Acute stent thrombosis

Acute stent thrombosis in a patient with stent underexpansion in the proximal left anterior descending artery.

Learning objective: To understand the role of stent underexpansion as the key risk factor for acute stent thrombosis

60 year old male with arterial hypertension, hypercholesterolemia and diabetes mellitus underwent urgent coronary angiography for the unstable coronary artery disease. The angiography revealed CTO of RCA, tight calcified proximal LAD lesion and borderline LCX stenosis. The LAD lesion was assumed culprit. The initial strategy for the patient was ad-hoc PCI of the LAD. Following the predilatation with 2.5mm and 3.0mm NC balloons two overlapping Biolimus stents were implanted:  3.5/18mm proximally and 2.5/18mm distally. The proximal stent was postdilated with NC balloon 3.5mm at 16 ATM. (Figure 1)  The intravascular ultrasound (IVUS) performed post procedure showed stent underexpansion with minimal stent area (MSA) of 3.9mm2 and significant disease in the distal referrence segment (minimal lumen area (MLA=3.2 mm2 ) and plaque burden of 60%). (Figure 2 and Figure 3) Despite suboptimal IVUS result the procedure was finished. Twenty hours after the procedure the patient experienced sudden onset of severe chest pain. The ECG showed early phase of anterior myocardial infarction with high T-waves in precordial leads. (Figure 4) Immediate coronary angiography showed acute LAD occlusion. (Figure 5). Despite several inflation with 3.0mm and 3.5mm NC balloon the flow could not be restored. (Figure 6) The patient was given GPIIb/IIIa inhibitor infusion and manual thrombectomy eventually restored TIMI 3 flow in the LAD. Additional 2.5/14mm Biolimus stent was implanted distally. (Figure 7) The final angiographic result was satisfactory.  However, no IVUS imaging was performed. The patient remained clinically stable and was discharged home 5 days after the second PCI.

Figure legend

Figure 1. Coronary angiography immediatelly prior to and after PCI of proximal LAD lession. Apart from significant LAD stenosis one should notice severe calcifications and collaterals to the CTO of RCA.

Figure 2. IVUS images after PCI of proximal LAD lession. 1- proximal reference, 2 – MSA site; lumen area of 3,9mm² , 3 - IVUS crossection showing good stent expansion, 4 - IVUS crossection of the distal LAD stent, 5 – IVUS crossection at distal reference site with MLA of 3,2mm² and plaque burden of 60%, 6-IVUS crossection at distal reference site with preserved lumen and mild plaque burden

Figure 3. Longitudinal IVUS reconstruction showing stent underexpansion

Figure 4. ECG changes in the very early phase of acute anterior myocardial infarction

Figure 5. Coronary angiography showing LAD occlusion due to the acute stent thrombosis and failure to open the artery with balloon inflations.

Figure 6. Coronary angiography after manual thrombectomy, additional stent implantation and complex postdilation with NC balloons.

Key learning points:

1. Adequate preparation of calcified lesion is essential. Rotablation should have been considered in this case
2. IVUS imaging is not enough. The operator must react to the imaging results
3. Stent underexpansion and significant reference disease are most important mechanistic risk factor of acute stent thrombosis.