Timing of Pedal Bypass Failure and Its Impact on the Need for Amputation

Color-Flow Duplex Hemodynamic Assessment of Runoff in Ischemic Lower Limb Revascularization

The objective of this study was to evaluate the existence of hemodynamic arterial flow correlation between preoperative duplex scanning (DS) and intraoperative direct outflow resistance (IDOR) measurements in ischemic lower limb revascularization.

Sixty-eight ischemic lower limbs were submitted to preoperative DS. Anatomic and hemodynamic arterial characteristics of the outflow system were recorded, and the results were considered in the distal anastomosis placement site decision making. IDOR measurements were obtained at the same arterial segment, and Pearson's correlation coefficient test was performed to study the preoperative DS power in predicting the intraoperative outflow resistance.

DS was technically satisfactory and helped define the distal anastomosis site in 93.2% of the cases (supragenicular popliteal artery, 19 [27.9%]; infragenicular popliteal artery, 10 [14.7%]; crural artery, 31 [57.4%]). A positive correlation could be found between preoperative DS and IDOR (0.450; p < .001). This correlation was particularly powerful in the crural artery (0.715; p < .001) when compared with the popliteal arterial segment (0.237; p = .192).

Preoperative DS may help define the best distal arterial and outflow segment to be revascularized based on anatomic and hemodynamic parameters. There is a positive flow correlation between preoperative DS and IDOR that seems to be stronger in crural revascularization surgery.

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

OBJECTIVE

Duplex ultrasound (DUS) imaging for vein bypass graft (VBG) surveillance is confounded by technical and physiologic factors that reduce the sensitivity for detecting impending graft failure. In contrast, three-dimensional computed tomography angiography (CTA) offers high-fidelity anatomic characterization of VBGs, but its utility in detecting at risk grafts is unknown. The current study analyzed the correlation between DUS and CTA for detection of vein graft stenosis and evaluated the relationship of the observed abnormalities to VBG failure.

METHODS

Consecutive lower extremity VBG patients underwent surveillance with concurrent DUS imaging and CTA at 1 week and at 1, 6, and 12 months postoperatively. A standardized algorithm was used for CT reconstruction and extraction of the lumen geometries at 1-mm intervals. At each interval, CT-derived cross-sectional areas were coregistered and correlated to DUS peak systolic velocities (PSVs) within six predesignated anatomic zones and then analyzed for outcome association. Vein graft failure was defined as pathologic change within a given anatomic zone resulting in thrombosis, amputation, or reintervention within the 6-month period after the observed time point.

RESULTS

The study recruited 54 patients, and 10 (18%) experienced failure ≤18 months of implantation. The expected inverse relationship between cross-sectional area and PSV was only weakly correlated (Spearman rank coefficient = -0.19). Moderate elevations in the PSV ratio (PSVr; 2-3.5) were frequently transient, with 14 of 18 grafts (78%) demonstrating ratio reduction on subsequent imaging. A PSVr ≥3.5 was associated with a 67% failure rate. CT stenosis <50% was highly correlated with success (0 failures); however, high-grade (>80%) CT stenosis was more likely to succeed than to fail (25%). Significant discordance between CT and DUS was found in 18 patients. Although 14 of these patients had CT stenosis >70% with a PSVr <3.5, subsequent failure occurred in only two. Conversely, graft failure occurred in three of four patients with CT stenosis <70% but PSVr >3.5. Focused analysis of these patients using computational fluid dynamic modeling demonstrated that vein side branches, local tortuosity, regional diameter variations, and venovenostomies were the drivers of these discrepancies.

CONCLUSIONS

This analysis demonstrated that a PSVr ≥3.5 is strongly correlated with VBG failure, whereas the natural history of moderately elevated PSVr (2-3.5) is largely clinically benign. Although minimum stenosis on the CT scan was highly predictive of success, high-grade CT stenosis was infrequently associated with failure. The interaction of anatomic features with the local flow dynamics was identified as the primary confounder for a direct correlation between CT and DUS imaging.

