Background: Adenosine triphosphate-sensitive potassium-channel openers are potent vasodilators that have been found to be cardioprotective during myocardial ischemia. The potassium-channel opener pinacidil was investigated to determine its efficacy as a cardioplegic agent.
Methods: A blood-perfused, parabiotic, isolated rabbit heart Langendorff preparation was used. Fifty-six hearts underwent 30 minutes of global normothermic ischemia after a 50-mL infusion of cardioplegia, followed by 60 minutes of reperfusion. The cardioplegia consisted of Krebs-Henseleit solution with either vehicle alone (control), 20 mmol KCl, or pinacidil (10, 50, 100, 150, or 200 mumol/L). The developed pressure was measured at baseline and after reperfusion. Coronary blood flow was measured with an in-line ultrasonic probe.
Results: Pinacidil (50 mumol/L), as opposed to potassium cardioplegia, provided significantly better postischemic percentage recovery of developed pressure compared with controls (68.3% +/- 4.0% versus 44.6% +/- 5.5%; p < 0.05). The time until electrical arrest was significantly shorter in the hyperkalemic group than in all other groups. Linear end-diastolic pressure-volume relationships revealed an increase in slope after ischemia in all groups. Coronary flow after 5 minutes of reperfusion was significantly higher in both the 50-mumol/L and 100-mumol/L pinacidil groups compared with traditional hyperkalemic arrest, and this returned to baseline after 15 minutes.
Conclusions: The potassium channel opener pinacidil provided dose-dependent myocardial protection during global ischemia in the blood-perfused rabbit heart model. Potassium-channel openers are a promising class of drugs that may provide an alternative to traditional hyperkalemic cardioplegia.