Immediate ventricular fibrillation and heart rate variability in dogs with acute ischemia

Acute ischemia alters autonomic neural tone and fosters ventricular fibrillation (VF) development. The authors report the relationship between heart rate variability (HRV) and the subsequent development of VF following acute left anterior descending (LAD) coronary artery ligation in 12 dogs. VF developed in 5 dogs following LAD ligation. In these dogs, HRV prior to LAD occlusion demonstrated an increased low to high frequency energy content ratio compared to dogs without VF. The conclusion is that increased low frequency energy in pre-ligation HRV is related to development of immediate VF. These findings suggest that VF occurs in ischemic dogs that have increased sympathetic and/or decreased parasympathetic activity prior to LAD ligation