People with implantable cardioverter-defibrillators are more likely to experience ventricular arrhythmias when they are exercising or are angry, according to research published in the September 10th rapid access issue of the journal Circulation.

"We were interested in finding what triggers these dangerous rhythms," says the study's senior author Diwakar Jain, M.D. "We were able to take recordings from the defibrillators, identify when arrhythmias occurred, and correlate that information with reports of mood and physical exertion."

Observational studies have suggested that psychological stress increases the risk of sudden death in the general population. According to the authors, only indirect or anecdotal evidence had previously suggested that anger and vigorous exercise play a significant role in arrhythmias.

Between 1996 and 1999, 240 patients completed diaries that reflected mood and physical exertion levels on a five-point intensity scale. After receiving a shock from their defibrillators, patients recorded the emotions they were feeling shortly before the shock. They served as their own controls by recording their emotions at the same time one week later (the control period).

A total of 42 patients (including 33 men, average age 65 years) had 107 confirmed ventricular arrhythmias requiring shock. Anger level was rated at three of five or higher in 15 percent of shock events versus 3 percent of control periods. The 15 percent who were shocked during emotional periods were driving, arguing, gambling, or had received bad news.

Patients were engaged in physical activity (level four of five or greater) within 15 minutes preceding 53 percent of shocks versus 32 percent of control periods. The exertion included walking slowly or vigorously, recreational activity, or physical activity at work.

Jain asserted that the study suggests anger management techniques and ways to block responses to physical stressors may help avoid arrhythmia incidents.