Optical transmembrane potential recordings during intracardiac defibrillation-strength shocks

被引:8
作者
Clark, DM
Pollard, AE
Ideker, RE
Knisley, SB
机构
[1] Univ Alabama Birmingham, Dept Physiol, Birmingham, AL 35294 USA
[2] Univ Alabama Birmingham, Dept Med, Div Cardiovasc Dis, Birmingham, AL 35294 USA
[3] Univ Alabama Birmingham, Dept Biomed Engn, Birmingham, AL 35294 USA
关键词
electrical stimulation; transmembrane potential; heart; defibrillation; action potential duration;
D O I
10.1023/A:1009801027049
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
Background: The prolongation of the action potential after defibrillation-strength shocks is believed to be a critical component of defibrillation. The response of the transmembrane potential to the shock may affect this prolongation. We studied the effects of an intracardiac shock on the transmembrane potential and action potential duration at multiple sites on the epicardium using a voltage-sensitive dye and optical mapping system. Methods and Results: A laser scanner recorded optical action potentials with voltage-sensitive dye at 63 spots on both the left and right ventricles of six isolated, perfused rabbit hearts. Hearts were paced with epicardial point stimulation followed by the delivery of a 2 A and 20 ms rectangular waveform shock during the relative refractory period. The shock was given between right atrial and right ventricular electrodes. Of 621 total spots analyzed, 241 spots hyperpolarized and 76 spots depolarized with a right ventricular anode, whereas 159 spots hyperpolarized and 145 spots depolarized with a right ventricular cathode (P < 0.05). Both hyperpolarized and depolarized spots exhibited prolonged action potential duration, although prolongation was greater with depolarizing responses (16.7 +/- 9 ms vs. 13.3 +/- 13.4 ms, p < 0.001). Hyperpolarized and depolarized spots were not randomly distributed, but clustered into regions. The size of the hyperpolarized regions was larger than the depolarized regions with RV anodal stimulation (27 +/- 20 spots/hyperpolarized region vs. 8.5 +/- 9 spots/depolarized region, p < 0.03) but not with RV cathodal stimulation. With reversal of electrode polarity, spots hyperpolarized near the shocking electrodes frequently did not reverse polarization but remained hyperpolarized. Conclusions: Distinct regions of either polarization occur during intracardiac defibrillation-strength shocks. Although hyperpolarizing membrane responses were observed more often than depolarizing responses, depolarizing membrane polarization resulted in greater action potential prolongation. The absence of sign change in polarization in some regions with shocks of opposite polarities suggests that nonlinear intrinsic membrane properties are operative during strong electrical stimulation.
引用
收藏
页码:109 / 120
页数:12
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