Natural history of carotid artery occlusion.

Carotid artery occlusion (CAO) is a risk factor for stroke ipsilateral to the occlusion and puts patients in a high-risk category when contralateral endarterectomy is performed. The purpose of this study was to evaluate the long-term outcomes of patients with internal CAO and to determine risk factors predictive of subsequent neurological event, contralateral carotid intervention, or death. Patients with internal CAO shown by duplex ultrasonography were retrospectively identified and followed between January 2002 and June 2010 (follow-up: 1-101 months, mean: 52 months) at a tertiary care hospital. All had multiple duplex examinations available for review. Chi-square analysis was used to determine risk factors for neurologic event, contralateral intervention, or all-cause morality. Multivariate Cox proportional hazard analysis was conducted using univariate risk factors with P values <0.1. Survival was estimated using the Kaplan-Meier method (P < 0.05 significant). Eighty patients with internal CAO were identified and available for analysis. On initial encounter, 30 (38%) were symptomatic, with 26 (87%) having symptoms referable to the side of the occluded internal carotid artery. During follow-up, seven (9%) had a neurologic event, of which six (86%) were referable to the occluded side; 14 (18%) patients underwent a contralateral operation. Nineteen (24%) patients died during the period of study. Although numerous variables of multivessel disease were significant with χ(2) analysis, there was no significant risk factor associated with neurologic event on multivariate analysis. However, the development of a hemodynamically significant stenosis (>50%) or occlusion of the external carotid artery (ECA) ipsilateral to the occlusion on follow-up (P < 0.027) was associated with increased risk of death. Kaplan-Meier analysis showed 7-year survival for patients with ECA disease at follow-up was significantly worse (16.2% ± 10.3% [n = 21] vs. 79% ± 8.7% [n = 59]; P < 0.00001). Frequently, patients present with neurological symptoms referable to the side of the internal CAO. Eighty-six percent of neurologic events that occur in follow-up are attributable to the side of the occluded carotid, indicating that the occluded side continues to contribute to neurologic morbidity over time. Multivariate analysis revealed no single factor to be predictive of subsequent neurologic events. With significant risk of death in patients found to have ipsilateral ECA stenosis during follow-up, it seems reasonable to continue surveillance of the occluded carotid.

B-mode ultrasonographic characterization of carotid atherosclerotic plaques in symptomatic and asymptomatic patients.

OBJECTIVE: To identify features on B-mode ultrasonography (US) prevalent in symptomatic plaques and correlate these findings with histopathologic markers of plaque instability. METHODS: Carotid endarterectomy (CEA) plaques from symptomatic and asymptomatic patients with critical stenoses (>70%) were qualitatively assessed using preoperative B-mode US for echolucency and calcific acoustic shadowing. US echolucency was quantitated ex vivo using computerized techniques for gray-scale median (GSM) analysis. Histopathologic correlates for US plaque echolucency (percentage of necrotic core area) and acoustic shadowing (percentage of calcification area) were determined. RESULTS: Fifty CEA plaques were collected from 48 patients (46 unilateral and two bilateral); 26 of these plaques were from symptomatic patients. Age, degree of stenosis, and atherosclerotic risk factors were similar for the symptomatic and asymptomatic patients. Using preoperative B-mode US, 58%, 35%, and 7% of symptomatic plaques and 18%, 41%, and 41% of asymptomatic plaques were found to be echolucent, echogenic, and calcific, respectively (P < .05). Using ex-vivo B-mode US and GSM analysis, symptomatic plaques were more echolucent (41 +/- 19) than asymptomatic plaques (60 +/- 13), P < .03. A strong inverse correlation was found between the percent plaque necrotic area core and GSM (R = -0.9, P < .001). Percentage of calcification area in plaques with acoustic shadowing was 66% and only 27% in those without acoustic shadowing (P < .05). CONCLUSIONS: Using B-mode US, symptomatic plaques are more echolucent and less calcified than asymptomatic plaques and are associated with a greater degree of histopathologic plaque necrosis. Such features are indicative of plaque instability and should be considered in the decision-making algorithm when selecting patients with high-grade asymptomatic carotid stenosis for intervention.

Frequency of critical stenosis in primary arteriovenous fistulae before hemodialysis access: should duplex ultrasound surveillance be the standard of care?

