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

Leukocyte filtration and aprotinin: synergistic anti-inflammatory protection

Cardiopulmonary bypass activates an array of cellular and humoral inflammatory mechanisms that culminate in diverse or organ-specific injury. A manifestation of inflammatory injury to the heart, atrial fibrillation ranks among the most frequent and potentially life-threatening postsurgical complications. Pulmonary manifestations of the inflammatory response are also of major concern. Neutrophils activated by passage through the extracorporeal circuit inflict local injury and provoke the inflammatory cascade by producing oxyradicals and proinflammatory factors. This study tested if a combination of leukocyte depletion and aprotinin suppression of neutrophils could minimize postbypass atrial fibrillation and pulmonary dysfunction. In part one, two randomized groups of 90 patients undergoing primary coronary artery bypass grafting received full Hammersmith aprotinin alone (control group) or combined with leukofiltration (study group) and were prospectively examined. The dual treatment decreased the incidence of postoperative atrial fibrillation (7 of 90, 7.8%) by 67% versus aprotinin alone (21 of 90, 23.3%). Respiratory gas exchange in these patients was assessed from pulmonary shunt fraction. In the first two hours postbypass, pulmonary shunt fraction in the dual treatment group increased 40% less than in the group receiving aprotinin alone (p = 0.002), and subsided more quickly and completely over the next six hours. In part two, the cardiopulmonary bypass group receiving aprotinin+leukofiltration was retrospectively compared with 45 patients undergoing off-pump coronary revascularization. A strong, albeit not statistically significant trend (p= 0.08) toward a lower incidence of atrial fibrillation was found in the dual treatment group versus the off-pump group (8 of 45, 17.8%). These findings suggest that combining mechanical and pharmacologic suppression of the systemic inflammatory response could mitigate its deleterious arrhythmic and pulmonary complications.

Aprotinin in Cardiac Surgery: A Review of Conventional and Novel Mechanisms of Action

Induction of the coagulation and inflammatory cascades can cause multiorgan dysfunction after cardiopulmonary bypass (CPB). In light of these observations, strategies that can stabilize the coagulation process as well as attenuate the inflammatory response during and after cardiac surgery are important. Aprotinin has effects on hemostasis. In addition, aprotinin may exert multiple biologically relevant effects in the context of cardiac surgery and CPB. For example, it decreases neutrophil and macrophage activation and chemotaxis, attenuates release and activation of proinflammatory cytokines, and reduces oxidative stress. Despite these perceived benefits, the routine use of aprotinin in cardiac surgery with CPB has been called into question. In this review, we examined this controversial drug by discussing the classical and novel pathways in which aprotinin may be operative in the context of cardiac surgery.

Aprotinin reduces cardiac troponin I release and inhibits apoptosis of polymorphonuclear cells during off-pump coronary artery bypass surgery

OBJECTIVES

In addition to blood-sparing effects, aprotinin may have cardioprotective and anti-inflammatory effects during cardiopulmonary bypass-assisted cardiac surgery. In this study, the authors examined whether aprotinin had cardioprotective and/or anti-inflammatory effects in patients undergoing off-pump coronary artery bypass grafting.

DESIGN

A prospective randomized clinical trial.

SETTING

University hospital.

PARTICIPANTS

Fifty patients were randomized to control (n = 25) or aprotinin treatment (n = 25) groups.

INTERVENTIONS

Aprotinin was given as a loading dose (2 x 10(6) KIU) followed by a continuous infusion at 5 x 10(5) KIU/h until skin closure.

MEASUREMENTS AND MAIN RESULTS

Blood samples for cardiac troponin I; interleukin-6, interleukin-8, and interleukin-10; tumor necrosis factor alpha; and elastase were taken after anesthesia induction, completion of revascularization, and 6 hours, 12 hours, and 24 hours after revascularization. Blood samples were taken to assess for apoptosis in polymorphonuclear cells. Baseline plasma levels for cardiac troponin I did not differ between groups but were significantly lower in aprotinin-treated patients at the time of revascularization (p = 0.03) and 6 hours (p = 0.004) and 24 hours (p = 0.03) later. Aprotinin significantly reduced apoptosis in polymorphonuclear cells compared with control-treated patients (p = 0.04). There were no differences in plasma cytokine or elastase levels between groups.

CONCLUSIONS

The authors conclude that aprotinin reduces perioperative cardiac troponin I release and attenuates apoptosis in polymorphonuclear cells but has no significant effects on plasma cytokine levels in patients undergoing off-pump coronary artery bypass graft surgery.

