Nielsen, Jens Cosedis (Denmark)
see Discussant report
List of Authors: Jens Cosedis Nielsen on behalf of the DANPACE investigators
Background: In patients with sick sinus syndrome (SSS), bradycardia can be treated with any pacemaker. Pacing the right ventricle may have deleterious effects, but it is unsettled whether rate adaptive single lead atrial (AAIR) pacing is superior to rate adaptive dual chamber (DDDR) pacing. Methods: Consecutive and eligible patients with SSS, normal QRS width, and without atrio-ventricular block referred for primary pacemaker implantation were randomized to AAIR or DDDR pacing and followed up after 3 months and each year up to 10 years. Hardware randomization was used. Analysis was intention-to-treat. Results: A total of 1,415 patients (73.0±11.3 years, 64.5% female) with SSS were randomly allocated to AAIR (N=707) or DDDR (N=708) pacing and could be followed for a mean of 5.4±2.6 (range 1.2-10.5) years. A total of 96.1% were treated as randomized, 93.4% in the AAIR group and 98.9% in the DDDR group. No patients were lost to follow up. All-cause mortality was 29.6% (209/707) in the AAIR group and 27.3% (193/708) in the DDDR group (hazard ratio 0.94 (0.77-1.14) for DDDR, p=0.53). The incidence of paroxysmal AF was lower in the DDDR group than in the AAIR group (HR 0.79 (0.64-0.97), p=0.024), also after correction for relevant baseline variables. Incidence of chronic atrial fibrillation, stroke and heart failure did not differ between groups. Significantly less patients in the DDDR group than in the AAIR group underwent re-operation during follow-up (HR 0.50 (0.39-0.66), p<0.001). Conclusion: All-cause mortality does not differ between patients with SSS treated with AAIR or DDDR pacing. DDDR pacing should be the preferred pacing mode in patients with SSS to reduce atrial fibrillation and re-operations.
Blomstrom-Lundqvist, Carina (Sweden)
see Presenter abstract
The DANPACE study is the first large multicentre, randomised controlled trial that assessed whether treatment with an AAIR pacemaker is superior to a DDDR pacemaker with regard to all cause mortality (primary endpoint), atrial fibrillation, stroke, heart failure hospitalization and pacemaker reoperation (secondary endpoints), in patients with Sick Sinus Syndrome (SSS). The study was powered to detect a 6 % absolute difference in all cause mortality (primary endpoint) between the two device arms, requiring 1900 patients to be included. A total of 1415 patients were randomised to AAIR devices (707 patients) and DDDR devices (708 patients) and followed for a mean 5.5 years, indicating that the trial terminated prematurely. Overall mortality rates did not differ significantly between patients with AAIR devices and those with DDDR devices (p= 0.53). Nor was there a significant difference between the two device groups with respect to stroke (p=0.65) and signs of heart failure, as indicated by NYHA class at last follow up (p=0.43), diuretics at last follow up (p=0.89), and hospitalization for heart failure (p=0.9). The study showed a significantly lower rate of atrial fibrillation in the DDD device group than in the AAI device group (p=0.024), a difference that was observed already at 6 months or earlier after randomisation. Re-operation was significantly less frequent in the dual chamber pacing group compared with the single lead atrial pacing group (p=<0.001). Multivariate analysis confirmed the lower rate of atrial fibrillation (adjusted hazard ratio 1.24, 95 % CI 1.01-1.52, p- value =0.042), and the lower rate of reoperation (adjusted HR 2.00, 95 % CI 1.54-2.61, p-value < 0.001) with dual chamber versus single lead atrial pacemakers. The authors therefore concluded that single lead atrial pacemaker devices should no longer be used for patients with sick sinus syndrome related to the higher risk for re-operation and the higher rate of atrial fibrillation. They further conclude that the DDDR pacing with an AV interval < 220 milliseconds is the preferred pacing mode for SSS. The observation that atrial fibrillation occurred more frequently in the AAIR device group than in the DDDR group was unexpected and contradicts an earlier Danish study, which reported a lower rate of atrial fibrillation for patients with AAIR devices than for those with DDDR devices (7.4 % versus 17.5 - 23.3%), and also a more recent study (SAVE PACe) showing a lower rate of persistent atrial fibrillation in sinus node disease patients assigned to dual chamber minimal ventricular pacing than in those with conventional dual chamber pacing (7.9 % versus 12,7%, p=0.009). An important consideration in the assessment of trials that compare pacing modes is the percent of pacing among the study patients. A patient paced only for very infrequent sinus pauses will probably have a similar outcome regardless of any different effects between the two pacing configurations. In the DANPACE study, the percent of atrial pacing was similar in the AAIR group (58 + 29 %), and the DDDR group (59 + 31%, p=0.52) but the percentage of ventricular beats that were paced in the DDDR group was only 65 + 33 %, which is lower than in the above SAVE PACe trial (99 %) and thus may partly explain the lack of deleterious effects usually observed with ventricular pacing regarding occurrence of atrial fibrillation and increased mortality. The study further demonstrated that the vast majority (83 %) of SSS patients with AAIR devices remained as randomised, at last follow up. Further studies with long term outcomes and economic evaluation of the most optimal pacing modes are therefore needed to identify the preferred pacing device for patients with SSS without evident need for ventricular pacing.
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