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A device that closes off the left atrial appendage may provide the same stroke protection as warfarin (Coumadin) in nonvalvular atrial fibrillation, researchers affirmed.

The WATCHMAN reduced a composite endpoint of stroke, cardiovascular death, and systemic embolic events by 38% compared with warfarin (3.0 versus 4.9 events per 100 patient-years), David R. Holmes, MD, of the Mayo Clinic in Rochester, Minn., and colleagues reported in the Aug. 15 issue of The Lancet.

Although these primary efficacy results met noninferiority criteria, the device did significantly increase bleeding and procedure-related complication rates (rate ratio 1.69, 95% Bayesian credible interval 1.01 to 3.19).

These findings from the PROTECT AF trial were largely similar to those reported at the American College of Cardiology meeting in March, with the researchers again suggesting the procedure as an alternative to chronic warfarin. (See ACC: Device May Prevent Stroke in AF Patients)

Whereas the study excluded patients deemed unsuitable for long-term warfarin, some cardiologists at the conference were reluctant to consider the procedure for those who could tolerate warfarin.

A commentary accompanying the Lancet paper agreed that patients unsuitable for long-term warfarin may be the best candidates for left atrial appendage occlusion.

In the commentary, Dominick McCabe, PhD, Justin Kinsella, and W. Oliver Tobin, MD, PhD -- all of Adelaide and Meath Hospital, incorporating the National Children's Hospital of Trinity College Dublin in Ireland -- cautioned that routine use is not yet warranted for a diverse population of patients with nonvalvular atrial fibrillation.

They noted that the study had few events in controls and short follow-up, with the potential for long-term risk of paradoxical embolism and cardiac arrhythmias still unknown.

The trial included 707 patients with nonvalvular atrial fibrillation who had at least one risk factor for stroke -- such as prior stroke or transient ischemic attack, congestive heart failure, diabetes, hypertension, or age 75 or older.

Patients were randomized to chronic warfarin treatment or percutaneous placement of the WATCHMAN device.

The device group got heparin at implantation, and 86% were able to discontinue warfarin at 45 days after transesophageal echocardiography showed successful occlusion of the left atrial appendage. They also received aspirin and clopidogrel (Plavix) for six months after randomization, then long-term aspirin monotherapy.

At two years, both treatment groups had a similar intent-to-treat cumulative event rate (5.9% device, 95% CI 3.1 to 8.8, versus 8.3% control, 95% CI 4.0 to 12.5).

The results tended to be better for device group patients who successfully discontinued warfarin compared with controls (1.9 versus 4.6 per 100 patient-years, RR 0.40, 95% CI 0.19 to 0.91).

For the individual outcome measures, the results included:

• Similar cumulative mortality at one year (3.0% device versus 3.1%, P=NS)
• No significant difference in cumulative mortality at two years (5.9% versus 9.1%)
• More ischemic stroke with the device (1.1% procedure related versus 0.0%), although no difference after the periprocedural time frame (1.3 versus 1.6 events per 100 patient-years)
• 90% fewer hemorrhagic strokes with the device (0.2% versus 2.5%)
• Device embolization occurred in 0.6% of patients

Serious pericardial effusion was the most common of the primary safety events (4.8%), but none resulted in permanent impairment or death.

"It is expected that these event rates will further decrease with increased operator training and experience," Holmes' group said.