Activation times for "emergency backup" programs.

A bench study was performed on 42 different pulse generators (PGs) to evaluate the time required to actuate and "emergency backup" (EBU) program. PGs were programmed to loss of capture before the EBU programming key was activated. Activation times for the EBU pause were measured on an ECG strip from the first noncaptured beat to the first recaptured beat while the total pause was measured between the two captured beats. Each test was performed five times. Special features for temporary threshold testing were also evaluated. Mean activation times for EBU pauses ranged from 1.46-11.90 seconds with total pauses of 2.18-12.94 seconds. Significant differences were observed for EBU activation times from the same PG but utilizing older and newer generation programmers, e.g., 10.90 (old) versus 4.54 seconds (new) for a mean EBU pause. Extreme variations existed in EBU activation times for programmers with multiple "EBU keys" for the same PG, e.g., 12.94 versus 4.96 seconds for the mean total pause. The special features for temporary threshold testing resulted in mean EBU pauses measuring 0.62-2.88 seconds and mean total pauses of 1.21-3.76 seconds. The special features were significantly faster than manual activation of the "EBU key" for regaining capture with few exceptions. Activation times were complicated by multiple programmers for the same PG and several "EBU keys" on the same programmer.

No output or runaway?

A 75-year-old male was implanted with a Telectronics Meta DDDR model 1250 pacemaker 47 months ago. The patient was evaluated in-office for symptomatic complaints of dizziness, palpitations, and "too slow or too fast" pulse rates. Upon examination, the device displayed sudden no output manifestations for which the device had been recalled. However, the device further displayed erratic paced rates to 200 ppm, switching between VVIR and DDDR modes. To the best of our knowledge, this is a previously unreported manifestation in this recalled device and needs to be addressed due to its potentially hazardous patient effects.

A verified report of spurious programming: a case study.

A case of unintentional misprogramming is described in which a DDDR pacemaker, programmed to the VVIR mode, reverted to the originally programmed parameters and mode. The misprogramming requires that a particular sequence of steps be followed and has been verified by the manufacturer. This misprogramming may be clinically significant and can be reproduced in an entire family of current pacemakers based on the same software platform.

Analysis of the effectiveness of in-office and transtelephonic follow-up in terms of pacemaker system complications.

A study was undertaken to determine the most effective method of pacemaker follow-up in terms of the total number of complications detected and yield per follow-up in single and dual chamber pacing systems. The analysis involved 9,786 patient records from 635 patients. The records were reviewed with respect to method of follow-up, number of chambers paced, and complications detected. Complications included: oversensing, undersensing, noncapture, pocket and diaphragmatic stimulation, pacemaker mediated tachycardia, crosstalk, pulse generator malfunction, lead malfunction, infection/erosion, premature end of service, exit block, and other miscellaneous problems. Eight thousand two hundred eighty-eight of the 9,786 follow-ups were performed in the office while 1,498 were transtelephonic. Single chamber pacing systems were implanted in 329 patients and 306 were dual chamber systems. A total of 599 complications were detected. Analysis yielded a per patient complication rate of 5.1% (single chamber) and 8.4% (dual chamber) for in-office follow-up. This compared to a transtelephonic follow-up per patient complication rate of only 0.3% (single chamber) and 1.0% (dual chamber). In-office pacemaker follow-up is significantly more effective (P < 0.001) than transtelephonic follow-up in detecting both single and dual chamber pacemaker system complications.

Performance of a 3.2-mm to 6-mm adaptor.

A study was undertaken to evaluate the performance of a 366-08 adaptor that adapts an in-line bipolar 3.2-mm connector to a 6-mm pulse generator connector. A total of 14 adaptors were implanted in individual patients. Eight of the 14 adaptors failed, an additional failure is probable. The average follow-up time was 32.1 months. The most likely cause of failure was the spring-loaded mechanism of the adaptor, which fatigues with time. All eight of the documented failures presented with loss of capture and were accompanied by increased measured lead impedances. In addition, some failed systems demonstrated loss of sensing. As a result, prophylactic replacement of ventricular lead systems incorporating this adaptor would be advisable. Otherwise, more frequent monitoring with lead impedance measurements may suffice.

Evaluation of an in-line bipolar polyurethane ventricular pacing lead.

