IMPAIRMENT OF CONTRACTION INCREASES SENSITIVITY OF EPICARDIAL LYMPH PRESSURE FOR LEFT-VENTRICULAR PRESSURE

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