Influence of site of stimulation on measurement of ventricular vulnerability in the normal and ischemic feline heart.
Site of stimulation is an important variable in the inducibility of ventricular tachycardia in both non-human animal infarction models and in humans; that is, proximity of the stimulating electrode to the site of reentry facilitates the induction of sustained arrhythmia. Whether site of stimulation is decisive in measurement of vulnerability to ventricular fibrillation (VF) during acute coronary occlusion has not been fully evaluated. We measured VF thresholds in 9 chloralose-anesthetized cats at 2 right ventricular and 3 left ventricular sites (2 endocardial, 3 intramural) before and after abrupt occlusion of the anterior descending coronary artery. VF thresholds were measured using a single stimulus of increasing intensity delivered during ventricular drive. Although VF thresholds were lower at endocardial sites, there were no significant differences in VF threshold among any of the sites tested at control. After occlusion, VF thresholds fell to a similar extent at all 5 sites tested. The percent reduction in VF threshold at any site was not influenced by the sequence of testing. VF may be precipitated from multiple sites and, unlike ventricular tachycardia, does not represent an isolated focus of arrhythmogenicity.
D000818:Animals; D002304:Cardiac Pacing, Artificial; D002415:Cats; D005260:Female; D006352:Heart Ventricles / Q000503:physiopathology; D008297:Male; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology*; D014693:Ventricular Fibrillation / Q000209:etiology / Q000503:physiopathology*