Ventricular fibrillation in rats with cardiac fibrosis

Previous studies have shown that administration of angiotensin II (Ang II) causes atrial and ventricular fibrosis in rats, as is found in patients with chronic heart failure. We hypothesize that fibrosis creates a substrate that promotes the induction of ventricular fibrillation (VF). Fourteen, eight-week old, Sprague-Dawley rats were studied. Eleven received a four-week treatment of Ang II (9 μg/hr) from an implanted mini-pump. After treatment, the chest was opened, and 50 Hz stimulation at a strength of three times the pacing threshold was applied across the atria and ventricles for 2.5, 5, and 10 s. VF was more inducible in treated rats (6 of 11) than untreated rats (0 of 3, P < 0.05). Three of 12 VF episodes were sustained (> 10 s) while the remaining VF episodes were nonsustained (> 30 ms and < 10 s) after stimulation ended. Our results suggest that cardiac fibrosis induced by Ang II treatment creates a substrate for sustained VF.