Demographics and use of completion imaging
Overall, we studied 6115 CEAs, performed in 5638 patients by 73 surgeons. Completion assessment of patency was performed in 5554 CEAs (91%); however, in 3520 (58%) this consisted only of Doppler insonation, and not completion imaging, defined as duplex scanning or arteriography. Completion imaging was used in 2033 CEAs (33%) comprising DUS imaging in 1919 (94%), arteriography in 94 (5%), and both arteriography and DUS imaging in 20 (1%). Patient, surgeon, and hospital characteristics were compared between CEAs in which completion imaging was and was not performed (; ).
Table I. A
Patient, surgeon, and hospital characteristics associated with performing completion imaging (CI) after carotid endarterectomy (CEA)a
Appendix Table I (online only)
Patient, surgeon, and hospital characteristics associated with performing completion imaging (CI) after carotid endarterectomy (CEA)
Several patient-level and operative factors were associated with the use of completion imaging (; ). This model had reasonable discriminative ability (area under the receiver operating curve = 0.72). Unfortunately, intraoperative factors that may further delineate the decision to use completion imaging are not contained in our data set and therefore were not available for analysis.
Table I. B
Multivariate analysis of factors associated with performing completion imaging after carotid endarterectomy (CEA)a
Surgeon practice patterns
Of the 73 surgeons in our study, 37 (51%) rarely, 16 (22%) selectively, and 20 (27%) routinely used completion imaging (). Although 54% of CEAs were performed by the 37 surgeons who rarely used completion imaging, 29% of CEAs were performed by the 20 surgeons who routinely used completion imaging. The 16 surgeons who selectively used completion imaging performed 17% of CEAs in our study.
Surgeon volume during the study period was nearly identical in the groups of surgeons classified as rare (mean, 90 cases per surgeon; range, 5-585) and routine (mean, 88; range 5-378) and was lower in the selective group (mean, 40; range, 5-174). However, within each category of surgeon practice pattern, there was wide variation in individual surgeon case volume. Because our main outcome measures occurred relatively infrequently, this limited our ability to analyze the effect of volume on 30-day stroke/death at the individual surgeon level.
Association between surgeon practice pattern and outcomes
Crude 30-day stroke/death rates were significantly lower among surgeons who selectively used completion imaging and were higher in surgeons who routinely used completion imaging (1.7% rarely, 1.2% selectively, 2.4% routinely, P
= .05; ). When we risk-adjusted 30-day stroke/death rates for patient characteristics known to independently predict stroke/death, including age (≥70 years), contralateral internal carotid artery occlusion, use of antiplatelet agent, presence of congestive heart failure, emergency procedure, preoperative ipsilateral cortical symptoms,27
we found that the differences across surgeon practice patterns were not statistically significant, but still demonstrated the same direction and magnitude of effect for selective-use surgeons (odds ratio [OR], 0.75; 95% confidence interval [CI], 0.40-1.41; P
= .366) and for routine-use surgeons (OR, 1.42; 95% CI, .93-2.17; P
= .106; ).
Thirty-day stroke or death rate among surgeons who rarely, selectively, or routinely use completion imaging in carotid endarterectomy
Multivariate analysis of factors associated with 30-day stroke/death after carotid endarterectomy
In our second main outcome measure, restenosis >70% at 1 year, crude differences across surgeon practice patterns were not statistically significant (2.8% rarely, 1.1% selective, 1.1% routine, P = .09). However, Kaplan-Meier survival curves demonstrated a trend toward a slightly lower risk of restenosis among surgeons who performed selective or routine completion imaging (). Of all patients diagnosed with restenosis >70% at 1 year, only four underwent reintervention (repeat CEA or carotid stent) due to symptoms.
Kaplan-Meier plot shows proportion of patients free from ipsilateral carotid artery restenosis (>70%) 1 year after carotid endarterectomy across surgeon practice pattern.
When we risk-adjusted 1-year restenosis rates for patient characteristics known to independently predict restenosis, including type of closure (primary vs patched), contralateral carotid artery stenosis, and dialysis,28
selective use of completion imaging was associated with a significantly lower risk of stenosis at 1 year, with a hazard ratio (HR) for restenosis in selective-use compared to rare-use of 0.52 (95% CI, 0.29-.092, P
= .024; ). However, routine use of completion imaging had little effect on the risk of restenosis, with an HR for restenosis in routine-use compared to rare-use of 0.92 (95% CI, 0.61-1.38, P
= .676). As in our prior work, we confirmed that there are significant associations between primary closure, contralateral carotid artery stenosis, and restenosis.28
Multivariate Cox proportional hazards model used to predict restenosis rates at long-term follow-up after carotid endarterectomy
Re-exploration prompted by completion imaging and operative report audit
Overall, intraoperative carotid artery re-exploration occurred in 178 CEAs, comprising 2.9% of all CEAs and 8.8% of CEAs with completion imaging. The rate of re-exploration was significantly higher among routine-use surgeons compared with selective or rare-use surgeons (7.6% routine, 0.8% selective, 0.9% rare, P < .001 between routine/selective, P = .001 between routine/rare). Of the 31 patients who underwent re-exploration without completion imaging, 25 had Doppler insonation of the endarterectomy before re-exploration.
Of these 178 CEAs, we audited 90 available operative reports from cases where re-exploration was prompted by findings on completion imaging. The most common finding on completion imaging was flap/debris/plaque (77 of 90, 86%; ). Examples of these abnormalities are shown in .
Indications for arterial re-exploration (n = 90), as identified by completion imaging (left). Intraoperative findings on re-exploration (right).
Fig 4 Abnormalities discovered by intraoperative completion imaging after carotid endarterectomy. Panels 1 and 1a show longitudinal and cross-sectional B-mode images from a patient undergoing completion duplex ultrasound imaging which shows free-floating debris (more ...)
Operative findings at re-exploration
The most common finding upon re-exploration was also flap/debris/plaque (67 of 88, 76%). In 10 of 88 patients (11%), however, the abnormal completion imaging study represented a false positive, in that no identifiable technical defects were detected on re-exploration. Two of these 10 patients underwent intervention (additional tacking sutures) even though no discrete abnormality was found ().
Overall, 88 arteries were surgically re-explored, and 2 additional patients underwent arteriography and stent placement without surgical re-exploration. In 79 of 90 re-explorations (88%) the intervention involved removing or tacking excess debris/plaque. In 8 cases (9%), no intervention was performed.
Thirty-day stroke or death in patients undergoing re-exploration
Among the 178 patients who underwent re-exploration, 6 strokes (3 minor, 3 major) and 1 death occurred ≤30 days. These events were evenly distributed across the categories of completion imaging findings. Crude 30-day stroke/death rates were 3.9% in the 178 cases with arterial re-exploration compared with 1.7% in those patients who were not re-explored (P = .028). However, these differences were attenuated when we risk-adjusted for patient characteristics predictive of 30-day stroke or death (adjusted OR, 2.1; 95% CI, 0.9-5.0; P = .076).
Effect of completion imaging on 30-day stroke or death (patient level analysis)
To investigate our presumption that completion imaging is used most commonly in CEAs where stroke risk is higher, we compared the rates of 30-day stroke/death between patients who underwent completion imaging with those who did not. Crude 30-day stroke/death rates were higher in patients where completion imaging is performed (2.6% vs 1.3%; P < .001). Further, after adjusting for patient characteristics associated with 30-day stroke/death, the odds of stroke/death remained significantly higher in patients undergoing completion imaging (OR, 1.9; 95% CI, 1.2-2.7; P = .002), suggesting that differences in outcome were not due to differences in patient characteristics.