Correlation between the aPTT and clinical events in acute coronary syndromes treated with unfractionated heparin

The primary objective of this study is to analyse relationship between activated partial thromboplastin time (aPTT) and clinical events in patients with unstable coronary artery disease.

Unfractionated heparin (UFH) is considered as a standard therapy in the management of unstable coronary artery disease. His efficacy is concerned to low rate of adverse events, but it shows lack of correlation between aPTT and clinical outcomes.

Thirty patients with acute coronary syndromes were randomised to receive weight-adjusted unfractionated heparin (Heparin-"Biochemie" 25.000 IU/5 ml), according to Rashke nomogram. Six hours after the initial bolus dose, the aPTT was measured and the heparin infusion was adjusted. Relationship between the aPTT and the day of onset of recurrent angina (RA), myocardial infarction (MI), heart failure (HF), death, and target vascular revasularization (TVR) during six months follow-up was evaluated.

At 6 h, 40 % of patients achieved the target level of aPTT (60-85 sec). Also, 40 % patients were below the target range, 41.6 % had aPTT less than 30 sec and 20 % were above the target range. We noted significant difference between heparin dosing and aPTT (p=0.0000). But we did not find significant difference between aPTT and outcomes as RA and MI (p=1.0, p=0.42). Pearson Product Moment Correlation shows negative correlations between aPTT and the day of onset of RA (r=-0.05) and TVR (r=-0.23), and pozitive correlations for MI (r=0.35) and death (r=0.87).

The level of aPTT shows discordance with the onset of clinical events and is a weak predictor of outcomes (Tab. 2, Fig. 7, Ref 5).