Improved myocardial recovery from ischemia. Treatment with low-dose adenosine triphosphate-magnesium chloride

To evaluate the effects of adenosine 5-triphosphate-magnesium chloride (ATP-MgCl2) on myocardial function following ischemia, mongrel dogs were placed on cardiopulmonary bypass with separate coronary perfusion pressures at 80 mm Hg. An intraventricular balloon was used to assess cardiac function as the area under the pressure-volume curve (PV), compliance (C), and cardiac contractility (dP/dT). Control measurements were made of coronary flow (Q), myocardial oxygen consumption and PV, C, and dP/dT. Myocardial ischemia was then induced for 45 minutes, followed by reperfusion (R). In group 1 (n = 5), no ATP-MgCl2 was infused into the coronary perfusion line. In group 2 (n = 5), low-dose ATP-MgCl2 (0.13 mg/min/kg) was infused during the first 30 minutes of reperfusion (R0 to R30), and in group 3 (n = 5), high-dose ATP-MgCl2 (3.2 mg/min/kg) was infused from R0 to R30. Use of ATP-MgCl2 therapy produced marked coronary vasodilation. After 20 minutes of reperfusion (R20), coronary resistance was 81% +/- 12%, 55% +/- 15%, and 31% +/- 3% of control in groups 1, 2, and 3, respectively. The high-dose ATP-MgCl2 (group 3) caused a marked systemic hypotension, but the low-dose ATP-MgCl2 (group 2) did not. After 75 minutes of reperfusion (R75), compliance was decreased in all groups. In groups 1 and 3, both function (PV) and dP/dT were significantly decreased. However, for group 2 (low-dose ATP-MgCl2), function (PV), and dP/dT were not different from the control group, indicating an excellent recovery. Thus, at low doses, ATP-MgCl2 appears to be a promising adjunct to the treatment of the ischemic myocardium.