{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T01:22:47Z","timestamp":1785892967699,"version":"3.56.0"},"reference-count":51,"publisher":"BMJ","issue":"10","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Heart"],"published-print":{"date-parts":[[2008,10]]},"abstract":"<jats:sec>\n                  <jats:title\/>\n                  <jats:p>Symptoms of impaired consciousness (syncope and pre-syncope) occur in 15\u201325% 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<jats:sup>\u2013<\/jats:sup>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.<\/jats:p>\n                  <jats:p>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.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1136\/hrt.2008.141507","type":"journal-article","created":{"date-parts":[[2008,7,24]],"date-time":"2008-07-24T20:25:25Z","timestamp":1216931125000},"page":"1312-1317","source":"Crossref","is-referenced-by-count":31,"title":["Episodic syncope in hypertrophic cardiomyopathy: evidence for inappropriate vasodilation"],"prefix":"10.1136","volume":"94","author":[{"given":"K","family":"Prasad","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"L","family":"Williams","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"R","family":"Campbell","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"P M","family":"Elliott","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"W J","family":"McKenna","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M","family":"Frenneaux","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2008,7,24]]},"reference":[{"key":"2025092007221501000_94.10.1312.1","unstructured":"McKenna WJ Elliott PM . Hypertrophic cardiomyopathy. In: Topol E J , ed. Textbook of cardiovascular medicine. 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