Coronary stent thrombosis

Coronary stent thrombosis or scaffold thrombosis refers to a recent acute thrombus or occlusion in a coronary segment previously treated with a coronary stent or scaffold. It is a severe complication of percutaneous coronary intervention (PCI) and a major adverse cardiovascular event.

Epidemiology

Coronary stent thrombosis was up to 10% ¹ in the past but the incidence was reduced considerably in the recent past ².

Risk factors

Factors that increase the likelihood of developing coronary stent thrombosis include ^1,2:

• procedure-related
  • complex lesion
  • residual dissection
  • implantation of an undersized coronary stent
• stent-related
  • drug-eluting stents (1^st generation)
• patient-related
  • premature discontinuation of dual antiplatelet therapy
  • diabetes mellitus
  • underlying malignancy
  • high platelet reactivity

Associations

Coronary stent thrombosis is associated with impaired arterial healing and uncovered struts ¹.

Clinical presentation

The typical clinical presentation of stent thrombosis is that of myocardial infarction and includes the detection of a typical rise and fall in cardiac troponin above the 99^th percentile URL and one following ^3,4:

• symptoms of acute myocardial ischemia
• new ischemic ECG changes
• new pathological Q-waves

The following time intervals of stent or scaffold thrombosis after implantation are distinguished ^1-4:

• early: <30 days (acute ≤24 hours, subacute 1-30 days)  
• late: >30 days to 1 year
• very late: >1 year

Complications

Complications of coronary stent thrombosis include ^1-3:

• myocardial infarction
• cardiac arrest
• sudden cardiac death

Pathology

Stent thrombosis is characterized by an acute thrombus or occlusion of a previously stented coronary segment including the adjacent 5 mm proximal or distal to the stent or in a branch arising from the stented segment ⁴.

Etiology

Causes and pathogenic mechanisms of stent thrombosis include the following ^1,2:

• interruption or early dual-antiplatelet therapy
• stent malapposition or underexpansion
• impaired arterial healing/re-endothelialization and uncovered stent struts
• localized hypersensitivity reactions
• neoatherosclerosis
• stent dismantling (in bioresorbable scaffolds)

Radiographic features

Coronary stent thrombosis requires emergency invasive coronary angiography with repeat percutaneous coronary intervention and in this case, any additional imaging will delay treatment. However, there might be occasions, where imaging modalities will reveal findings indicating the diagnosis which have not been previously detected by other means.

Radiographic features are not different from type 1 myocardial infarction and include the following features in an ischemic pattern ³:

• new loss of viable myocardium
• new regional wall motion abnormalities

Echocardiography

Echocardiography might detect new wall motion abnormalities.

CT

Coronary CTA might show stent thrombosis/occlusion.

Coronary angiography

Coronary angiography within emergency repeat percutaneous coronary intervention is the modality of choice to document the diagnosis and will prove stent thrombosis following thrombectomy ⁴.

MRI

MRI might show signs of acute myocardial infarction corresponding to the respective coronary vascular territory including:

• cine imaging: new regional wall motion abnormalities
• T2/STIR black blood: hyperintensity indicating myocardial edema and the ‘area at risk’
• perfusion imaging:  diminished or delayed uptake
• IRGE/PSIR: new subendocardial to transmural late gadolinium enhancement ± no reflow phenomenon

Radiology report

The radiological report should include a description of the following features based on the AHA coronary artery segment and cardiac segmentation models:

Coronary angiography/coronary CTA:

• stent occlusion
• location of the stent
• coronary artery stenoses

Echocardiography/cardiac MRI/nuclear medicine:

• regional wall motion abnormalities
• non-viable myocardium

Treatment and prognosis

The management of coronary stent thrombosis requires emergency percutaneous coronary intervention with revascularization ¹.

Differential diagnosis

Stent thrombosis can mimic the appearance or presentation of the following clinical conditions ¹:

• myocardial infarction (type 1 and type 2)
• aortic dissection
• myocarditis