Effects of half-dose aprotinin in off-pump coronary artery bypass grafting

OBJECTIVE

The effects of half-dose aprotinin in off-pump coronary artery bypass (OPCAB) surgery have not yet been described. The present prospective study was designed to investigate its effects in OPCAB.

METHODS

Seventy-six patients were randomized into two groups, receiving aprotinin (1 x 10(6) Kallikrein-inactivating units [KIU] loading dose before surgery and 5 x 10(5) KIU/h during surgery, gross dose: 2.5 x 10(6) KIU, n=36) and saline solution (control, n=40) respectively. Perioperative blood samples were collected. Hematologic and hemostatic parameters including platelet adhesion rate, D-dimer, and fibrinopeptide-A (FPA) were analyzed. Perioperative CKMB release was measured. Volume of blood loss, blood transfusion, and other clinical data were recorded throughout the perioperative period.

RESULTS

Postoperative blood loss was significantly reduced in patients treated with aprotinin (2 hours; median [25th-75th]: aprotinin: 90.0 [70.0-125.0] ml, control: 145.0 [70.0-180.0] ml, P<0.05; 6 hours: aprotinin: 150.0 [100.0-220.0] ml, control: 225.0 [200.0-347.5.0] ml, P<0.01; 24 hours: aprotinin: 370.0 [220.0-510.0] ml, control: 655.0 [500.0-920.0] ml, P<0.01). The number of patients receiving blood transfusion in each group was similar. Levels of D-dimer rose significantly after surgery, and were significantly lower in the aprotinin group than in the controls (end of surgery, aprotinin, 0.4 [0.2-0.5] mg/l versus controls, 1.4 [0.8-2.3] mg/l; 2 hours, aprotinin, 0.3 [0.2-0.4] mg/l versus controls, 0.9 [0.5-1.4] mg/l; 6 hours, aprotinin, 0.3 [0.2-0.5] mg/l versus controls, 0.6 [0.4-0.9] mg/l; 24 hours, aprotinin, 0.3 [0.2-0.4] mg/l versus controls, 0.5 [0.4-0.9] mg/l; ANOVA for repeated measures, P<0.01). Platelet adhesion rate and FPA levels remained at baseline levels after the operation in the two groups. Early clinical outcomes were similar in the groups. Levels of CKMB were significantly lower in the aprotinin group than in the controls (6 hours after surgery, aprotinin, 10.0 [8.0-16.0] U/l versus controls, 15.5 [11.0-20.3] U/l; 12 hours, aprotinin, 13.5 [10.0-20.0] U/l versus controls, 19.0 [12.8-24.3] U/l; 24 hours, aprotinin, 19.0 [13.5-33.8] U/l versus controls, 25.0 [15.0-43.3] U/l; 72 hours, aprotinin, 13.0 [8.0-18.0] U/l versus controls, 16.0 [10.0-29.0] U/l; ANOVA for repeated measures, P=0.018).

CONCLUSION

The results indicated that half-dose aprotinin limits fibrinolysis and myocardial injury, and reduces blood loss after OPCAB surgery.

Aprotinin use in thoracic aortic surgery: Safety and outcomes

OBJECTIVES

Previous studies of aprotinin use in thoracic aortic surgery, limited in size and design, reported minimal information regarding outcomes other than blood loss and transfusion. The evaluation of impact of aprotinin on surgical outcomes in a large sample is needed.

METHODS

Patients at Yale New Haven Hospital undergoing thoracic aortic surgery (aneurysm repair, dissections, penetrating ulcers, intramural hematomas) between 1995 and 2003 were considered for inclusion. Each patient receiving aprotinin was matched to a control per preoperative profile (age, gender, urgency of surgery, dissection/location of aortic disease). Data (surgical specifics, demographic variables, comorbidities, disease location-related variables, preoperative medications, intraoperative medications, surgical/operative data) were abstracted from the records of successfully matched aprotinin-treated patients and controls (n = 168). Comparison and determination of success of matching were performed using bivariate analyses. Outcome variables were compared using statistical tests for paired data. Supplementary unpaired and regression analyses were also performed.

RESULTS

Baseline demographics of groups were similar, although controls had reduced history of aortic disease, but greater intraoperative use of lysine analogs (P < .05). Aprotinin significantly reduced platelet transfusion (P < .05). Paired bivariate analyses showed a tendency toward reduced ventilation time, pulmonary complications, and permanent arrhythmias (P < .05) associated with aprotinin. Supplementary analyses were supportive only for pulmonary complications and permanent arrhythmias.

