Search AV Extension and Managed Ventricular Pacing for Promoting Atrioventricular Conduction - SAVE PACe
The goal of the trial was to evaluate the effect on atrial fibrillation of dual-chamber minimal ventricular pacing compared with conventional dual-chamber pacing in patients with sinus-node disease.
Patients Screened: 1,321
Patients Enrolled: 1,065
Mean Follow Up: Mean, 1.7 years
Mean Patient Age: Mean age, 72 years
Symptomatic bradycardia due to sinus-node disease, met criteria for treatment with permanent implantation of a pacemaker, age >18 years, had a QRS interval of ≤120 msec, and passed a test of atrial pacing (an AV conduction ratio of 1:1 during atrial pacing at 100 bpm)
Persistent atrial fibrillation, ≥2 cardioversions for atrial fibrillation in the prior 6 months, second- or third-degree AV block, or life expectancy <2 years
Time to persistent atrial fibrillation
Hospitalizations for heart failure and the percentages of atrial and ventricular paced beats over time
All patients received dual-chamber pacemakers, either the Kappa 700, Kappa 900, EnPulse, or EnRhythm. Patients were then randomized to dual-chamber minimal ventricular pacing (n = 530) or conventional dual-chamber pacing (n = 535). Patients but not physicians were blinded to treatment assignment.
The atrioventricular (AV) interval with conventional dual-chamber pacing was 120-180 msec. The minimal pacing group programming allowed for automatic lengthening of or elimination of the pacemaker's AV interval in order to withhold ventricular pacing and prevent ventricular desynchronization. Dual-chamber pacing was maintained in the event of AV block.
The trial was discontinued early after an interim analysis met the prespecified criteria for superiority of the dual-chamber minimal ventricular pacing on persistent atrial fibrillation compared with conventional dual-chamber pacing group.
At study entry, mean ejection fraction was 58% and only 20% had a history of heart failure. Previous atrial fibrillation was present in 38% of patients and 20% were on an antiarrhythmic agent. Minimum pacing rate was set at 61 bpm in each group and the detection of atrial fibrillation was 179 bpm.
The median percentage of ventricular beats paced was lower in the dual-chamber minimal ventricular pacing group compared with the conventional dual-chamber pacing group (9.1% vs. 99.0%, p < 0.001). There was no difference in the percentage of atrial beats paced between the two groups (71.4% vs. 70.4%, p = 0.96). The primary endpoint of persistent atrial fibrillation occurred in significantly fewer patients in the dual-chamber minimal ventricular pacing group (7.9%) compared with the conventional dual-chamber pacing (12.7%; hazard ratio 0.60, 95% confidence interval 0.41-0.88; p = 0.009).
There was no difference in the mortality rate between the two groups (4.9% for dual-chamber minimal ventricular pacing vs. 5.4% for conventional dual-chamber pacing, p = 0.54). There was also no difference in hospitalization for heart failure (2.8% vs. 3.1%, respectively, p = 0.62). Cardioversion was performed in 4.2% of the dual-chamber minimal ventricular pacing group and 4.9% for conventional dual-chamber pacing group (p = 0.58).
Among patients with sinus-node disease, use of dual-chamber minimal ventricular pacing was associated with a reduction in atrial fibrillation compared with conventional dual-chamber pacing through a mean follow-up of 1.7 years.
Right ventricular stimulation during dual-chamber pacing has been thought to be the culprit factor in the adverse effects on left ventricular pump function, leading to no mortality benefit with dual-chamber pacing, and in some cases, increased heart failure. The present study sought to evaluate whether minimizing right ventricular stimulation would result in a reduction in atrial fibrillation.
Dual-chamber minimal ventricular pacing was associated with reduced ventricular desynchronization and with a reduction in atrial fibrillation. Despite these reductions, there was no difference in mortality between the two groups, although the trial was underpowered to detect such a difference.
Sweeney MO, Bank AJ, Nsah E, et al. Minimizing ventricular pacing to reduce atrial fibrillation in sinus-node disease. N Engl J Med 2007;357:1000-8.
Keywords: Atrioventricular Block, Follow-Up Studies, Electric Countershock, Heart Failure, Pacemaker, Artificial, Confidence Intervals
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