Procedure Does Not Reduce Stroke Risk in Patients with Atrial Fibrillation

Left atrial appendage obliteration reduces stroke risk in patients with nonvalvular atrial fibrillation (AF), but a new study suggests that the procedure does not reduce stroke risk in AF patients after bioprosthetic mitral valve replacement.

Researchers in Beijing retrospectively studied 173 AF patients who underwent bioprosthetic mitral valve replacement, including 81 patients who also underwent left atrial appendage obliteration via the endocardial running suture method.

Over a mean follow up period of 40 months (±17 months), postoperative AF was observed in 136 of the patients. Of those, 13.97% suffered some form of thrombosis during follow-up, but incidence rates did not differ significantly between those patients who also underwent left atrial appendage obliteration and those who did not. Thrombosis was observed in 10 of 79 (12.7%) in the former group and 9 of 57 (15.8%) of the latter group. Multivariate analysis determined that the probability of the difference stemming from chance was more than half (p=0.0603).

“Surgical left atrial appendage obliteration in patients with valvular AF undergoing bioprosthetic mitral valve replacement did not reduce thrombosis events, even when the CHA₂DS₂-VASc score was ≥ 2 points,” the study authors wrote in Herz.

The findings of the new study are surprising because previous research has found that left atrial appendage obliteration is associated with lower stroke risk in patients who undergo mitral valve replacement and in certain types of AF patients (though the new study seems to be the first of any size to examine the effects of appendage obliteration in AF patients who undergo valve replacement).

The most cited work on stroke reduction among patients with mitral valve prosthesis seems to be a retrospective analysis that appeared 13 years ago in the Journal of the American College of Cardiology. The researchers studied 205 patients who had undergone mitral valve replacement and compared outcomes among a number of subgroups, including the 58 patients who had also undergone ligation of the left atrial appendage (LAA).

“Multivariate analysis identified the absence of LAA ligation (odds ratio [OR], 6.7; 95% confidence interval [CI], 1.5-31.0; p = 0.02) and the presence of left atrial thrombus as the only independent predictors of occurrence of an embolic event. Moreover, when the identification of an incomplete LAA ligation was considered together with the absence of LAA ligation, risk of embolism increased up to 11.9 x (OR, 11.9; 95% CI, 1.5-93.6; p = 0.02),” the study authors wrote.

Several prior studies have found that left atrial appendage obliteration is associated with lower stroke risk in some AF patients. Among the most cited of these is a review and analysis that appeared in the Annals of Thoracic Surgery nearly 20 years ago. A pair of Mayo Clinic researchers reviewed 23 studies and found, overall, that 446 of 3,504 (13%) rheumatic AF patients, and 222 of 1,288 (17%) nonrheumatic AF patients had a documented left atrial thrombus.

“Thrombi were localized to, or were present in the left atrial appendage and extended into the left atrial cavity in 254 of 446 (57%) of patients with rheumatic atrial fibrillation. In contrast, 201 of 222 (91%) of nonrheumatic atrial fibrillation-related left atrial thrombi were isolated to, or originated in the left atrial appendage (p < 0.0001),” the study authors wrote. “These data suggest that left atrial appendage obliteration is a strategy of potential value for stroke prophylaxis in nonrheumatic atrial fibrillation.”