Clinical course and analysis of ten fatal cases of clozapine-induced myocarditis and comparison with 66 surviving cases.

Background: Fatal clozapine-induced myocarditis has not been investigated systematically. We describe the clinical course of 10 fatal cases of myocarditis with clozapine and identify factors associated with fatality.

Methods: Cases of myocarditis were documented from the patient's medical records and fatal cases also from autopsy reports.

Results: The fatal cases of myocarditis occurred 1996-2009 and were diagnosed at autopsy. Before death, three had no symptoms of illness and only three had cardiac-specific diagnostic results. None was investigated by cardiac imaging techniques, and in none was myocarditis suspected before death. Duration of clozapine for the fatal cases was 14-33 days with an outlier at 4.5 months. Only 3 cases had significant coronary artery disease at autopsy. Comparison of these ten cases with 66 non-fatal cases indicated no significant difference in gender, age, smoking status, dose at onset or concomitant sodium valproate. However, obesity (BMI > 30 kg/m2) was significantly more frequent among fatal than non-fatal cases (60% vs. 26%; p < 0.03) and duration of clozapine was significantly longer for fatal cases (20.8 vs. 17.0 days; p < 0.006), after exclusion of one outlier. Creatine kinase (CK) > 1000 U/L was also associated with death (p = 0.0004).

Conclusions: Routine monitoring for myocarditis for the first 4 weeks of clozapine, and discontinuation of clozapine in the presence of evidence consistent with myocarditis may assist to prevent fatalities occurring from early-onset myocarditis. Investigation by cardiac imaging will give a measure of severity and need for intervention. Obesity may increase the risk of mortality and CK > 1000 U/L may indicate life-threatening illness.