Does prostacyclin (PGI2) cardioplegic infusion improve myocardial protection after ischemic arrest?

Prostacyclin Reduces Incidence of Myocardial Damage After Coronary Endarterectomy

BACKGROUND

After coronary endarterectomy, patients have an increased incidence of perioperative myocardial infarction. This study was undertaken to evaluate the possible reduction of perioperative myocardial damage after coronary endarterectomy by intravenous utilization of prostacyclin.

METHODS

Elective coronary artery bypass grafting was performed in 1,190 patients with diffuse and distal coronary artery disease, in whom endarterectomy of one or more vessels was used as a treatment. All procedures were done with cardiopulmonary bypass. There were 584 patients in the prostacyclin-treated group, and 606 patients in the control group. Prostacyclin (10 ng x kg(-1) x min(-1)) was started 20 minutes before the cross-clamp removal, or at the time of rewarming, and was continued during the first 24 hours after surgery. The incidence of perioperative myocardial damage was detected by creatine kinase-MB enzyme measurement, and electrocardiographic and left ventricular function changes.

RESULTS

A significant decrease in perioperative myocardial damage was detected in the group treated with prostacyclin with respect to the control group.

CONCLUSIONS

Prostacyclin infusion initiated during revascularization and continued in the early postoperative course could be successfully employed for the prevention of thrombocyte aggregation and potentially decrease the overall incidence of significant myocardial damage after coronary endarterectomy.

Beneficial effects of iloprost cardioplegia in ischemic arrest in isolated working rat heart

To determine whether the prostacyclin analog iloprost plays a beneficial role in crystalloid cardioplegia in isolated working rat hearts, 20 isolated rat hearts were studied after sustaining 90 min of cardioplegic arrest under hypothermia (20 degrees C). The findings indicated that thromboxane A2 (TXA2) levels in coronary effluent were increased during reperfusion. Iloprost (12 nm/l) inhibited the release of TXA2 and improved the recovery of cardiac hemodynamics after ischemia. These data demonstrated that cardiac-derived TXA2 appeared to mediate reperfusion injury after prolonged aortic clamp or cardiac transplantation and iloprost cardioplegic infusion resulted in the inhibition of release of cardiac-derived TXA2 and in a better preservation of cardiac function after ischemic arrest.

Beneficial effects of prostacyclin treatment on reperfusion of the myocardium

A total of 20 patients with coronary artery disease were studied in order to assess the benefits of prostacyclin administration on reperfusion of the ischaemic myocardium after cardiopulmonary bypass. Ten received prostacyclin (25 ng/kg per min) while ten were untreated controls. There was no difference between groups with regard to age, preoperative ejection fraction and aortic cross-clamping times. There were no in-hospital deaths in either group. The administration of prostacyclin significantly altered the metabolic side effects of reperfusion followed by hypothermic cardioplegic arrest. Myocardial oxygen consumption after cardiopulmonary bypass was significantly higher in the prostacyclin-treated group than in controls (18.5 ml versus 13 ml; P < 0.01). Prostacyclin treatment significantly reduced the leucocyte activity: leukotriene B4 concentrations were 58 pmol/l in prostacyclin-treated patients compared with 93 pmol/l in controls (P < 0.01). Such recovery of metabolic status during reperfusion resulted in better haemodynamic function in patients receiving prostacyclin.

Prostacyclin and thromboxane levels in pleural space fluid during cardiopulmonary bypass

Prostaglandins exhibit a variety of cardiovascular actions that may affect the hemodynamic recovery of the ischemic myocardium after cardiopulmonary bypass. We have observed a decrease in the mean arterial pressure on autotransfusion of the accumulated pleural cavity fluid during operation. One aim of this study was to determine the concentrations of prostacyclin and thromboxane A2 in the pleural cavity fluid by measuring their stable metabolites, 6-keto-PGF1 alpha and thromboxane B2, respectively, in 8 consecutive patients undergoing myocardial revascularization, and to compare them with the arterial levels. A second aim was to quantify the hemodynamic effect of the pleural cavity fluid during operation. The concentration of 6-keto-PGF1 alpha in the pleural cavity fluid was significantly higher than the arterial concentration (mean, 21.6 +/- 18.2 ng/mL; p < 0.01). The concentration of thromboxane B2 was also raised compared with the arterial concentration (mean, 3.62 +/- 5.96 ng/mL; p < 0.2). The percentage fall in the mean arterial pressure was 29.7% +/- 8.86% (p < 0.02), which was transient and lasted 1 to 3.5 minutes. The hemoglobin concentration, potassium level, and pH were also measured. This study shows that the pleural cavity fluid during cardiac operations contains significant amounts of endogenous prostacyclin. Considering the potential benefit of prostacyclin on the recovering myocardium, we believe that this fluid should be transfused as a volume replacement, keeping in mind the transient phase of hemodynamic instability.

Prostacyclin and vascular function: implications for hypertension and atherosclerosis

Prostacyclin and endothelium-derived relaxing factor (or nitric oxide) are unstable mediators produced by the vascular endothelium, that are important for local regulation of platelet behavior and blood flow. This review focuses on the basic biochemistry and pharmacology of prostacyclin, its interactions with nitric oxide and nitrovasodilator drugs, and the implications of disturbances in this system for vascular disease, particularly hypertension and atherosclerosis. Prostacyclin and its stable analogs are also finding limited therapeutic applications in preservation of platelet function, pulmonary hypertension, and investigation into the cytoprotective and antiatherosclerotic properties is continuing.

Evaluation of prostacyclin analogue OP-41483 as an adjunct to crystalloid cardioplegia in infants and children

A chemically stable prostacyclin analogue (PGI2-A, carbacyclin, OP-41483) was evaluated as an adjunct to potassium cardioplegia in infants (n = 13) and children (n = 32), in whom the current potassium cardioplegia may be limited in its effects. PGI2-A was added in a dose of 300 micrograms/L to the potassium cardioplegic solution. Postoperatively, peak levels of the myocardial-specific isoenzyme of creatine kinase (MB-CK) were compared for the PGI2 group and a control group (n = 65). In patients 1 year of age or older (n = 32 and 49 for the PGI2 and control groups, respectively), the MB-CK level was significantly lower in the PGI2 group only when compared between the subgroups with an aortic cross-clamp time of 120 minutes or more (n = 9 and 10; MB-CK level, 35.2 +/- 15.6 vs 68.3 +/- 32.4 IU/L;p less than 0.05). In patients less than 1 year of age, in whom aortic cross-clamp times were generally less than 120 minutes, the MB-CK level was also lower in the PGI2-A group than in the control group (n = 13 and 16; MB-CK level, 33.6 +/- 14.3 vs 61.6 +/- 36.3 IU/L;p less than 0.05). Infants less than 6 months of age (n = 18) underwent ultrastructural assessment of left ventricular myocardial biopsy specimens, and the PGI2-A group showed better results in mitochondrial and intracellular edema scores. This clinical trial showed beneficial effects of PGI2-A used with crystalloid potassium cardioplegia in infants and children.