The Contribution of Mechanical Effects to Ventricular Arrhythmias during Acute Regional Ischemia

Abstract

Arrhythmias during acute regional ischemia can cause sudden cardiac death. Our goal was to investigate the mechanical contribution to ventricular arrhythmias in this setting. Experiments were conducted in Langendorff-perfused rabbit hearts. The anterior branch of the left circumflex coronary artery was ligated for 60 min in three groups: (i) physiologically-loaded left ventricle (Loaded); (ii) unloaded left ventricle (Unloaded); and (iii) physiologically-loaded, non-contracting left ventricle (Non-contracting). Loaded hearts had a significantly higher incidence of arrhythmias than Unloaded and Non-contracting hearts, peaking at 30-35 min, with activation often arising from the ischemic border. This suggests mechanical effects during ischemia are necessary for ventricular arrhythmias. To investigate whether altered mechanics are sufficient for arrhythmia induction, hearts were locally perfused with blebbistatin to cause regional loss of contraction. This did not result in arrhythmias, suggesting that mechanical effects are necessary, but not sufficient, for ventricular arrhythmias during acute regional ischemia in isolated rabbit hearts.