Stress Can Cause Heart to Misfire

Anger and frustration are more likely to kick a susceptible heart into potentially fatal irregular rhythm than exercise is, U.S.-based researchers reported.

Tests on patients with an implanted defibrillator -- a pacemaker-like device which kicks in to shock the heart back to a normal rhythm -- suggest that mental stress affects the heart through a different pathway that does strenuous exercise, the researchers said.

"There is folklore and epidemiological evidence that aggravation can trigger heart attacks," said Willem Kop of the Uniformed Services University of the Health Sciences in Bethesda, Maryland.

But he said his was the first study to actually show that being angry or mentally stressed can cause arrhythmia, or an irregular heartbeat, among high-risk patients.

These disruptions from mental stress are seen at significantly lower heart rates than those related to exercise, said Kop, who led the study.

Writing in the journal Circulation, Kop and colleagues said they used electrocardiograms to measure fluctuations in heart rate called T-wave alternans, which can precede arrhythmias, in 23 patients with an average age of 62. All the patients had implantable cardioverter defibrillators, or ICDs.

To stress the volunteers, the researchers asked them to recall a recent incident that angered them and also made them subtract multiples of the number seven from a four-digit sum, while interrupting them and telling them to do better.

They also tested 17 healthy volunteers without heart trouble who were matched for age and gender.

Heart medications were withheld from most of the patients before testing, including ACE inhibitors, long-acting nitrates, beta-blockers and calcium channel blockers, they said.

After adjusting for heart rate, mental stress and exercise provoked higher T-wave alternans responses in defibrillator patients than in the volunteers without the devices.

Kop said this suggests that different nervous system mechanisms are involved when mental stress affects the heart that when exercise does.