Clinical and electrophysiologic course of sinus node disease: five-year follow-up study

Predictors of stroke in patients paced for sick sinus syndrome

OBJECTIVES

This study was an analysis of factors associated with stroke in a population of patients paced for sinus node dysfunction in a large prospective clinical trial (Mode Selection Trial [MOST]).

BACKGROUND

The effects of dual-chamber versus single-chamber ventricular pacing on subsequent stroke in patients with sinus node dysfunction are not known.

METHODS

A total of 2,010 patients with sinus node dysfunction were randomized to ventricular or dual-chamber pacing and followed for a median of 33.1 months.

RESULTS

The median participant age was 74 years. During 5,664 patient-years of follow-up, 90 strokes (11 hemorrhagic) occurred. By life-table analysis, the rate of stroke was 2.2% (95% confidence interval [CI] 1.6 to 2.9) at one year and 5.8% (95% CI 4.5 to 7.1) at four years. The incidence of stroke was not significantly different in dual-chamber (4%) as compared with ventricular-paced patients (4.9%) (hazard ratio [HR] 0.82, 95% CI 0.54 to 1.25, p = 0.36). Multivariable analysis demonstrated that significant predictors of stroke included prior stroke or transient ischemic attack, Caucasian race, hypertension, prior systemic embolism, and New York Heart Association functional class III or IV (p < 0.05); pacing mode remained non-significant after adjustment for these factors (p = 0.37). Clinically reported atrial fibrillation after implantation was a risk factor for stroke in this cohort after adjustment for other predictors of stroke (p = 0.042, HR 1.68 [95% CI 1.02 to 2.76]).

CONCLUSIONS

Clinical characteristics, but not mode of pacing, were associated with subsequent stroke in patients paced for sinus node dysfunction.

Abnormal Right Atrial Electrograms Predict the Transition to Chronic Atrial Fibrillation in Paced Patients with Sick Sinus Syndrome

Although pacing therapy for sick sinus syndrome (SSS) is established, the risk of developing chronic atrial fibrillation (CAF) makes pacing therapy infeasible in some patients. We evaluated whether electrophysiological characteristics of atrial muscle can serve as predictors of the transition to CAF after pacemaker implantation in patients with SSS. Eighty-nine patients with SSS underwent electrophysiological study before pacing therapy. Catheter mapping of 12 right atrial sites was performed during sinus rhythm during electrophysiological. An abnormal atrial electrogram was defined as having a duration of 100 ms or longer, or eight or more fragmented deflections, or both. Right atrial extrastimulation was also performed for atrial vulnerability. After electrophysiological study, all patients underwent pacemaker implantation and were followed up. During the follow-up period of 85 +/- 50 months, development of CAF was observed in 12 patients (group A). The remaining 77 patients remained in sinus rhythm (group B). There were significantly more abnormal atrial electrograms in group A than group B (2.7 +/- 2.3 vs 0.8 +/- 1.2; P < 0.001). The distribution of abnormal atrial electrograms was also greater in group A; patients in group A had more abnormal atrial electrograms than patients in group B in both the high and middle right atrium (P < 0.005 and P < 0.01, respectively). Kaplan-Meier analysis showed that almost 50% of the paced patients with abnormal atrial electrograms (n = 42) developed CAF (P < 0.005). Our data suggest that the existence of abnormal atrial electrograms is predictive of the transition to CAF in paced patients with SSS.

[Clinical safety and efficacy of single-chamber atrial pacing in sick sinus syndrome: long-term follow-up]

INTRODUCTION AND OBJECTIVES

Although atrial pacing is a more physiological mode of stimulation in sinus node dysfunction, the pacing modes most often are used DDD and VVI. The aim of our study was to demonstrate that AAI/AAIR pacing is effective and safe by analyzing the complications and mortality of this pacing mode in a long-term follow-up study.

PATIENTS AND METHOD

Between 1982 and 2000 definitive AAI-mode pacemakers were implanted for sinus node dysfunction in mode AAI in 160 patients. We analyzed the clinical characteristics, evolution, and complications of the AAI pacing mode during a follow-up of 5.4 4.5 years.

