Heart attack survivors have a 12 percent increased risk for sudden cardiac death.An implantable defibrillator can jump start the heart after sudden cardiac arrest and reduce the risk for death.

Heart Attacks
A heart attack occurs when the blood supply to a part of heart muscle is cut off, depriving the tissue of oxygen and causing the affected area to die. The blockage can be caused by a clot or debris that becomes trapped in a narrowed coronary artery, or when fatty deposits and plaque build up enough to clog the artery.

According to the American Heart Association, more than 12.5 million Americans will have a heart attack this year. The average age for a first heart attack is 64.5 for men and 70.3 for women. In 2006, 587,000 Americans died of a heart attack. Those who survive have up to a 15 times higher risk of death than those who haven’t had a heart attack.

Sudden Cardiac Arrest after Heart Attack
Sudden cardiac arrest is a condition in which the heart unexpectedly stops beating. It’s usually precipitated by an abnormal heart beat (ventricular fibrillation) which causes the lower chambers of the heart to beat rapidly and irregularly. The heart can’t effectively pump during this chaotic rhythm and eventually, the muscle quivers and stops beating. If the person is not revived (i.e., an electrical shock is delivered to the heart muscle), death occurs rapidly (called sudden cardiac death).

According to the National Heart, Lung and Blood Institute, annually, up to 450,000 Americans experience sudden cardiac arrest. 95 percent of patients die, most within a few minutes. Two of the most important risk factors for sudden cardiac arrest are prior heart attack and coronary artery disease. These conditions can cause scarring and affect the way electrical impulses move through the heart. An abnormal heart rhythm can be triggered when the electrical impulses follow an abnormal pathway.

Reducing the Risk of Sudden Cardiac Arrest
During the first three months after a heart attack, researchers estimate survivors have about a 12 percent risk for sudden cardiac death. Normally, for people with life-threatening arrhythmias, doctors may recommend implantation of a defibrillator, a device which monitors heart rhythms. When a dangerous arrhythmia is detected, a small electrical charge is emitted to shock the heart and restore a normal heart rhythm. But implantation of a defibrillator in every heart attack survivor would be costly, and, in a majority of patients, not necessary.

Parag Patel, D.O., Interventional Cardiologist with Advocate Lutheran General Hospital in Park Ridge, IL, says the greatest uncertainty for sudden cardiac arrest comes within the first two months after a heart attack. After that, patients who still have weak heart muscles (as determined by a low ejection fraction, or the rate at which the blood leaves the heart) are more likely to benefit from a defibrillator. But even among those, there are patients who never require a shock.

Researchers are now conducting a clinical trial to determine if doctors can predict which heart attack survivors would most benefit from a defibrillator. The Phase III study is called Evaluating the Effectiveness of the LifeVest Defibrillator and Improving Methods for Determining the Use of Implantable Cardioverter Defibrillators, or the VEST/PREDICTS study.

The VEST/PREDICTS study is divided into two parts. In the first part, patients who have had a recent heart attack will be randomly assigned to one of two groups. The first group will receive usual care. Those in the second group will wear a LifeVest, a type of defibrillator that is worn outside the body. The LifeVest must be removed for showering, but will be worn as close to 24 hours a day as possible. At the end of two months, all participants will return for further assessment.

The second part of the study begins right after the first part ends. At the two month assessment, those from either group who are found to have poor heart function will get an implantable defibrillator. Everyone else will have a different implantable device (called Reveal) that monitors and records arrhythmias, but doesn’t treat them. The information from the Reveal device will be transmitted by a wireless connection to a computer and sent to a monitoring station. The second half of the study will last from one to eight years. Doctors will follow the natural history of heart function and any medication or therapy changes needed by the patient.

Patel is hopeful the information gained from the VEST/PREDICTS study will provide clues as to who is at greatest risk for sudden cardiac arrest after a heart attack and who may benefit most from a defibrillator. Participation in the VEST/PREDICTS study is by invitation only. For more information, go to http://www.clinicaltrials.gov, then type the trial identification number in the search box: NCT00628966.

AUDIENCE INQUIRY
The VEST/PREDICTS study is enrolling by invitation only. For more information, go to http://www.clinicaltrials.gov, then type the trial identification number in the search box: NCT00628966.

For information on the LifeVest, go to http://www.zoll.lifecor.com

For general information on heart attack, cardiac arrest or heart rhythm problems:
American Heart Association, http://www.americanheart.org
Heart Rhythm Society, http://www.hrsonline.org
National Heart, Lung and Blood Institute, http://www.nhlbi.nih.gov

Research compiled and edited by Barbara J. Fister

© 2010 Medstar Television, Inc. All Rights Reserved
 

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