A study was undertaken to evaluate the performance of the Medtronic 4012 polyurethane in-line bipolar pacing electrode. One hundred twenty six patients implanted with the 4012 lead were followed by our clinic with 116 of these leads implanted at our institution. Patients were followed a minimum of every 4 months. Testing included the performance of stimulation thresholds, sensing thresholds, and provocative maneuvers to evaluate for myopotential inhibition testing a minimum of every eight months. There were 12 documented lead failures of the total 126 patients. Further analysis was limited to the ten failures occurring in the 116 leads implanted at our center. All ten failed leads utilized the suture anchoring sleeve. Six of the leads were left cephalic implants, three were right cephalic, and one was right subclavian. Manifestations of failure included: seven oversensing abnormalities, three undersensing, four loss of ventricular capture, one premature end of service, four lead impedance decreases to < 250 omega and some presentations in combination. No leads were explanted for evaluation. The Kaplan-Meier product limit method was used to estimate the time to lead failure. The probability of not experiencing a lead failure within the first 4 years of implant is estimated to be 0.9103 (SE = 0.0338). Pacemaker dependent patients implanted with the 4012 lead should be given special consideration for prophylactic replacement.

Activation times for "emergency back-up" programs.

A bench study was performed on 34 different pulse generators to evaluate the time necessary to actuate an "emergency back-up" (EBU) program. Pacemakers were programmed to loss of capture before the EBU was activated. Two pauses were measured that included the total pause from captured beat to captured beat and the time from the first pacing artifact showing loss of capture to the first captured beat resulting from EBU activation. Special features for threshold testing such as temporary pacing, auto threshold, Vario, and an alternating pulse ventricular threshold test were also evaluated. Activation times of the EBU ranged from 1.8 to 11.1 seconds with total pauses of 2.7 to 13.2 seconds, respectively. There were considerable variations in EBU times even within a single manufacturers' pulse generators. The special features for threshold testing resulted in pauses measuring 0.6 to 3.0 seconds with total pauses of 1.2 to 4.0 seconds, respectively, and in all cases were faster than using the EBU. Utilization of the EBU to regain capture during threshold testing in pacemaker dependent patients may result in prolonged pauses and syncope or near syncopal episodes.

Comparison of low rate dual chamber pacing to activity responsive rate variable ventricular pacing.

A study was undertaken to evaluate exercise performance in 18 dual chamber pacemaker patients believed to be chronotropically incompetent. All patients were paced in a DDD AV synchronous mode at 80 beats per minute (beats/min) as well as an externally triggered, activity responsive VVIR mode. Patients underwent two single blind, randomized symptom-limited treadmill tests (Sheffield protocol). Four of the 18 patients achieved intrinsic rates greater than 100 beats/min and were deleted from the primary study. It was noted that all four of these patients performed best with intrinsic rate response and AV synchrony. Thirteen of the remaining 14 patients demonstrated improved exercise tolerance in the VVIR mode. Average exercise time in the VVIR mode (7:25 +/- 3:12 min) was significantly greater (P less than 0.05) than the DDD mode (6:01 +/- 2:27 min). Work performed was significantly greater (P less than 0.05) in the VVIR mode (4.77 +/- 1.97 METS) than in the DDD mode (3.78 +/- 0.77 METS). Maximum heart rates were 83.86 +/- 5.11 beats/min in DDD mode versus 116.00 +/- 10.56 beats/min in VVIR mode. The results demonstrated that improved exercise tolerance can be achieved with single chamber rate variable pacing compared to DDD pacing in patients with chronotropic incompetence. However, potential symptoms associated with loss of AV synchrony should be ruled out.

An advanced data base pacemaker follow-up system that's customizable.

In an effort to deal with the volumes of information gathered from pacemaker follow-up, the obvious need for a computerized data base was realized. In order to meet specific goals and needs, an advanced relational data base program was custom designed for pacemaker follow-up. The program has the ability to store and report all follow-up data throughout the life of each patient on a relatively few page report. The software also includes files for generator specifications, recalls and pulse generator and lead prices and warranties. The program is quite flexible and can be customized to particular follow-up clinics.

Crosstalk during bipolar pacing.

Bipolar sensing pulse generators were thought to have eliminated crosstalk problems evident in unipolar systems. Crosstalk has been observed in the Model 284-02 bipolar sensing pacemakers. These intermittent problems were resolved by decreasing atrial output, decreasing ventricular sensitivity or increasing the ventricular blanking period. Three patients had pacemaker crosstalk, two experienced symptoms analogous to pacemaker syndrome.