Characterization of healing following atherosclerotic carotid plaque rupture in acutely symptomatic patients: an exploratory study using in vivo cardiovascular magnetic resonance

Abstract

Background: Carotid plaque rupture, characterized by ruptured fibrous cap (FC), is associated with subsequent cerebrovascular events. However, ruptured FC may heal following stroke and convey decreased risk of future events. This study aims to characterize the healing process of ruptured FC by assessing the lumen conditions, quantified by the lumen curvature and roughness, using in vivo carotid cardiovascular magnetic resonance (CMR).

Methods: Patients suffering from transient ischemic attack underwent high resolution carotid MR imaging within 72 hours of the acute cerebrovascular ischemic event. CMR imaging was repeated at 3 and 12 months in 26 patients, in whom FC rupture/erosion was observed on baseline images and subsequent cerebrovascular events were recorded during the follow-up period. Lumen curvature and roughness were quantified from carotid CMR images and changes in these values were monitored on follow-up imaging.

Results: Healing of ruptured plaque was observed in patients (23 out of 26) without any ischemic symptom recurrence as shown by the lumen surface becoming smoother during the follow-up period, characterized by decreasing maximum lumen curvature (p < 0.05), increasing minimum lumen curvature (p < 0.05) and decreasing lumen roughness (p < 0.05) during the one year follow-up period.

Conclusions: Carotid plaque healing can be assessed by quantification of the lumen curvature and roughness and the incidence of recurrent cerebrovascular events may be high in plaques that do not heal with time. The assessment of plaque healing may facilitate risk stratification of recent stroke patients on the basis of CMR results.

Figure 1

In vivo CMR-images showing the healing process which can be characterized using lumen curvature. (A): T₁ CMR image at baseline (0 month; 0 M) showing ruptured fibrous cap (red arrow) and the healing observed after 3 and 12 months (3 M and 12 M); (B): the corresponding lumen contours and the lumen curvature curves.

Figure 2

Schematic drawing showing the definition of lumen curvature and roughness. (A): The lumen curvature at a can be computed from the circle determined by a and the two adjacent points, a₁ and a₂; (B): The definition of roughness. Red line: lumen contour; Dash black line: the circle best fitting the lumen contour.

Figure 3

Comparison of maximum curvature, minimum curvature and lumen roughness over time. In summary, the lumen became smoother while healing occurred in the patient group (n = 23) without recurrent events. (A): maximum lumen curvature decreased with time; (B) minimum lumen curvature increased with time; and (C) the lumen roughness decreased.

Figure 4

A patient who suffered from a recurrent event during CMR follow-up period with insufficient healed lumen erosions.