Drug-induced QRS morphology and duration changes.

Drug-induced ECG changes may affect all components of the ECG curve. The attention of regulatory agencies, researchers and clinicians has been directed towards drug-induced QT-interval prolongation and its well-documented proarrhythmia. This presentation focuses on druginduced changes, i.e., morphology, amplitude and QRS complex duration (QRSd). A great variety of pharmacological agents (e.g., class IA and IC antiarrhythmics, antihistamines, antidepressants, antipsychotics) exert an influence on the QRSd. The QRSd is assessed by a variety of ECG methodologies. Standardization of measurements of QRSd ensures the comparability of results by different ECG modalities, and of serial QRSd assessments. Some analgesics and hypoglycemic agents influence the amplitude of QRS complexes by way of their propensity to cause peripheral oedema (extracardiac mechanism). Perhaps a new culture could evolve in which the entire ECG curve, from the onset of the P-wave to the offset of the U-wave, will be used in the evaluation and monitoring of drug safety, with emphasis primarily on the standard ECG.