CONCLUSIONS

The current evaluation substantiates previous reports that aprotinin may be safe to use and likely to improve some outcomes of thoracic aortic surgery. However, further studies for rare safety and efficacy end points are warranted.

Antithrombotic controversies in off-pump coronary bypass

The purpose of this article is to evaluate the use of perioperative antithrombotics in patients undergoing surgical revascularization of the coronary vessels. Although there is a general agreement about the use of anticoagulation during off-pump coronary revascularization (OPCAB), the degree of the required anticoagulation varies from one center to another. The review is divided into four major sections. The first section describes the pathophysiology of the coagulation system in cardiac surgery with and without the use of cardiopulmonary bypass. In this section, we also discuss the interactions between the coagulation system and the inflammatory response to cardiac surgery. The second section examines the role of prophylactic antithrombosis in patients referred to surgical revascularization, and their role in bleeding complications associated with surgery. Heparinization and neutralizing its anticoagulative effects during coronary surgery are discussed in the third section. The fourth section examines the evidence that the inflammatory response contributes to adverse peri-operative events, in particular organ dysfunction, and potential therapeutic strategies to control this response. The review concludes with a summary of potential future research directions and key deficiencies in our knowledge regarding the use of anticoagulants in cardiac surgery.

The preischemic combination of the sodium–hydrogen exchanger inhibitor cariporide and the adenosine agonist AMP579 acts additively to reduce porcine myocardial infarct size

BACKGROUND

We tested whether the combination of two known cardioprotective agents, the type-1 sodium-hydrogen exchanger inhibitor cariporide plus the adenosine A(1)/A(2a) receptor agonist AMP579 ([1S-[1a,2b,3b, 4a(S*)]]-4-[7-[[2-(3-chloro-2-thienyl)-1-methylpropyl]amino]-[(3)H]-imidazo[4,5-b]pyridyl-3-yl]cyclopentane carboxamide), acted additively to reduce myocardial infarct size.

STUDY DESIGN

Pigs underwent 1 hour of coronary artery occlusion and 3 hours reperfusion. Vehicle-treated controls were compared with animals treated before ischemia with low-dose and high-dose cariporide and AMP579, and low-dose cariporide plus AMP579. The effects of both agents, alone and in combination, were also tested in isolated porcine polymorphonuclear neutrophils (PMNs). The PMN respiratory burst was induced with phorbol 12-myristate 13-acetate and quantified by the increase in 2',7'-dichlorofluorescein fluorescence, measured by flow cytometry.

RESULTS

Infarct size in the control pigs was 65 +/- 1% of the area at risk. Cariporide dose-dependently reduced infarct size to 39 +/- 2% and 24 +/- 3% in the low- and high-dose groups, respectively. Infarct size was 54 +/- 3% in the low-dose AMP579 group and 47 +/- 3% with high dose. The combination of low doses of cariporide and AMP579 reduced infarction to 25 +/- 6% of the area at risk. In the PMN studies, cariporide and AMP579 alone had no effect on 2',7'-dichlorofluorescein fluorescence, but the combination of the two agents reduced the PMN 2',7'-dichlorofluorescein increase to 79 +/- 5% of the vehicle control response.

CONCLUSIONS

The preischemic combination of low doses of cariporide and AMP579 decreased myocardial infarct size more than either agent used alone in low concentration, indicating an additive effect of the two agents. Given the effects that cariporide plus AMP579 combination exerted on PMN activity, it appears that this combination has the potential to reduce PMN-mediated effects during myocardial reperfusion.

Reduction of myocardial reperfusion injury by aprotinin after regional ischemia and cardioplegic arrest

BACKGROUND

Surgical coronary revascularization with cardiopulmonary bypass and cardioplegia has been associated with reperfusion injury. The serine protease inhibitor aprotinin has been suggested to reduce reperfusion injury, yet a clinically relevant study examining regional ischemia under conditions of cardiopulmonary bypass and cardioplegia has not been performed.

METHODS

Pigs were subjected to 30 minutes of regional myocardial ischemia by distal left anterior descending coronary artery occlusion, followed by 60 minutes of cardiopulmonary bypass with 45 minutes of cardioplegic arrest and 90 minutes of post-cardiopulmonary bypass reperfusion. The treatment group (n = 6) was administered aprotinin systemically (40,000 kallikrein-inhibiting units [KIU]/kg intravenous loading dose, 40,000 KIU/kg pump prime, and 10,000 KIU x kg(-1) x h(-1) intravenous continuous infusion). Control animals (n = 6) received crystalloid solution. Global and regional myocardial functions were analyzed by the left ventricular+dP/dt and the percentage segment shortening, respectively. Left ventricular infarct size was measured by tetrazolium staining. Tissue myeloperoxidase activity was measured. Myocardial sections were immunohistochemically stained for nitrotyrosine. Coronary microvessel function was studied by videomicroscopy.

