Lawrence J. Gessman

Accuracy and clinical utility of transtelephonic pacemaker follow-up.

The diagnostic accuracy of transtelephonic pacemaker monitoring (TTM) has been quantified in a retrospective study involving 369 patients in three U.S. cardiac centers. Using existing medical records, TTM findings in a total of 413 reports were judged for equivalence to the findings of subsequent physical examinations in pacemaker clinics. This study found TTM follow‐up testing to have a sensitivity of 94.6%, specificity of 98.5%, positive predictive value of 93.3%, and negative predictive value of 98.8%. The study also documents the clinical utility of TTM in identifying various modes of pacemaker malfunctions and instances of significant arrhythmia.

Chronotropic Response of an Activity Detecting Pacemaker Compared with the Normal Sinus Node

We compared the rate responsiveness of an activity‐detecting muitiprogrammable, single chamber pacemaker (Medtronic Acfivitrax) to rate responsiveness of the normal sinus node. This pacemaker changes its basic pacing rate in response to physical activity. The rate responsiveness is programmable by selecting one of three activity thresholds, and one of 10 rate response settings. The study included a group of six normal volunteers and 12 patients implanted with Activitrax to examine the similarity of the pacemaker rate to normal sinus rhythm during acceleration and deceleration. The pacemaker was set to Activity mode, at a basic rate of 60 bpm. In voiunteers, the device was externally secured on the chest wall and tested at two programmed settings. When programmed at a high threshold of activity and high rate response in voiunteers, there was no significant difference in maximum normal sinus rates and pacemaker rates during arm waving, jumping in place, and walking during stress testing. At a medium activity threshold, the only significant difference occurred during submaximal stess testing, when the maximum sinus rate achieved was 141 ± 19 bpm and the maximum pacing rate was 105 ± 8 bpm (p < .02). The pacemaker behaved in a similar manner in patients, successfully simulating the typical fast acceleration and slow deceleration of a normal sinus node in exercise testing. There was no difference in pacer response when implanted in abdominal or in/raclavicular locations. The implanted units have functioned normally over a follow‐up period of nine to 22 months. Activitrax can be programmed to achieve physiologic pacing rates in response to normal daiiy activities with appropriate programming.

U.S. Experience with the AddVent VDD(R) Pacing System

The AddVent pacemaker generator and model 1328C AV single‐pass lead is a new pacemaker system capable of VDD or VDDR modes. The purpose of this study was to present the initial experience with AddVent in the United States and Canada. Between May 10, 1995 and May 3, 1996, 53 devices were implanted in 52 patients and followed for a mean of 217 (±39) days. At the predischarge, 1‐, 3‐, and 6‐month follow‐up evaluations, atrial sensing thresholds and ventricular sensing and capture thresholds were measured in the supine, sitting, and standing positions to evaluate stability of atrial sensing with respect to body posture at rest. At the 1‐month follow‐up, a treadmill exercise test was performed to evaluate atrial sensing during exercise and to evaluate two new features of the AddVent called “sensor‐mediated rate smoothing” and “preferential P wave sensing.” Atrial sensing thresholds were not significantly different (P > 0.05) among body postures for any follow‐up period or among follow‐up periods for each posture. At rest, the percentage of appropriately tracked P waves observed was > 99% at each follow‐up period. During treadmill exercise, the percentage of appropriately tracked P waves was > 98.7%. Appropriate preferential P wave sensing and sensor‐mediated rate smoothing (VDDR mode) was observed. The AddVent pacing system provides safe and effective pacing therapy. Several features of VDDR pacing offer advantages over standard VDD pacing.

Esophageal P‐Synchronous Pacing

An esophageal electrode can be employed to provide atrial sensing which then can be used to change from temporary right ventriculor (VVI) pacing to P‐synchronous (VAT) pacing. Two cases of postoperative aortic valve replacement, each with new complete heart block (CHB) and dopamine dependency, are presented. In both cases, establishment of P‐synchronous pacing resulted in improved hemodynamic status characterized by successful weaning from dopamine and maintenance of adequafe cardiac output (CO).