For survivors of anterior-wall MI who were not candidates for implantation of a cardioverter–defibrillator, access to a home automated external defibrillator (AED) did not significantly improve survival, compared with reliance on conventional resuscitation methods, according to results from the Home Automated External Defibrillator Trial (HAT) presented Tuesday by Gust H. Bardy, MD, at the 2008 American College of Cardiology (ACC) Scientific Sessions in Chicago.
Every two to three minutes, someone in the U.S. experiences a sudden cardiac arrest, usually in the home. As a result, there are approximately 166,200 out-of-hospital cardiac arrests annually. Rescuing the patients at home presents logistical problems for emergency medical services (EMS) systems that are routinely challenged to reach patients in a timely manner with potentially life-saving care.
The National Heart, Lung, and Blood Institute sponsored the international, multicenter HAT trial, published Tuesday in the New England Journal of Medicine. Philips Medical Systems and Laerdal Medical, as a subsidiary distributor, provided the HeartStart AEDs free of charge, which normally cost $1,300 for the FDA-approved over-the-counter sale.
Bardy of the Seattle Institute for Cardiac Research said that the HAT trial sought to determine whether access to an AED can improve survival rates in patients at relatively low risk of sudden cardiac arrest by providing immediate, home-based defibrillation.
From Jan. 23, 2003, to Oct. 20, 2005, a total of 7,001 patients underwent randomization at 178 clinical sites in seven countries; 3,506 patients were assigned to the control group, and 3,495 were assigned to the AED group. The patients were enrolled at centers in the United States, Canada, Australia, the United Kingdom, New Zealand, the Netherlands and Germany.
The median age of the patients was 62 years; 17.4 percent were women, and 12.9 percent were members of an ethnic minority group. At baseline, all patients had an anterior-wall MI; 64.4 percent had a Q-wave event, and 35.6 percent had a non–Q-wave event.
After an average follow-up of three years, the researchers reported that a total of 450 patients died. Of these patients, 228 (6.5 percent) were in the control group, and 222 (6.4 percent) were in the AED group, producing a similar risk of death to the control group.
Bardy reported that 169 of the 450 deaths (37.6 percent) were deemed to be caused by tachyarrhythmia (i.e., consistent with ventricular fibrillation or ventricular tachycardia). Of the 169 deaths from cardiac tachyarrhythmia, 160 were from sudden cardiac arrest. He said that 38 patients were resuscitated from sudden cardiac arrest and survived for at least 48 hours.
Home defibrillators currently account for less than $20 million of the $192 million market for portable defibrillators outside of hospitals, Mike Arani, an analyst with the market research firm Frost & Sullivan, told the New York Times. Advocates of the technology had hoped that positive results from the clinical trial might encourage investments to drive down the price to as little as $500, potentially leading to a surge in sales, the NY Times reported.
The researchers found that “placing an AED in the home did not reduce overall mortality in patients with a previous anterior-wall MI who did not have an indication for implantation of a cardioverter–defibrillator, as compared with standard response training for cardiac arrest.”
The investigators also noted that the “training of the patients and their spouses or companions may have been an additional factor limiting the likelihood of a demonstrable benefit. All participants in the control group received resuscitation training, with frequent reminders; such education is not reflective of real-world instruction after MI.”
However, the researchers still hope to find a method of improving survival in post-MI patients.
“We are looking at ways to really improve survival in patients who have survived a heart attack,” said Bardy. “The HAT study gives us important insights into the challenges and opportunities related to at-home care for these patients, even if they are not considered to be traditionally high-risk.”