Inhibition of thrombin during reperfusion improves immediate postischemic myocardial function and modulates apoptosis in a porcine model of cardiopulmonary bypass.
OBJECTIVE
Transient left-ventricular dysfunction because of myocardial reperfusion injury is a significant problem after cardiac surgery, but the underlying complex pathophysiology is still poorly understood. The authors studied early functional recovery of the postischemic myocardium and explored potential effects of thrombin inhibition on procoagulatory, proinflammatory, and proapoptotic features of myocardial ischemia-reperfusion injury.


METHODS
A randomized, blinded study.


METHODS
University research laboratory.


METHODS
Porcine model.


METHODS
Twenty pigs undergoing 60 minutes of aortic clamping and 75 minutes of normothermic cardiopulmonary bypass (CPB) received an intravenous bolus of r-hirudin (10 mg, 0.4mg/kg, n = 10) or placebo (n = 10) 15 minutes before aortic declamping, followed by a 135-minute intravenous infusion of r-hirudin (3.75 mg, 0.15 mg/kg/h) or placebo.


RESULTS
Hemodynamic parameters were measured before CPB, after weaning from CPB, and at 30, 60, 90, and 120 minutes after aortic declamping. Blood was sampled, and myocardial biopsies were taken before CPB, just before aortic declamping, during reperfusion, and after 120 minutes of reperfusion to measure thrombin antithrombin complexes and to quantitate leukocyte infiltration (myeloperoxidase activity) for histologic evaluation and detection of apoptosis with caspase-3 and the TUNEL method. The r-hirudin group showed significantly higher stroke volume and cardiac output than the control group at 60 minutes and at 90 minutes after aortic declamping (p < 0.05). Microthrombosis was not observed in either group, indicating sufficient anticoagulation and excluding intravascular clots as explanations for LV dysfunction in the current experiment. Instead, ample myocardial activation of inflammation was present, but only a trend of r-hirudin-associated anti-inflammatory effect was observed. Compared with the controls, TUNEL-positive myocytes were detected significantly less frequently in the r-hirudin group (0.05 +/- 0.06 v 0.13 +/- 0.07 TUNEL-positive nuclei %, p = 0.042).


CONCLUSIONS
The improved cardiac recovery in the r-hirudin group during reperfusion after cardioplegia-induced cardiac arrest was associated with significant differences in cardiomyocyte apoptosis and anti-inflammatory effects. Thus, in clinical cardiac surgery, inhibition of reperfusion- induced thrombin may offer beneficial effects by mechanisms other than direct anticoagulation.
Jormalainen
Mikko
M
Department of Cardiothoracic Surgery, University of Helsinki, Helsinki, Finland. mikko.jormalainen@hus.fi
Vento
Antti E
AE
Lukkarinen
Heikki
H
Kääpä
Pekka
P
Kytö
Ville
V
Lauronen
Jouni
J
Paavonen
Timo
T
Suojaranta-Ylinen
Raili
R
Petäjä
Jari
J
D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D002315:Cardiopulmonary Bypass / Q000295:instrumentation; D053938:DNA Fragmentation / Q000187:drug effects; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005343:Fibrinolytic Agents / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006629:Hirudins / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology; D011897:Random Allocation; D013552:Swine; D013917:Thrombin / Q000037:antagonists & inhibitors* / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D017725:Ventricular Pressure / Q000187:drug effects; D014914:Whole Blood Coagulation Time
D005343:Fibrinolytic Agents; D006629:Hirudins; D013917:Thrombin