RESULTS

Myocardial infarct size was decreased with aprotinin treatment (27.0% +/- 3.5% vs 45.3% +/- 3.0%, aprotinin vs control; P <.05). Myocardium from the ischemic territory showed diminished nitrotyrosine staining in aprotinin-treated animals versus controls, and this was significant by grade (1.3 +/- 0.2 vs 3.2 +/- 0.2, aprotinin vs control; P <.01). In the aprotinin group, coronary microvessel relaxation improved most in response to the endothelium-dependent agonist adenosine diphosphate (44.7% +/- 3.2% vs 19.7% +/- 1.7%, aprotinin vs control; P <.01). No significant improvements in myocardial function were observed with aprotinin treatment.

CONCLUSIONS

Aprotinin reduces reperfusion injury after regional ischemia and cardioplegic arrest. Protease inhibition may represent a molecular strategy to prevent postoperative myocardial injury after surgical revascularization with cardiopulmonary bypass.

Sodium-hydrogen exchange inhibition attenuates in vivo porcine myocardial stunning

BACKGROUND

Inhibition of the sodium-hydrogen exchanger isoform 1 with HOE-642 (cariporide) has been shown to protect against ischemia-reperfusion injury and to decrease myocardial cell death in numerous animal preparations; however the effects of cariporide in stunned myocardium are not as well understood. We sought to determine whether cariporide attenuated myocardial stunning in vivo.

METHODS

Open chest anesthetized pigs (22-33 kg) were subjected to 15 min of left anterior descending coronary artery (LAD) occlusion followed by 3 h of reperfusion. Regional ventricular function was assessed by segment shortening. Contractility was measured by stroke work and by load-insensitive preload recruitable stroke work and preload recruitable stroke work area. Vehicle or HOE-642 (1 mg/kg, IV) was administered 10 min before LAD occlusion.

RESULTS

Cariporide treatment significantly improved postischemic segment shortening, stroke work, preload recruitable stroke work, and preload recruitable stroke work area and had no systemic hemodynamic effects. After 3 h of reperfusion, control animals recovered 33% +/- 4% and 33% +/- 3% of preischemic LAD segment shortening and preload recruitable stroke work area values, respectively, whereas animals treated with HOE-642 recovered 59% +/- 6% and 57% +/- 6%, respectively (p < 0.05). Seven (39%) of 17 control animals exhibited ventricular fibrillation during reperfusion; none of the cariporide-treated pigs fibrillated.

CONCLUSIONS

Sodium-hydrogen exchange inhibition can attenuate postischemic myocardial stunning in addition to its well-described anti-infarct properties. Inhibition of the sodium-hydrogen exchanger may be beneficial in patients susceptible to postischemic myocardial dysfunction associated with cardiac surgery.

Is timing everything? Therapeutic potential of modulators of cardiac Na(+) transporters

Sodium ion (Na(+)) transporters have roles in the modulation of cardiomyocyte pH and Na(+) and Ca(2+) handling. Activation of the cardiac Na(+)-H(+) exchanger 1 (NHE1) during ischaemia induces arrhythmias, myocardial stunning and irreversible cell injury. As the benefits of NHE1 inhibitors (e.g., amiloride, cariporide) in models of myocardial infarction are usually much greater when used as pretreatment, rather than during or after ischaemia, it is probably not surprising that clinical trials with cariporide in ischaemia have shown little shortterm benefit. NHE1 inhibitors have been shown to be beneficial in animal models of ventricular fibrillation and resuscitation, cardioplegia, hypertrophy and heart failure, and their therapeutic potential in these conditions should be further developed. The Na(+)-HCO(3)(-) cotransporter (NBC) is also stimulated by intracellular acidification, and part of the benefit of angiotensin-converting enzyme inhibitors after myocardial infarction may be due to inhibition of the NBC. Selective inhibitors of the NBC are required to determine the therapeutic potential of this mechanism. The Na(+)-Ca(2+) exchanger (NCX) has a major role in cardiac Na(+) and Ca(2+) homeostasis and influences cardiac electrical activity. The NCX also has a role in ischaemia/infarction, arrhythmias, hypertrophy and heart failure. NCX inhibitors may have beneficial effects in animal models of ischaemia and reperfusion injury and the therapeutic benefit of these should be further studied in animal models.

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.