Hemodynamic impact of coronary stenosis using computed tomography: comparison between noninvasive fractional flow reserve and 3D fusion of coronary angiography with stress myocardial perfusion

Abstract

Vasodilator-stress CT perfusion imaging in addition to CT coronary angiography (CTCA) may provide a single-test alternative to nuclear stress testing, commonly used to assess hemodynamic significance of stenosis. Another alternative is fractional flow reserve (FFR) calculated from cardiac CT images. We studied the concordance between these two approaches and their relationship to outcomes. We prospectively studied 150 patients with chest pain, who underwent CTCA and regadenoson CT. CTCA images were interpreted for presence and severity of stenosis. Fused 3D displays of subendocardial X-ray attenuation with coronary arteries were created to detect stress perfusion defects (SPD) in each coronary territory. In patients with stenosis > 25%, CT-FFR was quantified. Significant stenosis was determined by: (1) combination of stenosis > 50% with an SPD, (2) CT-FFR ≤ 0.80. Patients were followed-up for 36 ± 25 months for death, myocardial infarction or revascularization. After excluding patients with normal arteries and technical/quality issues, in final analysis of 76 patients, CTCA depicted stenosis > 70% in 13/224 arteries, 50-70% in 24, and < 50% in 187. CT-FFR ≤ 0.80 was found in 41/224 arteries, and combination of SPD with > 50% stenosis in 31/224 arteries. Inter-technique agreement was 89%. Despite high incidence of abnormal CT-FFR (30/76 patients), only 7 patients experienced adverse outcomes; 6/7 also had SPDs. Only 1/9 patients with CT-FFR ≤ 0.80 but normal perfusion had an event. Fusion of CTCA and stress perfusion can help determine the hemodynamic impact of stenosis in one test, in good agreement with CT-FFR. Adding stress CT perfusion analysis may help risk-stratify patients with abnormal CT-FFR.

Keywords: Cardiovascular CT; Fusion imaging; Myocardial perfusion; Vasodilator stress.

Fig. 1

Schematic diagram of the study design (see text for details)

Fig. 2

Flowchart of patient enrollment through the formation of the final study group (see text for details)

Fig. 3

Example of combined 3D display of myocardial perfusion during vasodilator stress and the coronary arteries obtained in a patient with no significant stenosis (left and right panels). The four snapshots depict the different views with fairly uniform subendocardial perfusion during vasodilator stress, reflected by the red hues. The snapshot of CT-FFR analysis (center) shows normal FFR in all three major coronary arteries, reflected by values > 0.80

Fig. 4

Example of CT images obtained during vasodilator stress in a patient with an intermediate grade stenosis, resulting in 50–60% luminal narrowing. Subendocardial perfusion defect can be seen in the antero-septal and septal walls (arrows) in the different cross-sections of the heart

Fig. 5

Example of CT-FFR snapshots (top) and corresponding views of the combined 3D display of myocardial perfusion during vasodilator stress and the coronary arteries (bottom), obtained during vasodilator stress in a patient with an intermediate grade stenosis, resulting in 50–60% luminal narrowing in the proximal LAD. Reduced CT-FFR can be seen distal to the lesion (top), concomitant with a large perfusion abnormality encompassing the antero-septal and septal walls (bottom; blue hues)

Fig. 6

Example of 3D display obtained in a patient with complex multivessel disease, with approximately 60% stenosis in the mid LAD and a similar lesion in the distal RCA, shown in the same format as in Fig. 3. Both lesions were determined to be significant by CT-FFR analysis, resulting in values < 0.80 (center). An extensive perfusion defect is seen in the anterior and antero-septal walls extending to the apex, supplied by the LAD artery (top left and right; blue hues), and another one in the inferior wall along the course of the RCA (bottom right), while perfusion in the lateral wall supplied by the stenosis-free LCX artery appears to be normal (bottom left; red hues)

Fig. 7

Inter-technique agreement for stress perfusion defects (SPD) fused with CTCA, and also for the combination with stenosis > 50% on CTCA, both against CT-FFR, presented on a by-artery basis. See text for details

Fig. 8

Example of a combined 3D display depicting a large subendocardial stress perfusion defect covering infero-septal, inferior and inferolateral walls, in the presence of normal RCA and LCX arteries (arrows; left and right panels). Examination of the raw CT images of this patient revealed a large streak artifact caused by the spinal vertebrae (arrows; middle panel)