Intra-arterial Fractional Flow Reserve Measurements Provide an Objective Assessment of the Functional Significance of Peripheral Arterial Stenoses.

OBJECTIVE: Peripheral arterial stenoses (PAS) are commonly investigated with duplex ultrasound (DUS) and angiography, but these are not functional tests. Fractional flow reserve (FFR), a pressure based index, functionally assesses the ischaemic potential of coronary stenoses, but its utility in PAS is unknown. FFR in the peripheral vasculature in patients with limb ischaemia was investigated. METHODS: Patients scheduled for angioplasty and or stenting of isolated iliac and superficial femoral artery stenoses were recruited. Resting trans-lesional pressure gradient (Pd/Pa) and FFR were measured after adenosine provoked hyperaemia using an intra-arterial 0.014 inch flow and pressure sensing wire (ComboWire XT, Philips). Prior to revascularisation, exercise ABPI (eABPI) and DUS derived peak systolic velocity ratio (PSVR) of the index lesion were determined. Calf muscle oxygenation was measured using blood oxygenation level dependent cardiovascular magnetic resonance prior to and after revascularisation. RESULTS: Forty-one patients (32, 78%, male, mean age 65 ± 11 years) with 61 stenoses (iliac 32; femoral 29) were studied. For lesions < 80% stenosis, resting Pd/Pa was not influenced by the degree of stenosis (p = .074); however, FFR was discriminatory, decreasing as the severity of stenosis increased (p = .019). An FFR of < 0.60 was associated with critical limb threatening ischaemia (area under the curve [AUC] 0.87; 95% CI 0.75 - 0.95), in this study performing better than angiographic % stenosis (0.79; 0.63 - 0.89), eABPI (0.72; 0.57 - 0.83), and PSVR (0.65; 0.51 - 0.78). FFR correlated strongly with calf oxygenation (rho, 0.76; p < .001). A greater increase in FFR signalled resolution of symptoms and signs (ΔFFR 0.25 ± 0.15 vs. 0.13 ± 0.09; p = .009) and a post-angioplasty and stenting FFR of > 0.74 predicted successful revascularisation (combined sensitivity and specificity of 95%; AUC 0.98; 0.91 - 1.00). CONCLUSION: This pilot study demonstrates that FFR can objectively measure the functional significance of PAS that compares favourably with visual and DUS based assessments. Its role as a quality control adjunct that confirms optimal vessel patency after angioplasty and or stenting also merits further investigation.

Understanding Patient Acceptance of Risk with Treatment Options for Intermittent Claudication.

BACKGROUND: Intermittent claudication has a major impact on the quality of life and functional ability of the patient. However, when treating these patients, management is largely influenced by vascular surgeons' perceptions of risk. There is little information available regarding the level of risk that patients perceive to be acceptable, when considering complications of treatment. This study investigates patients' acceptance of risk associated with current management options for intermittent claudication and explores factors associated with greater risk acceptance. METHODS: Patients with confirmed intermittent claudication presenting to vascular clinic and supervised exercise classes were surveyed in a single-center prospective study. A standard gamble-type method was used to measure patients' acceptance of risk associated with medical treatment, angioplasty, and surgical bypass. Level of risk acceptance was correlated to patient factors. RESULTS: Fifty patients were surveyed; 74% were male, median age was 68 years (interquartile range [IQR] 59-74), maximal walking distance was 100 m (IQR 70-200), and ankle-brachial pressure index was 0.65 (IQR 0.60-0.78). Median risk acceptance for treatment failure was 70% for medical treatment, 50% for angioplasty, and 40% for surgical bypass. Median risk acceptance for major amputation and death was 0% for all 3 management options. Claudicants with maximal walking distance <100 m accepted higher risk of treatment failure (P = 0.0005 for medical treatment, P = 0.0038 for angioplasty), and death with medical treatment (P = 0.0009). There was no significance between claudication distance and risk acceptance of major amputation with any treatment modality or death with angioplasty or surgical bypass. There was no significant correlation among level of risk acceptance and age, gender, or diabetic status. CONCLUSIONS: Claudicants are prepared to accept significant risk of treatment failure, in order to gain benefit, but regardless of claudication distance, patients have low acceptance of the risk of amputation or death. Patient acceptance of risk should be considered when planning management.

Blood Oxygenation Level-Dependent CMR-Derived Measures in Critical Limb Ischemia and Changes With Revascularization.

