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Comparing the Effects of Clozapine with Non-clozapine on Heart Rate Variability in Patients with Schizophrenia

Hui-Ying Chou, Yueh-Ming Tai, Hsin-Te Huang

Objectives: With portable wireless heart rate detector, we intended in this
study to investigate autonomic nervous activities with heart rate variability analysis
during different daily activities in patients with schizophrenia treated with clozapine
and non-clozapine antipsychotic drugs. Methods: We enrolled 30 male
inpatients with schizophrenia (9 with clozapine treatment, 21 with non-clozapine
antipsychotic treatment) participated. They received a 24-hr electrocardiogram recordings
during 24 hours daily-life activities as usual and 3-minute step-test exercise.
Their records were manually divided into fi ve periods of activities, namely,
daytime, nap, sleep, exercise, and after exercise. Results: Compared to those with
non-clozapine antipsychotics, the patients with clozapine were found to be signifi -
cantly associated with increased heart rates and elevated low frequency/high-frequency
ratio during all fi ve daily activities (all p < 0.001). Clozapine group was
also demonstrated signifi cantly decreased high frequency band power only in after-
exercise state (p < 0.01). The signifi cant difference in resting heart rate recovery
ratios between two groups was found (p < 0.01) especially at the third and
fourth minutes after exercise (all p < 0.01). Conclusion: In line with existing studies,
the results confi rmed changes in autonomic nervous activity in patients treated
with clozapine, with marked difference at all day activities and heart rate recovery
after exercise. These changes are primarily due to drug-related elevation in sympathetic
activity and inhibition in vagal tone, independent of age, depression and
severity of symptoms. The data also suggested a possible risk of cardiovascular
adversity in the clozapine treatment among patients with chronic schizophrenia
especially after exercises.
Key Word clozapine, schizophrenia, vagal tone, heart rate recovery after exercise
Editorial Committe, Taiwanese Journal of Psychiatry
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