The Connecticut Cardiovascular Consortium: a unique, state-wide research collaboration to advance clinical outcomes in patients with heart disease.

The establishment of "best clinical practices" founded upon evidence-based medicine has become an increasingly important priority. Frequently, management guidelines are derived from published research data and disseminated among practitioners to help optimize patient care. The ultimate clinical impact of these guidelines in the "real world," however, is often clouded by an incomplete assessment of patient outcomes throughout the continuum of health-care delivery models. In order to address this gap in clinical outcome assessment, we propose to establish the Connecticut Cardiovascular Consortium. The Consortium will consist of a collaborative partnership among all 31 Connecticut hospitals working in concert with Connecticut Office of Health Care Access (OHCA). The primary objective of the Consortium will be to assess, compare, and optimize clinical outcomes among Connecticut residents with cardiovascular disease. As an initial goal for the Consortium, we further propose to undertake a prospective, observational study of Connecticut residents who present with ST Segment Elevation Acute Myocardial Infarction (STEMI). Recent advances in pharmacologic and mechanical reperfusion for STEMI have resulted in a need to define the optimal use of these therapies in the community at large. The primary purpose of this study will be to determine the relative merits of different treatment patterns for STEMI with regard to the use of fibrinolytic therapy and percutaneous coronary intervention (PCI). Particular emphasis will be placed on assessing the relative benefits of urgent mechanical revascularization performed at the state's seven tertiary facilities with PCI capability compared to all other treatment modalities. Successful completion of this unique collaborative endeavor is expected to have significant impact on improved patient care and on current health-care policy for medical resource allocation. Moreover, continued collaboration of health-care providers within the Connecticut Cardiovascular Consortium infrastructure should serve as a useful mechanism for ongoing improvements in evidence-based cardiovascular medicine and clinical research in the state of Connecticut.

Assessment of atrial capture in committed atrioventricular sequential (DVI) pacing systems.

Two patients with committed dual unipolar AV sequential pacing systems are presented in whom atrial capture was unable to be demonstrated on the surface electrocardiogram. The bedside examination is proposed as a means of identifying the presence or absence of atrial capture with subsequent confirmation by M-mode echocardiographs and jugular venous pulse tracings. Mode, rate, and output programmability may aid in the evaluation of these pacing systems. Intentional reduction of the ventricular output to subthreshold levels in pacemakers capable of this degree of programmability will permit the rapid bedside confirmation of atrial capture without the need for expensive and time-consuming noninvasive tests.

Patient-initiated autonomous pacemaker tachycardia.

Multiparameter programmable DDD pacemakers are said to have an uncountable number of possible parameter combinations. It is probable that a number of these combinations, particularly when triggered by one or more critically timed native events, will result in bizarre and unanticipated rhythms sustained entirely within the timing circuit of the pulse generator. We report the occurrence and analysis of one such rhythm termed a sustained autonomous pacemaker tachycardia. In this rhythm, both atrial and ventricular outputs occur at the maximum tracking rate of the pacemaker with an apparently shortened AV interval. Once initiated, the ability to sustain the tachycardia requires that the maximum tracking rate interval exceed the atrial escape interval. It will then continue until the pulse generator is programmed to parameters that alter this critical timing or a properly timed ventricular sensed event occurs. It is anticipated that this will be only one of many similar rhythms encountered in patients treated with complex devices from all the manufacturers. In the future, once such a rhythm is noted and its mechanism identified, modifications of the basic circuit design will allow these parameters to be used without danger to the patient and without having to limit the options of the device.

Five-year performance of the Medtronic 6971 polyurethane endocardial electrode.

There is a considerable debate over the long-term performance of polyurethane electrodes. Observation to date has demonstrated surface cracking and some clinical failures in patients. Since 1978 we have implanted about 82 6971 Unipolar Medtronic electrodes in the ventricle. In 33 patients, lead integrity was assessed by chronic thresholds determined by decreasing pulse width and pulse amplitude. Sensing functions were assessed by electrocardiographic rhythm analysis. At a follow-up between 7 and 67 months, chronic thresholds at 2.50 volts were 0.08 +/- 0.04 milliseconds in 26 patients with Medtronic Pulse generators (Models 8423, 5985, and 7000). In two patients with similar units, no loss of capture was seen even at 0.05 milliseconds. Three patients, one with Cordis Unit (233F) showed loss of capture at 0.20 milliseconds at 2.00 MA, the other with a Pacesetter unit (255-6) showed loss of capture at 0.20 milliseconds, at 2.50 volts. One patient with Intermedics unit (283) lost capture at 0.07 milliseconds at 2.70 volts. Insulation breaks seen in two patients were demonstrated by pectoral stimulation and pacemaker oversensing. In addition, 24-hour long-term electrocardiographic monitoring was performed in 22 patients between 23 to 70 months. Appropriate pacemaker function was seen except in one patient who demonstrated oversensing. Interruption in insulation was demonstrated at the ligature site at exploration. Thus, in this series of patients who were paced in the ventricle by the 6971 Medtronic electrode, only two patients have demonstrated insulation failure. The incidence of insulation break in this polyurethane unipolar electrode is uncommon and occurs at further stress points.