Recommendations for extraction of chronically implanted transvenous pacing and defibrillator leads: indications, facilities, training. North American Society of Pacing and Electrophysiology Lead Extraction Conference Faculty.

The procedure of lead removal has recently matured into a definable, teachable art with its own specific tools and techniques. It is now time to recognize and formalize the practice of lead removal according to the current methods of medicine and the health care industry. In addition, since at this time the only prospective scientific study of lead extraction is the PLEXES trial, we suggest that studies relating to the techniques of and indications for lead extraction be designed. Recommendations for a common set of definitions, for a framework of training and reviewing physicians in the art, for general methods of reimbursement, and for consistency among clinical trials have been made. Implementation of these recommendations will require additional effort and cooperation from practicing physicians, medical societies, hospital administrations, and industry.

Blind axillar venous access.

The axillary vein has been suggested as an alternate site for venous access to avoid the "subclavian crush phenomenon. " Many techniques have been used to access this structure. They include complicated anatomical landmarks, contrast venography, Doppler, and ultrasound. A simple technique using the basic anatomical landmark of the deltopectoral groove and a blind venous stick has been used successfully in 165 of 168 consecutive pacemaker and ICD procedures; there were only three failures. These required an alternate approach. With a thorough knowledge of the regional anatomy, the axillary vein can be safely used as a primary site of venous access.

Bioimpedance in the pacemaker clinic.

Thoracic electrical bioimpedance (TEB) provides a rapid, accurate, cost-effective method of optimizing the atrioventricular delay in dual-chamber pacemakers. In addition to measurements of cardiac output, TEB provides other hemodynamic indices such as systolic time interval, left cardiac work index, and end diastolic index. The availability of this additional data can assist the clinician in the objective determination of the optimal atrioventricular delay for individual patients. Thoracic electrical bioimpedance is completely noninvasive and takes only minutes to perform.

Clinical experience with passive-fixation coradial bipolar endocardial pacing leads. ThinLine Clinical Investigators.

Bipolar, transvenous, passive-fixation leads (ThinLine, Sulzer Intermedics Inc., Angleton, TX, USA) incorporating coradial individually coated conductor coils, and a redundant external 55D polyurethane insulation sheath were developed. The diameter of the new leads (< 5 Fr) is in the range of available unipolar leads and is considerably smaller than conventional bipolar pacing leads. From January 9, 1994 to November 12, 1996, 1,536 model 432-04 (523 atrial) and 430-10 (1,013 ventricular) leads were implanted in 1,068 patients at 50 US and 5 Canadian centers to evaluate their safety and efficacy. The study included a general phase, with follow-ups at 1, 3, 6, 12, 18, and 24 months; and a randomized intensive phase with collection of more data and additional 2- and 6-week follow-ups. Capture and sensing thresholds, lead impedance, and handling characteristics were evaluated. Clinical events were monitored and performance was compared to that of two commercially available conventional (coaxial) leads: Sulzer Intermedics models 432-03 (atrial) and 430-07 (ventricular). During a total of 17,530 device months, there were two lead failures, no lead related deaths, 32 explants, 37 complications, and no unexpected adverse device effects. Capture thresholds were lower than those for coaxial controls with identical electrodes, sensing was comparable, lead impedances were within clinically acceptable ranges, and investigators found overall handling characteristics good to excellent. ThinLine coradial bipolar leads are safe and effective for cardiac pacing and sensing.

Initial experience with 1.5-mm2 high impedance, steroid-eluting pacing electrodes.

