Functional and metabolic preservation of the immature myocardium with verapamil following global ischemia.

This study investigated the effects of the calcium antagonist verapamil on the functional and biochemical recovery of the immature heart following 30 minutes of normothermic ischemia. Verapamil (0.2 mg per kilogram of body weight) was infused into the aortic root in 5 puppies (8 to 10 weeks of age) prior to cardiopulmonary bypass. Five additional puppies received saline solution as a control. Left ventricular developed pressure, rate of rise of left ventricular pressure (dP/dt), left ventricular endsystolic pressure-diameter relationship (emax), compliance, and water content were assessed before and after bypass. Serial myocardial biopsies for adenosine triphosphate (ATP) and creatine phosphate were obtained. Puppies pretreated with verapamil recovered more than 80% of the preischemic left ventricular developed pressure, dP/dt, and emax in contrast to 50% recovery in the controls (p less than 0.05). The ATP content declined 40% during the interval of ischemia in the control puppies, versus 14.6% in the verapamil-treated puppies (p less than 0.05). Myocardial compliance was preserved in the verapamil-treated puppies and was associated with significantly less myocardial water content (78% versus 80.1% in the controls)(p less than 0.01). This study demonstrates the protective effects of verapamil on the immature heart during ischemic arrest. These results suggest that verapamil may be a useful adjunct to current methods of protecting the infant heart during cardiopulmonary bypass.