Critical Complication Post Percutaneous Coronary Intervention: Acute Stent Thrombosis

The academic research consortium criteria (ARC criteria) defines AST as thrombosis detected within the 5mm proximal or distal to the newly placed coronary stents during coronary angiogram [1]. In the situation where a patient begins to have chest symptoms, physicians should be on high alert for acute stent thrombosis [2]. AST has a prevalence of 0.5 to 1 %, with a mortality rate up to 20 to 45 %. Post-stenting thrombotic events can lead to myocardial infarction, deadly cardiac arrhythmia and irreversible heart failure. Even with early intervention, large areas of myocardial infarction and heart failure leads to poor prognosis [3,4].


Introduction
The academic research consortium criteria (ARC criteria) defines AST as thrombosis detected within the 5mm proximal or distal to the newly placed coronary stents during coronary angiogram [1]. In the situation where a patient begins to have chest symptoms, physicians should be on high alert for acute stent thrombosis [2]. AST has a prevalence of 0.5 to 1 %, with a mortality rate up to 20 to 45 %. Post-stenting thrombotic events can lead to myocardial infarction, deadly cardiac arrhythmia and irreversible heart failure. Even with early intervention, large areas of myocardial infarction and heart failure leads to poor prognosis [3,4].
Risk factors of AST include low left ventricular ejection fraction (LVEF), unstable angina, coagulopathy, diabetes mellitus and End-Stage Renal Disease (ESRD) [5,6]. Clinically, patients may present with conscious disturbance, low blood pressure, shortness of breath, reduced urine output and poor perfusion of peripheral vessels. If left unrecognized, progressive damage to heart function will occur [3]. Therefore, it is of paramount that first line workers are constantly monitoring patient's general condition, ECG changes, and variation of lab data such as cardiac enzymes and renal function [7]. Differentiating AST from occlusion of other vessels or end coronary vessel thrombosis is also important as their clinical signs may be similar [5]. This is a 65-year-old male patient developed chest symptoms one hour after receiving PCI. Although the nurse practitioner suspected it might be acute coronary syndrome (ACS), his symptoms were not typical and the ECG and the cardiac enzymes were within normal limits, the diagnosis of AST was thus delayed.

Case report
This is a 65-year-old male with a known medical history of hypertension, hyperuricemia and hyperlipidemia. Patient first complained of intermittent chest pain after exertion for one year.
His chest pain is limited to the left anterior chest and is associated with dyspnea and cold sweating. Exercising ECG revealed ST segment depression with chest tightness, compatible with coronary artery disease. Coronary angiography showed severe occlusion of left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA) ( Table 1). Three Drug-eluting stents (DES) were deployed from Left main (LM) to LAD, LAD proximal to middle, LAD middle to distal. Balloon angioplasty was done to LM and LCX.

Discussion
Acute stent thrombosis (AST) denotes an ischemic change to the heart due to thrombosis of recently placed coronary artery stents within the first 24 hours of PCI. Based on the time of events can be classified into early (acute or subacute), late, and very late stage [8]. Among these, the acute AST is the rarest but also deadliest with mortality rate up to 45% [2]. When patient complains of chest symptoms, continuous monitoring of ECG is essential. In Taiwan, our cardiac association recommends ECG to be obtained within the first 10 minutes of symptoms. If the first ECG was insignificant or inconclusive, a 12 leads ECG should be obtained for every 15 to 30 minutes [9]. If clinically confirmed or highly suspected, early coronary angiogram should be performed in establishing early diagnosis and treatment [6]. Close monitoring of input and output (I/O), bodyweight, and cardiac sonography for signs of heart failure after receiving PCI are considered as routines. Prescribing statins early with a target LDL less than 70 mg/dl to help reduce cardiac mortalities and ischemic stroke of the brain [10]. Beta-blockers should be given to patients without pulmonary edema, signs of shock, and who are hemodynamically stable to improve left ventricle function and overall survival [11]. Angiotensin-converting enzyme inhibitors (ACEI) or ARB reduces 30-day mortalities in patients with a LVEF <40%, diabetics, and hypertension [10].
Several causes of AST have been established in the past. Based on a systematic review, predictors of early ST were include patient, lesion, device, and procedure (  [14] examined the validity of the score in 569 patients who had STEMI and underwent PCI and found the risk score was significantly higher in those who developed AST. Baseline platelet count and insulin-dependent diabetes mellitus were statistically significant in predicting AST. Patients with a total score of 5 or higher were at a 5-fold risk than 0 those with a scoreless or equal to 2. Demonstrating a linear relationship between the score and the risk of developing AST, with a specificity of 91% and sensitivity of 30%.

American Journal of Biomedical Science & Research
Copy@ Ching-Wen Wei biodegradable polymer-coated and polymer-free devices reduce polymer induced reactions; self-expandable stents for bifurcation lesions. When main vessels are found to have occlusions, IVUS or Optical coherence tomography (OCT) can be used for optimal stent size choice to reduce the effect of procedure-related factors [15].
Acute stent thrombosis can be linked to P2Y12, a chemoreceptor for adenosine diphosphate (ADP). Antiplatelet or anticoagulation agents should be administered early to prevent AST [16]. Drugs including Aspirin which inhibits TAX2 in prevention and treatment of ACS and ischemic stroke. Clopidogrel and Ticagrelor bind to ADP P2Y12 receptor to prevent platelet activation. Glycoprotein IIb/IIIa inhibitors such as Abciximab, Tirofiban, Eptifibatide for unstable angina and NSTEMI. In 2018, European Heart Association guidelines was reported, in patients without bleeding tendency and previous bleeding histories in prevention of AST before PCI as a dual antiplatelet therapy [17].

Conclusion
Our case experienced acute chest symptoms one hour after PCI.
This case was educational to first line workers, which keep monitor ECG post PCI to early detect of AST was important if patient complained chest pain. It could be help minimize the damage done to the myocardium and prompt early intervention and reperfusion and ultimately prevent mortality.