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Tip
Sheet: Medical Science & Health Tip sheets highlight timely news and events at Washington University in St. Louis. For more information on any of the stories below or for assistance in arranging interviews, please see the contact information listed with each story. For comments on the Medical Science & Health news tips service, please contact the editor, Jim Dryden at (314) 286-0110 or drydenj@msnotes.wustl.edu. Half of all failed hearts stop suddenly; a new device reduces the risk of death by 40 percent Media assistance: Gila Z. Reckess - (314) 286-0109 Source: Mitchell N. Faddis' Web page Source: More information on Faddis Source: Gregory A. Ewald's Web page Source: More information on Ewald Source: Joseph G. Rogers' Web page Source: More information on Rogers [St. Louis, Mo., February 2003] - Roughly 5 million Americans suffer from congestive heart failure. That means their hearts cannot sufficiently supply the body with blood. This mechanical malfunction can occur for a number of reasons, but the cause is largely irrelevant for the sickest patients -- They require either a heart transplant or a device that can act like a new heart to take over for the old one. On the other end of the spectrum, patients with less severe heart failure often can control their conditions using medications.
"This trial was the largest in history to test an implanted pacemaker or defibrillator, and it represents a landmark study for the treatment of congestive heart failure," says Faddis. "I think it is one of the most important therapies developed in the last decade for the treatment of severe heart disease." The trial, called COMPANION (Comparison of Medical Therapy, Pacing and Defibrillation in Chronic Heart Failure), was sponsored by Guidant Co. It evaluated the ability of a two-component device to prevent life-threatening heart-rhythm abnormalities. The device is both a biventricular pacemaker -- to supply electrical signals to both lower chambers of the heart -- and a defibrillator, which can jolt the heart back to life if it suddenly stops beating properly.
In some patients, the electrical system is completely askew, but the mechanical system is relatively healthy. Those people benefit from traditional pacemakers, which serve as surrogates for the malfunctioning component of the electrical system, either the sinus node or the atrioventricular node. In roughly one-third of patients with congestive heart failure, the sinus and atrioventricular nodes are functioning well, but two of the three sub-branches are effectively broken. As a result, the electric signal fails to reach the right and left lower chambers at the same time. When the left side contracts, the right side is relaxed and vice versa. Blood then sloshes back and forth, rather than being forced outward by a two-sided, synchronized effort. A weakened heart only has a small amount of mechanical energy left to contract the heart muscles. If the same patient also experiences a time delay between contraction of the right and left sides of the heart, the limited mechanical energy left over is used up before enough blood can be pumped out. Traditional pacemakers supply two wires to the heart: one to the upper right chamber; one to the lower right chamber. The biventricular pacemaker adds a third wire, which connects to the lower left chamber. With this third wire, the pumping action of the heart's right and left lower chambers is re-coordinated. That's why the COMPANION trial looked at whether biventricular pacing could improve patients' quality of life and help prevent sudden death in heart failure patients who have not experienced rhythm abnormalities, but who still have trouble breathing, despite medical treatment. "Many of our patients had a dramatically positive response," says Faddis. "This treatment has the potential to drastically improve the quality and duration of life for about 30 percent of all patients who are severely limited by weak hearts, and it was particularly gratifying to be a part of trial because of the improvements that so many of my patients experienced." |
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