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Scientists Discover the Source of Arterial Embolism in the Popliteal Arteries

By uncovering ulcerated plaque in the femoropopliteal artery as the source of embolism in the popliteal arteries, the study is expected to advance future treatments for peripheral arterial disease.

New research by a group of scientists at the Department of Cardiovascular Medicine, Osaka City University Graduate School of Medicine, has demonstrated for the first time that the thrombus generated by ulcerated plaque (UP) found in the femoropopliteal artery (FPA) is the source of embolisation of the popliteal artery. These findings are expected to lay the foundation for the development of better therapeutic strategies for peripheral arterial disease (PAD).

PAD is a common circulatory disorder in which narrowed arteries reduce blood flow to one’s extremities. While many people suffering from PAD hardly display symptoms, some experience leg pain or cramping when walking – a condition known as claudication – because their legs do not receive sufficient blood flow to keep up with the demand. As it is primarily caused by the build-up of fatty plaque in the arteries, also known as atherosclerosis, PAD is often successfully treated by making lifestyle changes such as exercising and following a healthy diet.

However, there are other factors that could determine the likely course of PAD, one of which is the extent of infrapopliteal lesion. According to recent pathological studies, embolisation by an upstream thrombus, or a blood clot that occurs in and occlude the blood vessel, is one of the primary mechanisms for the formation of infrapopliteal lesions. Unfortunately, the precise location where a thrombus forms in the body of PAD patients has remained unknown.

“Previous reports used coronary artery findings to determine thrombus formation in the FPAs,” explained Tomohiro Yamaguchi MD, lead author of the study, “However, this creates complications due to critically different anatomical features among vessels between coronary arteries and FPA.”

In their recent study involving 31 patients who underwent endovascular therapy and angioscopy, the Osaka City University researchers has identified 23 patients with irregular plaque build-up in the FPA. These plaque build-ups were then categorised as UP. Through assessments using angioscopy, the scientists later discovered that 22 of these patients had mural thrombi in the FPA and on the UP. This ratio is substantially higher than in patients where no UP was observed. Furthermore, linear regression analyses showed that UP was strongly correlated with the angiographic runoff score (ARS), an index that reflects the degree by which the popliteal artery becomes narrowed or blocked. The popliteal artery provides numerous branches of blood supply to the structures of the knee and the lower extremity.

In addition, although the maximum yellow plaque colour grade taken from coronary artery findings did not show any significant association with infrapopliteal ARS, the detection of UP was highly linked to a poor ARS. This suggests that the formation of a thrombus in the FPA occurs via a mechanism different to thrombus development in the coronary artery.

“Although recent advances in catheterisation for PAD have been remarkable, treatment results are still inadequate,” said Dr. Takanori Yamazaki, who collaborated in the study. “We believe that a detailed assessment of the nature of plaque in femoropopliteal arteries, as found in this study, will help to explain the mechanism of the disease and develop optimal treatment methods.” [APBN]

Source: Yamaguchi et al. (2022). Angioscopic Ulcerated Plaques in the Femoropopliteal Artery Associated with Impaired Infrapopliteal Runoff. Journal of Vascular and Interventional Radiology, 33(2), 97-103.el.