Role of ATP-sensitive K+ channel on ECG ST segment elevation during a bout of myocardial ischemia. A study on epicardial mapping in dogs

Abstract

Background: ATP-sensitive K+ channels are activated when the myocardium becomes ischemic. However, the role of the ATP-sensitive K+ current in the emergence of ECG ST changes during ischemia remained unclarified.

Methods and results: The left anterior descending coronary artery (LAD) was cannulated and perfused with arterial blood from the carotid artery through a bypass tube in 8 anesthetized, open-chest dogs. An array of 60 unipolar electrodes mounted on a sock was used to record epicardial electrograms of the whole heart. Pinacidil (10 micrograms.kg-1 x min-1), an ATP-sensitive K+ channel opener, was infused into the bypass tube for 2 minutes, and the electrograms were recorded before and after the infusion. The elevation of the ST segment and the increase of QRST area were observed spatially over the LAD-perfused region. At the electrode showing the largest ST segment elevation, the activation recovery interval, an index of action potential duration, was shortened from 202 +/- 9 to 111 +/- 18 milliseconds (P < .001). These electrographic changes were similar to those noted in 2-minute coronary occlusion (n = 8). The extent of ST segment elevation during coronary occlusion was attenuated after the intravenous pretreatment with glibenclamide (0.3 mg/kg), a blocker of the KATP channel (n = 5).

Conclusions: The findings of this study suggest that the activation of ATP-sensitive K+ channels during a bout of acute myocardial ischemia plays an important role in the emergence of ECG ST elevation.