Indications for dual-chamber pacing

Incidence and management of pacemaker-related complications during dual-chamber pacing

To evaluate the complication rate during AV universal pacing (DDD), 41 consecutive patients with complete heart block were studied and followed up for 2-30 (mean 10.8) months. The Cordis Sequicor Theta was used in 6 patients and the Siemens-Elema 674 in 35. Clinical problems related to the pacemaker treatment occurred in 12 patients (pacemaker tachycardia triggered by retrograde atrial activation in 2, atrial oversensing in 3 and undersensing in 2, ventricular oversensing in 2 and undersensing in 1). Ventricular fibrillation occurred during threshold measurement in one patient. Seven of the problems could be ascribed to the DDD mode. Four of these 7 problems could be solved by reprogramming the pacemaker. A nonprogrammable atrial refractory period in the Cordis Sequicor was found to be a limitation in patients with endless loop tachycardia. In 3 cases reoperation had to be performed. In another 3 cases there were problems with ventricular sensing which in one could be solved by reprogramming. Apart from ventricular fibrillation, which could not be ascribed to the DDD mode, there were no serious problems in the clinical management of the patients.

Short atrioventricular delay reduces the degree of mitral regurgitation in patients with a sequential dual-chamber pacemaker

This study was performed in a population of sequential dual-chamber pacemaker-patients with isolated mitral regurgitation (MR) to identify the "ideal atrioventricular (AV) delay" and to determine the effect of sequential pacing with the ideal AV delay on MR degree. Twenty consecutive patients (age 69 +/- 7 years; 45% men) hospitalized at our institution for symptomatic III degree AV block and isolated MR were studied. All received a dual-chamber pacemaker programmed in DDD at a rate of 70 pulses/minute. The ideal AV delay was selected using echo-color Doppler parameters; it was defined as that resulting in a lower degree of MR and in the highest cardiac output. The mean "optimal short" AV delay resulted in 98 +/- 7 ms. At short AV delay we observed a significant reduction in MR severity (regurgitant fraction from 48 +/- 12% to 25 +/- 10% and jet area from 15 +/- 2 to 9 +/- 2 cm2; p <0.0001) together with an increase in stroke volume (68 +/- 16 vs 88 +/- 15 ml; p = 0.007) and mitral early-to-late peak velocity ratio (0.79 +/- 0.33 vs 1.38 +/- 0.37; p <0.0001). In conclusion, a short AV delay may be used to improve cardiac output in sequential paced patients with pure, isolated MR.

The importance of different atrioventricular delay for left ventricular filling in sequential pacing: clinical implications

We assessed the influence and clinical consequences of different AV delay on ventricular filling in 30 patients (mean age 60 +/- 5 years) who had DDD pacemakers for AV block. All 30 patients presented a normal ejection fraction, but in 18 cases (Group I), an echo-Doppler examination revealed ventricular hypertrophy (mean end-diastolic wall thickness of 1.4 +/- 0.16 cm, LV mass index 155 +/- 17 g/m2), and an abnormal relaxation pattern (isovolumetric relaxation time = 124.72 +/- 11.82; early to late peak velocity = 0.6 +/- 0.03; deceleration time = 296.83 +/- 34.02 ms). Group II included the remaining 12 patients who had a normal filling pattern. In all 30 patients, the pattern was reassessed following modification of the AV delay (200, 150, 100, and 75 ms). Patients at baseline (AV delay of 200 ms) also underwent an exercise test with determination of respiratory gas exchange. In Group I, 13 (72.5%) patients were classified as Weber class B (VO2 Max 16.8 +/- 1.7 mL/min per kg); and 5 (27.5%) were Class A (VO2 Max 22.5 +/- 1.4 mL/min per kg). In Group II, all 12 patients were classified as Weber Class A. In Group II, changes in AV delay caused no consistent variations in filling pattern, and therefore AV delay was not modified. In Group I patients, since reduction to 100 ms resulted in normalization of the filling pattern, the AV delay was programmed to 100 ms. A graded exercise test repeated after 6 months' follow-up showed an improved Weber class in 13 patients (from B to A) and greater VO2 Max in the remaining five already in Class A. We concluded that, in sequential paced patients with normal ejection fraction but abnormal relaxation pattern, modification in AV delay can induce normalization of filling and improvement in cardiac functional capacity.

Permanent cardiac pacemakers in the elderly

OBJECTIVE

To review (1) Changes in cardiac impulse generation, conduction, and ventricular filling in normal aging and disease; (2) Pacemaker technology and nomenclature; (3) Expert guidelines about pacemaker use; (4) Studies of pacemaker effectiveness and utilization.

DESIGN

Articles were identified through a Medline search, review of articles' bibliographies, and contact with pacemaker manufacturer representatives for information on device features and costs. These articles were reviewed, and the relevant data are presented.

RESULTS

Abnormalities in impulse generation and conduction are common in the elderly. Pacemaker use is higher in the elderly than in other population groups. Hemodynamic changes associated with aging include an increased contribution of atrial contraction to ventricular filling. Pacemakers, which maintain the synchrony between the atria and ventricles, may be particularly advantageous in the elderly for this reason. Rate-responsive ventricular pacemakers improve the quality of life compared with fixed rate devices in some patients over the age of 75. Dual-chamber, sequential pacemakers are more likely to reduce symptoms of pacemaker syndrome than ventricular pacemakers and probably also prolong survival and reduce risk of atrial fibrillation in certain groups of patients. However, dual chamber devices are more expensive and require more frequent follow-up. Pacemaker utilization can vary widely by region. Decisions about pacemakers require explicit tradeoffs between risk and quality of life on one hand and cost on the other. In many clinical situations, there is controversy as to whether pacemakers should be used.

