Sequential noninvasive assessment of left ventricular size, regional wall thickness and function during 3 hours of coronary artery occlusion and reperfusion: differential effects of reflow in dogs with small vs large areas at risk.

The present study was undertaken to determine noninvasively the sequential changes in left ventricular (LV) size, wall thickness and regional contractile function occuring during 3 h of proximal left anterior descending coronary artery occlusion (CAO), and their modification by reperfusion (REP) over a 7-day period. Twenty, closed-chest, anesthetized dogs underwent CAO for 3 h and were reperfused for 7 days. Hemodynamics (aortic, LV pressure, LV dP/dt) and regional LV function were measured sequentially during CAO and reperfusion. The animals were killed at 7 days and infarct size was measured using the triphenyl-tetrazolium-chloride technique. Regional function (systolic fractional area change, FAC) was measured in 40 LV segments of 5 two-dimensional echo short-axis planes (8 segments per section). At three hours of CAO, 14 dogs developed extensive areas of akinesis or dyskinesis in more than 6 segments (Group I, large risk area), whreas 6 dogs developed akinesis or dyskinesis in 6 segments of less (Group II, small risk area). Four dogs died between 12 and 48 h after REP in Group I and none of Group II died. Recovery of regional function after REP was significantly different between Groups I and II: in hypokinetic segments, FAC improved from 16.7 + or - 0.9% (mean + or - SEM) at 3 h of CAO to 25.4 + or - 3.2% at 24 h and to 34.9 + or - 2.0% at 7 days (66.3 + or - 3.4% of baeline) after REP in Group I; in Group II, FAC increased from 16.6 + or - 1.5% at 3 h of CAO to 48.5 + or - 7.4%...