Less afterload sensitivity in short-term hibernating than in acutely ischemic and stunned myocardium

Short-term hibernating myocardium is characterized by reduced contractile function during persistent moderate ischemia, the recovery of metabolic parameters, and the absence of necrosis. To study the afterload dependence of regional wall excursion in short-term hibernating myocardium, in 11 enflurane-anesthetized swine the left anterior descending coronary artery was cannulated and hypoperfused for 90 min to reduce anterior systolic wall thickening (WT, sonomicrometry) by 60%. Under control conditions, at 5 and 90 min ischemia the descending thoracic aorta was acutely constricted to increase left ventricular (LV) pressure by 30 mmHg. Under control conditions, increased LV pressure resulted in decreased WT [i.e., a negative slope of the relationship between WT and LV end-systolic pressure: -11.2 +/- 4.2 (SD) microm/mmHg]. This slope was further significantly decreased at 5 min ischemia (-26.5 +/- 8.8 microm/mmHg) but returned toward control values in short-term hibernating myocardium at 90 min ischemia (-17.2 +/- 6.6 microm/mmHg). At 30 min reperfusion, the slope was once more significantly decreased (-27.8 +/- 8.1 microm/mmHg). In conclusion, WT in short-term hibernating myocardium is less afterload dependent than in acutely ischemic and reperfused myocardium.