Distinctive atherosclerotic features in coronary and peripheral arteries
Coronary and peripheral arteries share many anatomical features. Both vessels are muscular arteries characterized by a media layer enriched in smooth muscle cells, whereas elastin is limited to the internal and external elastic laminae 3.
The current treatments for atherosclerotic artery disease including percutaneous interventional techniques such as balloon angioplasty, stenting, and atherectomy are similarly applied in the two districts, but the long-term results are more successful when used for treating coronary artery disease compared with peripheral artery disease 4,5.
Thus, a different plaque composition has been taken into account to explain this discrepancy. In fact, previous ex-vivo studies have highlighted that peripheral artery disease is characterized by fibrotic lesions with less inflammation 6. In addition, peripheral arteries are commonly affected by medial calcification, which is a nonatherosclerotic deposition of calcium in the media layer that can cause significant stiffening of the arterial wall and a reduction in its ability to respond to vasodilator stimuli 7.
This phenomenon is rarely encountered in coronary arteries, where the most common type of calcium deposition is represented by intimal atherosclerotic calcification 3.
Indeed, although many studies have been carried out to assess coronary artery disease features, only a limited number of works have investigated the plaque composition of peripheral arteries and few reports have compared coronary and peripheral arteries in terms of plaque composition.
In this issue, Yin et al.8 add an important piece of information on the differences between coronary and peripheral arteries in terms of plaque composition. They carried out an in-vivo study using preintervention intravascular ultrasound (IVUS) to assess both quantitative and qualitative features of coronary arteries and under-the-knee peripheral arteries (tibial or peroneal artery). These two vascular districts are composed by vessels of a similar diameter.
In the present paper, the authors compared 42 peripheral lesions from the Complete Lesion Assessment with FFR and IVUS TechnologY trial and 79 coronary lesions from the Assessment of Dual AntiPlatelet Therapy With Drug Eluting Stents. Patients were matched 1 : 2 for age, sex, diabetes mellitus, hypertension, hyperlipidemia, and renal insufficiency.
The authors found that compared with coronary artery disease, atherosclerotic lesions in tibial and peroneal arteries were longer, had more concentric, diffuse, and calcified plaques and had smaller vessel volumes.
The extension of both superficial and deep calcium was greater in peripheral lesions than in coronary plaques.
The authors concluded that the higher prevalence of concentric plaque together with the increased amount of calcium in peripheral arteries may explain why peripheral interventional procedures are associated with an increased risk of failure compared with coronary procedures.
A limitation of the present study is that the authors did not further distinguish plaque composition between coronary and peripheral arteries.
This is probably because of the fact that the intravascular technique, used to assess both coronary and peripheral arteries, was IVUS, which has a high accuracy in the detection of calcified lesions, but it has a limited capability of distinguishing between fibrous plaque and lipid-rich tissue 9.
In addition, large calcifications produce an acoustic shadowing that may prevent an accurate analysis of adjacent regions and visualization of tissue behind regions of calcification 9.