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Antiarrhythmic versus antifibrillatory actions: inference from experimental studies
B R Lucchesi1, L Chi, G S Friedrichs
1Department of Pharmacology, University of Michigan Medical School, Ann Arbor.
Abstract:
Pathophysiology of the coronary circulation is a major contributor to altering the myocardial substrate, rendering the heart susceptible to the onset of arrhythmias associated with sudden cardiac death. Antiarrhythmic drug therapy for the prevention of sudden cardiac death has been provided primarily on the basis of trial and error and in some instances based on ill-suited preclinical evaluations. The findings of the Cardiac Arrhythmia Suppression Trial (CAST) requires a reexamination of the manner in which antiarrhythmic drugs are developed before entering into clinical testing. The major deficiency in this area of experimental investigation has been the lack of animal models that would permit preclinical studies to identify potentially useful or deleterious therapeutic agents. Further, CAST has emphasized the need to distinguish between pharmacologic interventions that suppresses nonlethal disturbances of cardiac rhythm as opposed to those agents capable of preventing lethal ventricular tachycardia or ventricular fibrillation. Preclinical models for the testing of antifibrillatory agents must consider the fact that the superimposition of transient ischemic events on an underlying pathophysiologic substrate makes the heart susceptible to lethal arrhythmias. Proarrhythmic events, not observed in the normal heart, may become manifest only when the myocardial substrate has been altered. We describe a model of sudden cardiac death that may more closely simulate the clinical state in humans who are at risk. The experimental results show a good correlation with clinical data regarding agents known to reduce the incidence of lethal arrhythmias as well as those showing proarrhythmic actions.
Insights
Developing new antiarrhythmic drugs requires better animal models. A new sudden cardiac death model simulates human risk, improving the identification of drugs that prevent lethal arrhythmias without causing harm.
Area of Science:
- Cardiovascular Pathophysiology
- Pharmacology
- Translational Medicine
Background:
- Coronary circulation pathophysiology alters myocardial substrate, increasing susceptibility to life-threatening arrhythmias and sudden cardiac death.
- Current antiarrhythmic drug therapy relies heavily on trial-and-error and inadequate preclinical models.
- The Cardiac Arrhythmia Suppression Trial (CAST) highlighted the need to re-evaluate antiarrhythmic drug development strategies.
Purpose of the Study:
- To address the deficiency in preclinical models for evaluating antiarrhythmic agents.
- To develop an animal model that more accurately simulates the clinical conditions of sudden cardiac death risk in humans.
- To differentiate between drugs suppressing nonlethal arrhythmias and those preventing lethal ventricular arrhythmias.
Main Methods:
- Development of a novel animal model for sudden cardiac death.
- This model incorporates transient ischemic events superimposed on an altered pathophysiologic substrate.
- Testing of known antiarrhythmic and proarrhythmic agents within this model.
Main Results:
- The developed model closely simulates the clinical state of humans at risk for sudden cardiac death.
- Experimental results demonstrated good correlation with clinical data for agents affecting lethal arrhythmias.
- The model successfully identified both beneficial antifibrillatory and potentially harmful proarrhythmic drug actions.
Conclusions:
- A validated animal model is crucial for effective preclinical assessment of antiarrhythmic drugs.
- This new model provides a more reliable platform for identifying drugs that prevent sudden cardiac death.
- Distinguishing between suppression of nonlethal and prevention of lethal arrhythmias is critical for drug development.