Abstract:
Coronary artery disease (CAD) is a major contributor to global morbidity and mortality, with
atherosclerosis recognised as the primary underlying cause. For patients undergoing percutaneous
coronary intervention (PCI), unfractionated heparin is routinely administered to minimise
the risk of stent-associated thrombosis. In Sri Lanka, intraoperative monitoring of anticoagulation
is typically carried out using activated clotting time (ACT), whereas in many other countries,
activated partial thromboplastin time (aPTT) remains a widely accepted method. This
study evaluated the relationship between heparin dose, ACT, and aPTT measured under standard
laboratory conditions (37°C) and at room temperature (RT), with the aim of developing a
practical intraoperative monitoring method. A prospective cross-sectional study was conducted
involving 77 PCI patients at Sri Jayewardenepura General Hospital. Data on demographics,
heparin dose, ACT, and pre- and post-heparin aPTT (both 37°C and RT) were collected. Statistical
analysis included correlation, regression, and ROC curve analysis. No strong correlation
was observed between heparin dose and ACT (r = 0.469). However, aPTT at 37°c strongly
correlated with ACT (r = 0.920, p <0.001) and moderately at RT (r = 0.676, p <0.001). Regression
analysis showed that ACT could be predicted from aPTT at 37 °C alone (r² = 0.675)
and improved with the inclusion of heparin dose (r² = 0.723). ROC analysis established cutoffs
predicting ACT >300 s: aPTT_37 °C >141.5 s (100% sensitivity, 92% specificity, AUC
0.950) and aPTT_RT >429.5 s (82.3% sensitivity, 71.7% specificity, AUC 0.857). aPTT at
37°c demonstrates strong predictive accuracy for ACT and may serve as a reliable alternative
monitoring parameter. The modified aPTT_RT method offers a practical intraoperative option
with reasonable diagnostic performance. These findings support the integration of aPTT into
PCI anticoagulation monitoring protocols, with further validation recommended through larger,
multicenter studies.
