ELECTROMECHANICAL ASSOCIATION IN REGIONALLY STUNNED SWINE MYOCARDIUM

Background: Postischemic myocardial dysfunction (''stunned'' myocardiu m) is a common problem after cardiac surgery and cardiac transplantati on. A ''low-voltage'' QRS complex in the electrocardiogram is also oft en seen in patients with severe cardiac dysfunction. The authors inves tigated the relationship between mechanical function and electrographi c characteristics in postischemic swine myocardium, and determined whe ther inotropic stimulation with dobutamine alters the electrogram whil e 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 d obutamine (1-25 mug . kg-1 . min-1) before and after 10 or 15 min of i schemia followed by 1 h of reperfusion. Results. Wall thickening was a bolished after ischemia and reperfusion, and QRS amplitude decreased 2 5% in the endocardium and 29% in the epicardium. Dobutamine infusion r estored 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 (mea n +/- 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 bet ween local electrical and mechanical events in postischemic swine myoc ardium.