RESULTS

The sample was made up of 104 women and 56 men with an average age of 72 12 years. During follow-up, it was necessary to change the pacing mode for symptomatic bradycardia in 11 patients (annual incidence 1.2%), which was caused by second or third-degree atrioventricular block in 7 patients (annual incidence 0.8%), and chronic atrial fibrillation with bradycardia in 4 patients (annual incidence 0.4%). During follow-up, atrial arrhythmias occurred in 32 patients (annual incidence 3.7%), stroke in 4 patients (annual incidence 0.4%), and 27 patients (annual incidence 3.1%) died.

CONCLUSIONS

The AAI/AAIR pacing mode was safe and effective in sinus node dysfunction, with a low percentage of pacing changes required for progression to atrioventricular block, low incidence of atrial arrhythmias, stroke and low mortality during long term follow-up.

Atrioventricular conduction during long-term follow-up of patients with sick sinus syndrome

BACKGROUND

It has been claimed that patients with sick sinus syndrome have an increased risk of developing AV block, but this has never been assessed prospectively. The aim of the present study was to evaluate in a prospective trial AV conduction during the long-term follow-up of patients with sick sinus syndrome.

METHODS

Two hundred twenty-five consecutive patients with sick sinus syndrome and intact AV conduction were randomized to undergo single-chamber atrial pacing (110 patients) or single-chamber ventricular pacing (115 patients). Follow-up after 3 months and then yearly included measurement of the PQ interval and, in patients with atrial pacemakers, determination of the atrial stimulus-Q intervals at pacing rates of 100 and 120 bpm. The occurrence of AV block in the atrial group was recorded. During follow-up (mean, 5.5+/-2.4 years), there was no change in PQ interval in either group and no change in atrial stimulus-Q intervals or Wenckebach block point in the atrial group. Four of 110 patients in the atrial group developed grade 2 to 3 AV block that required upgrading of the pacemaker (0.6% per year). Two of these 4 patients had right bundle-branch block at pacemaker implantation.

CONCLUSIONS

AV conduction, estimated as PQ interval and atrial stimulus-Q interval at atrial pacing rates of 100 and 120 bpm and the Wenckebach block point, remains stable during long-term follow-up. Thus, treatment with single-chamber atrial pacing is safe and can be recommended to patients with sick sinus syndrome without bundle-branch block.

Platelet aggregability in patients with a VVI pacemaker

Several studies have suggested an increased incidence of thromboembolic events in patients with VVI pacemaker (VVI patients); furthermore, other authors have demonstrated that a treatment with anticoagulants or antiplatelet drugs may be effective in reducing thromboembolic events, thus suggesting an increased formation of platelet thrombi in these patients. In this respect, platelet aggregability was investigated in ten VVI patients and ten age- and sex-matched subjects. beta-thromboglobulin (beta-Tg) and platelet factor 4 (PF4) plasma levels were determined as well as platelet aggregation induced by ADP, collagen, epinephrine, and arachidonic acid. Plasma beta-Tg levels were increased in the patient group (86 +/- 24 vs 24 +/- 13 ng/mL; P < 0.001) in presence of normal PF4 values (14 +/- 11 vs 13 +/- 6 ng/mL; NS). Aggregation curves showed abnormal values of maximal amplitude, slope, and lag time. In particular, maximal amplitude was significantly higher in VVI patients as compared with controls (ADP P < 0.01, collagen P < 0.001, adrenaline P < 0.01, arachidonic acid P < 0.05). These findings strongly suggest an increase of platelet activity in VVI patients.

Efficacy of ticlopidine in the prevention of thromboembolic events in patients with VVI pacemakers

This study was designed to evaluate whether long-term treatment with ticlopidine reduces the incidence of thromboembolic episodes in patients with a VVI pacemaker. One hundred eleven patients with a VVI pacemaker were randomly assigned to two groups: group A (52 patients) was treated with ticlopidine at the dose of 250 mg a day; and group B (59 patients) was not treated and served as a control group. The primary analysis of efficacy of ticlopidine was based on the occurrence of thromboembolic episodes and of cardiovascular and cerebrovascular deaths. The mean follow-up period was 66 months. In group A, there was a significant reduction in the incidence of thromboembolic episodes (P less than 0.05) with a smaller incidence of total cardiovascular and cerebrovascular deaths (8 in group A and 18 in group B; P = 0.05) as compared with group B. Twelve percent of patients had moderate side effects with 1 dropout (epistaxis). Our data confirm the high incidence of thromboembolic events in patients with a VVI pacemaker and demonstrate the efficacy of ticlopidine in preventing them.

