Assessment of Bleeding Events in Clinical Trials—Proposal of a New Classification

Present classifications of bleeding events used in antithrombotic and/or antiplatelet clinical trials are based on the criteria developed by the Thrombolysis In Myocardial Infarction (TIMI) and Global Use of Strategies to Open Coronary Arteries (GUSTO) groups. Introduced more than a decade ago, the 2 classifications used the criteria to better categorize hemorrhagic events after therapy with thrombolytic agents. Recent advances in interventional cardiology, resulting in a domination of percutaneous intracoronary procedures over systemic drug-induced thrombolysis, have substantially changed the clinical characteristics and magnitude of bleeding complications. Moreover, disturbances of the coagulation cascade, as well as platelet inhibition caused directly by antithrombotic and antiplatelet agents, share very specific and well-recognized clinical features not reflected in the existing classifications. Bleeding events after aspirin or clopidogrel, and especially those after more delicate antiplatelet regimens with dipyridamole used in patients after ischemic stroke or transient ischemic attack, are impossible to classify by the present guidelines, other than categorically triaging them altogether to the “minor” category. Uniting entirely different bleeding events as “minor” under-rates their importance and diminishes affiliated risks, creating an illusion that they do not require monitoring and/or changes in antiplatelet or antithrombotic regimens. In reality, such unrecognized and unreported mild complications may transform into more serious bleeds or lead to noncompliance. Unauthorized withdrawal from antiplatelet agents in turn causes rebound platelet activation and higher risk for secondary vascular events. In conclusion, a new classification of bleeding events is introduced (the BleedScore), based on a point accumulation depending on the severity of hemorrhage, which is believed to be more suitable for the assessment of modern, more delicate antithrombotic and antiplatelet therapies, particularly for their realistic assessment in clinical trials.