Coronary Flow Velocity and Disturbed Flow Predict Adverse Clinical Outcome After Coronary Angioplasty

Abstract

Objective-Laminar flow becomes disturbed at high velocities, reducing shear stress and augmenting vascular inflammation and proliferation, processes that are pivotal in restenosis and atherogenesis. We hypothesized that disturbed blood flow after coronary angioplasty is associated with adverse long-term clinical outcome. Methods and Results-The cineangiograms from 97 patients undergoing laser-assisted coronary angioplasty were analyzed. Coronary blood flow velocity, the residual lesion dimensions, and the Reynolds number (an index of disturbed flow) were measured by using a frame-counting technique and quantitative coronary angiography. Cox proportional hazards were used to assess the relative risk of adverse events (target-vessel revascularization, myocardial infarction, or death) over a mean 2.5 years after the index procedure. There were 41 adverse events during 245 patient years of follow-up (17% per year of follow-up). The risk of an adverse event was increased for patients with a high flow velocity (Ͼ250 mm/s; relative risk 2.5, 95% CI 1.3 to 4.7) or a high Reynolds number (Ͼ200) at the stenosis inlet (relative risk 2.1, 95% CI 1.1 to 4.1) at the end of the procedure. Adjustment for other factors did not alter these results. Key Words: disturbed coronary flow Ⅲ Reynolds number Ⅲ outcomes Ⅲ angioplasty T he clinical outcome after percutaneous coronary interventions is related to the risk of restenosis, which is related to the postprocedural minimal luminal diameter, [1][2][3][4] and to disease progression. These events could also be determined by disturbed laminar blood flow at residual stenoses, which creates shear stresses that adversely affect the biology of the arterial wall. [5][6][7][8][9][10][11][12][13] Normal laminar blood flow acts on endothelial cells to generate molecules that promote a vasodilatory, anticoagulant, anti-inflammatory, and growthinhibitory surface. [5][6][7][8][9][10][11][12][13] Disturbed laminar blood flow is more likely to occur at higher flow velocities and creates sites of abnormally low and high shear stress, and these are sensed by the endothelium. Abnormally low shear stress in particular activates endothelial cell genes and their products to stimulate vascular inflammation, smooth muscle cell proliferation, and a procoagulant surface. [5][6][7][8][9][10][11][12][13] Disturbed laminar blood flow is prone to occur in vascular segments with high Reynolds numbers (calculated as velocityϫdiameterϫdensity/viscosity), 14 especially at sites of mild luminal narrowing (Figure 1). Percutaneous coronary interventions aim to favorably alter stenosis severity but may not restore normal laminar flow. The present study examines the hypothesis that coronary flow velocity and disturbed laminar blood flow at a residual coronary lesion after successful laser-assisted coronary intervention are associated with adverse long-term clinical outcomes. We studied this cohort because this ablative technique creates a lumen that is relatively free of dissections (avoiding complex flow patterns and ma...

The role of shear stress in the pathogenesis of atherosclerosis

“…174 Numerous models have been proposed to explain the changes in shear stress. These include the creation of disturbed shear secondary to the significantly elevated flow velocities, 175 prolonged inflammatory response to the stent promoting vascular SMC proliferation/migration 176 and the stent design itself modulating local shear gradients. 177 It is intriguing to observe that intimal hyperplasia has also been shown to occur in regions of low shear stress proximally and distally to the stent itself, 178 suggesting that the stent may indeed have more far-reaching influences on arterial architecture.…”

PECAM-1 Is Necessary for Flow-Induced Vascular Remodeling

“…The impaired IMT and vascular remodeling in PECAM-1 −/− carotids raises the possibility that PECAM-1 participates in the regulation of the inflammatory response elicited by ligation. Because proximal to the site of stenosis (or ligation), disturbed shear stress prevails and adversely affects the biology of the arterial wall 24, we used an in vitro system to apply disturbed shear stress to ECs that express (PE-RC) or lack (PE-KO) PECAM-1. PE-RC and PE-KO ECs were exposed to oscillatory flow to allow sustained activation of NFκB, which was assessed by either staining with the phospho-p65 Ab (Fig.S1), or measuring transcriptional activation of NFκB using a luciferase reporter (Fig.…”

Endothelial dysfunction and restenosis following percutaneous coronary intervention

“…Blood flow volume at baseline was estimated using the method described by Kinlay and colleagues [12]. Average blood flow velocity was measured using the TIMI frame- count method filmed at 15 frames per second: blood flow velocity = (15 × length/frame count) mm/s.…”