OBJECTIVE: Increasing use of primary arteriovenous fistulae (pAVFs) is a desired goal in hemodialysis patients (National Kidney Foundation /Dialysis Outcome Quality Initiative guidelines). However, in many instances, pAVFs fail to adequately mature due to ill-defined mechanisms. We therefore investigated pAVFs with color duplex ultrasound (CDU) surveillance 4 to 12 weeks postoperatively to identify hemodynamically significant abnormalities that may contribute to pAVF failure. METHODS: From March 2001 to October 2003, 54 upper extremity pAVFs were subjected to CDU assessment before access. A peak systolic velocity ratio (SVR) of >/=2:1 was used to detect >/=50% stenosis involving arterial inflow and venous outflow, whereas an SVR of >/=3:1 was used to detect >/=50% anastomotic stenosis. CDU findings were compared with preoperative vein mapping and postoperative fistulography when available. RESULTS: Of 54 pAVFs, there were 23 brachiocephalic, 14 radiocephalic, and 17 basilic vein transpositions. By CDU surveillance, 11 (20%) were occluded and 14 (26%) were negative. Twenty-nine (54%) pAVFs had 38 hemodynamically significant CDU abnormalities. These included 16 (42%) venous outflow, 13 (34%) anastomotic, and 2 (5%) inflow stenoses. In seven (18%), branch steal with reduced flow was found. In 35 of 54 (65%) pAVFs, preoperative vein mapping was available and demonstrated adequate vein size (>/=3 mm) and outflow in 86% of cases. Twenty-one fistulograms (38%) were available for verifying the CDU abnormalities. In each fistulogram, the arterial inflow, anastomosis, and venous outflow were compared with the CDU findings (63 segments). The sensitivity, specificity, and accuracy of CDU in detecting pAVF stenoses >/=50% were 93%, 94%, was 97%, respectively. CONCLUSIONS: Before initiation of hemodialysis, an unexpectedly high prevalence of critical stenoses was found in patent pAVFs using CDU surveillance. These de novo stenoses appear to develop rapidly after arterialization of the upper extremity superficial veins and can be reliably detected by CDU surveillance. Turbulent flow conditions in pAVFs may play a role in inducing progressive vein wall and valve leaflet intimal thickening, although stenoses may be due to venous abnormalities that predate AVF placement. Routine CDU surveillance of pAVFs should be considered to identify and correct flow-limiting stenoses that may compromise pAVF long-term patency and use.

Reliability of common femoral artery hemodynamics in assessing the severity of aortoiliac inflow disease.

OBJECTIVES: We investigated the utility of color duplex ultrasound (CDU)-derived common femoral artery (CFA) hemodynamics for detecting significant aortoiliac occlusive disease and predicting its severity. METHODS: From January 1997 to June 2001, 132 consecutive patients with lower extremity arterial insufficiency underwent both femoropopliteal CDU scanning and aortography with runoff studies. CDU-derived CFA waveform contour (monophasic, biphasic, or triphasic), peak systolic velocity (PSV), and acceleration time were recorded for each patient. Severity of aortoiliac occlusive disease was classified by arteriography into three distinct groups: normal or minimal disease (<50%, group 1), significant focal or diffuse stenoses (>/=50%, group 2), or total occlusion (group 3). Using probability and receiver operating characteristic curve analysis, waveform contour and PSV were compared alone and in combination with the arteriographic groups to identify waveform contours and threshold PSV, which may accurately differentiate the three categories of aortoiliac occlusive disease. RESULTS: Of 214 limbs available for study, 112 composed group 1, 70 composed group 2, and 32 composed group 3. Concomitant femoropopliteal disease was present in 47% of limbs in group 1, 53% of limbs in group 2, and 34% of limbs in group III. An abnormal CFA waveform contour (monophasic or biphasic) differentiated group 1 from groups 2 and 3, with 95% sensitivity, 89% specificity, 89% positive predictive value (PPV), 95% negative predictive value (NPV), and 92% accuracy. Mean PSV and acceleration time for monophasic and biphasic waveforms were 39 cm/sec +/- 19, 178 msec +/- 36 vs 95 cm/sec +/- 67, 97 msec +/- 31 respectively (P <.05). In differentiating between groups 2 and 3, the specificity, PPV, and accuracy for CFA PSV of