Heart rate variability and clozapine in patients suffering from schizophrenia

Objectives Recent studies describe autonomic dysregulation in patients suffering from schizophrenia especially a decreased vagal modulation in heart rate. It is well known that heart rate variability (HRV), a measure allowing the assessment of the activity of autonomic nervous system (ANS), is highly influenced by treatments but this is poorly taken into account in the field of psychiatry. For example, clozapine is known to be responsible for induced tachycardia that could drastically influence the data analysis, leading to the confusion in conclusions drawn of a diminished HRV in schizophrenic patients. In order to improve HRV data analysis in patients suffering from schizophrenia, we propose to evaluate the impact of clozapine on this measure. Methods We conducted a prospective study of schizophrenic patients who were referred to the Caen University Hospital for the exploration of the autonomic nervous system. Twenty-four patients were examined between December 2014 and November 2016: 11 patients under clozapine, 12 patients under neuroleptic therapy and one with beta-blocker that was excluded from the study. Results There was no difference between groups in age, gender, age of onset, duration of illness or severity of illness assessed with the PANSS total score. However, heart rate was significantly higher in patients with clozapine than in other patients (100.2 vs 77.6 bpm), HRV was significantly lower during rest (34.7 vs 8.3) and in the deep breathing test assessed by RMSSD (49.4 vs 10.5). The Valsalva ratio was also lower in the clozapine population (2.0 vs 1.5). There was no difference between the two populations during the orthostatistic test. Conclusion Our results show that clozapine treatment profoundly influences HRV in schizophrenic patients. This must be taken into account in further studies to better understand ANS activity in this population.