More research needed on cardiac resynchronization therapy and atrial fibrillation

February 4, 2013 – The DCRI’s Sana Al-Khatib, MD, and colleagues conducted a meta-study to determine the relationship between CRT and AF.

The connection between cardiac resynchronization therapy (CRT) and atrial fibrillation (AF) remains unclear and requires more study, according to a meta-analysis performed by DCRI and Duke researchers.

The study, which was published online in the journal Current Cardiology Reports, was conducted by the DCRI’s Paul L. Hess, MD; Vic Hasselblad, PhD; and Sana M. Al-Khatib, MD (pictured); and Kevin Jackson, MD, of the Division of Cardiology at Duke’s School of Medicine.

CRT involves implanting a pacemaker in a patient’s chest to regulate the action of the heart’s right and left ventricles. CRT is widely used to treat heart failure, although some studies have indicated that patients with AF (an irregular heartbeat) could also benefit from it. However, researchers were uncertain how much influence CRT has on AF. To better understand how CRT could help AF patients, the DCRI and Duke researchers performed a systematic search of the relevant literature.

Using the MEDLINE database, the researchers searched for the terms “cardiac resynchronization therapy” or “cardiac pacing, artificial” and “atrial fibrillation.” Bibliographies of selected manuscripts were manually searched for additional relevant citations. Studies that were not peer-reviewed, lacked new data, or included patients younger than 18 years old were excluded. In the original search, 739 studies were located. Most of these were excluded by the aforementioned criteria. Forty-four studies were selected for full review; of these, nine met all of the inclusion criteria. Review of the bibliographies of these studies yielded five additional studies. Two of the five papers were excluded due to the absence of new data, yielding 12 studies deemed appropriate for inclusion in the study.

Of these 12 studies, 10 were observational, and two were secondary analyses of clinical trials examining the impact of CRT on AF. The most common comparison was the burden of AF before and after CRT placement. Most of the sample sizes were small, with fewer than 100 patients. Most of the patients studied were male and 60 years of age or older. The median duration of follow-up ranged from 6 to 36 months. Four studies examined the effect of CRT on the development of new-onset AF. Three studies analyzed the effect of CRT on paroxysmal, or sporadic, AF. Another four studies explored the influence of CRT on permanent AF before and after CRT placement. The final study did not report baseline characteristics.

After reviewing all of the relevant literature, the DCRI and Duke researchers concluded that little data exist on CRT and AF, and much of what exists is observational. They also noted that although 10 studies suggested that CRT has a favorable impact on AF, a secondary analysis of a large randomized clinical trial showed no effect of CRT on new-onset AF. Finally, the researchers concluded that most studies have been limited to those in whom CRT is currently indicated. Overall, they noted, there is a need for more randomized clinical trials of CRT patients with AF, particularly those who do not meet the traditional CRT criteria.