Micro-CT-Based Quantification of Extracted Thrombus Burden Characteristics and Association With Angiographic Outcomes in Patients With ST-Elevation Myocardial Infarction: The QUEST-STEMI Study

Abstract

Background: Angiographic detection of thrombus in STEMI is associated with adverse outcomes. However, routine thrombus aspiration failed to demonstrate the anticipated benefit. Hence, management of high coronary thrombus burden remains challenging. We sought to assess for the first time extracted thrombotic material characteristics utilizing micro-computed tomography (micro-CT). Methods: One hundred thirteen STEMI patients undergoing thrombus aspiration were enrolled. Micro-CT was undertaken to quantify retrieved thrombus volume, surface, and density. Correlation of these indices with angiographic and electrocardiographic outcomes was performed. Results: Mean aspirated thrombus volume, surface, and density (±standard deviation) were 15.71 ± 20.10 mm³, 302.89 ± 692.54 mm², and 3139.04 ± 901.88 Hounsfield units, respectively. Aspirated volume and surface were significantly higher (p < 0.001) in patients with higher angiographic thrombus burden. After multivariable analysis, independent predictors for thrombus volume were reference vessel diameter (RVD) (p = 0.011), right coronary artery (RCA) (p = 0.039), and smoking (p = 0.027), whereas RVD (p = 0.018) and RCA (p = 0.019) were predictive for thrombus surface. Thrombus volume and surface were independently associated with distal embolization (p = 0.007 and p = 0.028, respectively), no-reflow phenomenon (p = 0.002 and p = 0.006, respectively), and angiographically evident residual thrombus (p = 0.007 and p = 0.002, respectively). Higher thrombus density was correlated with worse pre-procedural TIMI flow (p < 0.001). Patients with higher aspirated volume and surface developed less ST resolution (p = 0.042 and p = 0.023, respectively). Conclusions: Angiographic outcomes linked with worse prognosis were more frequent among patients with larger extracted thrombus. Despite retrieving larger thrombus load in these patients, current thrombectomy devices fail to deal with thrombotic material adequately. Further studies of novel thrombus aspiration technologies are warranted to improve patient outcomes. Clinical Trial Registration: QUEST-STEMI trial ClinicalTrials.gov number: NCT03429608 Date of registration: February 12, 2018. The study was prospectively registered.

Keywords: ST-elevation myocardial infarction; interventional cardiology; micro-computed tomography; thrombus; thrombus aspiration.

Figure 1

Thrombus analysis via micro-computed tomography. (A) Thrombi are mounted on a specific head inside SkyScan 1172; (B,C) Representative computer generated renderings of thrombi. Clots were stained using 0.3% phosphotungstic acid and scanned via SkyScan 1172. NRecon (Bruker, Kontich, Belgium) software was used for the reconstruction of the projections.

Figure 2

3D color visualization of a thrombus sample. A 3D model of a thrombus sample was created using CTAn software (Bruker, Kontich, Belgium), and color visualization was performed via CTVol software (Bruker, Kontich, Belgium). Erythrocyte-rich regions were rendered in red, whereas platelet-rich regions were rendered in white.

Figure 3

Main findings of the QUEST STEMI study. (A) Association of thrombus volume with angiographic thrombus classification by modified TIMI thrombus grade classification [Grade 2: 4.64 (2.66–8.92) mm³, Grade 3: 4.21 (3.72–8.80) mm³, Grade 4: 15.94 (10.60–19.51) mm³]. (B) Association of thrombus volume with smoking history [yes: 13.14 (9.31–16.35) mm³, no: 4.64 (2.66–8.69) mm³]. (C–E) Association of thrombus volume with angiographic outcomes {(C) distal embolization [yes: 18.70 (9.27–24.52) mm³, no: 9.61 (6.61–13.82) mm³], (D) no-reflow phenomenon: [yes: 18.98 (15.79–32.26) mm³, no: 9.31 (6.61–13.65) mm³], and (E) angiographically evident residual thrombus [yes: 25.81 (9.31–39.87) mm³, no: 9.61 (6.61–13.65) mm³]}. (F,G) Association of thrombus volume with electrocardiographic outcomes [complete ST resolution; 8.12 (5.93–10.31) mm³, partial ST resolution; 13.74 (6.42–16.97) mm³ and absent ST resolution: 26.26 (7.31–45.26) mm³]. (H) Association of thrombus surface with reference vessel diameter [RVD: 2.5 mm: 150.30 (±175.22) mm², 3 mm: 187.54 (±152.22) mm², 3.5 mm: 233.21 (±198.23) mm², 4 mm: 539.17 (±1388.82) mm², 4.5 mm: 855.73 (±78.26) mm²]. (I) Association of thrombus density with pre-procedural TIMI flow [TIMI 0: 3322 (3023–53523) HU, TIMI I: 3171 (2863–3331) HU, TIMI II: 2574 (2307–3564) HU, TIMI III: 2152 (2019–2594) HU].

Figure 4

Visual overview of the main findings of the QUEST STEMI study. (A) Independent predictors of large aspirated thrombus and (B) Angiographic outcomes linked with large aspirated thrombus.