The rate of dysrhythmias requiring a shock from an implanted cardioverter-defibrillator more than doubled among New York City-area heart patients the month after the September 11, 2001 terrorist attacks, according to a presentation at the American Heart Association's Scientific Sessions.

Researchers obtained device data on the 30 days preceding the attack and the 30 days following it for 200 patients (average age, 69 years) who were treated at six clinics within 100 miles of the World Trade Center. The devices had been implanted an average of 2.5 years before the terrorist attacks. In the month before the attack, 3.5 percent (seven patients) had dysrhythmias that required electrical shocks. In the 30 days after the attack, 8 percent (sixteen patients) did- a 2.3-fold increase.

The results provide compelling evidence of the impact of stress on the heart, said Marcin Kowalski, M.D., a physician in New York City. Even more important, he added, was the importance of the devices as a life-saving intervention.

"These patients all had potentially lethal arrhythmias in the 30 days after the attack, and they were all successfully treated [by implantable cardioverter-defibrillators]," Kowalski noted. "This is just another example showing that patients really benefit [from the devices] and that implantable cardioverter-defibrillators can help save lives."

Previous studies have evaluated how stressful events such as earthquakes and missile attacks have affected the heart in terms of myocardial infarction and sudden death.

"These previous studies showed a spike in the occurrence of heart attack or sudden death for a short period after the incidents," says Jonathan S. Steinberg, M.D., also of New York City. "The increase in cardiac events tends to be short-lived and very closely coupled to the inciting event, such as an earthquake."

The increases in discharge did not occur until 3 days after the terrorist attack and continued to occur at a cumulative rate throughout the remainder of the 30-day study period. The discharge rate returned to pre-attack levels and remained at 2 percent to 3 percent per month during several additional months of monitoring.

Why the pattern of longer-term increase in dysrhythmia differed from the short-term patterns seen in other studies is unclear. A future study will evaluate whether proximity to the attack site - specifically, living closer to Ground Zero - influenced a patient’s likelihood of having an arrhythmia after the terrorist attack. Several medical centers around the country will participate in this investigation.

"Physicians and patients need to be aware that real-life, stressful events can trigger arrhythmias," Steinberg said. "Physicians should encourage patients with implantable cardioverter-defibrillators to practice stress-reduction and stress-avoidance techniques. It's also important to protect patients against the effects of increased nervous-system stimulation by giving them beta-blockers."

Additional research may enable physicians to develop treatment guidelines for cardiac patients that can be implemented after an event such as a terrorist attack to protect patients from the effects of sustained high stress.