CONCLUSIONS

Pacemakers provide definite benefits to some patients, whereas in others, the likelihood of benefit is uncertain. More sophisticated devices may provide some additional benefit, but they are more costly. Further data is still required to define precisely which groups of patients substantially benefit from complex and expensive pacing modalities compared with simpler ones.

Should surgeons still be implanting pacemakers?

Cardiac pacing has undergone major changes in the areas of manpower, technology, and cost over the past 10 years. Arguments have been made to eliminate cardiac surgical involvement in pacing on the basis of these three areas of change: implantations are increasingly performed by nonsurgeons, surgeons have not kept up with the technologic advances in pacing, and consolidation of bradypacing resources is necessary during a time when reimbursement has declined significantly. This study examined two eras of pacing therapy at an institution where pacemaker implantation has always been performed by cardiothoracic surgeons. The purpose of the study was to critically analyze (1) the current role (if any) of cardiothoracic surgeons in delivery of pacemaker therapy and (2) the current results of cardiothoracic surgical involvement in pacemaker implantation. In 1,562 procedures performed between 1986 and 1992, the infection rate was 0.51% and the overall complication rate (both short-term and long-term) was 5.2%. During era 1 (1/1/86 to 6/30/89), 80% of implants were single-chamber and follow-up was incomplete and dependent in many instances on the referring cardiologist/internist. For the implantations performed in the second era (7/1/89 to 12/31/92) as part of an established Pacemaker Service, complete clinical and transtelephonic follow-up services were provided by this coordinated medical-surgical approach. During era 2, 53.9% of implants were dual-chamber (79% during 1992). Total and infectious complication rates remained low in era 2 despite this change in technology.(ABSTRACT TRUNCATED AT 250 WORDS)

Pacemaker hemodynamics: clinical implications

Our review of the current literature and experience in caring for pacemaker patients suggests that a consideration of hemodynamics is a logical way to approach pacemaker selection and programming. Multiple clinical factors enter into the selection of a pacemaker or pacemaker programming settings in each case. It appears that in patients with sinus node disease, atrial-inhibited or dual-chamber pacing provides the best chance for preventing the development of chronic atrial fibrillation with its attendant risks of embolism and stroke. It is clear that AV synchrony has beneficial hemodynamic effects at rest in most patients. The results of Labovitz would suggest that in patients with marked left atrial enlargement, this may be less so. The results of Stewart et al would further suggest that in patients with retrograde VA conduction, dual-chamber pacing is preferable. Retrograde VA conduction can be intermittent and this makes it difficult to use its absence on a single test to decide on the type of pacemaker to use. It appears that baseline left ventricular function does not determine the relative improvement in cardiac output observed with AV synchrony or rate-adaptive pacing. However, in patients with severe congestive heart failure even a small improvement in cardiac output may result in significant clinical improvement. Studies have shown that in any given patient, there may be an optimal AV interval at rest. In general, this ranges from 100 to 150 milliseconds. In normal individuals the optimal AV interval shortens with increased heart rate during exercise in a predictable and linear fashion. The hemodynamic benefits of a shortened AV interval with faster heart rates in pacemaker patients have not yet been shown. Intuitively, however, this would appear to be a desirable approach and will probably be added to the design of future generations of dual-chamber pacemakers. Studies of the effect of different pacing modes on secretion of atrial natriuretic factor are intriguing and may contribute more to our understanding of pacing hemodynamics in the future. During exercise, heart rate increase is more important than AV synchrony and this has been shown by several studies. Thus, in active patients with chronotropic incompetence due to sick sinus syndrome, the addition of rate-adaptive pacing is important. Because single-chamber rate-adaptive atrial pacing leaves the patient exposed to the risk of future development of AV block and DDD pacing does not provide chronotropic support, it is likely that the new rate-adaptive dual-chamber (DDDR) devices will be used in a significant number of these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Survey of cardiac pacing in the United States in 1989

A survey of physicians who implant permanent cardiac pacemakers was conducted to identify practice patterns related to pacemaker-implantation frequency, hospital and implantation-facility characteristics, indications for pacing and pulse-generator replacement, preferences regarding device types, pacing modes, follow-up methods and frequency, and type and frequency of pacing-related complications. Questionnaires were sent to 11,414 potential physician respondents and 6 pacemaker manufacturers. Implanters' opinions were solicited regarding such issues as the importance of various device features and capabilities, the appropriateness of practice guidelines, and the efficacy of quality-assurance measures. In 1989, 89,445 primary pacemaker implantations and 21,055 pulse-generator replacements were performed by approximately 7,919 physicians at about 3,400 U.S. centers. Typically, a pacemaker manufacturer's sales representative played an active role in 80% of cases. Since the last survey, which examined pacing practices in 1985, primary implantations of dual-chamber pacemakers increased from 22 to 32%, and the proportion of adaptive-rate pacemakers increased from 1 to 40% of primary implants. The "typical" implanter used bipolar electrode systems in 90% of cases, single-chamber pacemakers in 70%, and the introducer method in 95% of lead placements. Significant differences in practice patterns were found among subsets of the survey respondents. Surgeons tended to work alone, use simpler, single-chamber pacemakers, and leave follow-up to others. Electrode stability tended to be better among implanters in nonacademic environments. The quadrennial survey continues to provide useful information on an easily identifiable and traceable patient population, but the process would be greatly simplified by the adoption of a "universal" reporting system such as that used in Europe.

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.