Study the feasibility of using activated partial thromboplastin time to monitor the heparin treatment of patients undergoing percutaneous coronary interventions

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.