J.P. Eiberg

Duplex Ultrasound Scanning of Peripheral Arterial Disease of the Lower Limb

OBJECTIVES To assess the reliability and applicability of duplex ultrasound scanning (DUS) of lower limb arteries, compared with digital subtraction angiography (DSA), in patients with peripheral arterial disease (PAD). DESIGN A prospective, blinded, comparative study. MATERIALS AND METHODS A total of 169 patients were examined by DUS and DSA. Intermittent claudication (IC) was present in 42 (25%) patients and critical limb ischaemia (CLI) in 127 (75%) patients. To allow segment-to-segment comparison, the arterial tree was divided into 15 segments. In total, 2535 segments were examined using kappa (κ) statistics to test the agreement. RESULTS The agreement between DUS and DSA was very good (κ>0.8) or good (0.8 ≥ κ>0.6) in most segments, but moderate (0.6 ≥ κ>0.4) in the tibio-peroneal trunk and the peroneal artery. Agreement between the two techniques was significantly better in the supragenicular (κ=0.75 (95% confidence interval (CI): 0.70-0.80)) than in the infragenicular segments (κ=0.63 (0.59-0.67)) (p<0.001). Similarly, the technical success rate was significantly higher in the supragenicular segments (DUS: 100%; DSA: 99%) than in the infragenicular segments (both 93%) (p<0.001). DUS was the best technique for imaging of the distal crural arteries (92% vs. 97%; p<0.001) and DSA was the best technique for imaging of the proximal crural arteries (95% vs. 91%; p<0.01). Neither the agreement nor the technical success rate was influenced by the severity of PAD, that is, IC versus CLI. CONCLUSION The agreement between DUS and DSA was generally good, irrespective of the severity of ischaemia. DUS performed better in the supragenicular arteries than in the infragenicular arteries. However, DUS compared favourably with DSA in both tibial vessels, particularly in the distal part, which makes DUS a useful non-invasive alternative to DSA.

Volume Estimation of the Aortic Sac after EVAR Using 3-D Ultrasound – A Novel, Accurate and Promising Technique

OBJECTIVES Volume estimation is more sensitive than diameter measurement for detection of aneurysm growth after endovascular aneurysm repair (EVAR), but this has only been confirmed on three-dimensional, reconstructed computer tomography (3-D CT). The potential of 3-D ultrasound (3-D US) for volume estimation in EVAR surveillance is unknown. DESIGN Prospective validation study comparing 3-D US with 3-D CT, using 3-D CT as the gold standard. MATERIALS AND METHODS From August 2011 to March 2012, 93 consecutive EVAR patients were enrolled and examined with both 3-D US and CT angiography (CTA). Image data were analysed in a mutual blinded setup using a 3-D interactive segmentation technique. RESULTS The technical success rate of 3D-US was 98% (91/93). In 91 EVAR patients (F/M; 10/81) eligible for further analysis, the mean maximum volume (SD) was 126 (58) ml using 3-D US and 128 (58) ml using 3-D CT. The mean difference was 1 ml (0.4%) and the limits of agreement were -14 to 16 ml (-11; 12%). CONCLUSION Volume estimation of the aortic sac after EVAR using 3-D US is a feasible and accurate method using 3-D CT as the gold standard.

Effects of large conductance Ca2+-activated K+ channels on nitroglycerin-mediated vasorelaxation in humans

Nitric oxide (NO)-induced vasorelaxation and the regulation of endothelial superoxide anion levels is partly mediated by vascular large conductance Ca(2+)-activated K(+) (BK(Ca)) channels. Nitroglycerin acts through the release of NO and its effect is modulated by changes in endothelial superoxide levels. This study examines the effect of BK(Ca) channel blockade on nitroglycerin-induced vasorelaxation in human arterial and venous vascular segments and whether responses to BK(Ca) channel blockade are influenced by the development of venous nitroglycerin tolerance. Dose-relaxation curves to nitroglycerin (10(-10)-10(-4) M) were obtained in segments of the saphenous vein and the left mammary artery. Studies were performed with and without pre-incubation with the BK(Ca) channel blocker iberiotoxin (10(-7) M) and venous tolerance to nitroglycerin were induced by a 24-h i.v. infusion (0.5 microg/kg/min). Iberiotoxin reduced the vasorelaxant effect of nitroglycerin (E(max)) by 60% in endothelium-intact arteries and 13% in endothelium-denuded arteries (P<0.05). Development of nitroglycerin tolerance did not affect the response to iberiotoxin in the venous vascular segments (P>0.05) and (compared to arterial segments) veins were less sensitive to BK(Ca) channel blockade (30% reduction in E(max)) or endothelial removal. The results suggest that primarily arterial effects of nitroglycerin are significantly inhibited by changes in the activity of the endothelial BK(Ca) channels. Although endothelial BK(Ca) are likely regulators of mechanisms underlying arterial tolerance development to nitroglycerin, they do not appear to play a role in human venous nitroglycerin tolerance development.

