Potassium channel openers: are they effective as pretreatment or additives to cardioplegia?

Background. This study was designed to test the hypothesis that the potassium channel opener pinacidil (Pin) as a pretreatment (PT) agent or additive to St. Thomas’ solution (StT) could enhance myocardial protection. Methods. In a parabiotic rabbit Langendorff model, 36 hearts underwent global normothermic ischemia (1 hour) followed by reperfusion (30 minutes). Cardioplegia (50 mL, every 20 minutes) consisted of: StT; PinPT/StT, where Pin PT preceded StT arrest; Pin alone; Pin in StT (Pin/StT); and Pin in low potassium StT. Systolic function after reperfusion (percent recovery of developed pressure) and compliance (diastolic slope from pressure–volume relationship) were measured. Results. There was no significant difference between StT and PinPT/StT in percent recovery of developed pressure (51.54% ± 3.5%, 42.17% ± 4.0%, respectively) or compliance. Likewise, no significant differences occurred between Pin, StT, Pin/StT, and Pin in low potassium StT in percent recovery of developed pressure (58.99% ± 4.8%, 51.54% ± 3.5%, 53.09% ± 3.2%, 66.43% ± 7.3%, respectively) or compliance. Conclusions. Pin is as effective a cardioplegic agent as StT; however, its use as a pretreatment or additive to traditional and Pin in low potassium StT provided no additional benefit in functional recovery.