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Electrocardiogram changes and arrhythmias in venlafaxine overdose
1Charles Darwin University, Darwin and Department of Clinical Toxicology and Pharmacology, Calvary Mater Newcastle Hospital, Waratah, Australia. geoffrey.isbister@menzies.edu.au
British Journal of Clinical Pharmacology
|June 26, 2009
Summary
Venlafaxine overdose typically causes minor electrocardiogram (ECG) changes, with few major arrhythmias. Large doses may be associated with abnormal QT intervals, but QRS widening is uncommon.
Area of Science:
- Clinical Toxicology
- Cardiology
- Pharmacology
Background:
- Venlafaxine is a widely prescribed antidepressant.
- Overdoses can lead to various clinical effects, necessitating understanding of cardiac implications.
Purpose of the Study:
- To evaluate electrocardiogram (ECG) parameters, hemodynamic changes, and arrhythmias after venlafaxine overdose.
- To identify potential correlations between ingested dose and cardiac abnormalities.
Main Methods:
- Retrospective analysis of 369 venlafaxine overdose cases in 273 patients.
- Inclusion of demographic data, ingestion details, heart rate, blood pressure, and ECG parameters (QT, QRS).
- Manual ECG measurement and analysis, including QT-HR nomogram plotting.
Main Results:
- Tachycardia (54%) and mild hypertension (40%) were common; severe hypertension (3%) and hypotension (5%) were rare.
- No arrhythmias were detected on telemetry; conduction defects were infrequent (7/369), often pre-existing.
- Abnormal QT-HR pairs occurred in 6% of cases, more frequent with larger venlafaxine doses.
- Median QRS width was 85 ms, with QRS >120 ms in only 7% of patients.
Conclusions:
- Venlafaxine overdose is associated with minimal QT and QRS interval abnormalities.
- Major arrhythmias are unlikely, though large doses may pose a slightly higher risk.
- Significant conduction defects are rare in venlafaxine overdose.
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