ISSN 1002-1027  CN 11-2952/G2

Acta scientiarum naturalium Universitatis Pekinensis

Previous Articles     Next Articles

Myocardial Vulnerability to Biphasic Shocks: the Rightward Shift of ULV vs. LLV Might Be Responsible for Its High Defibrillation Efficacy

LI Cuilan1, LIU Taifeng1, BEHRENS Steffen2, FRANZ Michael R2   

  1. 1College of Life Science, Department of Physiology and Biophysics, Peking University, Beijing, 100871; 2Cardiology Division of Medical Center, Georgetown University, Washington, DC, USA
  • Received:1996-09-20 Online:1997-07-20 Published:1997-07-20

Abstract: Biphasic shocks defibrillate more effectively than monophasic shocks, however, the mechanisms are still unknown. Isolated Langendorff-perfused rabbit hearts were paced at a cycle length of 500ms and the myocardial responses to shocks were recorded by MAP technique. A total of (84±11) biphasic T wave shocks were administered to each heart through two large shock plate electrodes flanking the bath to describe the area of vulnerability(AOV). The AOV was characterized by the induction of VF and was defined two-dimensionally by shock strength and coupling interval. ULV and LLV, which represent the upper and lower coner of AOV, respetively, occurred at shock strength of (373±62)V and (213±39)V, respectively. The coupling interval for ULV and LLV were (187±9) vs. (175±12)ms, p< 0.01, which resulted in a more complete repolarization level for ULV (84±9)% compare to that for LLV ((73±7)%, p< 0.01). The left and right borders of AOV (LBV, RBV) were (170±13)ms and (194±5)ms. The shock strength for RBV had a vertical upshift of (64±51)V (p< 0.01) compare to that for LBV. The rightward shift of the ULV timing compare to the LLV and the shock strength upshift of RBV vs. LBV resulted in a right-tilt of the AOV for biphasic shocks. This rightward shift of ULV timing vs. LLV might be responsible for its high defibrillation efficacy.