BACKGROUND: Use of blood oxygenation level-dependent cardiovascular magnetic resonance (BOLD-CMR) to assess perfusion in the lower limb has been hampered by poor reproducibility and a failure to reliably detect post-revascularization improvements in patients with critical limb ischemia (CLI). OBJECTIVES: This study sought to develop BOLD-CMR as an objective, reliable clinical tool for measuring calf muscle perfusion in patients with CLI. METHODS: The calf was imaged at 3-T in young healthy control subjects (n = 12), age-matched control subjects (n = 10), and patients with CLI (n = 34). Signal intensity time curves were generated for each muscle group and curve parameters, including signal reduction during ischemia (SRi) and gradient during reactive hyperemia (Grad). BOLD-CMR was used to assess changes in perfusion following revascularization in 12 CLI patients. Muscle biopsies (n = 28), obtained at the level of BOLD-CMR measurement and from healthy proximal muscle of patients undergoing lower limb amputation (n = 3), were analyzed for capillary-fiber ratio. RESULTS: There was good interuser and interscan reproducibility for Grad and SRi (all p < 0.0001). The ischemic limb had lower Grad and SRi compared with the contralateral asymptomatic limb, age-matched control subjects, and young control subjects (p < 0.001 for all comparisons). Successful revascularization resulted in improvement in Grad (p < 0.0001) and SRi (p < 0.0005). There was a significant correlation between capillary-fiber ratio (p < 0.01) in muscle biopsies from amputated limbs and Grad measured pre-operatively at the corresponding level. CONCLUSIONS: BOLD-CMR showed promise as a reliable tool for assessing perfusion in the lower limb musculature and merits further investigation in a clinical trial.

Postsurgical Inflammation as a Causative Mechanism of Venous Thromboembolism.

Surgery is associated with an increased risk of venous thromboembolic events (VTE) including deep vein thrombosis and pulmonary embolism. Although the current treatment regiments such as mechanical manipulation and administration of pharmacological prophylaxis significantly reduced the incidence of postsurgical VTE, they remain a major cause of postoperative morbidity and mortality worldwide. The pathophysiology of venous thrombosis traditionally emphasizes the series of factors that constitute Virchow triad of factors. However, inflammation can also be a part of this by giving rise to a hypercoagulable state and endothelial damage. The inflammatory response after surgery, which is initiated by a cytokine "storm" and occurs within hours of surgery, creates a prothrombotic environment that is further accentuated by several cellular processes including neutrophil extracellular traps formation, platelet activation, and the generation of tissue factor-bearing microparticles. Although such inflammatory markers are elevated in undergoing surgery, the precise mechanism by which they give rise to venous thrombosis is poorly understood. Here, we discuss the potential mechanisms linking inflammation to thrombosis, and highlight strategies that may minimize surgical inflammation and reduce the incidence of postoperative VTE.

Peripheral arterial disease.

Peripheral arterial disease (PAD) is an atherosclerotic-driven condition that remains underdiagnosed and undertreated. In diabetic patients, PAD begins early, progresses rapidly, and is frequently asymptomatic, making it difficult to diagnose. Strict management of the metabolic instigators and use of screening techniques for PAD in diabetes can facilitate early diagnosis and reduce progression. Exercise is an equally effective treatment option in improving walking distance. Early revascularization must be offered early in suitable patients. Surgical bypass and endovascular revascularization are complementary and the choice of intervention should be applied appropriately by a multidisciplinary vascular team on a selective, patient-specific basis.

Peripheral arterial disease and bypass surgery in the diabetic lower limb.

PAD is very common in people with diabetes and is one of the strongest predictors of developing nonhealing foot ulcers and suffering amputation. There is strong evidence to show that early detection of PAD and revascularization will reduce amputations. Despite this, many patients have no vascular assessment even when they present with a foot ulcer or before amputation. Even when identified, patients are referred late, which worsens their outcome. Currently there is no evidence to support surgical revascularization over endovascular treatments, but in reality the techniques are complementary and the choice of revascularization procedure should be determined by an experienced multidisciplinary vascular team. Surgical revascularization can achieve good results but careful patient selection, operative planning, and the use of autologous vein are necessary. What is clearly apparent is that at present not enough patients are being offered revascularization to prevent amputation.

Reducing errors in combined open/endovascular arterial procedures: influence of a structured mental rehearsal before the endovascular phase.

PURPOSE: To assess the incidence of errors before and after implementation of a structured mental rehearsal prior to the endovascular phase of combined open/endovascular arterial procedures. METHODS: Over 6 weeks, 15 combined open/endovascular procedures (7 abdominal aorta and 8 thoracic aorta) lasting 58 hours were evaluated by a trained observer. In a blinded fashion, 2 individuals scrutinized event logs for errors, which were categorized by type, by potential to cause patient harm (danger), and by potential to disrupt the procedure (delay). After 9 procedures, a focus group-devised structured mental rehearsal was implemented prior to the endovascular phase for 6 combined procedures. Error patterns were compared before and after implementation. Data are expressed as median (range). RESULTS: The error rate during the endovascular phase of the combined procedures was higher than the non-endovascular phase [7.64/hour (1.71-9.6) vs. 3.75/hour (1.71-5.54), respectively; p = 0.05]. Error rates during the endovascular phase were lower after the intervention compared to before [2.5/hour (1.4-6.0) vs. 7.6/hour (1.7-9.6), respectively; p = 0.05]. During the endovascular phase, danger and delay scores were also lower after the intervention [1.2/error (1.0-2.0) and 1.3/error (1.0-2.3), respectively] compared to before [1.75/error (1.4-2.5) and 2.0/error (1.3-2.5), respectively] (p = 0.036 and p = 0.036 for danger and delay, respectively). CONCLUSION: A structured mental rehearsal before critical stages of procedures may reduce the rate and severity of intraoperative error.