THE SUPERIORITY OF PINACIDIL OVER ADENOSINE CARDIOPLEGIA IN BLOOD-PERFUSED ISOLATED HEARTS

Background. Our laboratory has shown that the potassium-channel opener pinacidil is an effective cardioplegic agent. A theoretical benefit o f cardioplegia with potassium-channel openers is that it arrests the h eart at hyperpolarized membrane potentials, a state of minimal metabol ic requirement. This study was designed to examine another nondepolari zing agent, adenosine, and to test the hypothesis that it could provid e comparable cardioprotection or augment potassium-channel opener card ioplegia. Methods. Using the blood-perfused Langendorff technique, iso lated rabbit hearts were arrested for 30 minutes of global normothermi c ischemia. Cardioplegia consisted of either Krebs-Henseleit solution alone (control) or with pinacidil (50 mu mol/L), adenosine (200 mu mol /L to 1 mmol/ L), or pinacidil + adenosine (200 mu mol/L). Recovery of developed pressure and coronary now were recorded. Results. Postische mic functional recovery for control, pinacidil, adenosine, and adenosi ne + pinacidil groups was 44.1% +/- 3.4%, 59.5% +/- 5.2% (p < 0.05 ver sus control), 37.0% +/- 4.5%, and 56.0% +/- 2.9%, respectively. Conclu sions. Adenosine, alone or as adjunct to pinacidil cardioplegia, was n ot an effective cardioplegic agent, despite shorter times to electrome chanical arrest than control. The ineffectiveness of adenosine suggest s that the cardioprotective properties of potassium-channel openers in volve mechanisms other than the avoidance of membrane depolarization. (Ann Thorac Surg 1998;66:1329-36) (C) 1998 by The Society of Thoracic Surgeons