Atrial Therapy Efficacy and Safety Trial - ATTEST
The goal of the Atrial Therapy Efficacy and Safety Trial (ATTEST) is to evaluate preventive pacing and antitachycardia pacing (ATP) in patients with symptomatic atrial fibrillation (AF) or atrial tachycardia (AT).
Activation of the prevention and termination therapies would reduce the burden and frequency of atrial tachyarrhythmias.
Patients Enrolled: 368; 324 randomized
Mean Follow Up: 3 months
Mean Patient Age: Mean 69.9 ± 12.9 years
American Heart Association/American College of Cardiology class I or II indications for a standard dual-chamber pacemaker and a history of AT/AF (at least one episode of paroxysmal or persistent AT/AF documented by electrocardiogram within the past year and one symptomatic episode in the past three months). The authors hypothesized that the high proportion of ventricular pacing (median 99%) may have had a deleterious effect, and limited any benefit from the atrial therapies.
Permanent AF, an indication for an implantable defibrillator, or New York Heart Association functional class IV heart failure
1) Effect of atrial therapies on AT/AF burden, calculated by summing the daily time spent in AT/AF and dividing by the follow-up duration;
2) Total AT/AF frequency, calculated by summing the daily number of AT/AF episodes logged by the device and dividing by the duration of follow-up; and
3) System-related, complication-free survival, defined as clinical events with potential adverse effects requiring invasive interventions specifically related to the device, the implanted leads, or the implant procedure.
1) Accuracy of the detection algorithm (per investigator review of stored AT/AF episodes);
2) ATP efficacy (incidence of successful terminations based on the device counters); and
3) Symptomatic AT/AF frequency (calculated the same as total frequency, except only episodes were counted that were associated with ≥1 manual symptom markers.
All patients were implanted with a DDDRP pacemaker (AT500, Medtronic Inc., Minneapolis, Minnesota) with three atrial preventive pacing algorithms and two ATP algorithms. At implant, atrial detection was programmed ON in all patients, and DDDR pacing was programmed at a lower rate of 60 ppm and an upper rate of 120 ppm. After one month, patients were randomized to all prevention and ATP therapies ON (n=153) or OFF (n=171).
Detection was confirmed in 99.9% of AT/AF episodes with stored electrograms (17,004/17,018), which occurred in 271 patients. The median amount of atrial pacing was 98% (IQ range 97% and 99%) in the ON group versus 75% (IQ range, 38% and 95%) in the OFF group (p<0.001). For ventricular pacing, the median percentage was 99% (IQ range, 95% to 100%) in the ON group versus 98% (IQ range, 81% to 100%) in the OFF group (p=0.005).
Using device-defined criteria for successful termination, ATP terminated 54% of the 15,789 treated episodes in the ON group. No significant differences occurred in AT/AF burden (4.2 h/mo vs. 1.1 h/mo, p=0.20), total frequency (1.3 episodes/mo ON vs. 1.2 episodes/mo OFF, p=0.65), or symptomatic frequency (p=0.62) between the ON and OFF groups, respectively, during the three-month study period.
There were no differences in burden or total frequency in subgroup analysis by presence of episodes during the run-in period, baseline characteristics, or the use of antiarrhythmic drugs. System-related, complication-free survival at four months was 90.2% by Kaplan-Meier estimate, with the most frequent complications being atrial lead dislodgement (n=11), ventricular lead dislodgement (n=5), and pericardial effusion (n=4).
Among patients with symptomatic AF or AT, there was no difference in the burden or frequency of atrial tachyarrhythmias with atrial prevention and termination therapies combined in a DDDRP pacemaker, despite an increase in the relative amount of atrial pacing and an ATP efficacy of 54%.
The authors hypothesized that the high proportion of ventricular pacing (median 99%) may have had a negative effect and limited any potential benefit from the atrial therapies. Additionally, bradycardia-induced AT/AF may have been suppressed by the DDDR pacing. An important limitation of the trial was that the device stored 35 episodes between interrogations and, as such, only about 10% of all episodes logged by the daily counters were available for review. Additionally, the daily counters did not store the episode type (AT or AF).
Lee MA, Weachter R, Pollak S, et al. The effect of atrial pacing therapies on atrial tachyarrhythmia burden and frequency. Results of a randomized trial in patients with bradycardia and atrial tachyarrhythmias. J Am Coll Cardiol 2003;41:1926–32.
Keywords: Kaplan-Meier Estimate, Pacemaker, Artificial, Bradycardia, Electrocardiography, Pericardial Effusion, Tachycardia
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