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Quinidine syncope: torsade de pointes with low quinidine plasma concentrations
European Journal of Cardiology
|December 1, 1976
Summary
Oral quinidine can cause torsades de pointes, a dangerous ventricular arrhythmia, even at low plasma concentrations. This risk exists even in patients without significant heart disease, highlighting the need for careful monitoring.
Area of Science:
- Cardiology
- Clinical Pharmacology
- Electrophysiology
Background:
- Supraventricular arrhythmias require effective antiarrhythmic drug therapy.
- Quinidine is an antiarrhythmic medication used to manage cardiac rhythm disorders.
Observation:
- Two patients without ischemic heart disease developed syncopal episodes.
- These episodes were attributed to torsades de pointes, a specific ventricular tachyarrhythmia.
Findings:
- Both patients experienced torsades de pointes despite low serum quinidine levels.
- Prolonged Q-T interval was observed, while QRS duration remained normal.
Implications:
- Quinidine can induce torsades de pointes even at subtherapeutic concentrations.
- This suggests a potential idiosyncratic reaction or heightened sensitivity in certain patients.
- Careful electrocardiographic monitoring for Q-T interval prolongation is crucial during quinidine therapy, irrespective of baseline cardiac health.