Surveillance and follow-up after revascularization for critical limb ischemia

The purpose of a structured and cost-effective surveillance program after surgical or endovascular intervention for critical limb ischemia is to optimize limb salvage and preserve arterial repair function. Surveillance programs should include clinical, vascular laboratory, and radiographic follow-up, and, when a high-grade progressive stenosis is identified, appropriately timed intervention should be performed. Because many patients with critical limb ischemia are older and many are frail with limited mobility, optimizing the durability of arterial intervention and keeping these patients ambulatory is an important factor in retaining an independent lifestyle and quality of life. Despite the importance of surveillance after arterial intervention, there is a lack of consensus in the literature regarding the efficacy of surveillance, how it should be performed, and well-defined evidence-based guidelines. This review provides an up-to-date scrutiny on this topic and provides recommendations for optimal testing methods, limitations of surveillance testing, and when and how to intervene. These recommendations should be considered in the care of the patient with critical limb ischemia, but with the understanding that patients vary widely and care should be individualized.

Chapter VI: Follow-up after revascularisation

Structured follow-up after revascularisation for chronic critical limb ischaemia (CLI) aims at sustained treatment success and continued best patient care. Thereby, efforts need to address three fundamental domains: (A) best medical therapy, both to protect the arterial reconstruction locally and to reduce atherosclerotic burden systemically; (B) surveillance of the arterial reconstruction; and (C) timely initiation of repeat interventions. As most CLI patients are elderly and frail, sustained resolution of CLI and preserved ambulatory capacity may decide over independent living and overall prognosis. Despite this importance, previous guidelines have largely ignored follow-up after CLI; arguably because of a striking lack of evidence and because of a widespread assumption that, in the context of CLI, efficacy of initial revascularisation will determine prognosis during the short remaining life expectancy. This chapter of the current CLI guidelines aims to challenge this disposition and to recommend evidentially best clinical practice by critically appraising available evidence in all of the above domains, including antiplatelet and antithrombotic therapy, clinical surveillance, use of duplex ultrasound, and indications for and preferred type of repeat interventions for failing and failed reconstructions. However, as corresponding studies are rarely performed among CLI patients specifically, evidence has to be consulted that derives from expanded patient populations. Therefore, most recommendations are based on extrapolations or subgroup analyses, which leads to an almost systematic degradation of their strength. Endovascular reconstruction and surgical bypass are considered separately, as are specific contexts such as diabetes or renal failure; and critical issues are highlighted throughout to inform future studies.

Early and five-year amputation and survival rate of diabetic patients with critical limb ischemia: data of a cohort study of 564 patients

OBJECTIVE

To evaluate the early and late major amputation and survival rates and related risk factors in diabetic patients with critical limb ischemia (CLI).

DESIGN

Retrospective study.

METHODS

Revascularization feasibility, major amputation, survival rate and related risk factors were recorded in 564 diabetic patients consecutively hospitalized for CLI from 1999 to 2003 and followed until June 2005.

RESULTS

Peripheral angioplasty (PTA) was carried out in 420 (74.5%), bypass graft (BPG) in 117 (20.7%) patients. In 27 (4.8%) patients both PTA and BPG were not possible. Twenty-three above-the-ankle amputations (4.1%) were performed at 30 days: 6 in PTA patients, 3 in BPG patients, 14 in non revascularized patients. In the follow-up of 558 patients (98.9%), 62 repeated PTAs and 9 new BPGs, 32 new major amputations (16 in PTA patients, 14 in BPG patients and 2 in non-revascularized patients) were performed. Major amputation was associated with absence of revascularization (OR 35.9, p < 0.001, CI 12.9-99.7), occlusion of each of the three crural arteries (OR 8.20, p = 0.022, CI 1.35-49.6), wound infection (OR 2.1, p = 0.004 CI 1.3-3.6), dialysis (OR 4.7, p = 0.001 CI 1.9-11.7) increase in TcPO2 after revascularization (OR 0.80, p < 0.001 CI 0.74-0.87). One hundred seventy three patients died during follow-up and this was associated with age (HR 1.05, p < 0.001 CI 1.03-1.07), history of cardiac disease (HR 2.16, p < 0.001 CI 1.53-3.06), dialysis (HR 3.52, p < 0.001 CI 2.08-5.97), absence of revascularization (HR 1.68, p < 0.001, CI 1.29-2.19) and impaired ejection fraction (HR 1.08, p < 0.001, CI 1.05-1.09).

CONCLUSIONS

In diabetic patients with CLI the revascularization is feasible in most cases and allows a low rate of early major amputation. This rate is higher in the follow-up period. Major amputation is very high in patients where revascularization is not feasible while the high mortality rate is due to the serious comorbidities observed in these patients.