Enoxaparin in unstable coronary artery disease

In the Dr Cannon’s editorial, concerning the role of enoxaparin in ST elevation myocardial infarction, published in the issue of 15 April 2002, it is stated that in the only direct comparison of two molecular weight heparins in unstable angina and non-ST myocardial infarction, enoxaparin had a significantly lower rate of death, myocardial infarction or recurrent ischaemia than tinzaparin. This suggests that enoxaparin is in fact a superior low molecular weight heparin. This sentence is based on the EVET study, performed in 438 patients and published in abstract form. The primary end-points of this study were death, myocardial infarction, refractory angina and recurrence of unstable angina. The specified duration of treatments for both enoxaparin and tinzaparin was 7 days. Two aspects deserve comment: on the one hand, it is certainly surprising to find a study with four primary end-points. It would be interesting to know what was the accepted level of statistical significance for each one of the four primary endpoints. On the other hand, the results of the study do not concur with those expressed by Dr Cannon. In reality, regarding the primary end-points, enoxaparin was only better than tinzaparin in the recurrence of unstable angina at 7 days. No statistical significant differences were observed between the two treatment groups with respect to death, myocardial infarction or refractory angina. Although it is true that compared with unfractionated heparin no benefit was seen with either dalteparin in the FRIC study or nadroparin in the FRAX.I.S. study (whereas enoxaparin was superior in the ESSENCE and TIMI 11B [6] studies) some possible explanations should be discussed. In the FRIC and FRAX.I.S. studies, LMWHs were administered during the same period of time: 6 and 6 2 days, respectively, whereas results for the primary outcome at day 8 in the TIMI 11B study were derived from a comparison of enoxaparin administered for 8 days with UFH