« Back

Data suggest AT/AF burden stratifies risk of thromboembolic events

Friday, April 04 2008 | Comments

---

What's This? By Courtneay Parsons

Device-detected atrial tachycardia/atrial fibrillation (AT/AF) burden may be useful for stratifying the risk for thromboembolic events (TE), according to data from the TRENDS study.

Dr. Taya Glotzer and colleagues evaluated the relationship between device-detected AT/AF and TE risk in 2,486 patients who had >=1 stroke risk factor and a Class I or II indication for a dual-chamber pacemaker, a dual-chamber internal cardioverter defibrillator, or a dual-chamber cardiovascular resynchronization therapy device.

The retrospective analysis followed patients for a mean of 1.4 years after device implantation. The investigators reviewed device data for the occurrence of TE. Data were evaluated in rolling 30-day windows (ie, window 1, days 1-30; window 2, days 2-32; etc). For each 30-day window, AT/AF burden was defined as the longest AT/AF duration on any given day.

Forty TE events occurred during follow-up, yielding a low annualized TE event rate of 1.2% (95% CI, 0.8%-1.6%).

The median value for the maximum daily AT/AF burden in all 30-day windows with a nonzero AT/AF burden was 5.5 hours. In evaluating TE risk associated with AT/AF burden, researchers categorized each 30-day window as zero burden (76%), low burden (<5.5 hr; 12%), or high burden (>=5.5 hr; 12%).

The annualized TE event rates for the zero-burden, low-burden, and high-burden subsets were 1.1%, 1.1%, and 2.4%, respectively. In a model that adjusted for stroke risk factors at baseline, time-dependent AT/AF burden, and time-dependent warfarin and aspirin use, the high-burden subset was associated with a hazard ratio for TE events of 2.20 (95% CI, 0.96-5.05; P=.06) relative to the zero-burden subset. The corresponding HR for low-burden subset was 0.98 (95% CI, 0.34-2.82; P=.97).

Dr. Glotzer acknowledged that the TRENDS data are limited by the surprisingly low number of TE events, which resulted in broad confidence intervals for HRs, and the retrospective nature of the study.

However, she concluded, "Our results suggest that device-detected AT/AF burden >=5.5 hours on any day during the preceding 30 days doubles the risk for TEs, independent of known risk factors and antithrombotic therapy." (Presentation 412-13.)

Print  |  E-mail