We have developed a nondepolarizing
solution (
NDS) that retards myocardial
calcium accumulation during
cardioplegia. This study compares 1) the membrane resting potential (Em) in Purkinje fibers during
cardioplegia induced by
NDS or University of Wisconsin
solution (UW) at normothermia and
hypothermia for 6 h, 2) left ventricular (LV) diastolic function of isolated canine hearts preserved with
NDS or UW for 6- and 12 h in
hypothermia to elucidate the relationship between diastolic function and myocyte physiology (n = 8, each group), and 3) the effect of Non-depolarizing
solution (
NDS) compared with Bretschneider's
HTK solution on LV diastolic function in isolated rabbit hearts using the Langendorff model in normothermia (n = 10, each group). The membrane resting potential (Em) was as follows:
NDS in normothermia, -71 mV (2 min), -65 mV (30 min), and -52 mV (60 min);
NDS in
hypothermia, -40 mV (1 h) and -32 mV (6 h), while UW in
hypothermia 0 mV (6 h). Myocardial
calcium accumulation during reperfusion in the
NDS groups was minimal and significantly lower than in the UW groups after the 6- and 12 h preservations. Postreperfusion myocardial cyclic adenosin monophosphate (cAMP) and adenosin
triphosphate (
ATP) concentrations in the
NDS groups were closer to normal than in the UW groups after the 6- and 12 h preservations. The postreperfusion myocardial Ca concentration correlated with the cAMP (r = -0.68, n = 25, P = 0.003) and cyclic
guanosine monophosphate (cGMP) concentrations (r = -0.69, n = 25, P = 0.003). The left ventricular end-diastolic pressure (LVEDP) after reperfusion correlated with myocardial
ATP (r = -0.65, n = 25, P = 0.003) and Ca concentrations (r = -0.68, n = 25, P = 0005). However, the parameter indicating LV elasticity (max LV -dp/dt) correlated with neither the Ca or
ATP concentration following reperfusion.
NDS prevented stiffness (increased LVEDP) better than HTK during normethermic
cardioplegia for 30 min. These results in vitro suggest that
NDS prevents myocardial Ca accumulation, depletion of
ATP and cAMP, and preserves LV diastolic function, particularly stiffness after reperfusion, for up to 12 h. Furthermore, the myocardial Ca concentration is inversely correlated with the cAMP and cGMP concentrations.