Prednisone Prevents Inducible Atrial Flutter in the Canine Sterile Pericarditis Model

Abstract

Atrial fibrillation (AF) and atrial flutter (AFL) are common following cardiac surgery and are associated with significant morbidity. We tested the hypothesis that suppression of the inflammatory response with steroids would significantly modify the inducibility of postoperative AF/AFL in the canine sterile pericarditis model. Twenty-three dogs were studied daily from creation of pericarditis to the fourth postoperative day: 11 dogs were treated with oral prednisone (PRED) starting 2 days preoperatively until the end of the study; 12 dogs were controls (CON). EP testing was performed daily using epicardial electrodes placed at initial surgery. High-resolution (404 sites) epicardial mapping was performed during the terminal study. Baseline and daily CRP levels were obtained in all dogs. Sustained AFL was absent in PRED (0%) versus CON dogs (91%; P < 0.001); AF induced in the early postoperative course in PRED dogs was of very short CL (mean 66 ms). Tissue inflammation was significantly attenuated in PRED dogs. Thresholds were lower in PRED versus CON dogs, significantly so on postoperative day (POD) 3. There was a trend toward lower ERPs in the PRED group at all CLs. CRP levels were markedly reduced in PRED versus CON dogs (peak CRP 78 +/- 7 mg/L vs 231 +/- 21 mg/L, P < 0.001), and returned to baseline in PRED dogs by POD 4, correlating with a virtual absence of sustained arrhythmia. During open chest mapping studies on POD 4, PRED dogs showed only nonsustained AF/AFL. Prednisone eliminated postoperative AFL, affected all EP parameters studied, and attenuated the inflammatory response associated with pericarditis.