Applications of intraoperative Duplex ultrasound in vascular surgery: a systematic review

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations, an electronic database search was conducted using MEDLINE to include articles from January 1950 through to February 2020 written in English. Reference lists were examined from the retrieved full-text articles. ClinicalTrials.gov was searched for in-progress trials.

In our search strategy, we used the following key terms: “ultrasonography”, “Doppler”, “duplex”, “completion imaging”, “vascular surgical procedures”, “bypass grafting”, “lower limb arterial bypass”, “carotid artery endarterectomy” and “intra-operative”. Titles and abstracts were reviewed for relevance by two investigators (PN and BK) independently. Conference abstracts and protocol papers were not included. Full-text articles were then reviewed, and data collected on technique used, participants, interventions performed, outcomes and findings. Disagreements were resolved by consensus discussion with the senior author (UJ).

We sought studies that evaluated the use of IODUS during LEB or CEA. Restrictions were not placed on study type. However, studies only considering the natural progression of lesions (i.e., results not used to inform management decisions peri-operatively) were excluded.

For the use of IODUS for CEA, outcomes of interest included (1) stroke/mortality at 30 days and (2) flow abnormalities on follow-up imaging. For LEB, the outcome of interest was primary graft patency at 30 days. For both CEA and LEB, we also consider the natural history of cases with normal and abnormal completion imaging.

There were no randomised controlled trials comparing IODUS with no completion imaging or other completion imaging techniques. Sixteen studies investigated the role of IODUS in CEA: 3 were based on prospectively maintained registries; 9 were prospective single-centre studies; and 4 retrospective studies. Six studies investigated the role of IODUS for LEB: 4 were prospective (in one study data was Registry analysis); 2 were retrospective studies. There was considerable heterogeneity in terms of intervention, outcome measures and follow-up.

For completion assessment of CEA, there is conflicting evidence regarding the benefits of completion imaging from analysis of registry data [13‐15]. However, the largest of these studies (over 140,000 cases) reports a modest reduction in adjusted risk of stroke/mortality when using IODUS selectively (RR 0.74, CI 0.63–0.88, p = 0.001) [13]. The results also suggest that outcomes when using IODUS are at least as good as intraoperative angiography. An opposing result reported by Wallaert and colleagues, suggests a higher stroke rate when using completion imaging (risk adjusted OR 1.9, CI 1.2–2.7, p = 0.002). However, when comparing different practice patterns, they found that the lowest rates were seen in cases, where completion imaging was used selectively (routine 2.4%, selective 1.2%, rare 1.7%; p = 0.048). This suggests that selective practice may be the most effective strategy, although the criteria for selecting cases was not explored in any of the studies. Wallaert and colleagues also noted that the rate of restenosis at 1-year follow-up was highest for cases, where completion imaging was rarely used (routine 1.1%, selective 1.1%, rare 2.8%; p = 0.09) [14]. This may be due to the failure to detect residual defects which may progress during the follow-up period. Data from other studies suggests that ‘non-significant’ residual defects detected on IODUS are associated with higher rates of restenosis during the follow-up (range 2.1% to 20%) [7, 8, 17‐19]. These finding would suggests that although revision surgery can improve outcome, it is certainly not without risk and not all abnormalities detected on IODUS necessitate surgical revision. Isolated high velocities in the absence of other concerning waveform features, such as waveform broadening, or B-mode abnormalities may be related to vessel spasm [6]. If acted upon, these may add risk of complication. Parsa et al., have proposed protocolised imaging and interpretation guidance for both carotid and lower limb completion imaging [25].

There is paucity of evidence when considering the benefit of IODUS on patency rates following LEB. This may be because of perceived challenges in scanning smaller calibre vessels in a larger deeper surgical field. In the single study addressing IODUS, it was only used in 11% of cases [22], limiting its relevance.

A single paper comparing IODUS with other completion modalities. This study, by Gilbertson et al., compared angioscopy, angiography and IODUS and concluded that angioscopy and angiography were superior to IODUS in detecting residual cusps and un-ligated side branches. However, this study is also limited by its small sample size of 20 and was conducted almost 30 years ago.

Johnson and colleagues suggests that most benefit from IODUS scanning may be gained for in-situ and non-reversed translocated bypasses, as they have a significantly higher rate of lesions requiring revision [21]. Their results also report a 90-day secondary re-intervention rate of 37.7% in grafts with residual flow abnormalities. In comparison, grafts with normal flow, either without or following revision, revision rates of 2.4 and 3% respective, were reported. MacKenzie and colleagues report similarly, but with lower rates of secondary intervention in grafts with un-corrected flow abnormalities (11.1% within 7 months). This may have bearing on optimal post-operative surveillance strategy.

There is a need for well-designed prospective, multicentre randomised controlled trials to evaluate the effectiveness of IODUS in comparison to other modalities in reducing stroke/mortality outcomes in CEA procedures and primary patency in LEB. Further data are also required to determine the natural progression of different defects detected on IODUS to achieve evidence-based consensus on criteria for revision surgery.