Anti-Arrhythmic Effects of Exercise After an Implantable Cardioverter Defibrillator (ICD)

An ICD is a device designed to quickly detect a life-threatening, rapid heartbeat. Through a process called defibrillation, the ICD tries to convert an abnormal heart rhythm back to normal by delivering an electrical shock to the heart. The ICD continuously monitors heartbeats to ensure that they are normal, and it only delivers a shock to the heart when it senses a life-threatening rhythm. People who have experienced ventricular fibrillation, which is a severely abnormal heart rhythm, or ventricular tachycardia, which is a rapid heart beat that begins in the bottom chambers of the heart, are common recipients of an ICD. Other potential ICD recipients include people who have survived a heart attack, but have weak hearts; people with heart muscle problems; and people with reduced pumping function in their heart. People who have ICDs may benefit from aerobic exercise to improve their physical fitness and overall health. The purpose of this study is to evaluate the effectiveness of an exercise program at improving heart and lung function in people who have an ICD.

In this 6-month study, participants will be randomly assigned to either take part in the exercise program or receive usual care. At a baseline study visit, all participants will complete an exercise treadmill test, wear a Holter monitor to record heart activity for 24 hours, undergo blood collection, and complete questionnaires to assess quality of life, anxiety, and depression. Participants taking part in the exercise program will receive 1 hour of exercise education over the telephone. During Weeks 1 through 8, participants will stretch for 10 minutes and walk 1 hour daily for 5 days a week; during Weeks 9 through 24, participants will walk 30 minutes daily for 5 days a week. Participants will wear a Polar Heart Rate monitor to record their heart rate and a pedometer to keep track of the number of steps walked. They will also record details of their exercise in a daily activity log. Throughout the entire study, a study nurse will call participants on a weekly basis to check on their progress and to help resolve any exercise-related problems. At Weeks 8 and 24, all participants including those receiving usual care, will attend a study visit for repeat baseline evaluations. Study researchers will review medical records to collect various information, including the reason for needing an ICD, the type and settings of the ICD, medication use, medical history, current health problems, lab test results, echocardiogram images of the heart, and electrocardiogram (EKG) results.