriate vasodilation AID - 10.1136/hrt.2008.141507 DP - 2008 Oct 01 TA - Heart PG - 1312--1317 VI - 94 IP - 10 4099 - http://heart.bmj.com/content/94/10/1312.short 4100 - http://heart.bmj.com/content/94/10/1312.full SO - Heart2008 Oct 01; 94 AB - 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.