Is there an alternative to potassium arrest?

Background.: Mounting clinical and experimental evidence suggests that postoperative myocardial dysfunction is a frequent consequence of surgical global ischemia and reperfusion, despite our modern techniques of myocardial protection. The ubiquitous use of hyperkalemic depolarizing solutions in all forms of cardioplegia may be partly responsible for this phenomenon because of the known ongoing metabolic processes and damaging transmembrane ionic fluxes that occur at depolarized membrane potentials. Cardiac arrest at hyperpolarized potentials, the natural resting state of the heart, may avoid the shortcomings of depolarized arrest and provide an alternative means of myocardial protection. Methods.: An adenosine triphosphate-sensitive potassium channel opener, aprikalim, was used to induce hyperpolarized arrest. Aprikalim was able to produce sustained and reproducible electromechanical arrest that was reversible by reperfusion. Results.: In isolated heart models, when compared with depolarized hyperkalemic arrest, hyperpolarized arrest afforded better protection from global normothermic ischemia and resulted in better postischemic recovery of function upon reperfusion. Preliminary studies in a porcine cardiopulmonary bypass model also have revealed that hyperpolarized arrest can be achieved in a model more closely approximating the clinical setting, and can effectively protect the heart during normothermic surgical global ischemia. Conclusions.: Hyperpolarized cardiac arrest may offer an effective alternative to traditional potassium arrest.