Document Detail

The vulnerable period for low and high energy T-wave shocks: role of dispersion of repolarisation and effect of d-sotalol.
MedLine Citation:
PMID:  8759252     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: The induction of ventricular fibrillation (VF) by T-wave shocks has been related to dispersion of repolarisation, but only indirect evidence of this hypothesis exists. The effects of drugs prolonging repolarisation like d-sotalol on the vulnerability to T-wave shocks remain unknown. METHODS: In 9 isolated rabbit heart, 7 monophasic action potentials (MAPs) and an ECG were recorded simultaneously. Vulnerable periods were determined using two different shock strengths, one close to the fibrillation threshold and the other close to the upper limit of vulnerability, at baseline and after action potential prolongation by d-sotalol. RESULTS: The vulnerable period had a duration of 30 +/- 14 ms for the lower and 34 +/- 12 ms for the higher shock strength (P = NS). Coupling intervals of the vulnerable periods were 13 +/- 10 ms shorter for higher shock strengths as compared to lower shock strengths (P < 0.005). The vulnerable period for low shock strengths coincided with dispersion of MAPs at 90% repolarisation (r = 0.87-0.92, P < 0.005), and the vulnerable period for high shock strengths coincided with dispersion at 70% repolarisation (r = 0.82-0.93, P < 0.005). ECG parameters predicted the vulnerable periods less precisely than MAP repolarisation (r < or = 0.72). d-Sotalol prolonged MAP durations by an average of 33 ms at 70% and 39 ms at 90% repolarisation but did not alter the described relations, nor did it reduce dispersion of repolarisation or duration of the vulnerable periods. CONCLUSIONS: Dispersion of repolarisation determines vulnerable periods and might be part of the arrhythmogenic substrate promoting induction of VF by T-wave shocks. The coupling intervals of the vulnerable periods depend on the applied shock strength as well as repolarisation, with shock strengths close to the fibrillation threshold inducing VF during dispersion at 90% repolarisation and shock strengths close to the upper limit of vulnerability inducing VF during dispersion at 70% repolarisation. d-Sotalol reduces neither vulnerability to T-wave shocks nor dispersion of repolarisation in this isolated heart model.
P F Kirchhof; C L Fabritz; M Zabel; M R Franz
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Cardiovascular research     Volume:  31     ISSN:  0008-6363     ISO Abbreviation:  Cardiovasc. Res.     Publication Date:  1996 Jun 
Date Detail:
Created Date:  1996-10-11     Completed Date:  1996-10-11     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  0077427     Medline TA:  Cardiovasc Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  953-62     Citation Subset:  IM    
Cardiology Division, Veterans Administration, Medical Center, Washington, DC 20422, USA.
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MeSH Terms
Action Potentials / drug effects*
Electric Stimulation*
Electrocardiography / drug effects*
Heart Conduction System / drug effects*
Models, Cardiovascular
Sotalol / pharmacology*
Ventricular Fibrillation / physiopathology
Reg. No./Substance:

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