Morbidity and mortality of patients with sinus node disease: comparative effects of atrial and ventricular pacing

In patients with sinus node disease (SND), VVI pacing seems an inappropriate method of cardiac stimulation because of its potential adverse hemodynamic and arrhythmic effects. AAI-DDD pacing, preferred because of lower morbidity, may also determine a higher survival rate. We examined retrospectively two groups of patients with SND. Stimulated respectively with VVI pacing (group 1 = 57 patients) and AAI pacing (group 2 = 53 patients). The mean duration of the follow-up interval was 40.1 months for group 1 and 45 months for group 2. Ten patients (17.5%) in the VVI group and five (9.4%) in the AAI died. During the follow-up, in the VVI group three patients developed congestive heart failure and ten developed chronic atrial fibrillation, whereas only one case of heart failure and two with atrial fibrillation have been recorded in the AAI group. Moreover, four patients had embolic complications in group 1. Five patients (9.4%) with AAI pacing were converted to sequential pacing due to the occurrence of second-degree heart block. The statistical analysis was developed by the X2 test for the comparison of the proportion of the events (atrial fibrillation, congestive heart failure, embolic accidents) in the two groups: a significantly higher morbidity (P less than 0.01) was recorded in the AAI group. Survival is also higher in AAI patients, but the survival rate difference, calculated using the Mantel-Cox method, is not statistically significant. The findings of our study show that in SND the superiority of AAI pacing over VVI is statistically significant as far as morbidity is concerned, and we have also noticed an evident but not statistically significant superiority regarding mortality.

Atrial pacing: who do we pace and what do we expect? Experiences with 100 atrial pacemakers

The records of 100 patients with permanent atrial pacemakers implanted over a 7-year period were reviewed to assess the role and results of this mode of pacing. Indications for pacing were sick sinus syndrome in 91, carotid sinus hypersensitivity in 3, and use of an antitachycardia device in 6 patients. The mean follow-up period was 32.9 months. Symptomatic relief was good. Lead dislodgment occurred in 11 patients (usually in the first week). Threshold rises not amenable to reprogramming occurred in three patients and loss of sensing occurred in seven patients but only one required intervention. Overall, 21 patients required reoperation. The type of lead did not influence the need for reoperation that appeared to be related to the experience of the operator. Complete atrioventricular block occurred in three patients, two of whom had carotid sinus hypersensitivity and one had sick sinus syndrome. Chronic atrial fibrillation occurred in five patients, none of whom required revision of the pacemaker system. Atrial pacing is a satisfactory pacing mode in patients with sick sinus syndrome. Provided satisfactory atrioventricular conduction has been shown by incremental atrial pacing to at least 120 beats/min and carotid hypersensitivity is absent, progression to complete atrioventricular block is uncommon. Greater implanting skills are required for good results.

Atrial pacing: efficacy and safety

Atrial pacing has the advantages of simplicity, maintenance of AV synchrony, and economy. The major detraction has been the potential for deterioration of atrioventricular conduction. In this study, we followed 43 patients with sick sinus syndrome treated with atrial (AAI) pacing. Excellent initial implant parameters were obtained in all. Three early lead repositionings were required. Minor sensing and pacing problems could all otherwise be handled by reprogramming. Follow-up for a mean of 25 +/- 20 months demonstrated excellent performance of the pacing systems. Pacing and sensing thresholds and lead impedance indicated excellent lead performance. There were no late lead failures. Nine patients have had mild deterioration in atrioventricular conduction and one of these had a change to DDD pacing at the time of elective battery change. All patients are asymptomatic. Thus, chronic atrial pacing in selected patients is safe and reliable with good chronic lead performance and low risk of subsequent conduction system disease.

