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Published online: 2019-03-14
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Coronary artery height differences and their effect on fractional flow reserve

Firas Al-Janabi, Grigoris Karamasis, Chritopher M. Cook, Alamgir M. Kabir, Rohan O. Jagathesan, Nicholas M. Robinson, Jeremy W. Sayer, Rajesh K. Aggarwal, Gerald J. Clesham, Paul R. Kelly, Reto A. Gamma, Kare H. Tang, Thomas R. Keeble, John R. Davies
DOI: 10.5603/CJ.a2019.0031
·
Pubmed: 30912578

open access

Ahead of print
Original articles
Published online: 2019-03-14

Abstract

Background: Fractional flow reserve (FFR) uses pressure-based measurements to assess the severity of a coronary stenosis. Distal pressure (Pd) is often at a different vertical height to that of the proximal pressure (Pa). The difference in pressure between Pd and Pa due to hydrostatic pressure, may impact FFR calculation.

Methods: One hundred computed tomography coronary angiographies were used to measure height differences between the coronary ostia and points in the coronary tree. Mean heights were used to calculate the hydrostatic pressure effect in each artery, using a correction factor of 0.8 mmHg/cm. This was tested in a simulation of intermediate coronary stenosis to give the “corrected FFR” (cFFR) and percentage of values, which crossed a threshold of 0.8.

Results: The mean height from coronary ostium to distal left anterior descending (LAD) was +5.26 cm, distal circumflex (Cx) –3.35 cm, distal right coronary artery-posterior left ventricular artery (RCA-PLV) –5.74 cm and distal RCA-posterior descending artery (PDA) +1.83 cm. For LAD, correction resulted in a mean change in FFR of +0.042, –0.027 in the Cx, –0.046 in the PLV and +0.015 in the PDA. Using 200 random FFR values between 0.75 and 0.85, the resulting cFFR crossed the clinical treatment threshold of 0.8 in 43% of LAD, 27% of Cx, 47% of PLV and 15% of PDA cases.

Conclusions: There are significant vertical height differences between the distal artery (Pd) and its point of normalization (Pa). This is likely to have a modest effect on FFR calculation and the results in values crossing the treatment threshold. Operators should be mindful of this phenomenon when interpreting FFR values.

Abstract

Background: Fractional flow reserve (FFR) uses pressure-based measurements to assess the severity of a coronary stenosis. Distal pressure (Pd) is often at a different vertical height to that of the proximal pressure (Pa). The difference in pressure between Pd and Pa due to hydrostatic pressure, may impact FFR calculation.

Methods: One hundred computed tomography coronary angiographies were used to measure height differences between the coronary ostia and points in the coronary tree. Mean heights were used to calculate the hydrostatic pressure effect in each artery, using a correction factor of 0.8 mmHg/cm. This was tested in a simulation of intermediate coronary stenosis to give the “corrected FFR” (cFFR) and percentage of values, which crossed a threshold of 0.8.

Results: The mean height from coronary ostium to distal left anterior descending (LAD) was +5.26 cm, distal circumflex (Cx) –3.35 cm, distal right coronary artery-posterior left ventricular artery (RCA-PLV) –5.74 cm and distal RCA-posterior descending artery (PDA) +1.83 cm. For LAD, correction resulted in a mean change in FFR of +0.042, –0.027 in the Cx, –0.046 in the PLV and +0.015 in the PDA. Using 200 random FFR values between 0.75 and 0.85, the resulting cFFR crossed the clinical treatment threshold of 0.8 in 43% of LAD, 27% of Cx, 47% of PLV and 15% of PDA cases.

Conclusions: There are significant vertical height differences between the distal artery (Pd) and its point of normalization (Pa). This is likely to have a modest effect on FFR calculation and the results in values crossing the treatment threshold. Operators should be mindful of this phenomenon when interpreting FFR values.

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Keywords

hydrostatic pressure, computed tomography coronary angiography, coronary stenosis

About this article
Title

Coronary artery height differences and their effect on fractional flow reserve

Journal

Cardiology Journal

Issue

Ahead of print

Article type

Original Article

Published online

2019-03-14

DOI

10.5603/CJ.a2019.0031

Pubmed

30912578

Keywords

hydrostatic pressure
computed tomography coronary angiography
coronary stenosis

Authors

Firas Al-Janabi
Grigoris Karamasis
Chritopher M. Cook
Alamgir M. Kabir
Rohan O. Jagathesan
Nicholas M. Robinson
Jeremy W. Sayer
Rajesh K. Aggarwal
Gerald J. Clesham
Paul R. Kelly
Reto A. Gamma
Kare H. Tang
Thomas R. Keeble
John R. Davies

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