Abstract
Background: Whilst intravascular endoscopy can be used to identify lesions and assess the deployment of endovascular devices, it requires temporary blockage of the local blood flow during observation, posing a serious risk of ischaemia.Objective: To aid the design of a novel flow-blockage-free intravascular endoscope, we explored changes in the haemodynamic behaviour of the flush flow with respect to the flow injection speed and the system design.Methods: We first constructed the computational models for three candidate endoscope designs (i.e., Model A, B, and C). Using each of the three endoscopes, flow patterns in the target vessels (straight, bent, and twisted) under three different sets of boundary conditions (i.e., injection speed of the flush flow and the background blood flowrate) were then resolved through use of computational fluid dynamics and in vitro flow experiments. The design of endoscope and its optimal operating condition were evaluated in terms of the volume fraction within the vascular segment of interest, as well as the percentage of high-volume-fraction area (PHVFA) corresponding to three cross-sectional planes distal to the microcatheter tip.Results: With a mild narrowing at the endoscope neck, Model B exhibited the highest PHVFA, irrespective of location of the cross-sectional plane, compared with Models A and C which, respectively, had no narrowing and a moderate narrowing. The greatest difference in the PHVFA between the three models was observed on the cross-sectional plane 2 mm distal to the tip of the microcatheter (Model B: 33% vs. Model A: 18%). The background blood flowrate was found to have a strong impact on the resulting volume fraction of the flush flow close to the vascular wall, with the greatest difference being 44% (Model A).Conclusion: We found that the haemodynamic performance of endoscope Model B outperformed that of Models A and C, as it generated a flush flow that occupied the largest volume within the vascular segment of interest, suggesting that the endoscope design with a diameter narrowing of 30% at the endoscope neck might yield images of a better quality.
Highlights
MATERIALS AND METHODSWith the clinical need for more accurate diagnosis of intravascular lesions, intravascular endoscopy can be used to instantaneously visualise the lesions in vivo and assess the severity of disease (Ueda et al, 2004; Sun, 2013; Horie, 2021)
While the velocity magnitude and distribution remained similar between cases with endoscope Model A, B, and C, the background blood flowrate was found to have a stronger impact on the velocity magnitude and distribution of flush flow
Endoscope operating condition at BC III – the highest background blood flowrate - created the highest velocity for the flush flow
Summary
MATERIALS AND METHODSWith the clinical need for more accurate diagnosis of intravascular lesions, intravascular endoscopy can be used to instantaneously visualise the lesions in vivo and assess the severity of disease (Ueda et al, 2004; Sun, 2013; Horie, 2021). Current intravascular endoscopy available on the market still requires temporary blockage of the background blood flow with a balloon during observation or treatment, which can pose a serious risk of ischaemia especially when used in the coronary arteries (Li Q. et al, 2018). A novel design of intravascular endoscope has been proposed to avoid the potential risk of ischaemia while obtaining clear images of the target lesion. The mechanism is to generate a transparent volume by high-speed injection of a limpid fluid (e.g., destran or saline) through the microcatheter, to allow the endoscope camera to capture clear images of the target lesion (Nerandzic et al, 2021). Whilst intravascular endoscopy can be used to identify lesions and assess the deployment of endovascular devices, it requires temporary blockage of the local blood flow during observation, posing a serious risk of ischaemia
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