Elevated defibrillation threshold with venlafaxine therapy.

Depression is a common comorbidity in patients with heart failure or implantable cardioverter-defibrillators (ICDs). A 35-year-old woman with depression, nonischemic cardiomyopathy, and a history of cardiac arrest had an ICD implanted. During initial testing, the device failed to internally defibrillate the patient. Venlafaxine, an antidepressant with cardiac sodium channel blocking activity, was identified as a potential contributor to her elevated defibrillation threshold. After the venlafaxine was discontinued, the ICD was able to successfully internally defibrillate the patient. Clinicians should be aware of this potential adverse drug-device interaction. Further studies are needed to determine the clinical significance of venlafaxine therapy in patients with ICDs.