Abstract
Morphological characteristics of lesions have been widely studied in coronary artery disease and carotid artery disease, but the enigma still remains in evaluating precisely which morphological characteristics and findings will predict better outcome of endovascular treatment in patients with advanced arterial occlusive disease. In coronary arteries, echolucent zones identified using intravascular ultrasound were found to increase the risk of clinical instability. 1 Paraskevaidis et al. 2 studied the potential correlation between angiographic lesion morphology and the early and 1-year clinical outcomes in patients with unstable angina. They classified the morphology of the culprit lesion as simple or complex according to Ambrose's modified criteria.3,4 Simple lesions included concentric and eccentric lesions of type IA and type IB. Complex lesions included eccentric lesions of type IIA and IIB, multiple irregularities, tandem lesions, presence of thrombus, total occlusions, and TIMI flow grade <3 occlusions. 5 They concluded that angiographic classification of the culprit lesion as simple or complex was not correlated with the clinical outcome of patients with unstable angina, while the presence of thrombus, angulation of the lesion between 45° and 90°, and irregular contour of the culprit lesion were correlated.
It is generally agreed that ultrasonic assessment of plaque morphology in carotid artery disease, in addition to the degree of stenosis, is a predictor of the prognosis, identifying plaques at a higher risk of becoming clinically symptomatic. Subjects with echolucent atherosclerotic plaques have increased risk of ischemic cerebrovascular events independent of both degree of stenosis and cardiovascular risk factors.6,7 Heterogeneous plaques are associated with a higher incidence of cerebrovascular symptoms than homogeneous plaques for all grades of stenosis. 8
The link between echo plaque structure and prognosis does not appear to be limited to the carotid arteries but may apply to virtually all vascular districts where atherosclerotic plaques can be imaged by ultrasound technology. O'Farrell et al. 9 analyzed the prognostic value of carotid ultrasound lesion morphology in retinal ischemia; they found that the percentage stenosis caused by the carotid lesions, although more severe in the vascular event group, was not significantly different between the groups. Patients who suffered a vascular event in follow-up had significantly more complex heterogeneous lesions (vs. simple heterogeneous / homogeneous lesions) than patients who remained alive and well. They suggested that the criteria for selection for treatment should be based on lesion morphology as well as the degree of stenosis.
In this issue of the JEVT, Baumann et al. 10 describe the typical infrapopliteal lesion morphology (length, diameter, calcification) in a consecutive unselected series of 105 patients with critical limb ischemia (CLI) undergoing endovascular infrapopliteal revascularization. They were of the opinion that CLI patients treated in the randomized trials of drug-eluting stents (DES)11–13 had significantly shorter lesions than patients treated in a real-world clinical setting, so the reported results in favor of DES vs. bare metal stents or balloon angioplasty might not hold true in longer lesions. They did indeed find that infrapopliteal lesions in this challenging subset of patients were frequently of substantial length (mean treated lesion lengths of 87.1±43.8 mm in stenotic and 124.0±78.3 mm in occlusive disease) and burdened by significant calcification, unlike the cohorts in the randomized trials.11–13 Diabetes was not a predictor for increased lesion length, a difference in reference vessel diameters proximal and distal to the lesion, or greater calcification load. The authors suggested that these real-world data should be taken into consideration in the development of anti-restenosis concepts. However, they seem to have ignored other risk factors in their analysis, such as hyperlipidemia (66.7%), arterial hypertension (86.7%), and coronary artery disease (58.1%). It is now known that hypertension, diabetes, and smoking are strong risk factors for the development of severe CLI. 14
We suggest that only studies with larger sample sizes, including multiple cofactors in their final analysis, have a strong potential to reach a robust conclusions on the morphological characteristics of the infrapopliteal occlusive disease pattern in CLI patients and on their endovascular treatment options. However, we agree with the authors that these lesions seem to be longer in normal clinical practice, as we have observed in our own group of patients.