Title of Trial
The Effect of Atrial Pacing Therapies on Atrial Tachyarrhythmia Burden and Frequency: Results of a Randomized Trial in Patients With Bradycardia and Atrial Tachyarrhythmias (ATTEST)

Date and Citation of Primary Publication(s) or References
Lee MA. Weachter R. Pollak S. Kremers MS. Naik AM. Silverman R. Tuzi J. Wang W. Johnson LJ. Euler DE. ATTEST Investigators. The effect of atrial pacing therapies on atrial tachyarrhythmia burden and frequency: results of a randomized trial in patients with bradycardia and atrial tachyarrhythmias. Journal of the American College of Cardiology. 41(11):1926-32, 2003 Jun 4

Purpose of the Trial
The purpose of this study was to evaluate the effectiveness of an atrial therapy device utilizing preventative and antitacycardia pacing in patients with symptomatic atrial fibrillation.

Study Category
Atrial Fibrillation. Multicenter, prospective randomized trial

Patient Population
Not defined

Inclusion Criteria
Patients were eligible for enrollment if they had an ACC/AHA indication for a dual chamber pacemaker and a history of atrial tachycardia or fibrillation. To be eligible a documented episode of AT/AF had to have occurred in the prior year and one symptomatic episode in the preceding 3 months.

Exclusion Criteria
Permanent AF and indication for an implantable defibrillator or NYHA class IV CHF were exclusion criteria for this study.

Study Design
After enrollment, an AT500 (Medtronic Inc, Minneapolis, MN) was implanted. The device is a DDDR pacemaker with mode switching to DDIR during atrial tachyarrhythmias. Atrial antitachycardia pacing is available in rate adaptive burst or ramp modes. The device also can employ 3 preventative atrial pacing algorithms to attempt to prevent AF/AT recurrences, including overdrive atrial pacing to maintain pacing just above the intrinsic atrial rate during sinus rhythm, temporary atrial overdrive to prevent short-long intervals, and a post mode-switch overdrive to prevent arrhythmia recurrence.

After a one-month run in period, patients were randomized to either atrial prevention or termination on or off, and followed for three months.

Primary Endpoints
The primary endpoints in this study were AT/AF burden and total AT/AF frequency as measure by the device. The primary safety endpoint was freedom from device related complications.

Secondary Endpoints
Secondary endpoints were the accuracy of the detection algorithm as evaluated by review of stored electrograms, ATP efficacy in restoring sinus rhythm, and frequency of symptomatic atrial arrhythmias frequency recorded as manual symptom markers by patients.

Baseline Characteristics *

	ON (n=153)	OFF (n=171)
Male (%)	56.2	52.0
Mean age (years)	71.4	68.7
Primary indication (%)
AV block	9.2	12.9
Sinus node dysfunction	77.1	71.9
Other	13.7	14.0
CAD (%)	29.4	33.9
CHF (%)	2.0	5.8
HTN (%)	66.0	60.2
Persistent AF (%)	7.8	6.4
Paroxysmal AF (%)	78.4	79.5
Persistent Aflutter (%)	3.3	4.1
Paroxysmal Aflutter(%)	37.9	32.2

*no statistical difference in any measured baseline characteristic, or drug use at baseline or over time between the two groups.

Time to Follow-up
The average follow-up time was 82 days in the ON group, and 85 days in the OFF group (p=0.96).

Results

Period	Burden (h/month)	Total Frequency (episodes/month)	Symptomatic Frequency (episodes/month)
Run-in period
ON (n=153)	6.3	4.0	Therapies off
OFF (n=171)	0.8	1.1	Therapies off
p value	0.12	0.14
Study period
ON (n=153)	4.2	1.3	0.00
OFF (n=171)	1.1	1.2	0.00
p value	0.20	0.65	0.62

There were no significant difference between the two groups in the run in period or in follow up in either frequency, burden or symptomatic frequency of AT/AF. The efficacy of device ATP was 54% in converting atrial arrhythmias to sinus rhythm as evaluated by the device and the accuracy of the detection algorithm was 99.9%.

Sponsor
Medtronic Inc., Minneapolis, MN

Trial Status:  Completed