Atrial inhibited pacing in the sick sinus node syndrome: clinical value and the demand for rate responsiveness

A consecutive series of 66 patients (males = 32; mean age +/- SD = 71 +/- 9 years) given atrial inhibited pacemakers for sick sinus nodes were followed to study the incidence of lead failures, chronic atrial tachyarrhythmias, and atrioventricular conduction disturbances. The need for rate responsive pacing was also assessed. Pre and postoperative investigation could include carotid sinus massage, Holter monitoring, exercise testing, and invasive electrophysiology. The mean follow-up time +/- SD was 32 +/- 29 months (median = 26 months). Three patients (5%) had their pacemakers replaced due to lead failures (loss of sensing = 2; exit block = 1). Two pacemakers (3%) were replaced after 5 and 22 months due to atrial fibrillation. Four patients (6%) received new pacemakers because of development of second-degree or complete atrioventricular block after 1, 6, 12, and 31 months, respectively. During exercise, most patients (76%) responded with an increase in sinus rate at least as marked as that achievable with the currently available rate responsive pacemakers. Assuming careful patient selection, atrial inhibited pacing is well suited for many patients with sinus node dysfunction and preserved atrioventricular conduction. There is a limited need for rate responsive pacemakers in these patients.

The atrial pacemaker: retrospective analysis of complications and life expectancy in patients with sinus node dysfunction

The safety of atrial pacemakers is still a remaining cause of controversy. Since 1972, we have implanted 111 atrial pacemakers and we were able to follow-up 100 patients continuously. Mean follow-up time was 47 +/- 36 months (maximum 154 months) with a total population time of 391 patient years. Over a period of 10 years, the cumulative incidence of complete atrioventricular block was 4% (2 patients). The cumulative incidence of atrial fibrillation was 11% (5 patients). Lead-related complications were strongly dependent on the type of the lead and the mode of fixation. The cumulative incidence of all lead-related problems was 19% over a period of 5 years and 33% over a period of 10 years. The cumulative survival rate was 85% for 5 years and 61% for 10 years. These survival rates were not different from the survival rate of a matched cohort of the normal population. We conclude that atrial pacing could be done in patients with sick sinus syndrome. The risk of developing a complete atrioventricular block seems to be rather low. The main problem of the atrial pacemaker is the fixation of the lead which could be reduced by using screw-in-type leads.

Atrial pacing and the risk for AV block: is there a time for change in attitude?

A literature survey was performed to establish the prevalence of second and third degree AV block among patients with permanent atrial pacemakers because of sinus node disease. This study reviews data from 28 different studies on atrial pacing with a median follow-up of 36 months. The collected data shows a median annual incidence of second and third degree AV block of 0.6%, range 0%-4.5% with a total prevalence of 2.1%, range 0%-11.9%. There was no significant difference in follow-up time between studies that showed a low, compared with a high incidence of AV-block. Patients with sinus node disease treated with atrial pacing have a low risk of developing clinically important conduction disturbances.

Course of symptoms and spontaneous ECG in pacemaker patients: a 5-year follow-up study

We investigated the course of symptoms and the spontaneous ECG retrospectively in 308 patients who had received a pacemaker because of atrioventricular (AV) block (n = 115), sick sinus syndrome (SSS, n = 107), bradyarrhythmic atrial fibrillation (bradyarrhythmia, n = 51), carotid sinus syndrome (CSS, n = 16), complete bifascicular block associated with 1st degree AV block (n = 13) and with other indications (n = 6). The mean implantation time was 63 months. The clinical state of 93% of all patients improved after pacemaker implantation; their symptoms decreased markedly. Persisting syncopy in some patients with SSS, however, supports a restricted implantation policy. We rarely saw improved AV conduction in patients with AV block (11%). Furthermore, in patients with SSS, atrial fibrillation occurred significantly more often (35%) than in those with AV block (17%; P less than 0.01). Only 3% of patients with SSS developed 2nd and 3rd degree AV block within the observation period. In all patients with initial bifascicular block and additional 1st degree AV block, pacing prevented further syncopal attacks; four of them showed 3rd degree AV block at control, indicating that pacemaker implantation is mandatory in symptomatic patients with bifascicular disease and 1st degree AV block.

