Novel Patterns of Left Ventricular Mechanical Activity During Experimental Cardiac Arrest in Pigs

Abstract

We conducted an experimental study to evaluate the presence of coordinated left ventricular mechanical myocardial activity (LVMA) in two types of experimentally induced cardiac arrest: ventricular fibrillation (VF) and pulseless electrical activity (PEA). Twenty anesthetized domestic pigs were randomized 1:1 either to induction of VF or PEA. They were left in nonresuscitated cardiac arrest until the cessation of LVMA and microcirculation. Surface ECG, presence of LVMA by transthoracic echocardiography and sublingual microcirculation were recorded. One minute after induction of cardiac arrest, LVMA was identified in all experimental animals. In the PEA group, rate of LVMA was of 106±12/min. In the VF group, we identified two patterns of LVMA. Six animals exhibited contractions of high frequency (VFhigh group), four of low frequency (VFlow group) (334±12 vs. 125±32/min, p<0.001). A time from cardiac arrest induction to asystole (19.2±7.2 vs. 7.3±2.2 vs. 8.3±5.5 min, p=0.003), cessation of LVMA (11.3±5.6 vs. 4.4±0.4 vs. 7.4±2.9 min, p=0.027) and cessation of microcirculation (25.3±12.6 vs. 13.4±2.4 vs. 23.2±8.7 min, p=0.050) was significantly longer in VFlow group than in VFhigh and PEA group, respectively. Thus, LVMA is present in both VF and PEA type of induced cardiac arrest and moreover, VF may exhibit various patterns of LVMA.