Impairment of contraction increases sensitivity of epicardial lymph pressure for left ventricular pressure

In the present study, cardiac contraction was regionally impaired to investigate the relationship between contractility [maximum first time derivative of left ventricular pressure (dP /d t )] and P on epicardial lymph pressure (P ) generation. Measurements were performed in open-chest anesthetized dogs under control conditions and while local contraction was abolished by intracoronary administration of lidocaine. Lidocaine significantly lowered dP /d t and P pulse to 77 ± 9 (SD; n = 5) and 82 ± 5% of control, respectively, whereas P pulse increased to 186 ± 101%. The relative increase of maximum P to P related inversely to the change in dP /d t after lidocaine administration. Additional data were obtained when P was transiently increased by constriction of the descending aorta. The ratio of pulse P to P during aortic clamping increased after lidocaine administration, from 0.063 ± 0.03 to 0.15 ± 0.09. The results suggest that transmission of P to the cardiac lymphatic vasculature is enhanced when regional contraction is impaired. These findings imply that during normal, unimpaired contraction lymph vessels are shielded from high systolic P by the myocardium itself.