Long-term follow-up of patients with sick sinus syndrome: a comparison of clinical aspects among unpaced, ventricular inhibited paced, and physiologically paced groups

To analyze the prognosis of the sick sinus syndrome (SSS), we compared the clinical aspects among unpaced, ventricular paced, and physiologically paced patients who were followed over a long period. Unpaced intrinsic SSS was not always progressive and patients did not necessarily require permanent pacing. The incidence of concomitant AV conduction disturbance was 65.6% before pharmacologic autonomic block, (PAB), but this was significantly reduced to 31.7% after PAB. Follow-up study of the physiologically paced groups revealed no development of either new or more than second degree AVB. The VVI group had significantly more complications (68%) than the physiologically paced groups, mainly chronic atrial fibrillation (36%) and thromboembolism (20%). In addition, cardiothoracic ratio (CTR) in the VVI group was significantly greater compared with that in the physiologic groups. Nine deaths occurred during the follow-up period in the pacing groups, including six with VVI and three with physiologic pacing. In the VVI pacing group, heart failure and thromboembolism were most commonly the causes of death, while in the physiologic pacing groups, the causes of death were noncardiac. Although the survival rate in the ventricular paced group was not significantly different from that in the physiologic pacing groups, cardiac deaths were fewer in the latter group. Considering our clinical data, the decision to use ventricular pacing needs to be carefully weighed in patients with sick sinus syndrome, and physiologic pacing is more highly recommended.

Atrial fibrillation and embolic complications in paced patients

Atrial fibrillation (AF) and thromboembolism are discussed to be complications of the VVI mode. We reinvestigated the spontaneous ECG and the anamnesis of 246 pacemaker patients with the indications second and third degree atrioventricular block (AV block, n = lll), sick sinus syndrome (SSS, n = 101) and other indications (n = 34), all had shown sinus rhythm at implantation. The mean implantation time was 63 +/- 45 months (203 VVI and 43 dual chamber pacemakers).

THE RESULTS

(1) Atrial fibrillation was found in 63 patients (26%). Only one of them had a DDD pacemaker inserted, the implantation time of dual chamber devices being shorter, however, (2) The incidence of AF in patients with SSS (37%) was significantly higher (P less than 0.01) than in patients with AV block (19%). (3) Three patients suffered from strokes or transitory ischemic attacks in the follow-up, only one of them had AF at control.

CONCLUSIONS

Our results confirm that VVI stimulation favors AF long-term which is most likely due to irritation of the atrial rhythm by retrograde conduction. In our patients the incidence of thromboembolic complications was not higher in the group of patients with AF. However, from this study in surviving patients, we cannot exclude that we lost some patients due to severe stroke.

Ischemic stroke after cardiac pacemaker implantation in sick sinus syndrome

The risk of embolic stroke during sick sinus syndrome before cardiac pacemaker insertion is substantial, but stroke after pacemaker insertion has not been well studied. We observed 10 sick sinus syndrome patients who developed an ischemic stroke 4 days to 112 months after pacemaker insertion. Nine patients represented 6% of the 156 ischemic stroke patients observed during a 30-month period. Eight had a ventricular-demand pacemaker, one had a dual-chamber pacemaker, and one had an atrial-inhibited pacemaker. Six patients were in atrial fibrillation at stroke onset, but none had atrial fibrillation when the pacemaker was inserted. Six patients were taking aspirin, and one was anticoagulated when stroke occurred. Stroke in sick sinus syndrome after pacemaker insertion is not rare, and pacing does not appear to be protective. Sick sinus syndrome patients who convert to atrial fibrillation or who have a ventricular-demand pacemaker might represent high-risk groups for stroke.

