Therapeutic options for patients with heart failure just broadened—again. The recent introduction of biventricular pacing has meant a valuable addition to the cardiologist's toolbox, good news for the five million Americans who have congestive heart failure. Henry M. Spotnitz, MD, George M. Humphreys II Professor of Surgery at Columbia University College of Physicians and Surgeons and Vice Chairman for Research and Information Systems at the Department of Surgery, is working to gain the fullest potential of this extraordinary technology. He and his team are now researching ways to bring its benefit to other kinds of patients and to optimize its function for those who benefit from it already.
The first of two trials being conducted by Dr. Spotnitz investigates the use of biventricular pacing in patients who develop acute heart failure. The second seeks to maximize the effectiveness of the biventricular pacemaker by altering the location of pacemaker lead wires and the timing of their electrical stimulation.
While a standard pacemaker corrects a heart rhythm that is too slow or too fast, biventricular pacing corrects heartbeats that have normal rhythm, but are inefficient because the walls of the left ventricle (the main pumping chamber of the heart) fail to contract simultaneously. Such inefficiency occurs in 20 to 30% of people with heart failure.
Heart failure, marked by an inability of one or more of the heart's chambers to pump enough blood to meet the body's needs, can cause dangerous enlargement of the heart, leakage of blood through the mitral valve, congestion in the lungs, and symptoms such as shortness of breath and pain, swelling in the legs, kidney failure, and other problems. In chronic heart failure, the gradual development of the problem allows the heart to compensate by thickening or enlarging. When the condition develops suddenly, in acute heart failure, such as after a heart attack or a surgical procedure, the heart does not have time to compensate for electrical impulses that have gone awry, and it is often fatal.
Also called cardiac resynchronization therapy (CRT), biventricular pacing synchronizes contractions of the opposing walls of the left ventricle. In so doing, it coordinates the walls of the left ventricle to pump together correctly. Placement involves implantation of a dual-chamber pacemaker with a third lead-wire into the back of the heart. Biventricular pacing is a standard treatment for chronic heart failure today, offering improvement in patients' symptoms, exercise capacity, and quality and length of life. Dr. Spotnitz believes that the benefits of biventricular pacing for patients with chronic heart failure may also be applied to save the lives of patients with acute heart failure.
Trial 1: In the acute heart failure study, Dr. Spotnitz's team is comparing the effects of biventricular pacing with no pacing in patients with heart failure after undergoing coronary artery bypass grafting (CABG) surgery. "Immediately after open heart surgery, some patients require treatment for low cardiac output. Conventional drug treatments may pose dangers during this vulnerable time, including arrhythmias, impaired oxygenation of some areas of the heart, and increased oxygen consumption. Biventricular pacing may be able to restore the heart's function without causing these problems," Dr. Spotnitz explains.
Dr. Spotnitz believes that biventricular pacing will prove valuable for acute heart failure after open heart surgery, and that it is preferable to standard pacing. "There is a great deal of potential benefit for patients with both acute and chronic heart failure, but this is not well understood and requires systematic study," he says. So far, data indicate that compared to standard pacing, biventricular pacing increases the heart's output by 10%.
Trial 2: In the second study, Dr. Spotnitz is testing the effects of optimizing the location of the lead wires on the ventricles, and the timing of the electric impulses they send to the heart. "Studies have shown that adjusting the timing and the precise location are very important factors in determining how well a biventricular pacemaker works. Its effectiveness can be greatly increased by optimizing these parameters." To assess these factors, Dr. Spotnitz is leading a randomized trial testing different combinations of lead placement and timing. "There is a dramatic difference between the worst combination and the best combination of site location and timing," explains Dr. Spotnitz. "In the initial, exploratory stage of this trial, patients' cardiac output more than doubled when these parameters were optimized." At this time, Dr. Spotnitz is working with the Food and Drug Administration (FDA) to obtain an Investigational Device Exemption (IDE) to move to the next phase of the study.
"Biventricular pacemakers help some patients dramatically, and some not at all. In those who are not helped, is it because of the wrong combination of site location and timing? Or were they not good candidates for this therapy?" Dr. Spotnitz believes that when these and other questions are answered in clinical trials and this understanding is incorporated into the manufacture of devices, the benefits for all patients with heart failure will be substantial.
To learn more about biventricular pacing for heart failure, contact Henry M. Spotnitz, MD at 212.304.7810.
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