Control of Ca²⁺ influx by manipulation of Ca²⁺ and/or Ca²⁺ antagonist in cardioplegic arrest

Maximum deactivation of the contractile elements using Ca²⁺ minimizes oxygen requirements during global ischemia, Ca²⁺ antagonists and Ca²⁺-free cardioplegia solutions are methods by which the Ca²⁺ flux can be manipulated. This study was performed with 5 experimental groups: 1) Standard cardioplegia (with Ca²⁺), 2) Ca²⁺-free cardioplegia, 3) Ca²⁺-free cardioplegia plus verapamil (0.5 mg/L), 4) Verapamil cardioplegia (with Ca²⁺), and 5) Ca²⁺-free cardioplegia, in which verapamil was administered at the onset of reperfusion (0.5 mg/L). Cardiac functions, heart rate, edema formation, and creatine kinase concentration were measured before and after 70 min of ischemia at a myocardial temperature of 20 °C. Ca²⁺-free cardioplegia may be beneficial under hypothermic conditions, but the “Ca²⁺ paradox” was still a matter of concern. Reperfusion with verapamil did not protect from reperfusion-related injuries. However, the use of verapamil provided more protection than did standard or Ca²⁺-free cardioplegic solutions. Since verapamil did not maintain membrane integrity during ischemia when combined with Ca²⁺-free cardioplegic solutions (prominent edema formation was observed), its combination with Ca²⁺ containing cardioplegic solutions is recommended.