Experiences with atrial pacing

The records of 187 patients with permanent atrial pacemakers implanted between 1970 and 1980 were studied retrospectively to define the indications, outcome and short- and long-term complications of single-chamber atrial pacing. Pacemakers were implanted in 145 (77%) patients with tachybrady syndrome, 35 (19%) with sinus bradycardia and 7 (4%) with ventricular arrhythmia. Intact atrioventricular (AV) conduction was defined as absence of second- or third-degree heart block with incremental atrial pacing to a heart rate of 120 beats/min before implantation. The average follow-up was 30 months, including 87 patients (46%) who were followed an average of 48 months. Four patients developed significant conduction disease requiring placement of a ventricular lead. Complications included 4 lead fractures (all coronary sinus leads), 10 dislodgments (9 coronary sinus, 1 tined atrial "J") and 6 threshold rises requiring repositioning of the lead. Eight dislodgments occurred within an average of 5.6 days. The average increase in threshold that required repositioning occurred at 14 days. The average lead fracture occurred at 25 months. Atrial pacing is safe and effective for patients with sinoatrial node disorder (sick sinus syndrome) and intact AV conduction. Progression to clinically significant AV block is uncommon. Complications occur early with coronary sinus leads and are less common with newer leads.

Analysis of sinus cycle variation: a new method for evaluation of suspected sinus node dysfunction

Momentary sinus cycle variations in 30 patients with unequivocal sinus node disease (SND) were compared with those found in 18 healthy control subjects to assess their potential diagnostic value. The range of variation of sinus cycle length (SCL; standardized by dividing by mean SCL) and the maximal change in SCL between any two consecutive cycles (max delta SCL) were measured in short (about 1 minute) continuous ECG recordings from invasive electrophysiologic investigations. Age-stratified reference values from 1 minute surface ECG recordings obtained at rest during quiet breathing in about 70 healthy persons were applied. For diagnosing SND, an increased standardized variation range had a sensitivity of 63%, a specificity of 94%, and a predictive value of a positive test of 95%. The corresponding figures for an increased max delta SCL were 77%, 78%, and 85%, respectively. A combination of increased range of variation and increased max delta SCL was observed in 63% of the patients but not in any healthy subject, which gives a specificity and a predictive value of a positive test of 100% for this combination.

The natural history of sick sinus syndrome

A literature review has addressed the two major factors in disease progression in sick sinus syndrome: atrioventricular block and atrial fibrillation. An incidence of atrioventricular block of 8.4 percent in a follow-up period of 34.2 months is considered clinically significant and sufficient to justify use of a ventricular lead in pacemaker management. Atrial fibrillation occurs much more commonly (22.3%) in ventricular pacing than with atrial demand pacing (3.9%) in a 2 1/2 year observation period. Coincident with the reduction in arrhythmia achieved by atrial demand pacing is a significant reduction in systemic embolism (1.6% vs. 13%). This is considered largely to be due to the improved rhythm control with AAI pacing but also possibly to the avoidance of retrograde atrioventricular conduction. The benefits of AAI pacing in terms of mortality in sick sinus syndrome have not yet been fully assessed. In the future, DDI pacing is recommended with, in some patients, the addition of another sensor to provide rate responsiveness on exercise.

The future of single chamber pacing

Although dual chamber pacemakers have held much interest in pacing over the past several years, single chamber pacing remains the modality of choice, worldwide, in the greatest proportion of patients. Atrial or ventricular demand pacing is safe and effective in the majority of patients. In addition, sensors may be used to increase ventricular pacing rate in order to improve cardiac performance.

Atrial versus ventricular pacing in sinus node disease: a treatment comparison study

Treatment with conventional ventricular pacing does not seem to influence the natural course in patients with sinus node disease (SND). In the present study the natural course of SND was compared in patients treated with ventricular (VVI) and those treated with atrial (AAI) pacing. The study population comprised 168 patients, 89 with atrial and 79 with ventricular pacing. The two groups were comparable with respect to clinical characteristics, degree of severity of SND, and length of follow-up period (average 2 years). Development of chronic atrial fibrillation and congestive heart failure was significantly more common in patients with ventricular than in those with atrial pacing (30% vs 4%, p less than 0.001; 23% vs 7%, p less than 0.01). Second-degree atrioventricular block developed in 4% of the atrially paced patients. Thus, atrial pacing is apparently superior to ventricular pacing in patients with SND.