Abstract: Using isolated rabbit heart model,a comparative study of the effect of myocardial protection with cardioplegic solutions containing potassium,potassium-verapamil and potassium-verapamil-low sodium as their main components respectively was made.From the analysis of the results,the following conclusions are arrived: 1.Better protection can be achieved by addition of verapamil to conventional cold-potassium-cardioplegic solution.It helps to decrease the breakdown of adenosine triphosphate （ATP） during ischemie arrest,alleviates the damages of the myocardial ultrastructure,and reduces the coronary resistance.It also gives a better restoration of myocardial contractility. 2.A reduction of Na⁺ in cardioplegic solution from 130mEq/L to 95 mEq/L provides further protection to myocardium.