Automated External Defibrillators offer no benefit in cardiac arrests that occur at home in the HAT trial

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April 1, 2008 By Lauren Ciaglo [mailto: lciaglo@perfuse.org]

ACC 08-Chicago, IL: Results from the HAT (Home external Automated Defibrillator) trial demonstrate that survival rates did not improve among patients with access to a home AED compared with patients with only an EMS call and a companion with CPR training. The HAT trial results were presented by Dr. Gust H. Bardy at the American College of Cardiology 57th Annual Scientific Sessions today in Chicago.

Although the AEDs have been shown to improve survival rates in public places, its benefit in patients’ home is not known given the vast majority of sudden cardiac arrests (SCA) occur at home. The HAT study included 7,001 patients with prior anterior-wall myocardial infarction (MI) randomized to either the use of a home AED or to calling the EMS and performing CPR (control group). Patients in the study were not eligible for implantable cardioverter-defibrillators. The median age of patients was 62 years, 83 percent were male, and the median follow-up was 37.3 months.

The primary endpoint of the study was all-cause mortality with secondary endpoints consisting of death from SCA, survival from SCA witnessed at home, and the final outcome after the use of an AED.

After three and a half years of follow-up, a total of 450 patients died: 6.5% (n=228) in the control arm and 6.4% (n=222) in the AED arm. The risk of death was similar among the two groups (HR 0.97, 95% CI 0.81-1.17, p=0.77). At the four year follow-up, the mean annual mortality rate was 2.1% and 2.0% in each group, respectively. There was no difference in the primary endpoint among the prespecified subgroups according to age (>65 years vs. <65 years), sex, Q- vs. non-Q-wave MI, and nationality (U.S. vs. non-U.S.). The difference in treatment in patients with diabetes compared with non-diabetics was statistically significant (p=0.04).

Of the 450 deaths, 37.6% (n=169) were due to tachyarrhythmia, 21.3% were due to heart failure or non arrhythmic cardiac causes, and 37.8% (n=170) were due to non cardiac causes.

The investigators indicate that a likely limitation of the HAT trial is the efficacy and high use of modern pharmacotherapy combined with the high rate of prior revascularization in the patient population (72.2%); thus, the trial had less power than was initially projected. Additionally, training patients and their companions in CPR and frequently stressing the importance of calling EMS may have been a limiting factor because this education may not reflect real-world direction after MI.

Although the HAT trial found that placing an AED in the patient’s home yielded no reduction in overall mortality, it is noteworthy that this strategy may prove benficial among higher risk populations. Further studies should be performed to examine the possible benefits among other groups.

Source

1. Late Breaking Clinical Trials Session: American College of Cardiology 57th Annual Scientific Sessions April 1, 2008 Chicago
2. Bardy GH, et. al. Home Use of Automated External Defibrillators For Sudden Cardiac Arrest. New Engl J Med. April 2008: 358.

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