Atrioventricular pacemaker. Incidence and causes of reprogramming in long-term follow-up

Original Article

Atrioventricular Pacemaker. Incidence and Causes of Reprogramming in Long-term Follow-Up

Martino Martinelli Fº, Sylton de Arruda Melo, Silvana A. D. Nishióka, Anísio A. A. Pedrosa, Sérgio Freitas de Siqueira, Roberto Costa, Eduardo Sosa

São Paulo, SP - Brazil

OBJECTIVE: To assess the incidence of problems requiring reprogramming of atrioventricular pacemakers in a long-term follow-up, and also the causes for this procedure.

METHODS: During the period from May '98 to December '99, 657 patients were retrospectively studied, An actuarial curve for the event reprogramming of the stimulation mode was drawn.

RESULTS: The follow-up period ranged from 12 to 178 months (mean = 81 months). Eighty-two (12.4%) patients underwent reprogramming of the stimulation mode as follows: 63 (9.5%) changed to VVI,(R/C); 10 (1.5%) changed to DVI,C; 6 (0.9%) changed to VDD,C; and 3 (0.5%) changed to DOO. The causes for the reprogramming were as follows: arrhythmia conducted by the pacemaker in 39 (37.6%) patients; loss of atrial sensitivity or capture, or both, in 39 (38.6%) patients; and microfracture of atrial electrode in 5 (4.9%) patients. The stimulation mode reprogramming free probability after 15 years was 58%.

CONCLUSION: In a long-term follow-up, the atrioventricular pacemaker provided a low incidence of complications, a high probability of permanence in the DDD,C mode, and the most common cause of reprogramming was arrhythmia conducted by the pacemaker.

Key words atrioventricular pacemaker, reprogramming, DDD,Cmode

Atrioventricular stimulation, introduced by Nathan et al ¹ in 1963 with the ventricular pacing synchronous with the P wave, has been greatly improved since the 80's with the appearance of specific algorithmic functions, lithium batteries, and atrial electrodes of active fixation ².

Controversies in regard to the cost-benefit ratio of the ventricular (VVI,C) or the atrioventricular (DDD,C) pacemakers persist ^3-6. The major advantages related to dual chamber pacemakers are atrioventricular resynchronization in patients with atrioventricular block, and the ability to use the sinus node as a sensor, causing physiological variation in heart rate. In addition, in cases of sick sinus syndrome, atrioventricular stimulation prevents the consequences of the atrioventricular node disease progression, as well as the pacemaker syndrome⁷. Among the disadvantages of dual chamber pacing, we can cite its higher cost and technical difficulties for implantation and follow-up ⁸.

The most commonly reported complications of the atrioventricular system are loss of atrial sensitivity, atrial arrhythmias, and alterations in the stimulation threshold ^9,10. However, the relation between these findings and the therapeutical procedures has not been established.

The objective of this study was to assess the incidence of complications requiring reprogramming of the atrioventricular stimulation systems in a long-term follow-up, and also the major causes for this procedure.

Methods

At the pacing clinic of the heart institute, 4,250 pacemaker patients are regularly followed up, 2,820 of whom have atrioventricular stimulation systems. Among these, we selected 657 patients, who, during the period from May '98 to December '99, came to our institution searching for regular (clinical and electronic) pacing assessment. All of them had been followed up for at least one year and were retrospectively assessed (medical record and database), with special attention to system reprogramming recordings and the causes for this procedure. These data underwent statistical analysis, and a curve of the accumulated probability of permanence in the DDD,C mode was drawn (Kaplan-Meier).

In the study, 355 patients were males and 302 were females. Their ages ranged from 7 to 92 years (mean = 58 years and 2 months). The most common indication for pacemaker implantation was total atrioventricular block, observed in 359 patients. Other indications included the following: type II or advanced second-degree atrioventricular block in 138 patients, sick sinus syndrome in 115 patients, hypersensitivity of the carotid sinus in 34 patients, long QT syndrome in 8 patients, and others in 3 patients (Table I). Chagas' was the most common underlying heart disease present in 227 patients, followed by ischemic heart disease in 196 patients, hypertension in 92 patients, valvar heart disease in 71 patients, congenital heart disease in 28 patients, and other causes in 43 patients (Table II).

