Studies Confirm Value of Bystander AED Use, Blood Pressure Seasonality

The American Heart Association's Scientific Sessions 2007, being held through tomorrow in Orlando, are delivering their typical spate of important health news and research announcements. Two of the latest reports show that patients' high blood pressure improves in summer and worsens in winter, no matter where they live, and that bystanders' use of AEDs definitively saves more sudden cardiac arrest victims' lives than does CPR alone.

The five-year blood pressure study analyzed 443,632 high blood pressure patients' electronic health records from 15 VA hospitals in warmer and colder U.S. cities. Researchers found a significant seasonal variation in every city. "The bottom line is that regardless of whether you're in Anchorage, Alaska, or San Juan, Puerto Rico, there is a difference in high blood pressure returning to normal in the winter compared to the summer," said Dr. Ross D. Fletcher, the study's lead author and chief of staff at the VA Medical Center in Washington, D.C. The average age of veterans in the study was 66, with 51 percent classified as Caucasian, 21 percent as Hispanic, and 27 percent as black. Only 3.7 percent were women. Fletcher said weight gain and exercise may play a role in the seasonal variations.

The second study, reported Nov. 5 by AHA News, showed that CPR combined with a bystander's use of an automated external defibrillator more than doubled the chances of surviving out-of-hospital cardiac arrest when compared with using CPR alone. The authors estimated bystander CPR plus AED use in the United States and Canada saves 522 lives a year. "This is not a randomized, controlled study, but it describes what is going on in the real world, where people at the scene of a cardiac arrest are saving lives," Dr. Myron L. Weisfeldt, chairman of medicine at Johns Hopkins University in Baltimore and lead investigator of the study, said in the AHA News report. The study included 10,663 patients who had out-of-hospital cardiac arrests between Dec. 1, 2005, and Nov. 30, 2006, and were evaluated by EMS personnel. Bystanders performed CPR in 29.9 percent of the cases and used an AED with CPR in 2.4 percent. While 7 percent of the patients survived to hospital discharge, bystander CPR alone resulted in a 9 percent survival rate and bystanders CPR and AED use resulted in a 36 percent survival rate, according to the AHA News report.

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