Near infrared spectroscopy and optical coherence tomography derived plaque characteristics associated with increased plaque progression over 12-month follow up
Authors: Tomaniak M , Hartman E.M.J , Tovar Forero M.N , Wentzel J.J , Daemen J 
Published: November 2020

Abstract

Background
Serial intravascular ultrasound (IVUS) studies demonstrated patterns of either plaque progression, regression or stabilization during pharmacotherapy including statin. At present little is known on specific plaque characteristics that are associated with excessive plaque growth.

Purpose
To evaluate the utility of near infrared spectroscopy (NIRS) and optical coherence tomography (OCT) to identify characteristics of non-culprit plaques associated with an increase in wall thickness (WT).

Methods
In this prospective, single-center study, patients with acute coronary syndrome (ACS) underwent, after successful treatment of the culprit lesions, both NIRS-IVUS and OCT assessment of a non-culprit artery at baseline and 12-month follow-up. For each vessel, 1.5-mm segments were identified, matched and divided into 45° sectors. A sector was considered as NIRS positive or labeled as OCT-detected fibrous cap atheroma (FCA), lipid rich or fibrous plaque when &gt;75% of the sector area exhibited NIRS signal or specific OCT-detected feature. The relationship between change in IVUS-based WT, and the presence of NIRS positive signal or OCT-detected plaque components (FCA, lipid rich, fibrous) was evaluated using mixed ANCOVA, with NIRS status and OCT plaque components as fixed factors, and patient as random factor, adjusting for clustering effect of the data. All analyses of plaque WT change were adjusted for baseline WT. To examine the value of NIRS and OCT-detected plaque components in predicting plaque progression, a logistic mixed model was built with plaque progression defined as WT increase &gt;0.2mm over the 12-month follow-up.

Results
A total of 38 patients (92% male, 21% diabetic) with 9167 matched sectors were analyzed at baseline and 12 months. Mean change in WT between baseline and 12 months was 0.014mm (95% confidence interval [CI] 0.011–0.018, p&lt;0.001). Positive NIRS sectors showed more pronounced plaque progression than NIRS negative sectors (0.057mm, 95% CI 0.032–0.084 vs 0.014mm 95% CI 0.010–0.017, p=0.001) (Figure 1). FCA showed significant progression of WT over the 12-month follow-up (0.104mm, 95% CI 0.007–0.201), whereas a decrease in WT was observed in sectors with fibrous tissue (−0.031mm, 95% CI 0.048–0.014) (p=0.022). Baseline NIRS positive (OR 1.88, 95% CI 1.34–2.64) and OCT-detected lipid rich plaque (OR 1.47, 95% CI 1.20–1.81) were associated with 12-month plaque progression (&gt;0.2mm) by logistic regression.

Conclusions
Positive NIRS signal and OCT-detected lipid plaque components imaged at baseline in non-culprit coronary arteries of patients presenting with ACS could identify vessel wall regions prone to plaque progression over a 12-month period.
Figure 1. Plaque progression and NIRS

Funding Acknowledgement
Type of funding source: Other. Main funding source(s): M. Tomaniak acknowledges funding received as a Laureate of the European Society of Cardiology Research and Training Programme in the form of the ESC 2018 Grant.