Experimental Study of Cardiac Lymph in Myocardial Stunning

To clarify the pathophysiology of myocardial "stunning" from the viewpoint of the cardiac lymphatic system, lymph dynamics were studied in a fifteen-minute ischemic dog model. The influences of two interventions were evaluated: active lymph drainage by hyaluronidase (500 units/kg intravenously given on occlusion) and lymph stasis (loading 10 cmH 2 O of hydrostatic pressure on the cardiac lymphatic system on and after occlusion). Lymph flow of the control group did not significantly change despite remarkable decreases of both regional myocardial contractility (systolic strain) and regional myocardial blood flow (RBF). Meanwhile, active lymph drainage effectively improved systolic strain from the early reperfusion period (from 62 ± 4% to 77 ± 4% of baseline for control versus lymph drainage group, respectively, P < 0.05). Significant improvement of RBF was also noted within the endocardial side. Lymph stasis gradually deteriorated systolic strain (from 65 ± 5% to 45 ± 7% for control versus lymph stasis group at 240-minute reperfusion, respectively, P < 0.05) and was accompanied by an increase of myocardial water content. In pooling and analyzing the results obtained from these groups, a positive correlation was found between lymph flow and systolic strain, and it tended to be better during the early reperfusion period (r= 0.63, P < 0.01 at fifteen-minute reperfusion r=0.49, P < 0.05 at 240-minute reperfusion). The authors conclude that the process of myocardial "stunning" can be influenced by regulating lymph flow.