A Direct Comparison of Intravenous Enoxaparin With Unfractionated Heparin in Primary Percutaneous Coronary Intervention (From the ATOLL Trial)

Study Questions:

In a per-protocol analysis of the ATOLL (Acute Myocardial Infarction Treated With Primary Angioplasty and Intravenous Enoxaparin or Unfractionated Heparin to Lower Ischemic and Bleeding Events at Short- and Long-Term Follow-Up) trial, what are outcomes of enoxaparin compared to unfractionated heparin (UFH)?


This was a per-protocol analysis of the ATOLL trial, in which the following patients were excluded: those who did not receive any anticoagulant at the time of percutaneous coronary intervention (PCI), those who did not receive the randomized treatment, or those who were switched to another anticoagulant after PCI irrespective of the dosage regimen (curative or preventive). The primary endpoint was the occurrence during the first 30 days of follow-up of the composite of all-cause mortality, complications of myocardial infarction, procedural failure, or major bleeding.


Of 910 randomized patients, 795 patients (87.4%) were treated according to the protocol with consistent anticoagulation using intravenous enoxaparin (n = 400) or UFH (n = 395). Enoxaparin reduced the rate of the primary endpoint (relative risk, 0.76; 95% confidence interval, 0.62-0.94; p = 0.012).


In a per-protocol analysis of the ATOLL trial, enoxaparin was superior to UFH in reducing the study’s primary endpoint.


The authors presented a per-protocol analysis of the ATOLL trial, where the magnitude of the differences between enoxaparin and UFH were statistically significant. These differences were not so in the intent-to-treat analysis. Given limitations of per-protocol analyses and although the intent-to-treat findings were suggestive of a trend to superior efficacy of enoxaparin over UFH, it would be premature to change clinical practice based on these findings.

Clinical Topics: Anticoagulation Management, Invasive Cardiovascular Angiography and Intervention

Keywords: Enoxaparin, Heparin, Percutaneous Coronary Intervention

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