Antiplatelet therapy (APT) has become an important tool in the treatment and prevention of atherosclerotic events, particularly those associated with coronary artery disease. A large evidence base has evolved regarding the relationship between APT prescription in various clinical contexts and risk/benefit relationships. The Guidelines Committee of the Canadian Cardiovascular Society and Canadian Association of Interventional Cardiology publishes regular updates of its recommendations, taking into consideration the most recent clinical evidence. The present update to the 2011 and 2013 Canadian Cardiovascular Society APT guidelines incorporates new evidence on how to optimize APT use, particularly in situations in which few to no data were previously available. The recommendations update focuses on the following primary topics: (1) the duration of dual APT (DAPT) in patients who undergo percutaneous coronary intervention (PCI) for acute coronary syndrome and non-acute coronary syndrome indications; (2) management of DAPT in patients who undergo noncardiac surgery; (3) management of DAPT in patients who undergo elective and semiurgent coronary artery bypass graft surgery; (4) when and how to switch between different oral antiplatelet therapies; and (5) management of antiplatelet and anticoagulant therapy in patients who undergo PCI. For PCI patients, we specifically analyze the particular considerations in patients with atrial fibrillation, mechanical or bioprosthetic valves (including transcatheter aortic valve replacement), venous thromboembolic disease, and established left ventricular thrombus or possible left ventricular thrombus with reduced ejection fraction after ST-segment elevation myocardial infarction. In addition to specific recommendations, we provide values and preferences and practical tips to aid the practicing clinician in the day to day use of these important agents.

Key Points• Use of LMWH is associated with a lower risk of HIT and HITT compared with use of UFH.• The Avoid-Heparin Initiative resulted in a dramatic reduction in the burden of suspected HIT, adjudicated HIT, HITT, and associated costs.Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction occurring in up to 5% of patients exposed to unfractionated heparin (UFH). We examined the impact of a hospital-wide strategy for avoiding heparin on the incidence of HIT, HIT with thrombosis (HITT), and HIT-related costs. The Avoid-Heparin Initiative, implemented at a tertiary care hospital in Toronto, Ontario, Canada, since 2006, involved replacing UFH with lowmolecular-weight heparin (LMWH) for prophylactic and therapeutic indications. Consecutive cases with suspected HIT from 2003 through 2012 were reviewed. Rates of suspected HIT, adjudicated HIT, and HITT, along with HIT-related expenditures were compared in the pre-intervention (2003)(2004)(2005) and the avoid-heparin (2007)(2008)(2009)(2010)(2011)(2012) phases. The annual rate of suspected HIT decreased 42%, from 85.5 per 10 000 admissions in the pre-intervention phase to 49.0 per 10 000 admissions in the avoidheparin phase (P < .001). The annual rate of patients with a positive HIT assay decreased 63% from 16.5 to 6.1 per 10 000 admissions (P < .001), adjudicated HIT decreased 79% from 10.7 to 2.2 per 10 000 admissions (P < .001), and HITT decreased 91% from 4.6 to 0.4 per 10 000 admissions (P < .001). Hospital HIT-related expenditures decreased by $266 938 per year in the avoid-heparin phase. To the best of our knowledge, this is the first study demonstrating the success and feasibility of a hospital-wide HIT prevention strategy. (Blood. 2016;127(16):1954-1959

This is the first study to quantify the costs associated with suspected HIT cases. These cases increase the costs of hospital care and provide further justification for HIT prevention strategies.