Three-dimensional Ultrasound Improves the Accuracy of Diameter Measurement of the Residual Sac in EVAR Patients

OBJECTIVES Discrepancy between maximum diameters obtained with two-dimensional ultrasound and computed tomography (CT) after endovascular aneurysm repair (EVAR) is well known. The maximal diameter is ideally measured perpendicular to the centerline, a methodology so far only feasible with three-dimensional (3D) CT and magnetic resonance angiography (MRA). We aimed to investigate the agreement between 3D ultrasound and 3D CT and to determine reproducibility measures. METHODS Prospective study comparing 3D ultrasound with 3D CT in 124 consecutive patients seen 3 or 12 month after EVAR. RESULTS Replacing 2D with 3D ultrasound, the mean difference was improved from 6.0 mm to -1.3 mm (p < .001), and the range of variability was reduced from 9.4 mm to 6.6 mm (p = .009) using 3D CT as the gold standard. The mean difference between 3D ultrasound and 3D CT maximum diameter of the residual sac was -1.3 mm with upper and lower limits of agreement of 5.2 mm and -7.9 mm, respectively. Reproducibility measures of 3D ultrasound were ± 4 mm. CONCLUSION 3D ultrasound correlate significantly better to 3D CT than the currently used 2D ultrasound method when assessing maximum diameter of the residual sac after EVAR, and reproducibility measures were within clinical acceptable values.

Minimum Training Requirement in Ultrasound Imaging of Peripheral Arterial Disease

OBJECTIVES To demonstrate the minimum training requirement when performing ultrasound of peripheral arterial disease. DESIGN Prospective and blinded comparative study. MATERIAL 100 limbs in 100 consecutive patients suffering from peripheral arterial disease, 74% suffering critical limb ischemia, were enrolled during a 9 months period. METHODS One physician with limited ultrasound experience performed all the ultrasound examinations of the arteries of the most symptomatic limb. Before enrolling any patients 15 duplex ultrasound examinations were performed supervised by an experienced vascular technologist. All patients had a digital subtraction arteriography performed by an experienced vascular radiologist, unaware of the ultrasound result. RESULTS The number of insufficiently insonated segments (non-diagnostic segments) was significantly reduced during the study; from 9% among the initial 50 limbs to 2% among the last 50 limbs (P<0.0001). This improvement was evident only in the infragenicular segments, as the performance within the supragenicular segments was good from the beginning. There was no change in the agreement between ultrasound and arteriography from the initial 50 patients (overall Kappa=0.66, (95%-CI: 0.60-0.72); supragenicular Kappa=0.73 (95%-CI: 0.64-0.82); infragenicular Kappa=0.61 (95%-CI: 0.54-0.69)) to the last 50 patients (overall Kappa=0.66 (95%-CI: 0.60-0.72), supragenicular Kappa=0.67 (95%-CI: 0.57-0.76); infragenicular Kappa=0.66 (95%-CI: 0.58-0.73)). CONCLUSION The minimum training requirement in ultrasound imaging of peripheral arterial disease appears to be less than 50 ultrasound examinations (probably only 15 examinations) for the supragenicular segments and 100 examinations for the infragenicular segments.

Mortality and complications after aortic bifurcated bypass procedures for chronic aortoiliac occlusive disease.

OBJECTIVE Open surgery has given way to endovascular grafting in patients with aortoiliac occlusive disease. The growing use of endovascular grafts means that fewer patients with aortoiliac occlusive disease have open surgery. The declining open surgery caseload challenges the surgeons operative skills, particularly because open surgery is increasingly used in those patients who are unsuitable for endovascular repair and hence technically more demanding. We assessed the early outcome after aortic bifurcated bypass procedures during two decades of growing endovascular activity and identified preoperative risk factors. METHODS Data on patients with chronic limb ischemia were prospectively collected during a 20-year period (1993 to 2012). The data were obtained from the Danish Vascular Registry, assessed, and merged with data from The Danish Civil Registration System. RESULTS We identified 3623 aortobifemoral and 144 aortobiiliac bypass procedures. The annual caseload fell from 323 to 106 during the study period, but the 30-day mortality at 3.6% (95% confidence interval [CI], 3.0-4.1) and the 30-day major complication rate remained constant at 20% (95% CI, 18-21). Gangrene (odds ratio [OR], 3.3; 95% CI, 1.7-6.5; P = .005) was the most significant risk factor for 30-day mortality, followed by renal insufficiency (OR, 2.5; 95% CI, 1.1-5.8; P = .035) and cardiac disease (OR, 2.1; 95% CI, 1.4-3.1; P < .001). Multiorgan failure, mesenteric ischemia, need for dialysis, and cardiac complications were the most lethal complications, with mortality rates of 94%, 44%, 38%, and 34%, respectively. CONCLUSIONS Aortic bifurcated bypass is a high-risk procedure. Although open surgery has increasingly given way to endovascular repair, 30-day outcomes have remained stable during the past decade. Thus, it is still acceptable to consider an aortic bifurcated bypass whenever endovascular management is not feasible.

