Torsades de pointes and early afterdepolarizations
1Rockefeller University, New York, NY 10021-6399.
Cardiovascular Drugs and Therapy
|April 1, 1991
Summary
Torsades de pointes and other pause-induced arrhythmias may stem from early afterdepolarizations. This mechanism explains their shared characteristics, including onset, termination, and rate changes, offering new insights into cardiac arrhythmia.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Arrhythmias
Background:
- Torsades de pointes (TdP) is a specific type of ventricular tachycardia.
- Pause-induced or bradycardia-induced arrhythmias are a recognized group of cardiac rhythm disturbances.
- The underlying mechanisms of TdP and related arrhythmias are not fully elucidated.
Purpose of the Study:
- To propose that Torsades de pointes is part of a broader category of pause- or bradycardia-induced arrhythmias.
- To differentiate the causes of the characteristic ECG morphology ('twisting of the points') from the mechanisms initiating and sustaining the tachycardia.
- To explore the relationship between TdP, other pause-induced arrhythmias, and rhythmic activity originating from early afterdepolarizations.
Main Methods:
- Comparative analysis of clinical and electrophysiological features of TdP and other pause-induced arrhythmias.
- Review of existing literature on arrhythmia mechanisms, including early afterdepolarizations.
- Correlation of observed arrhythmia patterns with specific conditions like quinidine intoxication and hypokalemia.
Main Results:
- Torsades de pointes and other pause-induced arrhythmias share significant features with rhythmic activity initiated by early afterdepolarizations.
- Both types of arrhythmias occur after pauses or at low heart rates.
- Observed phenomena, including the short-long-short sequence, abrupt onset/termination, and rate modulation, are consistent with early afterdepolarization mechanisms.
Conclusions:
- Pause- or bradycardia-induced arrhythmias, including Torsades de pointes, may share a common underlying mechanism related to early afterdepolarizations.
- Early afterdepolarizations provide a unifying explanation for the diverse clinical manifestations of these arrhythmias.
- Understanding this mechanism could lead to improved diagnostic and therapeutic strategies for pause-dependent cardiac arrhythmias.
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