Stent thrombosis

A stent, like any foreign body that comes into contact with blood, can cause thrombosis at the site of implantation. The surface of the stent has the ability to "attract" platelets, but after a short time the metal surface is covered with precipitating proteins, which somewhat reduces the risk for stent thrombosis. In 2-4 weeks. After implantation of HTIC and a few months after implantation of SLP, coating of the protein film with an unintentional coating takes place, which sharply reduces the risk of stent thrombosis.

Temporary stent thrombosis characteristics

Type of thrombosis	Time of development
Acute	0 24 h
Subacute	24 hours - 30 days
Late	30 days 1 year
Very late	After 1 year or more

[1], [2]

Causes of stent thrombosis

The risk factors for acute stent thrombosis are stenting in acute myocardial infarction, intervention on venous shunts, lack of ASA, clopidogrel on the eve of the procedure, as well as inadequate coagulation during PCI, preservation of residual dissection. The main risk factors for subacute stent thrombosis are: retention of residual dissection, thrombus, protrusion of tissue through the stent cells into the lumen of the vessel, stenting of large and complicated lesions, as well as under-opening of the stent, and stopping the use of antiplatelet agents.

The risk of stent thrombosis in patients with ACS and type 2 diabetes is increased. In patients with ACS, the most important risk factors for stent thrombosis are severity of coronary artery disease, low hemoglobin level, small diameter of implantable stent, and lack of reception of thienopyridipes before the procedure.

Among all stent thromboses, the most common are subacute (41%) and acute TC (32%), late and very late stent thromboses account for about 26% of all cases. In contrast to late thrombosis, the frequency of development of acute and subacute stent thrombosis is the same with NPS and SLP. In at least one study, the use of stents coated with heparin reduced the incidence of acute carotid artery disease compared to conventional NPCs.

In early studies in which post-stenting was recommended, the use of ASA, dipyridamole and warfarin, the incidence of stent thrombosis reached 20%, and bleeding often developed. Later it was shown that in most cases acute TC occurs when the stent is underopen, which led to routine use of high pressure during stenting. In addition, the efficacy of a 4-week course of dual antiplatelet therapy (ASA + ticlopidine) after stenting was proven. All these measures have made it possible to reduce the incidence of acute and subacute stent thrombosis to less than 1%. The average time of onset of subacute TS decreased from 6 to 1-2 days. At the same time, the exclusion of warfarin from the obligatory TS prophylaxis regimen reduced the frequency of hemorrhagic complications. In the following, ticlopidine was almost universally replaced with clopidogrel, since at the same efficacy it is characterized by a lower incidence of adverse events.

Despite the reduction in frequency, stent thrombosis remains one of the most dangerous complications of stenting. As a rule, it manifests itself as a severe anginal infection, accompanied by ST segment elevation. In the STRESS study, mortality in subacute stent thrombosis was 20%, and in the remaining 80% of cases, Q-IM silt developed and emergency CABG was needed. In the last registers, the total 30-day mortality and MI frequency remain high - at the level of 15 and 78%, respectively. In the OPTIMIST study, mortality, even with PCI, for stent thrombosis was 12% at 30 days pi 17% at 6 months. The type of stent at which thrombosis developed does not affect short-term and long-term mortality. Adverse factors that worsen the 6-month prognosis in such patients are the absence of recovery of optimal blood flow, the implantation of the second stent for barely stent thrombosis, the three-vessel lesion, and the presence of 2 or more overlapping stents.

[3], [4], [5], [6], [7], [8], [9]

Treatment of stent thrombosis

Stent thrombosis is an emergency life-threatening situation. The procedure of choice is primary angioplasty, the task of which is the mechanical recanalization of the thrombosed stent. Restoration of antegrade blood flow can be achieved on average in 90% of cases, but the optimal result is observed only in 64% of cases. The optimal result was rarely achieved with PNA involvement, development of CLS, multivessel lesions, and also with distal embolization by thrombotic masses. During the procedure, the use of IIb / IIIa receptor blockers is recommended, especially in high-risk patients: hypercoagulability, thrombocytosis, long stent implantation, bifurcation lesion, small vessel diameter, residual dissection, no-reflow phenomenon. In most cases, balloon angioplasty is sufficient, possibly with the use of devices for thrombus aspiration. Reinstallation of the stent should be performed only in the case of pronounced residual dissection. According to the OPTIMIST register, stent implantation is required on average 45% of the time. If it is impossible to perform PCI, TLT is used.

The total frequency of repeated vehicle in the next 6 months. A high of about 16.2% (while according to the ARC classification, the frequency of proven, probable and possible TS is 6.7, 5.7 and 3.8% respectively). The average time to the occurrence of a repeated TC is 45 days (from 2 to 175 days). The type of stent does not affect the frequency of the repeated vehicle. In the case of repeated implantation of the stent in emergency PCI, the risk of repeated TS is increased 4-fold. Treatment of re-stent thrombosis is identical to the primary one. If there is insufficient platelet aggregation when taking standard double antiplatelet therapy (<50% of the norm), consider increasing the dose of clopidogrel up to 150 mg / day.

Thus, we can draw the following conclusions regarding stent thrombosis:

• The total frequency of stent thrombosis is about 1.5%.
• Depending on the time of occurrence after PCI, acute, subacute, late and very late TS are isolated.
• The most common is acute and subacute TS. After implantation of NPS, late TS appear very rarely, they are more typical for SLP.
• TS manifests a severe anginal episode, accompanied by ischemic dynamics on the ECG (usually with ST segment elevation).
• The method of choosing TC treatment is primary angioplasty, the task of which is the mechanical recanalization of the thrombosed stent. If it is not possible to perform PCI, TLT
• With PCI for TC, the second stent is implanted only with a pronounced residual dissection. During the procedure, the use of IIb / IIIa receptor blockers is recommended.
• The frequency of recurrence of the TC is high (about 16%) and does not depend on the type of stent.
• The main measures to prevent stent thrombosis - to ensure full disclosure of the stent and compliance with the timing of dual antiplatelet therapy.