Results

The mean follow-up duration was 81 months, ranging from 12 to 178 months. At the end of the study, 101 (15.3%) patients had undergone system reprogramming, 82 (12.4%) of them for changes in the stimulation mode, as follows: 63 (9.5%) changed to VVI,(R/C); 10 (1.5%) changed to DVI,C; 6 (0.9%) changed to VDD,C; and 3 (0.5%) changed to DOO. The findings regarding the other types of reprogramming are shown in table III.

The causes for changing the stimulation mode were as follows: arrhythmia conducted by the pacemaker in 38 (37.6%) patients; loss of atrial sensitivity or capture or both in 39 (38.6%) patients; microfracture of the atrial electrode in 5 (4.9%) patients; an increase in ventricular threshold in 8 (7.9%) patients; pectoral muscle stimulation in 6 (5.9) patients; and alteration in ventricular sensitivity in 5 (4.9%) patients (Table IV).

Forty-three patients underwent temporary reprogramming of the stimulation mode, 5 patients due to microfracture of the electrode (DOO mode) while awaiting surgical treatment and 38 patients due to arrhythmias conducted by the pacemaker. These latter underwent reprogramming for the VVI,C mode to undergo chemical or electrical cardioversion, and 15 of them did not return to the DDD,C mode because definitive reversion of the atrial rhythm to sinus rhythm was not possible.

The stimulation system reprogramming did not allow definitive correction in 13 patients who underwent surgical treatment. In regard to atrial leads, 3 changes and 5 repositionings were performed, and in regard to ventricular leads, 2 changes and 3 repositionings were performed.

Analysis of the event-free curve showed probability of reprogramming at 5, 10, and 15 years of 10%, 18%, and 42%, respectively. During follow-up, 12 deaths occurred (fig. 1).

Discussion

The extraordinary technological advance involving devices used for artificial cardiac stimulation throughout a relatively short period of time, from its introduction to the current days, has been marked by very well defined developmental phases. Starting with primary systems comprising one chamber with fixed frequency and no sensitivity, pacemakers with a progressive functional capacity have been manufactured until reaching the system characterized as physiological: atrioventricular, multifunctional, with frequency variation guided by the chronotropic response of the normal sinus node ^2,11-13.

Despite these favorable technological characteristics, the clinical consequences of this therapy have not yet been assessed enough to allow definitive conclusions. In addition, the complication rates attributed to the most sophisticated systems have been considered high and of difficult management, particularly for the nonspecialized physician ^3-6.

Several studies have shown the clinical and hemodynamic advantages of the DDD,C mode stimulation as compared with the VVI,C mode, both for total atrioventricular block and sick sinus syndrome ^4,6,10,14,15. The VVI,C pacemaker has been associated with a lower physical capacity ^4,15, a worse quality of life ^6,10,15, an enlargement of the cardiac silhouette ¹⁴, the pacemaker syndrome ¹⁶, and a higher mortality rate ¹⁷.

Other studies have shown no significant difference in regard to mortality ³ or functional capacity ⁵. Atrioventricular resynchronization, considered responsible for improving physical capacity by some authors ^4,14, was challenged by Chu-Pak Lau et al ¹⁸, who attributed this increment basically to variations in heart rate.

Mueller et al ¹⁹ have recently challenged the highest indices of complication attributed to DDD,C pacemakers by showing results similar to those of the ventricular systems (VVI,C).

In our study, rates related to reprogramming of the stimulation mode were low (12.4%). Gross et al ¹⁰, studying 486 patients in DDD,C mode, observed definitive change rates in 18% of the patients and established a relation between these findings and the presence of atrial fibrillation. We attribute these differences with our findings to criteria established by the authors in the therapeutical approach of atrial arrhythmia, more conservative in the indication of electrical cardioversion. Our protocol for this clinical situation is based on reestablishing sinus rhythm in regard to hemodynamic improvement, and also on the prophylaxis of thromboembolism. Electrical cardioversion is not contraindicated and should not be minimized in its indication, because as long as it is performed in special technical conditions and under the protection of the pacemaker generator, it is perfectly feasible. On the other hand, Markewitz et al ²⁰, without considering the causes for mode reprogramming in atrioventricular stimulation systems, observed very low indices (5%). In this study, 345 patients enroled during 5 years were followed-up for 6 years, the main objective being the maintenance of atrioventricular synchronism, independent of the mode (DDD, DDI, DVI, VDD).

