THERE AN ALTERNATIVE TO POTASSIUM ARREST

Background. Mounting clinical and experimental evidence suggests that postoperative myocardial dysfunction is a frequent consequence of surg ical global ischemia and reperfusion, despite our modern techniques of myocardial protection. The ubiquitous use of hyperkalemic depolarizin g 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. Meth ods. An adenosine triphosphate-sensitive potassium channel opener, apr ikalim, was used to induce hyperpolarized arrest. Aprikalim was able t o produce sustained and reproducible electromechanical arrest that was reversible by reperfusion. Results. In isolated heart models, when co mpared with depolarized hyperkalemic arrest, hyperpolarized arrest aff orded better protection from global normothermic ischemia and resulted in better postischemic recovery of function upon reperfusion. Prelimi nary studies in a porcine cardiopulmonary bypass model also have revea led that hyperpolarized arrest can be achieved in a model more closely approximating the clinical setting, and can effectively protect the h eart during normothermic surgical global ischemia. Conclusions. Hyperp olarized cardiac arrest may offer an effective alternative to traditio nal potassium arrest.