[Early detection of asymptomatic carotid disease in patients with obliterative arteriosclerosis of the lower extremities].

INTRODUCTION

Arterial occlusive disease is a systemic phenomenon frequently coexisting in more than one arterial system. Often in one arterial bed disease is manifested with symptoms, in another is asymptomatic. There are only several reports indicating the prevalence of carotid stenosis in patients with peripheral vascular disease. Asymptomatic carotid stenosis is defined as the presence of internal carotid/carotid bifurcation stenotic or occlusive lesions in patients with no signs or symptoms of cerebrovascular disease. Lesions are important causative factors in unheralded stroke. Two factors are particularly important: severity of stenosis and morphologic characteristics of the stenotic plaque. The recent largest completed clinical trial concerning asymptomatic carotid artery stenosis (completed 1995) ACAS (Asymptomatic Carotid Artery Study) established the benefit of surgical treatment vs. best medical treatment. The reduction in relative risk of stroke was 55% in favor of surgery. Population screening for carotid stenosis is inefficient and expensive. The current interest is focused on the efficacy of screening population at risk.

AIM OF THE STUDY

The aim of the study was to establish prevalence of asymptomatic carotid artery stenosis in patients with symptomatic lower extremities atherosclerosis. Furthermore, possibility for limiting screening to subgroups of patients concerning risk factors, carotid bruit and severity of lower extremities atherosclerosis, was examined.

PATIENTS AND METHODS

Over the study period 109 patients with symptomatic lower extremities atherosclerosis underwent routine carotid duplex examinations (on Acuson 128 XP-10) to detect the presence of asymptomatic carotid disease. Indication for hospitalization was pain at rest in 60% of patients, ulcer or gangrene in 25% and claudication in 15%. Patients with a history of previous carotid endarterectomy or symptomatic cerebrovascular disease, patients who underwent emergency operations, and patients with nonatherosclerotic disease were not included in the analysis. Internal carotid stenosis was determined by duplex ultrasound blood flow velocities according to a criterion of ACAS. Plaque morphology was classified according to Gray-Weale as type I (echolucent) to type IV (echogenic). Plaque surface was graded as smooth, irregular and ulcerated. Secondary analysis was performed to find out a subgroup of patients with symptomatic lower extremities atherosclerosis at significant risk for carotid artery stenosis in order to be maximally effective. We examined the relationship of carotid artery stenosis of 60% or grater or occlusion to the 1st degree of lower extremities atherosclerosis (determined by previous vascular surgery, preoperative ankle-systolic blood pressure index, clinical severity of disease); 2. age and gender; 3. risk factors of atherosclerosis (arterial hypertension, diabetes mellitus, hyperlipidaemia, smoking history, and alcohol consumption); and 4. carotid bruit. Data were analyzed using two-way contingency tables and chi 2 test, two-sample Student's test, and multivariate, stepwise logistic regression analysis.

RESULTS AND DISCUSSION

According to the criterion of ACAS, forty patients (36.69%) had haemodynamically significant carotid artery stenosis > 60% or occlusion, and 32 patients (29%) carotid artery stenosis > 70% or occlusion. These results confirm that patients with symptomatic lower extremities atherosclerosis are at risk for increased prevalence for simultaneous asymptomatic carotid artery stenosis. Using B-mode we assessed carotid plaque characteristics in a group of 40 patients with asymptomatic 50-99% carotid artery stenosis. Distribution of plaque morphology was as follows: type I (echolucent with thin echogenic cap) in 4 patients (9.30%), type II (substantially echolucent) in 10 (23.26%), type III (dominantly echogenic) in 19 (44.18%), and type IV (homogenous echogenic) in 10 patients (23.26%). Plaque types III and IV were more common in asymptomatic patients, but there was no significant association with fibrous component of plaque. Degree of internal carotid stenosis was unrelated to plaque morphology. Plaque surface was as follows: smooth in 8 patients (18.60%), irregular in 25 (58.14%) and ulcerated in 10 patients (23.26%). Presence of ulcerated surface in 6 plaques (14%) with 50-69% of carotid artery stenosis is worth mentioning because these patients could be a subgroup likely to suffer stroke without warning. Secondary analysis examined the relationship of carotid artery stenosis of 60% or grater or occlusion to different patient's characteristics. By multivariant analysis we found that significant carotid artery stenosis was associated with prior vascular surgery, in patients over 60 years of age, arterial hypertension, ASPI < 0.5, and carotid bruit (results were considered significant if p < 0.05). Probability that various factors influenced the prevalence of carotid artery stenosis was assessed by multivariate stepwise logistic regression analysis. Only carotid bruit was associated with carotid artery stenosis > 60% (t = 0.50; p = 0.01), with sensitivity of 67% and specificity of 56%.

CONCLUSION

Prevalence of asymptomatic carotid artery stenosis in patients with lower extremities atherosclerosis is relatively high. Limiting screening of specific subgroups for any demographic or medical characteristics is ineffective. Screening for asymptomatic carotid artery stenosis is indicated in all patients with lower extremities atherosclerosis except in whom prophylactic carotid endarterectomy is not recommended because of comorbid disease or extreme age.