Cardiovascular monitoring in patients prescribed clozapine

Wilson et al ¹ highlight the ongoing issue of poor physical health monitoring in patients prescribed clozapine. We recently presented a survey which investigated standards of physical health monitoring in adult patients (n=98) prescribed clozapine against standards set out by Maudsley Guidelines in which we found similarly high rates (53%) of clozapine augmentation and antipsychotic polypharmacy (details available from the authors on request). Moreover, cardiovascular monitoring was poor with only 30% of patients having had a baseline electrocardiogram prior to initiation of clozapine. Similarly, only 28% had yearly electrocardiogram monitoring performed once clozapine therapy had been established. Of those patients established on clozapine therapy, 34% were found to have asymptomatic sinus tachycardia, which was more commonly seen in patients prescribed additional antipsychotic medication than those prescribed clozapine alone (P<0.001). Clinical actions in response to asymptomatic sinus tachycardia varied enormously, with only 12% of cases having been discussed with local cardiology services.

These findings are of great concern when one considers that clozapine is associated with potentially life-threatening adverse cardiovascular conditions such as myocarditis and cardiomyopathy. ² While tachycardia is commonly seen during the early stages of clozapine treatment, occurring in up to 50% of patients, sustained tachycardia, defined as a heart rate >100 bpm for more than 6 months, can precipitate cardiomyopathy and appears to be an independent risk factor for sudden cardiac death. ³ Reducing clozapine dose and the use of rate-limiting drugs such as beta-blockers have been suggested as potential solutions to this problem, ⁴ although these options may not always be clinically appropriate and there appears to be a broad range of approaches in dealing with this.

In response to these findings we have introduced a system whereby initiation of clozapine therapy and its continued prescription by our pharmacy department is contingent on evidence of baseline and continued cardiovascular monitoring. We have also developed a shared care pathway with our local cardiology department ensuring that cardiac monitoring is optimised in this vulnerable patient group and that management of sustained tachycardia is jointly managed by both psychiatric and cardiology services. Information on this shared care pathway is available from the corresponding author.