%0 Journal Article
%T The limited utility of electrocardiography variables used to predict arrhythmia in psychotropic drug overdose
%A Nicholas A Buckley
%A Stephan Chevalier
%A I Anne Leditschke
%A Dianne L O'Connell
%A James Leitch
%A Susan M Pond
%J Critical Care
%D 2003
%I BioMed Central
%R 10.1186/cc2345
%X Thirty-nine patients with serious arrhythmias (ventricular tachycardia, supraventricular tachycardia or cardiac arrest) after tricyclic antidepressant overdose or thioridazine overdose were compared with 117 controls with clinically significant overdose matched to each case for the drug ingested. These patients with psychotropic drug overdose had presented for treatment to the Department of Clinical Toxicology, Newcastle and to the Princess Alexandra Hospital, Brisbane. The heart rate, the QRS width, the QTc and QT intervals, the QT dispersion, and the R wave and R/S ratios in aVR on the initial ECGs were compared in cases and controls.The cases had taken dothiepin (16 patients), doxepin (six patients), thioridazine (five patients), amitriptyline (five patients), nortriptyline (three patients), imipramine (one patient) and a combination of dothiepin and thioridazine (three patients). In 20 of the 39 patients with arrhythmias, the arrhythmia had been a presumed ventricular tachycardia. Of the other 19 patients, 15 patients had a supraventricular tachycardia, two patients had cardiac arrests (one asystole, one without ECG monitoring) and two patients had insufficient data recorded to make classification of the arrhythmias possible. The QRS was ≡ 100 ms in 82% of cases but also in 76% of controls. QRS ≡ 160 ms had a sensitivity of only 13% and occurred in 2% of controls. QRS > 120 ms, QTc > 500 and the R/S ratio in aVR appeared to have a stronger association with the occurrence of arrhythmia: QRS > 120 ms (odds ratio [OR], 3.56; 95% confidence interval [CI], 1.46每8.68), QTc > 500 (OR, 3.07; 95% CI, 1.33每7.07), and R/S ratio in aVR > 0.7 (OR, 16; 95% CI, 3.47每74). Excluding thioridazine overdoses and performing the analysis for tricyclic antidepressant overdoses alone gave increased odds ratios for QRS > 120 ms (OR, 4.83; 95% CI, 1.73每13.5) and QTc > 500 (OR, 4.5; 95% CI, 1.56每13) but had little effect on that for the R/S ratio in aVR > 0.7 (OR, 14.5; 95% CI, 3.10每68).E
%K arrhythmia
%K electrocardiography
%K overdose
%K sensitivity
%K specificity
%K thioridazine
%K tricyclic antidepressive agents
%U http://ccforum.com/content/7/5/R101