Our study showed that WBV at both shear rates was significantly higher in those undergoing amputation in patients with LEPAD who did not have the option of revascularization. Our study also showed that WBV is a strong independent risk factor for amputation in the same patient group.
Although the primary treatment recommended for CLTI patients is revascularization, different treatment protocols have been proposed for patients who cannot be revascularized due to various reasons. One of them is the hemodilution method. It is thought that the main effect of the hemodilution therapy is the positive effect on the plasma viscosity and the increased flow in the micro-vessels12,17,18. As a matter of fact, it has been shown in the literature that WBV is improved with hemodilution therapy. Kim et al.10 showed that despite the decrease in hemoglobin levels with hemodilution therapy in patients with CLTI, the tissue oxygen delivery index increased due to improved WBV, which was reflected in positive clinical results. Considering all of the above, it is seen that WBV is the treatment target that has an essential place in physiopathogenesis in patients with LEPAD. Especially in patients with multiple, long collateralized vascular obstructions, such as CLTI patients, WBV is an important factor determining endothelial shear stress, thus increasing its clinical importance in this patient group19.
In addition to the above, the atherosclerosis process is significantly influenced by hemorheological factors has been shown in the literature that increased blood viscosity plays a vital role in the atherosclerotic process by causing intravascular stasis and endothelial dysfunction20. A high degree of blood viscosity causes turbulent blood flow that exacerbates endothelial disruption and impairs endothelial integrity and function 21-23. Apart from the atherosclerotic process, endothelial shear stress also affects atherosclerotic plaque rupture and thrombosis formation 24,25. As the main determinant of endothelial shear stress, WBV has an important role in this physiopathological pathway. As a matter of fact, Erdogan et al. showed that WBV was significantly higher in patients presenting with acute arterial occlusion compared to the control group 26.
Viscometers such as falling-ball, capillary, and rotational viscometers are used for viscosity measurements27. However, access to these methods is limited in daily clinical practice. The formula we used in our study, defined by Simone, provides important data on WBV through total protein level and complete blood count, which we commonly use in routine practice. With the formula described by Simone, estimated WBV values can be obtained at different shear rates15. Compared to the viscometer-measured analysis, the estimated WBV values calculated with the formula described by Simone demonstrated a smaller degree of error15.
Limitations of this study, first, the study is a single-center and retrospective study which may cause selection bias. Secondly, platelet and erythrocyte aggregability and rigidity, which may influence blood viscosity, were not assessed. And lastly, blood viscosity was not directly measured in the study. Even though other studies have proven the validity of the extrapolation method, we employed in this study, investigating the correlation between estimated WBV and blood viscosity measured directly with a viscometer could increase the effectiveness of our study.
In our study, we showed that WBV calculated using simple laboratory tests predicts amputation in LEPAD patients who do not have the option of revascularization. Considering that the population in our study has no option for revascularization, the value of WBV as a predictor of amputation in these patients is vital for identifying high-risk patients and managing their treatment.