The correlation between computed tomography and duplex evaluation of autogenous vein bypass grafts and their relationship to failure

Distinct Temporal Pattern of the Prediction of Lumen Remodeling of Lower Extremity Vein Bypass Grafts by Initial Local Hemodynamics

We predicted human lower extremity vein bypass graft remodeling by hemodynamics. Computed tomography and duplex ultrasound scans of 55 patients were performed at 1 week and 1, 6, and 12 months post-implantation to obtain wall shear stress (WSS) and oscillatory shear index (OSI) at 1-mm intervals via computational fluid dynamics simulations. Graft remodeling was quantified by computed tomography-measured lumen diameter changes in the early (1 week-1 month), intermediate (1-6 months), and late (6-12 months) periods. Linear mixed-effect models were constructed to examine the overall relationship between remodeling and initial hemodynamics using the average data of all cross sections within the same graft. A significant association of graft remodeling with WSS (p < 0.001) and time (p = 0.001) was found; however, the effect size decreased with time (every 2.7 dyne/cm² increase of WSS was associated with a 0.39, 0.35, 0.002 mm diameter increase in the three periods, respectively). The association of remodeling with OSI was significant only in the intermediate period (every 0.1 increase of OSI was associated with a 0.25 mm lumen diameter decrease, p = 0.004). Therefore, the association of graft lumen remodeling with local hemodynamics has a distinct temporal pattern; WSS and OSI are predictive of remodeling only in certain postoperative periods.

Systematic review and meta-analysis of duplex ultrasound surveillance for infrainguinal vein bypass grafts

OBJECTIVE

Duplex ultrasound (DUS) surveillance of infrainguinal vein bypass grafts is widely practiced, but the evidence of its effectiveness compared with other methods of surveillance remains unclear.

METHODS

Following an a priori protocol developed by the guidelines committee from the Society for Vascular Surgery, this systematic review and meta-analysis included randomized and nonrandomized comparative studies that enrolled patients who underwent infrainguinal arterial reconstruction and received DUS surveillance for follow-up compared with any other method of surveillance. The search included MEDLINE, Embase, Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews, Cumulative Index to Nursing and Allied Health Literature, and Scopus through November 2016. Outcomes of interest included all-cause mortality, limb viability, and graft patency reports. Meta-analysis was performed using the random-effects model.

RESULTS

We included 15 studies. Compared with ankle-brachial index and clinical examination, DUS surveillance was not associated with a significant change in primary, secondary, or assisted primary patency or mortality. DUS surveillance was associated with a nonstatistically significant reduction in amputation rate (odds ratio, 0.70 [95% confidence interval, 0.23-2.13]). The quality of evidence was low because of imprecision (small number of events and wide confidence intervals) and high risk of bias in the primary literature.

CONCLUSIONS

A recommendation for routine DUS surveillance of infrainguinal vein grafts remains dependent on low-quality evidence. Considering that DUS offers the opportunity of early intervention and because of its noninvasive nature and low cost, vascular surgeons may incorporate DUS as they individualize the follow-up of lower extremity vein grafts.

Validation of a Decision Tree to Streamline Infrainguinal Vein Graft Surveillance

BACKGROUND

Duplex ultrasound (DU)-based graft surveillance remains controversial. The aim of this study was to assess the ability of a recently proposed decision tree in identifying high-risk grafts which would benefit from DU-based surveillance.

MATERIALS AND METHODS

Consecutive patients undergoing infrainguinal vein graft bypass from January 2008 to December 2015 were identified from the National Vascular registry and enrolled in a duplex surveillance program. An early postoperative DU was performed at a median of 6 weeks (range: 4-9 weeks). Grafts were classified into high risk or low risk based on the findings of the earliest postoperative scan and 4 established risk factors for graft failure (diabetes, smoking, infragenicular distal anastomosis, and revision bypass surgery) using a classification and regression tree (CRT). The accuracy of the CRT model was evaluated using area under receiver operator characteristic (AROC) curve.

RESULTS

About 278 vein graft bypasses were performed; 29 grafts had occluded by the first surveillance visit; 249 vein grafts were entered into surveillance. Sixty-four (23%) developed critical stenosis. Overall 30-month primary patency, primary-assisted patency, and secondary patency rates were 71.2%, 77.2%, and 80.1%, respectively. AROC for prediction of graft stenosis or occlusion was 83% (95% confidence interval [CI]: 78-87%). The sensitivity and specificity of the CRT model for prediction of graft stenosis or occlusion were 95% (95% CI: 88-98%) and 52.2% (95% CI: 45-60%).

CONCLUSIONS

A prediction model based on commonly recorded clinical variables and early postoperative DU scan is accurate at identifying grafts which are at high risk of failure. These high-risk grafts may benefit from DU-based surveillance.