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Slowed intrinsic heart rate is associated with reduced arrhythmic susceptibility in guinea-pig heart.
MedLine Citation:
PMID:  25334079     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Abstract Objectives. In the clinical setting, patients with slower resting heart rate are less prone to cardiovascular death compared to those with elevated heart rate. However, electrophysiological adaptations associated with slowed cardiac rhythm have not been thoroughly explored. In this study, relationships between intrinsic heart rate and arrhythmic susceptibility were examined by assessments of action potential duration (APD) rate adaptation and inducibility of repolarization alternans in sinoatrial node (SAN)-driven and atrioventricular (AV) blocked guinea-pig hearts perfused with Langendorff apparatus. Design. ECG, epicardial monophasic action potentials, and effective refractory periods (ERP) were assessed in normokalemic and hypokalemic conditions. Results. Slower basal heart rate in AV-blocked hearts was associated with prolonged ventricular repolarization during spontaneous beating, and with attenuated APD shortening at increased cardiac activation rates during dynamic pacing, when compared to SAN-driven hearts. During hypokalemic perfusion, the inducibility of repolarization alternans and tachyarrhythmia by rapid pacing was found to be lower in AV blocked hearts. This difference was ascribed to prolonged ERP in the setting of slowed basal heart rate, which prevented ventricular capture at critically short pacing intervals required to induce arrhythmia. Conclusions: Reduced basal heart rate is associated with electrophysiological changes that prevent electrical instability upon an abrupt cardiac acceleration.
Authors:
Oleg E Osadchii
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-10-21
Journal Detail:
Title:  Scandinavian cardiovascular journal : SCJ     Volume:  -     ISSN:  1651-2006     ISO Abbreviation:  Scand. Cardiovasc. J.     Publication Date:  2014 Oct 
Date Detail:
Created Date:  2014-10-21     Completed Date:  -     Revised Date:  2014-10-22    
Medline Journal Info:
Nlm Unique ID:  9708377     Medline TA:  Scand Cardiovasc J     Country:  -    
Other Details:
Languages:  ENG     Pagination:  1-19     Citation Subset:  -    
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