Electromechanical Association in Regionally Stunned Swine Myocardium

BACKGROUND: Postischemic myocardial dysfunction ("stunned" myocardium) is a common problem after cardiac surgery and cardiac transplantation. A "low-voltage" QRS complex in the electrocardiogram is also often seen in patients with severe cardiac dysfunction. The authors investigated the relationship between mechanical function and electrographic characteristics in postischemic swine myocardium, and determined whether inotropic stimulation with dobutamine alters the electrogram while improving mechanical function. METHODS: Regional wall thickening and regional electrogram from electrodes in the endo- and epicardium were measured in 12 pigs during intravenous infusion of several doses of dobutamine (1-25 micrograms.kg-1.min-1) before and after 10 or 15 min of ischemia followed by 1 h of reperfusion. RESULTS: Wall thickening was abolished after ischemia and reperfusion, and QRS amplitude decreased 25% in the endocardium and 29% in the epicardium. Dobutamine infusion restored both wall thickening and myocardial QRS amplitude to baseline values. The correlation between myocardial QRS amplitude and systolic wall thickening was significant in each animal (r = 0.88 +/- 0.02 (mean +/- 1 SEM, n = 12); median r = 0.89; range 0.74-0.95, P < 0.01, for all relations). CONCLUSIONS: This study showed a close association between local electrical and mechanical events in postischemic swine myocardium.