Anti-arrhythmic effects of levcromakalim in the ischaemic rat heart: a dual mechanism of action?

KATP Channels in the Cardiovascular System

KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.

Protection against ventricular arrhythmias and cardiac death using adenosine and lidocaine during regional ischemia in the in vivo rat

Despite decades of research, there are few effective ways to treat ventricular fibrillation (VF), ventricular tachycardia (VT), or cardiac ischemia that show a significant survival benefit. Our aim was to investigate the combined therapeutic effect of two common antiarrhythmic compounds, adenosine and lidocaine (AL), on mortality, arrhythmia frequency and duration, and infarct size in the rat model of regional ischemia. Sprague-Dawley rats (n = 49) were anesthetized with pentobarbital sodium (60 mg.ml(-1).kg(-1) i.p.) and instrumented for regional coronary occlusion (30 min) and reperfusion (120 min). Heart rate, blood pressure, and a lead II electrocardiogram were recorded. Intravenous pretreatment began 5 min before ischemia and extended throughout ischemia, terminating at the start of reperfusion. After 120 min, hearts were removed for infarct size measurement. Mortality occurred in 58% of saline controls (n = 12), 50% of adenosine only (305 microg.kg(-1).min(-1), n = 8), 0% in lidocaine only (608 microg.kg(-1).min(-1), n = 8), and 0% in AL at any dose (152, 305, or 407 microg.kg(-1).min(-1) adenosine plus 608 microg.kg(-1).min(-1) lidocaine, n = 7, 8, and 6). VT occurred in 100% of saline controls (18 +/- 9 episodes), 50% of adenosine-only (11 +/- 7 episodes), 83% of lidocaine-only (23 +/- 11 episodes), 60% of low-dose AL (2 +/- 1 episodes, P < 0.05), 57% of mid-dose AL (2 +/- 1 episodes, P < 0.05), and 67% of high-dose AL rats (6 +/- 3 episodes). VF occurred in 75% of saline controls (4 +/- 3 episodes), 100% of adenosine-only-treated rats (3 +/- 2 episodes), and 33% lidocaine-only-treated rats (2 +/- 1 episodes) of the rats tested. There was no deaths and no VF in the low- and mid-dose AL-treated rats during ischemia, and only one high-dose AL-treated rat experienced VF (25.5 sec). Infarct size was lower in all AL-treated rats but only reached significance with the mid-dose treatment (saline controls 61 +/- 5% vs. 38 +/- 6%, P < 0.05). We conclude that a constant infusion of a solution containing AL virtually abolished severe arrhythmias and prevented cardiac death in an in vivo rat model of acute myocardial ischemia and reperfusion. AL combinational therapy may provide a primary prevention therapeutic window in ischemic and nonischemic regions of the heart.