Discordance between anatomical and functional coronary stenosis severity

Abstract

BACKGROUND.: New developments have made 16-slice multidetector computed tomography (MDCT) a promising technique for detecting significant coronary stenoses. At present, there is a paucity of data on the relation between fractional flow reserve (FFR) measurement and MDCT stenosis detection. OBJECTIVE.: The aim of this study was to investigate the relation between the anatomical severity of coronary artery disease detected by MDCT and functional severity measured by fractional flow reserve (FFR). METHODS.: We studied 53 patients (39 men and 14 women, age 62.5+/-8.1 years) with single-vessel disease scheduled for percutaneous coronary intervention (PCI). All patients underwent MDCT scanning one day prior to PCI and FFR was measured before PCI in the target vessel. RESULTS.: MDCT analysis could be performed in 52 of 53 patients (98.1%) and all patients had adequate FFR and quantitative coronary angiography (QCA) measurements. The mean stenosis diameters calculated by MDCT and QCA were 67.0+/-11.6% and 60.8+/-11.6% respectively. No significant relation was found between MDCT and QCA (r=0.22, p=0.12) The mean FFR in all patients was 0.67+/-0.18. A relation of r=-0.46 (p=0.0006) between QCA and FFR was found. In contrast, no relation between MDCT and FFR could be demonstrated (r=-0.09, p=0.50). Furthermore, a high incidence of false-positive and false-negative findings was present in both diagnostic modalities. CONCLUSION.: There is no clear relation between the anatomical and functional severity of coronary artery disease as defined by MDCT and FFR. Therefore, functional assessment of coronary artery disease remains mandatory for clinical decisionmaking. (Neth Heart J 2007;15:5-11.).

Figure 1.

Correlation between diameter stenosis measurements by 16-slice multi-detector computed tomography (MDCT) and quantitative coronary angiography (QCA) (r=0.22, CI -0.06 to 0.47, p=0.12).

Figure 2.

Correlation between (A) 16-slice multidetector computed tomography (MDCT) and fractional flow reserve (FFR) (r=-0.09, CI=-0.36 to 0.19, p=0.50) and between (B) quantitative coronary angiography (QCA) and FFR (r=-0.46, CI=-0.65 to -0.22, p=0.0006).

Figure 3.

Relation between fractional flow reserve (FFR) measurements and results of 16-slice multidetector computed tomography (MDCT) and quantitative coronary angiography (QCA) analysis. Each dot represents outcome of one anatomical test in relation to FFR in a single patient. The dashed line represents the FFR cut-off value of 0.75.

Figure 4.

Example of mismatch between anatomical and functional severity of a stenosis in a patient with an FFR >0.75. (A) A significant stenosis of the right coronary artery (RCA) was seen on diagnostic coronary angiography and the stenosis calculated by QCA was 54%. (B) Three-dimensional reconstruction by MDCT with volume rendering in the same patient. View from anterior reveals the stenosis in the RCA (arrow). (C) Close-up multiplanar reformation image of the proximal RCA reveals a soft plaque (arrow). MDCT segment analysis (D) shows a significant stenosis of 74% (calculated) in the proximal RCA. (E) Despite these anatomical changes in the vessel, an FFR of 0.90 ([Pressure distal of the stenosis (Pd mean) in mmHg] / [Aortic pressure (Pa mean) in mmHg]=99/110=0.90) was found, indicating that the stenosis was not functionally significant.