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Human ventricular action potential duration during short and long cycles. Rapid modulation by ischemia
P Taggart1, P M Sutton, M R Boyett
1Department of Cardiology, Middlesex Hospital, London, UK.
Circulation
|November 15, 1996
Summary
Ischemia flattens the electrical restitution curve in the human endocardium, potentially explaining how premature beats or pauses trigger ventricular arrhythmias. This study investigated electrical restitution during coronary artery occlusion.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Arrhythmia Research
Background:
- Mechanisms of ventricular arrhythmias during ischemia are not fully understood.
- Electrical restitution, the relationship between action potential duration and cardiac cycle length, may play a role.
Purpose of the Study:
- To investigate the effect of ischemia on electrical restitution in the human ventricle.
- To explore the link between electrical restitution changes and arrhythmogenesis during ischemia.
Main Methods:
- Recorded monophasic action potentials (MAPs) from the right ventricular septum in patients undergoing coronary artery occlusion (LAD or RCA).
- Utilized test pulse sequences to assess action potential duration (APD) changes with altered cycle lengths.
- Compared MAPs during left anterior descending coronary artery (LAD) occlusion (ischemia) with right coronary artery (RCA) occlusion (control).
Main Results:
- LAD occlusion significantly shortened basic beat APD (260 to 236 ms) and flattened the APD/diastolic interval restitution slope.
- RCA occlusion (control) did not significantly alter basic beat APD or the restitution slope.
- Ischemia induced by LAD occlusion minimized, abolished, or reversed the normal APD/diastolic-interval relation.
Conclusions:
- Myocardial ischemia flattens the electrical restitution curve in the human endocardium.
- Altered electrical restitution during ischemia may contribute to the initiation of ventricular arrhythmias.
- Findings suggest a mechanism for ischemia-induced proarrhythmia.
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