News:Atrial tachyarrhythmia burden ≥5.5h in a day doubles the risk for thromboembolism in the TRENDS study

April 1, 2008 By Katherine Ogando [mailto:kogando@perfuse.org]

Though previous studies have demonstrated an association between AF and thromboembolic events (TE), it is unclear whether transient episodes of AF also increase the risk of stroke. Newer implantable devices are sensitive enough to capture the more subtle cardiac events, such as transient episodes of AF. With the increasing acuity and accuracy of implantable devices, the goal of the TRENDS study was to apply the information acquired from these devices toward improving patient care.

The authors hypothesized that a greater burden of AF detected by the device would be associated with an increased risk of stroke.

The TRENDS study was a prospective observational study enrolling 3045 patients from 116 sites. Of these, 2813 met inclusion criteria and 2486 had available device data. The mean age of the patient population was 71 years, and the population was moderate to high risk, with a mean CHADS2 risk score of 2.2.

Patients enrolled in the study had been implanted with a cardiac device able to monitor AT/AF burden, and had one or more of the following stroke risk factors: diabetes, heart failure, hypertension, age over 65 years, or prior stroke. In this study, AT/AF burden was calculated as the longest total duration of AT/AF in hours (h) on any given day during a 30-day rolling window before the first stroke or end of follow-up. The study had a mean follow-up period of 1.4 years, but data was downloaded from the devices every 3 months. The primary outcome was the occurrence of thromboembolic events (ischemic stroke, TIA, or systemic embolism).

Using the median value for AT/AF burden, 5.5 hours/day, the time varying burden was divided into groups of zero burden, low burden (less than 5.5 hours on each day or window), and high burden (≥ 5 hours on at least 1 day or window). There were 76% of windows with zero burden, as well as 12% of windows high and low burdens respectively. 40 thromboembolic events occurred in the study. The thomboembolic rate for the zero burden group was 1.1% per year, which was weighed against 1.7% per year for any AT/AF burden group. The subdivided quantities of the burden groups were: 2.4% for high burden (HR 2.20, 95% CI 0.96-5.05, p=0.06), and 1.1% for low burden (HR 0.98, 95% CI 0.34-2.82, p=0.97).

Independent of risk factors, the TRENDS study suggest that device-detected AT/AF burden ≥5.5 hours on any day during the preceding 30 days doubles the risk for thromboembolism. Compared to other studies, the authors found low rates of TE in the patient population of this particular study. This serves as a limitation, as the low number of events translates into broad confidence intervals, and may have limited the statistical power of the study.

Source

 * 1) Taya V. Glotzer, Emile G. Daoud, D. George Wyse, Daniel E. Singer, Michael D. Ezekowitz, Christopher E. Hilker, Clayton T. Miller, Dongfeng Qi, Paul D. Ziegler, on behalf of the TRENDS Study investigators.  As presented at ACC 2008.