Effects of coronary blood flow, myocardial contractility, and heart rate on cardiac lymph circulation in open-chest dogs. Use of a direct cannulation method for subepicardial lymph vessel.

The study was conducted to evaluate the effects of increased coronary blood flow (CBF), myocardial contractility, and heart rate on cardiac lymph circulation using a subepicardial lymph channel in anesthetized open-chest dogs. A subepicardial lymph vessel along the left anterior descending coronary artery (LAD) was cannulated directly with a small polyethylene tube, and lymph flow (LF) and protein concentration of lymph (PC) were measured. Coronary blood flow (CBF) was increased with intracoronary infusion of adenosine, and myocardial contractility with isoproterenol (isoprenaline) infusion. Effects of an increase in CBF using a constant flow system were also studied. Heart rate was increased by atrial pacing. The control cardiac LF in 17 adult mongrel dogs varied from 5.3 to 12.6 microliters/min (mean 8.4 +/- 2.8). With an increase in CBF, LF and protein efflux to lymph (PEF) increased both adenosine and isoproterenol infusion, while PC was decreased by adenosine and increased by isoproterenol. The increase in CBF using the constant flow system elicited the essentially similar extent of changes in LF and PC in relation to a change in CBF as those during infusion of adenosine. The increase in LF and PEF was significantly smaller during the infusion of adenosine than isoproterenol infusion in relation to a change in CBF. In contrast, pacing-induced tachycardia which caused a relative shortening of the diastolic phase in the heart cycle reduced LF and PEF despite of a slight increase in CBF. These findings suggest that CBF and relative duration of diastole in the heart cycle play an important role in regulation of lymph circulation, and isoproterenol can change capillary permeability in addition to increasing CBF.