Presence of external carotid artery plaque independently predicts mortality in patients without internal carotid artery atherosclerosis

Background: The presence of plaque in the external carotid artery (ECA) detected on carotid duplex ultrasound (CDU) is of unknown clinical significance and may not be reported in routine clinical practice. We hypothesize that ECA plaque in the absence of plaque in the other cervical vessels is a risk factor for increased all-cause mortality. Objectives: To determine the significance of ECA plaque on all-cause mortality in the absence of internal carotid artery (ICA) or common carotid artery (CCA) plaque. Methods: We queried the Non-Invasive Vascular Laboratory database for all CDUs performed between 1 January 2005 and 31 December 2005. All images were reviewed for the presence of plaque. Studies were included if plaque was absent in both the CCA and the ICA. Chart review was performed to obtain demographic and clinical information. All-cause mortality was determined using the Social Security Death Index. Results: A total of 500 patient studies met the inclusion criteria; 64 patients (12.8%) had plaque in one or both ECAs. There was no significant difference in age (mean 58.1 ± 14.8 years), race (82.5% white), or sex (64.4% male) between those with and without ECA plaque. There was a significant difference in all-cause mortality between patients with and without isolated ECA plaque after adjustment for age, sex, low-density lipoprotein cholesterol, smoking, hypertension, body mass index, and surgery within 30 days of CDU (adjusted hazard ratio 2.60, 95% CI 1.46–4.66, p<0.001). Conclusions: The presence of plaque isolated to the ECA is an independent predictor of all-cause mortality and may impart important prognostic information for patients referred for CDU.