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Attenuation of conduction delay by ischemic preconditioning reduces ischemia-induced ventricular arrhythmias
1Department of Cardiovascular Medicine, Okayama University Medical School, Japan.
Insights
Ischemic preconditioning significantly reduces heart arrhythmias during ischemia by shortening action potential duration and attenuating conduction delays. This protective effect highlights its antiarrhythmic potential in cardiac ischemia.
Area of Science:
- Cardiology
- Physiology
- Cardiac Electrophysiology
Background:
- Ischemic preconditioning is known to reduce ischemic injury.
- The precise antiarrhythmic mechanism of ischemic preconditioning during ischemia remains unclear.
Purpose of the Study:
- To investigate the effects of ischemic preconditioning on cardiac arrhythmias and electrophysiology during ischemia.
- To elucidate the antiarrhythmic mechanism of ischemic preconditioning.
Main Methods:
- Utilized Langendorff-perfused rat hearts (n=44).
- Compared a non-preconditioned group (PC(-)) with a preconditioned group (PC(+)) subjected to cycles of ischemia and reperfusion.
- Assessed arrhythmias, monophasic action potential duration (MAPD), and conduction time during global ischemia.
Main Results:
- Ischemic preconditioning (PC(+)) significantly reduced the incidence of ischemia-induced arrhythmias compared to the non-preconditioned group (PC(-)) (8.3% vs 38.9%).
- Preconditioning shortened monophasic action potential duration (MAPD) and attenuated conduction delay.
- Conduction time prolongation was more pronounced in non-preconditioned hearts with arrhythmias.
Conclusions:
- Ischemic preconditioning protects rat hearts against ischemia-induced arrhythmias.
- Attenuation of conduction delay during ischemia is a potential key factor in the antiarrhythmic action of ischemic preconditioning.
Abstract:
Ischemic preconditioning has been acknowledged as a powerful method of decreasing ischemic injury. However, the antiarrhythmic mechanism of ischemic preconditioning during ischemia is unclear. We studied the effects of ischemic preconditioning on arrhythmias and cardiac electrophysiology during ischemia in Langendorff rat hearts (n = 44). In the non-preconditioned group (PC(-); n = 24), the hearts underwent 5-min zero-flow global ischemia without any prior ischemic preconditioning. In the preconditioned group (PC(+); n = 20), the hearts were preconditioned by three cycles of 3-min zero-flow global ischemia and 5-min reperfusion before undergoing 5-min global ischemia. Ischemic preconditioning reduced the incidence of ischemia-induced arrhythmias (PC(-); 38.9%, PC(+): 8.3%, p < 0.05), shortened monophasic action potential duration (MAPD, P < 0.05), attenuated conduction delay (conduction time; PC(-): 234.2%, PC(+): 173.4%, P < 0.05) and increased the ventricular fibrillation threshold. Although the shortening of MAPD in PC(-) hearts was not influenced by the presence or absence of arrhythmias, conduction time prolongation at 3-min was more obvious in PC(-) hearts with arrhythmia than in PC(-) hearts without arrhythmia (PC(-) with arrhythmia: 220.2%, PC(-) without arrhythmia: 190.7%, P < 0.05). We concluded that ischemic preconditioning could protect the rat hearts from ischemia-induced arrhythmias and postulated that attenuation of conduction delay during ischemia might be an important factor in the antiarrhythmic action of ischemic preconditioning.