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The electrophysiological effects of calcium channel blockade during standard hyperkalemic hypothermic cardioplegic
Insights
Adding nifedipine to cardioplegic solution reduces low-amplitude electrical activity during cardiac arrest. This calcium blockade may prevent arrhythmias by inhibiting calcium-mediated conduction in the heart.
Area of Science:
- Cardiology
- Cardiac Electrophysiology
- Pharmacology
Background:
- Calcium channel blockers are used with cardioplegia, but their effect on cardiac conduction tissues during arrest is unknown.
- The development of arrhythmias after cardiac arrest is a significant clinical concern.
Purpose of the Study:
- To investigate the effect of nifedipine, a calcium channel blocker, on cardiac conduction tissues during cardioplegic arrest.
- To assess the impact of nifedipine on the development of arrhythmias post-arrest.
Main Methods:
- A canine model using standard clinical techniques was employed.
- A 32-channel data acquisition system measured electrophysiological variables before and after cardioplegic arrest.
- Nifedipine was added to a standard hyperkalemic hypothermic cardioplegic solution.
Main Results:
- Nifedipine shortened the time to and prolonged the duration of electrical arrest compared to standard solution.
- No negative impact on immediate post-arrest conduction function was observed.
- Nifedipine significantly reduced low-amplitude electrical activity (LEA) in atria and ventricles during arrest.
Conclusions:
- Nifedipine addition to cardioplegia appears safe for cardiac conduction.
- Reduced LEA by nifedipine suggests a link between calcium-mediated conduction and arrhythmias during arrest.
Abstract:
The addition of calcium channel-blocking agents to a standard hyperkalemic hypothermic cardioplegic solution has been examined both experimentally and clinically. None of these studies, however, have investigated the effect of calcium blockade during cardioplegic arrest on the specialized cardiac conduction tissues and on the subsequent development of arrhythmias after arrest. The present study examined the effect of adding nifedipine to standard cardioplegic solution administered in a canine experimental preparation modeled on routine clinical techniques. The time to and duration of electrical arrest following the administration of cardioplegia and the functional electrophysiological variables before and after arrest were measured using a 32-channel data acquisition system. The addition of nifedipine shortened the time to electrical arrest and prolonged the duration of arrest compared with standard potassium cardioplegic solution alone, without a deleterious effect on conduction function immediately after arrest. The occurrence of low-amplitude electrical activity (LEA) in both atria and ventricles during arrest was significantly reduced by the addition of nifedipine, thereby suggesting a possible correlation between LEA and calcium-mediated conduction occurring under conditions of standard cardioplegic arrest.