Chronic Rapid Atrial Pacing

• DOI: 10.1161/01.cir.91.5.1588
• Publication Date: 2012-06-12T00:34:42Z
• Authors: Carlos A. Morillo; George J. Klein; Douglas L. Jones; Colette M. Guiraudon
• Keywords: Atrium (architecture); Effective refractory period

Background Despite the clinical importance of atrial fibrillation (AF), development chronic nonvalvular AF models has been difficult. Animal sustained have developed primarily in short-term setting. Recently, ventricular myopathy and after several weeks continuous rapid pacing. We hypothesized that pacing would lead to myopathy, yielding a reproducible model AF. Methods Results Twenty-two halothane-anesthetized mongrel dogs underwent insertion transvenous at right appendage was continuously paced 400 beats per minute for 6 weeks. Two-dimensional echocardiography performed 11 assess effects on size. Atrial vulnerability defined as ability induce repetitive responses during programmed electrical stimulation assessed by extrastimulus burst-pacing techniques. Effective refractory period (ERP) measured two endocardial sites atrium. Sustained ≥15 minutes. In animals with AF, 10 quadripolar epicardial electrodes were surgically attached left atria. The local fibrillatory cycle length (AFCL) 20-second window, mean AFCL each site. Marked biatrial enlargement documented; pacing, atrium 7.8±1 cm 2 baseline versus 11.3±1 4.3±0.7 7.2±1.3 An increase area least 40% necessary strongly correlated inducibility ( r =.87). Electron microscopy tissue demonstrated structural changes characterized an mitochondrial size number disruption sarcoplasmic reticulum. After induced 18 (82%) nonsustained (9%). occurred spontaneously 4 (18%). Right ERP, lengths 300 milliseconds baseline, significantly shortened from 150±8 127±10 147±11 123±12 milliseconds, respectively P <.001). This finding highly predictive (90%). Increased (40%) ERP shortening induction (88%). Local well R =.93). Mean shorter (81±8 milliseconds) compared 94±9 <.05). posterior consistently found (74±5 milliseconds). Cryoablation this attempted dogs. 9 (82%; mean, 9.0±4.0; range, 5 14), terminated no longer serial cryoablation. Conclusions readily inducible most associated marked vulnerability. uniformly shown shortest AFCL. results restoration sinus rhythm prevention cryoablation suggest may be critical maintenance model.