UNLABELLED: In this human study, 21 atrial and 62 ventricular 1.5-mm2 unipolar steroid-eluting pacing electrodes were implanted in 64 patients. Pacing thresholds, lead impedance, and sensing measurements were measured via pacemaker telemetry within 24 hours postimplant, and at 1, 2, 3, 4, 6, 12, 24, and 52 weeks. Acute pacing impedances measured via a pacing systems analyzer were 1,039 +/- 292 (atrial) and 1,268 +/- 313 ohms (ventricular). A 10%-15% decline in the mean telemetered atrial and ventricular pacing impedances was observed at 1 week, but thereafter remained stable. Acute pacing thresholds at 0.5 ms were 0.5 +/- 0.3 V (atrial) and 0.4 +/- 0.1 V (ventricular). Filtered P and R wave amplitudes were 3.7 +/- 2.3 mV and 14.9 +/- 5.9 mV, respectively. In 21 patients, no complications related to the atrial electrode were observed. Of 62 patients with ventricular electrodes, 4 patients (6%) experienced complications and required surgical intervention. On these, causative factors included micro-dislodgment (1 patient), and perforation (1 patient). Sudden unexplained exit block occurred late (> 6 weeks) in two patients. In the remainder of patients, pacing thresholds and sensed electrogram amplitudes remained stable throughout the 52-week follow-up period. CONCLUSIONS: The present study validates that smaller surface (i.e., 1.5 mm2) steroid-eluting electrode designs offer excellent pacing and sensing performance with significantly higher pacing impedances. Although questions remain as to the cause of late exit block in two patients in this series, this relatively small surface electrode design offers promise toward achieving greater pacing efficiency and a theoretical 13%-16% (minimum) enhancement in permanent pacemaker longevity.

A comparison of external rate responsive pacemakers with identical implanted units.

Seven patients with previously implanted accelerometer-based DDDR pacemakers had an identically programmed external pacemaker taped onto their chest. Both units underwent a simultaneous test to set the sensitivity of the accelerometer. The units were then programmed to record the pacing rates for a 15-minute period. The patients underwent an exercise course that included walking and stairs. After the exercise, the patients sat for 3 minutes and the pacing rates from the test were telemetered. The pacing rate was compared at 2 minutes, 4 minutes, peak, and 3 minutes postexercise. The mean standard deviation (SED) for the external pacemaker was 97.9 at 3.53 ppm, 102 at 10.6 ppm, 106 at 8.94 ppm, and 71.3 at 2.29 ppm at 2, 4, peak, and decay, respectively. The mean SED for the implanted pacemaker was 98.1 at 5.76 ppm, 100 at 10.2 ppm, 104 8.24 ppm, 72.4 at 2.88 ppm at 2, 4, peak, and decay, respectively. Difference between pacemakers in ppm was 0.286, 2.0, 2.71, and 1.14 at 2, 4, peak, and decay, respectively. A 95% confidence interval in ppm was -5.28 to 5.85, -10.1 to 14.1, -7.30 to 12.7, and -1.89 to 4.17 at 2, 4, peak, and decay, respectively. In all patients there was a high confidence correlation between the implanted and external unit. An external unit can be used to predict the rate response of an accelerometer-based pacemaker without any adjustments to the pacing parameters.

Outpatient pacemaker procedures.

Over a 46-month period 181 pacemaker procedures were performed from an outpatient practice. Patients were admitted, operated on and discharged all within a 24-hour period. There were no pacemaker emergencies, major complications or emergency readmissions. The outpatient approach to permanent pacemaker procedures was not limited by the type of pacemaker procedure, pacemaker dependence, patient age or sex. The feasibility and safety of outpatient procedures is demonstrated.

Behavior of the ventricular triggering period of DDD pacemakers.

Fifty-seven patients with implanted DDD pulse generators (23 Intermedics Cosmos and 34 Medtronic Symbios) were studied to characterize the behavior of the so-called ventricular safety pace period or nonphysiologic AV delay (ventricular triggering period) in a variety of circumstances. The pulse generators were programmed to various combinations of upper rate, lower rate, and atrioventricular (AV) intervals. We then evaluated the response of the pulse generators to a variety of signals sensed by the ventricular channel during the ventricular triggering period (VTP). In the Cosmos DDD pulse generators, the VTP lengthened from its nominal value (100 ms) whenever the sum of the atrial escape (pacemaker VA) interval and the nominal value of the VTP was shorter than the upper rate limit interval. Extension of the VTP reflected the necessary delay required to maintain constancy of the (ventricular) upper rate limit interval. In contrast, the Medtronic Symbios DDD pulse generators exhibited constancy of the VTP even when the sum of the atrial escape (pacemaker VA) interval and the duration of the nonprogrammable VTP (110 ms) was shorter than the upper rate limit interval. This response was observed only with a programmed lower rate of 90 ppm, upper rate of 100 ppm, and AV interval of 250 ms. Under these circumstances, in the presence of crosstalk or myopotentials sensed in the VTP, the Symbios DDD pulse generator violated its ventricular upper rate limit interval, but remained faithful to its separate (but equal) atrial upper rate limit interval by omitting the succeeding atrial stimulus. The behavior of the VTP of DDD pulse generators, particularly its relation to the upper rate response, must be known for the proper interpretation of pacemaker function.

