Action of aprotinin in myocardial ischemia - an investigation using a plasma-free model

Cardioprotective effect of aprotinin on myocardial ischemia/reperfusion injury during cardiopulmonary bypass

BACKGROUND

Aprotinin is a serine protease inhibitor used extensively in cardiac operations to reduce postoperative bleeding. It also has cardioprotective effects in ischemia/reperfusion injury. In this study, the effects of aprotinin on the release of cardiac markers were evaluated in patients who had good ventricular function and were undergoing coronary artery bypass grafting with cardiopulmonary bypass (CPB).

METHODS AND RESULTS

Eighty male patients with an ejection fraction >or=40%, were randomized into either an aprotinin (Group-I; n=40) or control (Group-II; n=40) group. Patients in the aprotinin group received the full Hammersmith doses of aprotinin (2 x 10(6) KIU pre-CPB, 2 x 10(6) KIU at pump prime, 500,000 KIU/h during CPB), whereas the patients in the control group received only saline solutions. Cardiac troponin-I (cTnI) levels were measured before surgery, immediately after surgery, and at postoperative 6(th), 12(th), 24(th) h and 5(th) day. Creatine kinase (CK)-MB measurements were performed at the same time except for the postoperative 5(th) day. Cardiac index (CI), mixed venous oxygen saturation and lactate dehydrogenase (LDH) measurements were also performed.

CONCLUSION

Although all patients were in reasonable condition, less myocardial enzyme leakage occurred on the aprotinin group, suggesting that aprotinin has a protective effect on the myocardium beyond that achieved with blood cardioplegia and systemic hypothermia. Because of aprotinin's effects on multiple targets of metabolism, its protective value might increase in more complicated cases.

Aprotinin decreases ischemic damage during coronary revascularization

BACKGROUND AND AIM

This study sought to determine whether the favorable anti-inflammatory effects of aprotinin might limit ischemic damage during the revascularization of ischemic myocardium.

METHODS

Twenty pigs underwent 90 minutes of coronary occlusion followed by 45 minutes of blood cardioplegic arrest and 180 minutes of reperfusion. Ten animals received a loading dose of aprotinin (40,000 kallikrein inhibiting units/kg) during the start of coronary occlusion followed by an infusion of 20,000 kallikrein inhibiting units/kg/hour. Ten other animals received no aprotinin. Summary statistics are expressed as the mean +/- standard error.

RESULTS

The aprotinin-treated animals required less cardioversions for ventricular arrhythmias (1.0 +/- 0.7 vs. 3.6 +/- 0.6; p < 0.001), accumulated less lung water (1.0 +/- 0.2% change vs. 6.2 +/- 0.9% change; p = 0.038), had more complete coronary relaxation to bradykinin (34.1 +/- 5.9% change vs. 9.2 +/- 3.5% change; p = 0.01), and had reduced infarct size (area necrosis/area risk = 20 +/- 1.1% vs. 39 +/- 1.2%; p = 0.003).

CONCLUSIONS

Aprotinin limits ischemic injury during acute coronary revascularization by decreasing ventricular arrhythmias and lung edema, preserving endothelial function, and minimizing myocardial necrosis.

Aprotinin and preservation of myocardial function after ischemia-reperfusion injury

Ischemia-reperfusion injury, a complex process involving the generation and release of inflammatory cytokines, accumulation and infiltration of neutrophils and macrophages, release of oxygen free radicals, activation of proteases, and generation of nitric oxide (NO), may result in myocardial dysfunction and possible injury to other major organs. Aprotinin, a nonspecific serine protease inhibitor used to reduce the blood loss and transfusion requirements accompanying cardiac surgery, has dose-dependent effects on coagulation, fibrinolytic, and inflammatory variables. Data indicate that aprotinin may provide protection from ischemia-reperfusion injury. In myocardial tissue models of ischemia and reperfusion, aprotinin has been shown to reduce uptake of tumor necrosis factor-alpha (TNF-alpha), generation of NO, and accumulation of leukocytes. Improved myocardial function has been observed with aprotinin treatment in animal models of ischemia-reperfusion injury. In humans, data indicate that integrin expression associated with leukocyte transmigration as well as markers of myocardial damage are reduced in patients receiving aprotinin. Further, data suggest that patients who receive aprotinin may have a reduced need for inotropic support and a decreased incidence of postoperative atrial fibrillation. In all, review of this topic indicates that aprotinin may reduce aspects of ischemia-reperfusion injury and prospective clinical studies are needed to evaluate the impact of aprotinin on associated patient outcomes.

Na(+)/H(+)-exchange inhibition and aprotinin administration: promising tools for myocardial protection during minimally invasive CABG

OBJECTIVE

Minimally invasive coronary artery bypass grafting (CABG), carried out on the warm beating heart, does not allow conventional myocardial protection. The objective was to investigate the possibility of enhancing tolerance to ischemia during short episodes of coronary artery occlusion, based on a pharmacological approach using a selective Na(+)/H(+)-exchange inhibitor (cariporide) or a serine protease inhibitor (aprotinin).

METHODS

Four groups (n=6 in each group) of sheep were subjected to 20 min of normothermic regional ischemia (first lateral branch of the circumflex artery occlusion) followed by 1 h of reperfusion. Regional wall thickening was measured using sonomicrometry, and expressed as the percentage of thickening fraction compared with baseline. Group I was the control with no treatment, group II received cariporide (1 mg/kg administered over 2 min prior to ischemia), group III was treated with aprotinin (2.10(6) kallikrein inactivation units (KIU) load followed by 500.000 KIU/h). Group IV was treated with a combination of cariporide and aprotinin at the same concentrations as in groups II and III, respectively.

RESULTS

Wall thickening measurements showed that, compared with control, cariporide was largely able to suppress secondary loss of wall thickening after initial recovery during early reperfusion. Wall thickening in the ischemic/reperfused myocardial area improved from 10+/-31 to 51+/-17% at 1 h of reperfusion (P=0.002). Aprotinin improved wall thickening at the end of 1 h of reperfusion to 70+/-13% (P=0.0001). However, in this group, there was a transient loss of regional contractility similar in amplitude and time course to the one observed in the control group. A combination of cariporide and aprotinin suppressed transient contractile loss and resulted in improved wall thickening at the end of 1 h of reperfusion (65+/-22%, P=0.0002 vs. control). This value was not significantly different from the cariporide (P=0.263) or aprotinin (P=0.704) group.

CONCLUSION

These data indicate that both Na(+)/H(+)-exchange inhibition and aprotinin administration are promising tools for cardioprotection during minimally invasive CABG. A combination of both treatments is able to adequately suppress loss of contractility during early reperfusion as a consequence of reperfusion injury, and results in significantly improved wall thickening at the end of 1 h of reperfusion.

Role of aprotinin in the management of patients during and after cardiac surgery

Management of patients undergoing cardiac surgery has evolved in recent years as more is understood about the physiological changes and responses that occur during and after cardiopulmonary bypass (CPB). In particular, our understanding of the mechanisms involved in haemostasis and in the inflammatory response to bypass surgery, has allowed significant refinements in patient management. Improvements in the pharmacological conservation of blood loss have been striking, particularly with the development of the serine protease inhibitor, aprotinin (Trasylol, Bayer). Aprotinin represents a significant improvement, especially for patients at high risk, since it reduces the need for allogeneic and (sometimes scarce) blood products. However, in view of its cost, making an appropriate selection of patients most at risk of serious blood loss is a major consideration in the use of aprotinin. While its mechanisms of action are not well understood, the use of aprotinin also appears to reduce inflammatory response to CPB.