The influence of coronary plaque morphology assessed by optical coherence tomography on final microvascular function after stenting in patients with ST-elevation myocardial infarction

Abstract

Objectives: The index of microcirculatory resistance (IMR) provides a reproducible assessment of the status of coronary microvasculature in patients with ST-elevation myocardial infarction (STEMI). Frequency-domain optical coherence tomography (FD-OCT) enables detailed assessment of the morphology of coronary plaque.We sought to determine the influence of the initial culprit coronary plaque anatomy within the infarct-related artery on IMR after stenting in STEMI.

Patients and methods: In 25 STEMI patients IMR was measured immediately before and after stent implantation. FD-OCT imaging was performed at the same time points and atherothrombotic volume (ATV) before stenting, prolapsed+floating ATV after stenting and ΔATV was measured using three different strategies.

Results: There were no relationships between preprocedural IMR and FD-OCT parameters. Prestenting IMR was related only to pain to wire time (P: 0.02). Irrespective of the method adopted, the final IMR was related to prestenting ATV (ρ: 0.44, P: 0.03 for method I, ρ: 0.48, P: 0.02 for method II and ρ: 0.30, P: 0.06 for method III) and ΔATV (ρ: 0.41, P: 0.04 for method II and ρ: 0.44, P: 0.03 for method III).

Conclusion: IMR measured before stenting is independent of the appearances of the culprit coronary plaque within the infarct-related artery. IMR after stenting, and more importantly, the change in IMR after stenting, reflect the degree of distal embolization during stent implantation.

Conflict of interest statement

Conflict of interests: Prof Banning has received an unrestricted research funding from Boston Scientific. All other authors have no relationships relevant to the contents of this paper to disclose.

Figures

Figure 1. Study Flow Chart.

Figure 2. Pre-stenting FD-OCT run measures.

Panel A and B. Mathematical formulae adopted to calculate mean reference lumen areas and flow areas. Panel C. Calculation of flow area according to the presence of thrombus adherent to the vessel wall (red arrowheads), floating thrombus (yellow arrowheads), cavity associated with plaque rupture (white asterisk), and bridging lumen within the thrombus (green arrowhead). Note that contours of meausured flow area are highlighted in red in each image of Panel C. (BLA: bridging lumen area; CA: cavity area; FA: flow area; FAmeasured: measured flow area; FATA: floating atherothrombus area; LA: lumen area; ref: reference; ROI: region of interest)

Figure 3. The three methods for pre-stenting (athero)-thrombotic volume measurement.

Intra- and interobserver reproducibility are reported for each strategy. (h= cross section thickness; l: region of interest length n= number of frames within region of interest; R= mean proximal reference radius; r: mean distal reference radius)

Figure 4. Post-stenting FD-OCT run measures.

Panel A. Mathematical formulas adopted to calculate prolapsed+floating atherothrombotic volume and malapposed volume. Panel B. Examples of prolapsed atherothrombotic material (asterisks in subpanel a, b and c and red contour in subpanel a’), floating atherothrombotic material (yellow arrowhead in subpanel b and yellow contour in subpanel b’), bridging lumen (green arrow in subpanel c and green contour in subpanel c’) and malapposition († symbol in subpanel d and d’). (BLA: bridging lumen area; FATA: floating athero-thrombus area; LA: lumen contour; ref: reference; ROI: region of interest)

Figure 5. Relationship between post-stenting IMR, delta IMR and delta athero-thrombotic volume.

(∆ATV: delta athero-thrombus volume; IMR: index of microcirculatory resistance)