PubMed · 15825840
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Dorin Panescu. Cardiac resynchronization therapy.. https://doi.org/10.1109/memb.2005.1411342
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BACKGROUND: Cardiac resynchronization therapy (CRT) has been demonstrated to be an effective heart failure (HF) therapy. All pivotal trials of CRT to date have used atrial-synchronous biventricular pacing wherein there is no or minimal atrial pacing. In clinical practice, however, physicians often program CRT devices to have atrial rate support pacing, either by increasing the lower rate limit or by activating the rate sensor. OBJECTIVE: The purpose of this study is to evaluate the effect of empiric atrial support pacing in patients with HF who have received a CRT defibrillator (CRT-D) device. METHODS: PEGASUS CRT is a multicenter, 3-arm, randomized clinical trial of approximately 1200 patients receiving a CRT-D device. For the first 6 weeks after implant, devices are programmed to DDD with a lower rate limit of 40 beats/min. At 6 weeks, patients are randomized to DDD-40, DDD-70, or DDDR-40. All randomized patients are followed for 1 year, and at each visit, mortality, HF events, quality of life, New York Heart Association class, and atrial and ventricular arrhythmic episodes are evaluated. An exercise substudy will also be conducted, enrolling a minimum of 375 patients. Patients in this substudy will complete 2 cardiopulmonary exercise tests to evaluate the effect pacing mode has on exercise capacity. This randomized controlled trial will address whether empiric atrial support pacing is of clinical benefit to patients with HF who receive a CRT-D device.
BACKGROUND: Cardiac resynchronization therapy has been shown to be an effective treatment to improve functional status and prolong survival among patients with advanced congestive heart failure. However, as many as 30% of patients do not respond. Nonresponse may be due to suboptimal left ventricular lead placement. Studies have indicated that leads placed in the midlateral left ventricle (LV) wall usually result in improved dP/dT and increased pulse pressure, compared with other locations. When the surgeon is placing the leads thoracoscopically, however, in a chest with multiple adhesions, anatomic landmarks can be obscured. It is desirable to have an objective physiologic method to determine optimal lead placement. The optimal LV pacing site may be best determined by locating the site with the latest depolarization. METHODS: A pacing lead attached to a pulse analyzer was introduced through a thoracoscopic port and used as a mapping electrode to electrically map exposed areas of the left ventricle. The right ventricular pacing lead was also attached to the pulse analyzer and the interval between the right ventricular pulse and the LV depolarization (paced depolarization interval) was measured in 19 patients undergoing thoracoscopic LV lead placement. A site with a paced depolarization interval less than 110 ms was not accepted. RESULTS: Electrical mapping was possible in 19 of 29 consecutive patients in whom it was attempted. The most frequent reason for not mapping was the presence of extensive scarring. In 7 of 19 patients (36.8%) mapped, the site that would have been chosen by anatomic landmarks was not the site with the longest paced depolarization interval, and thus the lead placement was altered. CONCLUSIONS: The site with the longest paced depolarization interval is only selected 63.2% of the time when utilizing anatomic landmarks for placement. Nonresponse may be due to suboptimal LV lead placement. Measurement of paced depolarization intervals provides a physiologic method of determining optimal LV lead placement.
Complete heart block developed in more than 10% of C. Walton Lillehei's early patients undergoing closure of ventricular septal defects, and hospital mortality was 100% in this group of patients. This problem of early fatality from heart block was completely eliminated with the use of a myocardial electrode in combination with an external plug-in electric stimulator. This method of treatment, suggested by Dr John A. Johnson, a professor of physiology at the University of Minnesota, was first used by Dr Lillehei on January 30, 1957. The next 3 years would witness the development of a portable, external, battery-powered pacemaker, and then an implantable pacemaker available for thousands of patients susceptible to lethal Stokes-Adams attacks. Fifty years have passed, and in 2005, approximately 800,000 pacemakers were implanted worldwide.