In regard to the causes for reprogramming the system, our study has shown that arrhythmia conducted by the pa¾cemaker was the most common finding. In this category, we include all arrhythmias generated in the atrial chamber, such as fibrillation, tachycardia, atrial flutters, and others that trigger ventricular stimulation in an inadequate frequency and rhythm. In these cases, our general approach was temporary reprogramming to the VVI,C mode, immediate chemical or electrical cardioversion under the careful technique of protection and, depending on the result, the return to the DDD,C or DVI,C modes. In our study, this protocol was applied to 38 patients, and in 23 patients we obtained definitive success. Hummel et al ²¹ and Chamberlain-Webber et al ⁹ in a smaller series of patients observed similar rates of complication, but they did not report the indices of therapeutical success. In our study, 5 patients did not return to the condition of atrioventricular stimulation, remaining in VVI,C mode, because of failure in the attempt of cardioversion to sinus rhythm. Several authors ^9,21-23 have correlated this with the evolution of the underlying heart disease, which is usually associated with aggravation of the congestive heart failure functional class. Detollenaere et al ²² have shown that the incidence of these arrhythmias (12%) does not correlate with mortality. Ibrahim et al ²³ have observed that in the presence of sick sinus syndrome, the risk of pacemaker patients for developing atrial fibrillation is 1.5 times higher than that of those with disorders in atrioventricular conduction.

In our study, dysfunctions related to the presence of the atrial pacemaker lead, such as loss of atrial sensitivity in 21 patients, and capture in 18 patients, had indices of complication close to the mean reported by Chamberlain-Webber et al ⁹ and Gross et al ¹⁰. These dysfunctions also seem to be associated with the anatomic and functional conditions of the atrial chamber. On the other hand, microfracture of the electrode, which is an entity characterized by disruption in the lead causing noises and inhibition of the stimulation, is exclusively inherent in a technical defect in the system. No reference to this complication exists in the literature, and our study has shown that in these cases temporary programming of the DOO is safe and adequately protects against pacemaker inhibition caused by a defect while awaiting surgery (change of the pacemaker lead). In fact, the 5 patients with this dysfunction revealed no symptoms of low cerebral blood flow, including the 2 patients who awaited surgery for a long time.

The incidence of changes in ventricular stimulation and sensitivity threshold, as well as pectoral muscle stimulation, did not differ from the classical rates shown by studies performed in ventricular systems.

Our percentage of surgery, including the cases refractory to reprogramming, was much lower than that reported by Gross et al ¹⁰ and Ibrahim et al ²³, whose values were 4 and 9.6%, respectively.

The reprogramming-free probability throughout the follow-up was assessed only in regard to the stimulation mode, because this was the most common therapeutical procedure performed (82/101). Through the actuarial curve of this event, we could document the rates of permanence in DDD,C mode in regard to implantation time, the major aim of indicating a dual chamber system. The values found exceeded our expectation, as follows: by 5 years, only 10% of the patients did not remain in the initially programmed stimulation mode, and by 15 years, 58% of those who started the study remained in the DDD,C mode. These findings were not reported in the literature, which usually reports curves of events in patients with atrioventricular stimulation systems considering only mortality.

In conclusion, our study has shown that atrioventricular stimulation provides a low incidence of complications requiring reprogramming and a high probability of permanence in the initial stimulation mode (DDD,C) in a long-term follow-up. The causes of reprogramming were varied, the most common being arrhythmia conducted by the pacemaker.

Instituto do Coração do Hospital das Clínicas ¾ FMUSP

Mailing address: Martino Martinelli Fº ¾ InCor ¾ Av. Dr. Enéas C. Aguiar 44 ¾ 05403-000 ¾ São Paulo, SP, Brazil

English version by Stela Maris C. Gandour

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Publication Dates

• Publication in this collection
  02 Feb 2001
• Date of issue
  Jan 2001