Electrocardiographic abnormalities in patients treated with clozapine.
BACKGROUND
Cardiovascular side effects of clozapine are not uncommon, but few systematic studies of these effects have been performed. In this study, we reviewed data on the electrocardiographic (ECG) abnormalities in patients treated with clozapine.


METHODS
Sixty-one patients treated with clozapine were selected from the Seoul National University Hospital Treatment-Resistant Schizophrenia Clinic. A retrospective chart review was conducted to identify ECG abnormalities and cardiovascular side effects.


RESULTS
The prevalence of ECG abnormalities in patients who had been using antipsychotics other than clozapine was 13.6% at baseline, which increased significantly to 31.1% after commencement of clozapine treatment. Among the 53 patients without baseline ECG abnormalities, 13 showed new-onset ECG abnormalities after using clozapine. Normal ECG under previous antipsychotic medication reduced the risk of new-onset ECG abnormalities, whereas increased age was found to increase the risk. The occurrence of orthostatic hypotension or tachycardia was not related to the development of ECG abnormalities. Most of the newly developed abnormalities had little clinical significance, and they tended to occur during the initial phase of treatment. In 10 patients, ECGs normalized despite the continued use of clozapine. Clozapine increased corrected QT interval (QTc) in a dose-dependent fashion; however, the clinical significance of this observation is uncertain. Pathologic prolongation of QTc was found to be rare.


CONCLUSIONS
Although a substantial portion of patients treated with clozapine developed ECG abnormalities, most of the abnormalities were benign and did not hinder further treatment.
Kang
U G
UG
Department of Psychiatry, Seoul National University College of Medicine, Korea.
Kwon
J S
JS
Ahn
Y M
YM
Chung
S J
SJ
Ha
J H
JH
Koo
Y J
YJ
Kim
Y S
YS
D000293:Adolescent; D000328:Adult; D014150:Antipsychotic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D001145:Arrhythmias, Cardiac / Q000139:chemically induced* / Q000175:diagnosis* / Q000453:epidemiology; D003024:Clozapine / Q000009:adverse effects* / Q000627:therapeutic use; D015897:Comorbidity; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects / Q000706:statistics & numerical data*; D005260:Female; D006331:Heart Diseases / Q000139:chemically induced / Q000175:diagnosis*; D006801:Humans; D007024:Hypotension, Orthostatic / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012044:Regression Analysis; D012189:Retrospective Studies; D012737:Sex Factors; D013610:Tachycardia / Q000453:epidemiology
D014150:Antipsychotic Agents; D003024:Clozapine