Prolonged QT interval
predicts cardiac and all-cause mortality in the elderly.
Methadone is known to prolong the QT interval
and was used to verify the sensitivity of the analysis.
We expected that the increased awareness of the cardiotoxicity of psychotropics and interaction between medications would have made psychiatrists more adept at QT interval
and ECG abnormality interpretation, but this study indicates that the problem remains," the researchers wrote (The Psychiatrist 2008;32:291-4).
Doctors are generally concerned if patients experience an additional 30 milliseconds in their QT interval
from baseline," Sachin A.
The researchers included the methadone patients for comparison because this drug (used for pain relief and to wean addicts off heroin) is known to prolong QT interval
Drug-and non-drug-associated QT interval
The QT interval
consists of a short depolarization (the QRS complex) and a longer repolarization part (the ST segment and the T wave) (6).
Short QT syndrome is a rare form of hereditary channelopathy with an abnormally short QT interval
and a high propensity to atrial and ventricular fibrillation.
R-R interval was used to compute heart rate in order to calculate corrected QT interval
(QTc) with Bazett's formula.
Drugs that substantially prolong the QT interval
have been associated
12,14,24,25) The QT interval
represents the total time needed for the ventricles to depolarize and repolarize.
A comprehensive analysis of QT interval
assessments including the QTc interval was performed in AMP-516 per ICH E14 Guidance: Clinical Evaluation of QT/QTc Interval Prolongation and Proarrhythmic Potential for Non-Anti-arrhythmic Drugs (October 2005, ICH).