Danish Multicenter Randomised Study on AAI Versus DDD Pacing in Sick Sinus Syndrome - DANPACE


Over the past decade, the principal debate with respect to choice of pacemaker systems has concerned the relative merits of dual-chamber pacing, single-chamber ventricular pacing, and single-chamber atrial pacing. In patients with isolated sinus node dysfunction (SND), current guidelines recommend either an isolated atrial lead (AAIR) or a dual-chamber system (DDDR), based on the likelihood of development of atrioventricular (AV) block. The current trial sought to compare outcomes between AAIR and DDDR pacing (single- vs. dual-chamber) in patients with SND without obvious AV nodal disease.


AAIR pacing would be superior to DDDR pacing in patients with SND without obvious AV nodal disease.

Study Design

  • Parallel
  • Randomized
  • Blinded

Patient Populations:

  • Symptomatic bradycardia
  • Documented sino-atrial block or sinus-arrest with pauses >2 seconds or sinus bradycardia <40 bpm for more than 1 minute while awake
  • PR interval ≤0.22 seconds if age 18-70 years or PR interval ≤0.26 seconds if age ≥70 years
  • QRS width <0.12 seconds

    Number of screened applicants: 18,553
    Number of enrollees: 1,415
    Mean follow-up: 5.4 years
    Mean patient age: 73 years
    Percentage female: 65%
    New York Heart Association class: I: 71%, II: 24%, III: 4%, IV: 0%


  • AV block
  • Bundle branch block
  • Long-standing persistent AF (>12 months)
  • AF with ventricular rate <40 bpm for ≥1 minute or pauses >3 seconds
  • A positive test for carotid sinus hypersensitivity
  • Planned cardiac surgery
  • Life expectancy shorter than 1 year

Primary Endpoints:

  • All-cause mortality

Secondary Endpoints:

  • Paroxysmal AF
  • Chronic AF
  • Stroke
  • Peripheral embolism
  • Heart failure
  • Need for pacemaker reoperation

Drug/Procedures Used:

A bipolar lead was implanted in the right atrium, and in patients randomized to DDDR pacing, an additional lead was implanted in the right ventricle. An atrial pacing test was performed at 100 bpm in all patients, and 1:1 AV conduction was required for implantation of an AAIR pacemaker. In patients randomized to AAIR pacing demonstrating AV block when paced at 100 bpm, a ventricular lead and a DDDR pacemaker were implanted.

Patients with atrial fibrillation (AF) during implantation either underwent DC cardioversion or received a pacemaker system without an atrial pacing test at the implanter’s discretion. The rate adaptive function was activated in all pacemakers and programmed with a lower rate of 60 bpm and an upper rate of 130 bpm.

Concomitant Medications:

Anticoagulation (14%), sotalol (6.2%), other beta-blockers (20%), digoxin (9.5%), amiodarone (3.5%), and class I anti-arrhythmic drugs (2.4%)

Principal Findings:

A total of 1,415 patients were randomized, 707 to AAIR pacing and 708 to DDDR pacing. Baseline characteristics were fairly similar between the two arms. About 43% had a history of AF, with a mean left atrial diameter of 3.9 cm. An ejection fraction <50% was noted in 10% of the patients. The majority of patients were undergoing permanent pacemaker (PPM) implantation for dizzy spells (83%) or syncope (50%). The mean percentage of atrial pacing was 58% in the AAIR group and 59% in the DDDR group, whereas the mean percentage of ventricular pacing was 65% in the DDDR group. In the AAIR group, 585 patients (83%) never had a ventricular lead. In the remaining 122 patients, a ventricular lead was implanted at the first operation or at some point during follow-up.

After a mean follow-up of 5.4 years, there was no difference in all-cause mortality between the AAIR pacing and DDDR pacing arms (29.6% vs. 27.3%, hazard ratio 1.06, 95% confidence interval 0.88-1.29, p = 0.53). Paroxysmal AF was observed more frequently in the AAIR group than in the DDDR group (28.4% vs. 23.0%, p = 0.024), as were pacemaker reoperations (22.1% vs. 11.9%, p < 0.001). The incidence of CHF and stroke was similar (p > 0.05). The increase in the incidence of paroxysmal AF with AAIR pacing was noted in the per-protocol analysis as well.


The results of the DANPACE trial indicate that although there is no difference in all-cause mortality between AAIR pacing and DDDR pacing in patients with isolated SND without obvious AV nodal dysfunction and preserved left ventricular function, the incidences of paroxysmal AF and pacemaker reoperations were higher with AAIR pacing, thus supporting the use of DDDR pacing in these patients.

Current guidelines indicate that the choice of single- versus dual-chamber pacemaker in patients with SND depends on the likelihood of developing AV nodal dysfunction. An earlier Danish trial had demonstrated that AAIR pacing was superior to VVIR pacing in patients with isolated SND. In the current trial, only 83% of patients had isolated SND; the remainder were either noted to have AV nodal dysfunction at the time of PPM implantation, or developed AV nodal dysfunction over the course of follow-up. This trial thus suggests that most, if not all, patients undergoing PPM implantation for SND should receive a dual-chamber pacemaker, set at DDDR.


Nielsen JC, Thomsen PE, Højberg S, et al., on behalf of the DANPACE Investigators. A comparison of single-lead atrial pacing with dual-chamber pacing in sick sinus syndrome. Eur Heart J 2011;Feb 7:[Epub ahead of print].

Presented by Dr. Jens Nielsen at the European Society of Cardiology Congress, Stockholm, Sweden, August 2010.

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, EP Basic Science

Keywords: Stroke, Heart Atria, Follow-Up Studies, Ventricular Function, Left, Dichlorodiphenyldichloroethane, Sick Sinus Syndrome, Electric Countershock, Syncope, Atrioventricular Block, Reoperation, Pacemaker, Artificial, Bradycardia, Confidence Intervals, Heart Ventricles, Atrioventricular Node

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