Current Science

Kalimuthu Govindaraju ¹, Girish N. Viswanathan ², Irfan Anjum Badruddin ³, Sarfaraz Kamangar ³, N. J. Salman Ahmed ⁴, Abdullah A. A. A. Al-Rashed ⁵

Affiliations
1 Centre for Engineering Programs, HELP College of Arts and Technology, Kuala Lumpur, MY
2 Newcastle University, Newcastle upon Tyne, GB
3 Department of Mechanical Engineering, University of Malaya, MY
4 Centre for Energy Sciences, Department of Mechanical Engineering, University of Malaya, Kuala Lumpur, MY
5 Department of Automotive and Marine Engineering Technology, College of Technological Studies, The Public Authority for Applied Education and Training, KW

Abstract

The effect of coronary arterial wall curvature on noninvasive assessment of stenosis severity was studied by examining the fractional flow reserve (FFR), pressure drop coefficient (CDP) and lesion flow coefficient (LFC) under different angles of curvature of the arterial wall models. Computational simulation of hyperemic blood flow in curved arteries with different angles of curvature (0°, 30°, 60°, 90° and 120°) was developed in three severe categories of stenosis of 70% (moderate), 80% (intermediate), and 90% (severe) area stenoses (AS) to evaluate the effect of curvature on FFR, CDP and LFC. The numerical study showed that for a given percentage of AS, the curvature of the arterial wall augmented the flow resistance in addition to the resistance caused by the stenosis. Also, there are significant differences in FFR, CDP and LFC between a straight and a curved section. With an increase in artery wall curvature from 0° to 120°, FFR significantly decreases by 5%, 8% and 20% in 70%, 80% and 90% AS respectively. For a fixed stenosis severity, CDP significantly increases, whereas LFC decreases as the angle of curvature changes from straight to curved section. We conclude that the significant differences in FFR, CDP and LFC confirms that the functional significance of stenosis assessed non-invasively could lead to misjudgment of its severity. This will notably influence the intermediate stenosis severity. So the arterial wall curvature should be considered when assessing the significance of stenosis as an alternative to FFR.

Keywords

Blood Flow, Computational Fluid Dynamics, Non-Invasive Assessment, Stenosis Severity, Straight and Curved Arteries.

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Kalimuthu Govindaraju ¹, Irfan Anjum Badruddin ², Girish N. Viswanathan ³, Sarfaraz Kamangar ², N. J. Salman Ahmed ⁴, Abdullah A. A. A. Al-Rashed ⁵

Affiliations
1 Centre for Engineering Programs, HELP College of Arts and Technology, Kuala Lumpur, MY
2 Department of Mechanical Engineering, University of Malaya, MY
3 Derriford Hospital, Plymouth, GB
4 Centre for Energy Sciences, Department of Mechanical Engineering, University of Malaya, Kuala Lumpur, MY
5 Department of Automotive and Marine Engineering Technology, College of Technological Studies, The Public Authority for Applied Education and Training, KW

Abstract

Theoretical impact of left coronary bifurcation angulation (BA) variations and percentage of flow distribution variations (FDV) in coronary artery branches (CAB) on anatomic assessment of bifurcated lesions, is investigated by considering fractional flow reserve (FFR) as a standard diagnostic parameter. According to Medina classification, computational models of coronary bifurcation lesions types of (1, 0, 0), (0, 1, 0) and (0, 0, 1) were developed. The models included BA of 30°, 45°, 60° 75°, 90° and 120°. Computational fluid dynamics analysis was performed under hyperaemic flow condition and FFR was evaluated with percentage of FDV in CAB. For any fixed percentage of flow in the CAB and change in BA, FFR was significantly affected in the lesion type (1, 0, 0) whereas no significance was found in the lesion types (0, 1, 0) and (0, 0, 1). Percentage of FDV in CAB for any fixed BA significantly altered FFR in all the lesion types. Overall, 5%, 41% and 73% variations in FFR were found in (1, 0, 0), (0, 1, 0) and (0, 0, 1) respectively. The variation of BA could not be neglected in in vitro anatomical assessment for lesion type (1, 0, 0) but not in case of (0, 1, 0) and (0, 0, 1). Nevertheless, percentage of FDV in CAB is significantly altered FFR in the left coronary bifurcation lesions, which lead to underestimation of stenosis severity and postponement of coronary interventional procedure.

Keywords

Bifurcation Angulation, Computational Fluid Dynamics, Coronary Branch Flow, FFR, Left Coronary Artery.

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