ARTERIES OF LOW EXTRAMITAS
It is estimated that in 2016 around 120 million people were afflicted with lower extremity PAD and as much as 48% of them could have CAD or other CVD 51. Moreover, PAD can lead to acute limb ischemia, amputation, or even death. It is often caused by atherosclerotic plaque in the lower extremity artery (LEA) and classically it manifests as cramping and pain, which is alleviated by rest. These symptoms may present in different areas depending on the afflicted artery or be completely absent. Among risk factors of PAD, we can find many cardiovascular risks factors like age, tobacco usage, hypertension, and diabetes mellitus 52. The interest of researchers in LEA was usually directed toward femoral bifurcation and common femoral and superficial femoral arteries. The range of examinations differed from paper to paper, but most of the time was between 1-2 cm proximally and distally from bifurcation. Sometimes, other arteries like popliteal and tibial were described.
Khoury et al. showed that patients with CAD with extra coronary arteries assessed by the US had a significantly higher incidence of atherosclerotic plaques in the femoral arteries than those with normal coronary arteries (77% vs. 42%) 9. Moreover, the risk of CAD was significantly associated with femoral plaques (OR 5.6, p=0.02). Cho et. al observed a high prevalence of asymptomatic CAD in patients with lower extremity PAD 53. The prevalence of CAD in patients with PAD was 62%, and only 13% of them had angina and 72% had multi-vessel disease. Diabetes significantly increased the risk of CAD in patients with PAD and the odds risk (OR) of having multi-vessel CAD was 2.5 (1.1-5.9, p=0.037). In another study, Kumar et al. rated the sensitivity of PAD in predicting coronary artery stenosis as 80%, the specificity as 82%, and the accuracy as 81%54. The Peripheral Arterial Disease in Interventional Patients Study (PIPS), a prospective cohort study revealed, that among patients who had confirmed CAD by CA (n=5745), those with PAD had a higher prevalence of left main and multivessel CAD (87.2% vs. 75.5%, p=0.006), and previous coronary artery bypass surgery (CABG) (35.8% vs. 23.1%, p=0.008) 55. In post mortem study authors found among patients who died for stroke significant correlations between the deep femoral artery and left anterior descendent coronary arteries (r=0.513; p=0.012) 39.
During a 10-year follow-up observation after performing an ultrasound examination of carotid and femoral bifurcations, there was no CVE in the group with a completely normal ultrasonographical image of those arteries 56. With increased severity of lesions risk of both progression to more advanced group and CVE grew. Worth noting is that 68% of registered CVEs in the study group were myocardial infarctions (MI). In another observational study, femoral plaques were presented as an individual risk factor of CVE 57. Unfortunately, some research came to different conclusions as only irregular surface and ulcerations of plaques in common femoral arteries were found to be the sole predictors of major adverse CVE58. Classical cardiovascular risk (CVR) factors corresponded with the presence of subclinical atherosclerosis in femoral arteries. Femoral plaques alone are strongly associated with CCT- assessed CACS, however, adding CVR factors and carotid plaques to the model diagnostic OR was further increased 59. Traditional risk factors including previous CVE were also associated with the Ultrasonographic Lower Limbs Atherosclerosis (ULLA) score calculated during an ultrasonographical examination of LEA from femoropopliteal to para malleolar region 60. This way of examining patients is better in detecting PAD than the ankle-brachial index (ABI) 61. US assessment of femoral total plaque area (TPA), maximal plaque height (MPH), and IMT associated with severity of CAD detected by CA 62-64. Examination of femoral TPA had the biggest sensitivity of detecting CAD and was a better method than calculating ABI 62. However, we must bear in mind that reproducibility of IMT results is worse in older, and patients afflicted with CVDs. Moreover, it also decreases, when IMT increases 65. Another study noticed that the best way of assessing the risk may be sex- dependent. In women, the most important risk factor was femoral TPA, but in men, it was femoral MPH. However, in both women and men, the most representative lesions were localized in the proximal femoral artery 66. The elevated CVD risk is only partially attributable to shared CVD risk factors, such that at any given level of CVD risk factors, PAD is independently related to future CVD events and mortality67. PAD has also been shown to be predictive of future CVD events even when adjusted for other markers of subclinical atherosclerosis 68.