Potassium Channel Openers and Cardiac Surgery

Abstract

Cardiac operations offer the unique possibility of precisely planning the time at which the aortic crossclamp will be applied, thereby initiating the period of global ischemia. This provides the opportunity of using the timely implementation of preconditioning strategies as a novel approach to intraoperative myocardial protection based on the therapeutic exploitation of the heart’s natural defense mechanisms against ischemic injury. Efficacy, safety and practicality issues have lead to shift attention from ischemic to pharmacologic preconditioning regimens, the underlying rationale being to take advantage of the cardioprotective mediators of ischemic preconditioning whilst eliminating the detrimental effects inherent to any ischemic insult. Among these mediators, potassium channel openers (PCO) are receiving a growing deal of attention because of the recognition (reviewed in another chapter of this book) that they might act as the effectors of the intracellular signaling pathway leading to ischemic preconditioning. Since one of the drugs is currently available this reinforces the interest of establishing their potential role in the armamentarium of our myocardial preservation techniques. This role might indeed be important as, depending on the timing and modalities of their administration, PCO may play a multiplicity of roles and can be considered as preconditioning agents (if given before standard potassium arrest), hyperpolarizing cardioplegic agents (if given instead of potassium cardioplegia) or simple potentiators of arrest (if given as additives to potassium cardioplegia). In this review, these three potential applications will be successively discussed.