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Differences in Corrected QT Intervals at Minimal and Maximal Heart Rate May Identify Patients at Risk for Torsades de Pointes During Treatment with Antiarrhythmic Drugs
Author(s) -
BUCKINGHAM THOMAS A.,
BHUTTO ZAHIDA R.,
TELFER EDWARD A.,
ZBILUT JOSEPH
Publication year - 1994
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1111/j.1540-8167.1994.tb01179.x
Subject(s) - medicine , torsades de pointes , qt interval , cardiology , long qt syndrome , anesthesia
Change in QT Interval with HR May Predict Torsades. The mechanism of torsades de pointes as a proarrhythmic response to antiarrhythmic drugs is not clear. We hypothesized that the difference in the corrected QT interval (QT c , Bazett's formula) with varying autonomic tone and heart rate during 24‐hour ambulatory ECG would help identify patients at risk. Ten patients with antiarrhythmic drug‐induced torsades de pointes were compared with 28 controls. The QT c . at maximal and minimal heart rate during antiarrhythmic drug‐free ambulatory ECGs were measured. The mean QT c , at minimal heart rates for patients was 0.413 ± (KI02 seconds and 0.420 ± 0.072 seconds for controls (P = 0.715). The mean QT c , at maximal heart rates for patients was 0.555 ± 0.022 seconds and for controls was 0.439 ± 0.011 seconds (P = 0.00l). Mean QT c , between minimal and maximal heart rates were significantly different for patients (P = 0.015) but were not for controls (P = 0.151). Using an arbitrary QT, difference cutoff of 0.075 seconds, this approach identified patients at risk for antiarrhythmic drug‐induced torsades de pointes with a sensitivity of 70% (7 of 10) and a specificity of 89% (P < 0.003 by Chi‐square analysis with Vales’ correction). In conclusion, patients with antiarrhythmic drug‐induced torsades de pointes had a greater rise in QT c , from minimal to maximal heart rate during ambulatory ECG than controls. Further larger prospective trials will be required to establish the value of this approach to identify patients at risk for this type of proarrhythmia.