Changes in platelets and anticoagulant protein activity during adenosine-exercise single-photon emission computed tomography stress test.

INTRODUCTION

Activation of haemostasis during physical stress or during myocardial ischemia could be an important mechanism to trigger coronary and stent thrombosis. We examined changes in haemostatic parameters and its association with myocardial ischemia during adenosine-exercise-SPECT (adeno-EX) stress test in coronary patients at least 4 months after coronary stenting.

OBJECTIVE

The aim of this study was to examine relationship between changes in haemostatic parameters and stress induced myocardial ischemia quantified by perfusion scintigraphy in stented coronary patients.

METHODS

Thirty-seven patients on dual antiplatelet therapy (26 on clopidogrel plus aspirin and 11 on aspirin only) 4-8 months after successful intracoronary stent implantation were enrolled in the study. We determined the levels of platelet aggregability (PA) on ADP (PA-ADP) and epinephrine (PA-EPI), beta-thromboglobulin, platelet factor-4, protein C (PC) and antithrombin (AT) before and 15 minutes after intravenous injection of 150 micro/kg adenosine for4 minutes concomitant with supine ergo-bicycle exercise test for 50 W. The size of stress perfusion defect was measured 15 minutes after stress and in rest 4 hours later by 99mTc-tetrofosmin single photon emission computed tomography (SPECT) within 17 myocardial segments.

RESULTS

There were no differences between haemostatic parameters before and after stress. A significant myocardial ischemia after exercise was registered in 12 patients on combined antiaggregation therapy and in 5 patients on aspirin. In this preliminary report, because of a small number of patients in the aspirin group we did not analyse difference in the levels of haemostatic markers and their correlations with the size of perfusion defect. The only significant difference between measured haemostatic parameters in the patients with stress induced ischemia compared to the patients without it, was a lower level of AT activity after stress (81.0% vs. 87.5%; p = 0.027). Antithrombin activity before stress had significant negative correlation with the size of perfusion defect in rest (R2 = 0.219; p = 0.016) and PC activity before stress had significant linear correlation with stress perfusion defect (R2 = 0.248; p = 0.010).

CONCLUSION

Baseline activities of natural anticoagulant proteins AT and PC are associated with the size of myocardial perfusion defect during adeno-EX-SPECT test. Patients with significant stress-induced ischemia had lower levels of AT activity after stress.