Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3720_Библиотеки_им_академика_М_И_Перельмана

The advent of coronary artery stenting greatly improved the safety and efficacy of percutaneous coronary intervention (PCI), as it offered reduced rates of acute vessel closure and improved long-term patency rates. In the early phase of balloon angioplasty the procedure’s associated morbidity, mortality, and rates of need for emergent coronary artery bypass surgery due to dissections, acute vessel closure, and perforations were a source of great concern. For example, acute occlusion rates of 6.8% were encountered in the National Heart, Lung, and Blood Institute registry [1]. Coronary stents were then developed to maintain vessel patency postangioplasty, to manage acute occlusion, and to decrease substantially the rate of restenosis. However, stent thrombosis became the most recognized complication of coronary stenting.

As for the level of certainty pertaining to the identification of stent thrombosis, definite stent thrombosis is an event in which there are new ischemic symptoms, electrocardiographic (ECG) changes, rise and fall of cardiac biomarkers, and angiographic or pathologic evidence of stent thrombosis [2]. Probable stent thrombosis includes any unexplained death within 30 days of stent implantation or any myocardial infarction in the territory of the previously implanted stent without angiographic confirmation of stent thrombosis and without any other cause [2]. Possible stent thrombosis is defined as any unexplained death more than 30 days after stent implantation [2]. Armed with these definitions, studies of BMSs and DESs then became more consistent with adjudicating clinical end points and with accuracy in defining the incidence of stent thrombosis as newer-generation stents were introduced and improvements in medical therapy achieved.

DAPT had been shown early on as effective pharmacotherapy for rate reduction of stent thrombosis. Initially the use of aspirin and ticlopidine was shown to be superior to aspirin a lone or aspirin and warfarin in the STARS trial [6]. Further studies using clopidogrel compared with ticlopidine showed similar rates of cardiac events with better patient compliance and fewer noncardiac side effects [45e47]. Newer P2Y12 inhibitors prasugrel and ticagrelor demonstrated improved platelet inhibition and decreased rate of stent thrombosis compared with clopidogrel in the TRITON-TIMI 38 and PLATO trials, respectively [48,49]. In 2016 the American College of Cardiology and American Heart Association issued a focused updated guideline document on DAPT with recommendations for the agent of choice, as well as the duration of therapy, for BMSs and DESs in the treatment of stable CAD and ACS, for rate reduction of stent thrombosis as balanced with bleeding risks [50]. With low stent thrombosis rates associated with second- and third-generation DESs, very large trials are required to detect any difference in stent thrombosis based on DAPT duration. The DAPT study randomized 9961 patients 12 months after DES implantation to continue DAPT or placebo for an additional 18 months [51]. The prolonged DAPT group had a significantly lower incidence of stent thrombosis (0.4% vs. 1.4%), albeit at a cost of increased moderate or severe bleeding (2.5% vs. 1.6%). The study investigators also used these data to create a personalized score for individual patients to assist clinicians in reaching a decision concerning prolonged versus curtailed DAPT duration. This score is based on nine simple variables [52]. With an emphasis on personalized medicine in the current era it is also possible that genotype determination for clopidogrel metabolism will assist in pairing the patient with the proper antiplatelet medication and, consequently, decrease the phenomenon of stent thrombosis. The IGNITE registry data suggest that patients with loss-of-function alleles for the CYP2C19 gene carry a significantly higher incidence of adverse events with clopidogrel treatment [53]. At the time of publication, the TAILOR-PCI (Tailored Antiplatelet Therapy Following PCI) trial, a ran­domized trial, is under way to investigate the effects of genotype-guided antiplatelet therapy in patients post-PCI and is expected to provide further guidance. It should be noted that proper DAPT duration for BVS is difficult to “set in stone,” as most patients with late or very late ScT in clinical trials had stopped DAPT. Thus, a prolonged period of treatment should be preferable in the management of BVS patients [54].

Intraprocedural anticoagulation also plays a role in the prevention of stent thrombosis, mostly the acute stent throm­bosis. Both unfractionated heparin and bivalirudin are well studied and accepted as anticoagulants for PCI that utilizes either BMS or DES. Nevertheless, although associated with less bleeding, bivalirudin has been associated with an increased risk of acute stent thrombosis [55]. Glycoprotein IIb/IIIa receptor inhibitors and unfractionated heparin have been shown to prevent acute stent thrombosis in patients with STEMI; however, in the current era of more potent P2Y12 inhibitors their role is less appreciated [56].