Electrocautery and pacemakers: management of the paced patient subject to electrocautery.

Electrocautery, commonly used during surgery to maintain hemostasis, can have significant detrimental effects in the paced patient. Damage to the pulse generator, reprogramming of the pacemaker, changes in the capture threshold, and ventricular fibrillation can all be induced by electrocautery. Familiarity with the particular pacemaker in use is critical in minimizing these adverse effects. Preoperative evaluation of the patient's dependence on the pacemaker and evaluation of pacemaker function should be performed and documented. We recommend close intraoperative monitoring of heart rate and rhythm, and suggest that a pacemaker programmer be on hand in the surgical suite during the operation. A postoperative check of pacemaker function should be carried out so that electrocautery-induced pacemaker malfunction will not go unnoticed or uncorrected. Three cases are presented which clearly illustrate these points.

Resetting of DDD pacemakers due to EMI.

Multiprogrammable pacemakers have long been subject to inappropriate reprogramming and electromagnetic interference (EMI). A limited clinical experience with DDD pacing systems precludes the significance of such phenomena in these units. Since August 1981, in a series of 140 DDD systems, certain units demonstrated consistent and reproducible resetting to the back-up modes caused by electrocautery. One unit was permanently reset to the VOO mode. These observations suggest the need for renewed caution at the time of surgery; they also underscore the importance of a thorough understanding of any DDD system and careful follow-up so that such phenomena will not be misinterpreted as pacemaker failure, resulting in erroneous pacemaker removal.

Inframammary pulse generator placement for maximizing cosmetic effect.

Today with the expanding clinical role of cardiac pacing and more advanced methods of detecting pacing problems, more and more young patients are being identified as candidates for permanent pacing. Concern has been expressed by young female patients over the cosmetic effects of pacemaker surgery. Two young female patients were evaluated from a physiologic and cosmetic point of view. The electrodes were placed via the percutaneous approach. The pulse generator was treated as a breast implant using the usual recommended plastic surgeon's inframammary approach. In both cases, optimal cosmetic effect was achieved without any external evidence of the pacemaker system.

Use of the contralateral subclavian vein for placement of atrial electrodes in chronically VVI paced patients.

Two patients with documented pacemaker syndrome were referred for AV sequential pacing and were found to have inaccessible venous systems on the side of their original transvenous pacemaker placement. The contralateral subclavian vein was subsequently catheterized with an atrial electrode using the sheath-set technique. Then the proximal aspect of the atrial endocardial lead was tunneled to the original pacemaker pocket. Once accomplished, both (atrial and ventricular) leads were connected to an AV sequential pulse generator. The united pulse generator and lead were reinserted in the original pacemaker pocket.

A variation on the introducer technique for unlimited access to the subclavian vein.

An adaptation of the sheath set approach for permanent transvenous electrode placement has been carried out in fifteen patients. At the time of lead insertion, the sheath guide wire is left in place. If a second lead is desired or lead exchange becomes necessary, a second sheath is applied to the retained guide wire and a new lead inserted, thus avoiding a second subclavian puncture or new venous cutdown. This in effect offers a limitless access to the central venous system as long as the guide wire is left in place. This adaptation is especially suited for dual chamber pacing, where multiple leads may be required.

Single left pulmonary vein with normal pulmonary venous drainage: association with partial anomalous pulmonary venous return.

An unusual case of a single left pulmonary vein draining the left lung and joining the left atrium without venous obstruction is reported. This anomaly occurred in association with partial anomalous pulmonary venous return from the upper lobe of the right lung to the superior vena cava. A similar case has been previously reported from our laboratory. The diagnosis of a single left pulmonary vein can be made by routine chest roentgenography because of the characteristic radiologic appearance of this anomaly. It is important to distinguish this benign entity from more ominous pulmonary radiodensities.