Protective effect of methylprednisolone on ischaemic myocardium assessed by ventricular function

Low-dose propranolol for the protection of the left ventricle from ischaemic damage

Global myocardial ischaemia improves intracardiac operating conditions but damages the myocardium. Propranolol should reduce this damage but may impair postoperative myocardial contractility. An assessment of its protective effect during 90 minutes of normothermic ischaemia in canine hearts has been made. The early and late changes of contractility caused by low-dose propranolol were also recorded. A comparison of cardiac isovolumic contractile force, velocity, and compliance was made in three groups of dogs given 30 microgram/kg of propranolol with or without 90 minutes of cardiac ischaemia, or cardiac ischaemia without propranolol. Contractile force and velocity were significantly reduced by the propranolol, but recovered fully after 90 minutes. Ischaemia without propranolol reduced force and velocity of contraction significantly more than ischaemia with propranolol. Propranolol thus reduces operative ischaemic damage without itself impairing postoperative function.

Topical cardiac hypothermia: the effect of methylprednisolone sodium succinate

We evaluated the effects of methylprednisolone sodium succinate (MPSS) on 60 minutes of myocardial ischemia during profound (5 degrees C) topical cardiac hypothermia (ice chips) in a canine right heart bypass preparation. The ventricular function curve shifted to the right and downward, but not significantly, after ischemia, and stroke work declined significantly for both control and treated dogs. Contractility (rate of rise of left ventricular pressure and maximum velocity of the contractile element) declined for both groups but not significantly. Total coronary flow, oxygen consumption, and metabolism of lactate and pyruvate were not different for control and treated dogs. Ultrastructure of the outer and inner myocardium did not demonstrate benefit from MPSS. Intracellular and extracellular edema of moderate severity was slightly worse in the subendocardium, and reversible mitochondrial injury of a mild to moderate degreee was symmetrically present. Ice-related injury was not noted. We were unable to deomonstrate that pretreatment with MPSS favorably alters cardiodynamics or ultrastructure after 60 minutes of profound topical cardiac hypothermia.