Influence of Coronary Stenosis Geometry and Hemodynamic Parameters on Plaque Vulnerability

Abstract

목적: 관상동맥 협착 병변의 형태 및 혈류역학적 지표가 동맥경화반의 취약성에 미치는 영향을 관찰하고자 연구를 진행하였다. 배경: 동맥경화반 자체의 형태학적, 조직학적 특징과 동맥경화반의 취약성의 관련성에 대한 연구는 많았으나 관상동맥 협착 병변의 형태 및 혈류역학적 지표가 동맥경화반의 취약성에 미치는 영향에 대해선 잘 알려져 있지 않다. 방법 및 결과: 관상동맥조영술에서 40~70%협착을 보이는 환자 중 동시에 분획혈류예비량 및 침습적 영상검사 [Optical coherence tomography(OCT) or Intravascular ultrasound(IVUS)] 를 시행한 71명의 환자(73개 병변)에서 관찰연구를 진행하였다. 혈관의 분획혈류예비량 [fractional flow reserve(FFR)] 은 lipid rich plaque이 있는 혈관에서 없는 혈관보다 현저히 낮았고 [0.79(0.73-0.82) vs. 0.82(0.80-0.93) p=0.038]

압력의 변화 (△P) 는 microvessel(s)이 있는 병변에서 컸고 [12.5(8.0-21.3) vs. 7.5(5.0-14.8) p=0.045]

분획혈류예비량의 변화 (△FFR) 는 조영감쇄 죽상경화반(posterior attenuation)이 있는 병변에서 컸다 [0.19(0.11-0.36) vs. 0.10(0.08-0.16)]. Minimum lumen area(MLA) 와 5mm 떨어진 곳에서 측정한 Radius gradient(RG)는 선행 연구에서 계산한 방법으로 계산한 RG와 높은 재현성과 상관성을 보였다 [intraclass correlation coefficient (ICC) = 0.924

r = 0904 p < 0.001]. Downstream-dominant 병변에서 lipid rich plaque 및 조영감쇄는 downstream segment에서 제일 적게 관찰되었고 (upstream vs. MLA vs. downstream 53.3% vs. 53.3% vs. 13.3% p = 0.011)

maximum lipid arc 역시 downstream에서 제일 적게 관찰되었다 (upstream vs. MLA vs. downstream 35.7% vs. 64.3% vs. 0% p = 0.013). 결론: 혈류역학적 지표인 분획혈류예비력, 분획혈류예비력의 변화, 압력의 변화는 각각 lipid rich plaque, microvessel(s), 조영감쇄의 유무에 따라서 차이를 보였다. 종축 전단력 [axial plaque stress(APS)] 은 관상동맥 병변 취약성의 분포에 영향을 주지 않았다.

Objectives: The objective of this study was to investigate the influence of lesion geometry and hemodynamic parameters on plaque vulnerability. Background: The relationship among lesion geometry, hemodynamic forces acting on the plaque, location and presence of vulnerable features has not been explored. Methods: Seventy-one patients (73 lesions) with fractional flow reserve (FFR) measurement in addition to at least one imaging device [intravascular ultrasound (IVUS) or optical coherence tomography (OCT)] were enrolled. Differences of FFR, trans-stenotic FFR gradient (△FFR) and trans-stenotic pressure gradient (△P) between lesions with and without vulnerable features were investigated. Radius gradient (RG), measured by standard method and, also, measured on point of 2.5mm, 5mm, 7.5mm away from MLA point, were respectively calculated using IVUS. Axial plaque stress (APS) were calculated using intracoronary pressure and RG. Upstream-dominant lesions were defined as lesions with RGupstream>RGdownstream. The longitudinal distribution of APS between two segments [upstream, downstream divided by minimum lumen area (MLA)] was compared according to lesion asymmetry. Presence of vulnerable features was compared among three segments (upstream, MLA, downstream) according to lesion asymmetry. Results: FFR was significantly lower in lesions with lipid rich plaque than those without lipid rich plaque [0.79(0.73-0.82) vs. 0.82(0.80-0.93) p = 0.038]. Significantly bigger △P was shown in lesions with microvessel(s) [12.5(8.0-21.3) vs. 7.5(5.0-14.8) p= 0.045]. Significant bigger △FFR between lesions with posterior attenuation was shown compared to those without posterior attenuation [0.19(0.11-0.36) vs. 0.10(0.08-0.16) p = 0.038]. Among several different RG measurements, RG calculated from point of 5mm away from MLA showed not only the best reliability [intraclass correlation coefficient (ICC) = 0.924]] but the best correlation (r = 0.904 p < 0.001) with RG measured using standard method. The significantly higher APSs were observed in the upstream segments of upstream-dominant lesions than those of downstream-dominant lesions (9.78 ± 4.81 vs. 6.30 ± 3.89 p = 0.003) and downstream segments of downstream-dominant lesions than those of upstream-dominant lesions (8.25 ± 3.38 vs. 4.36 ± 2.68 p < 0.001). The frequency of lipid rich plaque in addition to posterior attenuated plaque was lowest in the downstream segments compared to the upstream and MLA segments of downstream-dominant lesions (upstream vs. MLA vs. downstream 53.3% vs. 53.3% vs. 13.3% p = 0.011). The appearance of maximum lipid arc and posterior attenuation arc was rarely observed in downstream segments of downstream-dominant lesions (upstream vs. MLA vs. downstream 35.7% vs. 64.3% vs. 0% p = 0.013). Conclusions: Hemodynamic parameters, FFR, △FFR and △P show differences between lesions with and without lipid rich plaque, microvessel(s) and posterior attenuation. While, APS seems not to play a crucial role in distribution of vulnerable features, its force directly impacting on plaque appears to contribute to plaque rupture only.