Analysis of data from the ExTRACT-TIMI 25 trial comparing enoxaparin against unfractionated heparin (UFH) in patients with acute ST-segment elevation myocardial infarction (STEMI), indicate that having severe renal dysfunction is associated with a high risk of a number of serious adverse outcomes including death, stroke and bleeding.
The main results of the study, reported last year, showed enoxaparin to be associated with a greater treatment benefit but more bleeding than UFH.
The study included over 20,000 patients, which allowed reliable sub-analyses to be carried out. This paper reports an analysis of results stratified by renal function.
Patients had acute STEMI and were to receive thrombolytic therapy; they were randomised to receive a short course of either enoxaparin or UFH, with the primary outcome being a composite of death from any cause or nonfatal recurrent MI in the first 30 days from randomisation. Major bleeding events were included in secondary outcomes.
Those aged over 75 or with reduced renal function (estimated creatinine clearance CrCl <30ml/min) received a lower dose of enoxaparin. Patients were stratified into four groups by CrCl (<30ml/min, 30–60ml/min, >60–90ml/min, and >90ml/min) and the effect of renal function on outcomes was analysed.
Patients with renal dysfunction were significantly older on average than those without – median age for those with CrCl <90ml/min was 52 years, whereas it was 78 years for those with CrCl <30ml/min. There was a similar relationship with other risk factors, such as presence of diabetes, hypertension or previous MI.
The analysis showed a clear association between renal function and risk of death, stroke, intracranial haemorrhage and major and minor bleeding. There was also a progressive decrease in the benefits from enoxaparin with greater renal dysfunction.
Overall, net clinical benefits favoured enoxaparin in patients with CrCl >60ml/min, which included nearly 80% of the total population; however in the remainder, the rates of major and minor bleeding with enoxaparin compared to UFH increased progressively with declining renal function.
The authors conclude from this analysis that in patients with renal dysfunction the net clinical benefit was similar for enoxaparin and UFH. Renal function is an important predictor of adverse outcome in patients with STEMI and should be taken into account when assessing antithrombotic regimens.
J Am Coll Cardiol 2007; 49: 2249-55