Comparison of hemodynamics, cardiac electrophysiology, and ventricular arrhythmia in an open- and a closed-chest porcine model of acute myocardial infarction

Abstract

Ventricular fibrillation (VF) during acute myocardial infarction (AMI) is an important contributor to sudden cardiac death. Large animal models are widely used to study AMI-induced arrhythmia, but the mode of AMI induction ranges from thoracotomy and surgical ligation of a coronary vessel (open chest) to minimally invasive techniques, including balloon occlusion (closed chest). How the choice of induction affects arrhythmia development is unclear. The aim of this study was to compare an open-chest and a closed-chest model with regard to hemodynamics, electrophysiology, and arrhythmia development. Forty-two female Danish Landrace pigs (20 open chest, 22 closed chest) were anesthetized, and occlusion of the mid-left anterior descending coronary artery was performed for 60 min. Opening the chest reduced blood pressure and cardiac output (Δ −22 mmHg, Δ −1.5 L/min from baseline, both P < 0.001 intragroup). Heart rate decreased with opening of the chest but increased with balloon placement ( P < 0.001). AMI-induced ST elevation was lower in the open-chest group ( P < 0.001). Premature ventricular contractions occurred in two distinct phases (0–15 and 15–40 min), the latter of which was delayed in the open-chest group ( P = 0.005). VF occurred in 7 out of 20 and 12 out of 22 pigs in the open-chest and closed-chest groups, respectively ( P = 0.337), with longer time-to-VF in the open-chest group (23.4 ± 1.2 min in open chest and 17.8 ± 1.4 min in closed chest; P = 0.007). In summary, opening the chest altered hemodynamic parameters and delayed the onset of ventricular arrhythmias. Hence, in the search for mechanisms and novel treatments of AMI-induced arrhythmia, caution should be taken when choosing between or comparing the results from these two models. NEW & NOTEWORTHY We demonstrated pronounced differences in hemodynamic parameters and time course of ventricular arrhythmias in regard to mode of infarct induction. Inducing myocardial infarction by thoracotomy and subsequent ligation decreased blood pressure and cardiac output and delayed the onset of ventricular arrhythmia, whereas balloon occlusion resulted in higher heart rates during infarct.