The Effect of EPLerenone on Ischemia Reperfusion Injury in Human myoCARDium (EPLICARD)

In the laboratory, the researchers will investigate whether the drug eplerenone improves contractile function after ischemia and reperfusion in heart tissue.

In animal studies, the mineralocorticoid receptor antagonist eplerenone appears to limit myocardial infarct size. This cardioprotective effect might explain, at least in part, the beneficial effect on mortality of eplerenone in patients with heart failure. Previous animal studies suggest that this cardioprotective effect is mediated by an increased formation of the endogenous nucleoside adenosine. Our objective is to study for the first time in human myocardial tissue ex vivo wether eplerenone limits ischemia reperfusion injury and whether this is mediated by adenosine receptor stimulation. From patients undergoing open heart surgery, the right atrial appendage will be harvested by the cardiothoracic surgeon. In the laboratory, two trabeculae will be dissected and suspended in an organ bath. Contraction will be induced by electrical field stimulation. Recovery of contractile force after a period of simulated ischemia and reperfusion will be used as an endpoint of ischemia-reperfusion injury. The trabeculae of each patient will be randomized to pretreatment with A)ischemic preconditioning (IP) of no IP as a positive control experiment; B)eplerenone or vehicle; C)eplerenone with or without caffeine; and D)aldosterone with and without eplerenone.

After baseline recordings of contractile function, the investigators will assign 2 trabeculae of each patient to either a stimulus for (1) ischemic preconditioning (IP) or (2) no IP. Subsequently, the trabeculae will be exposed to 90 min of ischemia, followed by 120 minutes of recovery. The investigators will measure the recovery of contractile function in both trabeculae. This experiment serves as a positive control, to ensure that our model is still working properly.

In the next patients, a similar ischemia-reperfusion experiment will be performed, but now the 2 trabeculae will be randomized to pretreatment with eplerenone or DMSO. The percentage recovery (compared to baseline) of contractile force of the trabeculae at the end of reperfusion will serve as the primary endpoint.

The recovery of contractile function (% of baseline) in human myocardial tissue after simulated ischemia and reperfusion in 2 trabeculae will be compared: 1 of the trabeculae will be exposed to eplerenone, the other to vehicle. We will use the experimental set up as described by Speechly-Dick et al. with small modifications to allow simultaneous measurement of 2 trabeculae from 1 patient. The two trabeculae will be dissected and vertically suspended in an organ bath and linked to a force transducer. During electrical field stimulation, we will calculate the developed force (difference between maximal tension during contraction and minimal tension during relaxation), maximal speed of tension development during contraction and maximal speed of tension during relaxation. We will average these parameters for baseline, and during the experiment. Functional recovery will be expressed as a percentage of baseline.

Inclusion Criteria: age>18 years willing to sign informed consent planned elective surgery with extracorporal circulation Exclusion Criteria: use of theophylline use of sulfonylureas use of oral antiarrhythmics (not beta blockers) use of dipyridamole, use of mineralocorticoid receptor antagonists atrial arrhythmias right ventricular failure known atrial enlargement

Riksen NP, Zhou Z, Oyen WJ, Jaspers R, Ramakers BP, Brouwer RM, Boerman OC, Steinmetz N, Smits P, Rongen GA. Caffeine prevents protection in two human models of ischemic preconditioning. J Am Coll Cardiol. 2006 Aug 15;48(4):700-7. doi: 10.1016/j.jacc.2006.04.083. Epub 2006 Jul 24.

Speechly-Dick ME, Grover GJ, Yellon DM. Does ischemic preconditioning in the human involve protein kinase C and the ATP-dependent K+ channel? Studies of contractile function after simulated ischemia in an atrial in vitro model. Circ Res. 1995 Nov;77(5):1030-5. doi: 10.1161/01.res.77.5.1030.