Ventricular tachyarrhythmias in regional myocardial hyperkalemia: efficacy of three antiarrhythmic agents
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This study shows that antiarrhythmic drugs effectively treat ventricular arrhythmias caused by potassium chloride infusion, a model for acute ischemia. These treatments improved survival rates and conduction times in canine models.
Area of Science:
- Cardiovascular Physiology
- Pharmacology
Background:
- Acute transmural ischemia triggers ST elevation, conduction delays, and ventricular arrhythmias.
- The efficacy of antiarrhythmic agents in regional hyperkalemia models is not well-established.
Purpose of the Study:
- To evaluate the antiarrhythmic effects of lidocaine, procainamide, and practolol in a canine model of acute myocardial infarction.
- To assess the impact of these agents on intramural conduction and survival rates during induced hyperkalemia.
Main Methods:
- Induction of regional hyperkalemia via potassium chloride infusion into the left anterior descending coronary artery in anesthetized canines.
- Administration of lidocaine, procainamide, or practolol to treatment groups.
- Monitoring of electrocardiographic changes (ST elevation), intramural conduction times, and survival rates over a 20-minute observation period.
Main Results:
- Untreated animals had a 9% survival rate.
- All three antiarrhythmic drug treatment groups showed reduced tachycardia incidence and a 74% survival rate.
- Treatment was associated with further prolongation of intramural conduction time in the ischemic region.
Conclusions:
- Lidocaine, procainamide, and practolol demonstrate significant antiarrhythmic efficacy in a canine model of ischemic arrhythmias.
- The observed efficacy may be linked to the transformation of unidirectional to bidirectional block, potentially modulated by potassium activity.
- Modulating transcellular potassium activity is a viable strategy for controlling ischemic arrhythmias.
Abstract:
Potassium chloride infusion into the left anterior descending coronary artery induces a sequence of events analogous to those occurring during acute transmural ischemia. These include ST elevation, intramural conduction delay, ventricular techyarrhythmias and fibrillation. The influence of antiarrhythmic agents in an intact anesthetized canine model have not previously been tested. We have evaluated the efficacy of lidocaine, procaine amide and practolol in animals during regional hyperkalemia. In the untreated, only 9% survided a 20 minute observation period. All three treatment groups exhibited a reduced incidence of tachycardia and 74% survived the test period. In each treatment group this was associated with a further prolongation of intramural conduction time in the affected wall. This antiarrhythmic efficacy, thought possibly to be due to transformation of unidirectional to bidirectional block, supports the view that modulation of transcellular potassium activity contributes to the control of ischemic arrhythmias.