Document Detail

Cardiac parasympathetic stimulation via QRS-synchronous low-energy shocks in humans.
MedLine Citation:
PMID:  9930904     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: In patients receiving test shocks to verify lead connections at implantation, we anecdotally have observed postshock delay. The purpose of this study was to determine whether QRS-synchronous low-energy shocks delivered by implantable defibrillators result in postshock cycle length prolongation, and to determine the mechanism of this phenomenon. METHODS AND RESULTS: Twenty-five patients undergoing defibrillator testing were studied, three with epicardial patches and 22 with transvenous leads. Each patient received QRS-synchronous shocks of 0.2, 0.4, 0.6, and 2.0 J in random order. Patients were further randomized to receive either saline or 2.0 mg atropine intravenously, and then given a second sequence of shocks. At baseline, the postshock cycle length (1,035+/-245 msec) was significantly longer than the preshock cycle length (968+/-177 msec, P = 0.01). In patients with a coronary sinus (CS) or superior vena cava (SVC) lead, the mean prolongation was 91+/-160 msec, compared with 12+/-106 msec for patients without such a lead (P < 0.0001). All energy levels resulted in significant postshock prolongation compared with preshock cycle lengths (P < 0.05). Postshock prolongation before atropine was 76+/-162 msec, compared with -13+/-52 msec afterward (P < 0.00001). Biphasic shocks resulted in greater postshock prolongation than monophasic shocks of equal energy. CONCLUSION: Low-energy shocks delivered during the QRS complex cause postshock cycle length prolongation in man. This effect required the presence of a CS or SVC lead. Atropine inhibited this effect, suggesting the phenomenon was mediated by direct cardiac parasympathetic nerve stimulation by the intracardiac shock.
P A Friedman; M R Hill; M S Stanton
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Publication Detail:
Type:  Clinical Trial; Comparative Study; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  10     ISSN:  1045-3873     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  1999 Jan 
Date Detail:
Created Date:  1999-03-30     Completed Date:  1999-03-30     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  10-6     Citation Subset:  IM    
Division of Cardiovascular Disease, Mayo Clinic, Rochester, Minnesota 55905, USA.
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MeSH Terms
Aged, 80 and over
Defibrillators, Implantable
Diagnosis, Differential
Electric Countershock*
Follow-Up Studies
Heart / innervation*
Middle Aged
Parasympathetic Nervous System / physiopathology*
Tachycardia, Supraventricular / diagnosis,  physiopathology,  therapy*
Tachycardia, Ventricular / diagnosis,  physiopathology,  therapy*
Treatment Outcome

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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