Whole-body MR Angiography with Body Coil Acquisition at 3 T in Patients with Peripheral Arterial Disease Using the Contrast Agent Gadofosveset Trisodium1

RATIONALE AND OBJECTIVES Whole-body magnetic resonance angiography (WB-MRA) at 3 T with body coil acquisition has not previously been investigated. In this study, WB-MRA was performed in this manner using the blood pool contrast agent gadofosveset trisodium. MATERIALS AND METHODS Eleven consecutive patients (five men, six women) with symptomatic peripheral arterial disease (two with critical limb ischemia, nine with claudication) were examined. Conventional digital subtraction angiography (DSA) of the aorta and the inflow and runoff arteries was used as the reference method. WB-MRA was performed using four slightly overlapping stations covering the arteries from the neck to the ankles. The arterial system was divided into 42 segments that were analyzed for the presence of significant arterial disease (> or =50% luminal narrowing or occlusion) by two blinded observers. RESULTS Sensitivities for detecting a significant arterial lesion with WB-MRA using gadofosveset as the contrast agent were 0.66 (95% confidence interval [CI], 0.49-0.79) and 0.68 (95% CI, 0.52-0.81) for the two observers. Specificities were 0.82 (95% CI, 0.74-0.88) and 0.93 (95% CI, 0.87-0.96), respectively. Intermodality agreement between WB-MRA and DSA was moderate to good, with overall kappa values of 0.44 (95% CI, 0.29-0.59) and 0.63 (95% CI, 0.5-0.77) for the two observers. Interobserver agreement for WB-MRA was good, at kappa = 0.60 (95% CI, 0.50-0.71). CONCLUSION WB-MRA at 3 T with body coil acquisition in patients with peripheral arterial disease showed good reproducibility but only moderate to good agreement with DSA. Further assessment of the methods clinical application is warranted.

Near-infrared spectroscopy during peripheral vascular surgery

Near-infrared spectroscopy was performed perioperatively on the dorsum of the foot in 14 patients who underwent infrainguinal bypass surgery using a prosthesis or the greater saphenous vein. Dual-wavelength continuous light spectroscopy was used to assess changes in tissue saturation before, during and after the operation. Following the use of peripheral vascular grafts an immediate postoperative increase in tissue saturation of median 28 (range -10 to +81) arbitrary units was noted (P < 0.01). Following distal clamping of the common femoral artery, maximal ischaemia corresponding to a median reduction in tissue saturation of 61 (range 6-94) units was reached after 26 (range 8-95) min (P < 0.01). The maximal tissue saturation following declamping was median 27 (range -16 to +100) units higher than the preoperative level (P < 0.01) and was reached after median 42 (range 8-125) min. The results indicate that near-infrared spectroscopy is appropriate for perioperative monitoring during vascular grafting.

O2 supplementation to secure the near-infrared spectroscopy determined brain and muscle oxygenation in vascular surgical patients: a presentation of 100 cases

This study addresses three questions for securing tissue oxygenation in brain (rScO2) and muscle (SmO2) for 100 patients (age 71 ± 6 years; mean ± SD) undergoing vascular surgery: (i) Does preoxygenation (inhaling 100% oxygen before anesthesia) increase tissue oxygenation, (ii) Does inhalation of 70% oxygen during surgery prevent a critical reduction in rScO2 (<50%), and (iii) is a decrease in rScO2 and/or SmO2 related to reduced blood pressure and/or cardiac output?Intravenous anesthesia was provided to all patients and the intraoperative inspired oxygen fraction was set to 0.70 while tissue oxygenation was determined by INVOS 5100C. Preoxygenation increased rScO2 (from 65 ± 8 to 72 ± 9%; P < 0.05) and SmO2 (from 75 ± 9 to 78 ± 9%; P < 0.05) and during surgery rScO2 and SmO2 were maintained at the baseline level in most patients. Following anesthesia and tracheal intubation an eventual change in rScO2 correlated to cardiac output and cardiac stroke volume (coefficient of contingence = 0.36; P = 0.0003) rather to a change in mean arterial pressure and for five patients rScO2 was reduced to below 50%. We conclude that (i) increased oxygen delivery enhances tissue oxygenation, (ii) oxygen supports tissue oxygenation but does not prevent a critical reduction in cerebral oxygenation sufficiently, and (iii) an eventual decrease in tissue oxygenation seems related to a reduction in cardiac output rather than to hypotension.

Popliteal Artery Entrapment Syndrome Ultrasound Imaging, Intraoperative Findings, and Clinical Outcome

Objectives: The purpose of this study was to report our experience with popliteal artery entrapment syndrome (PAES) with special emphasis on the applicability of duplex ultrasound scanning (DUS) when diagnosing PAES. In addition to examining the correlation between DUS and intraoperative findings in symptomatic limbs, the ultrasonic effect of plantar flexion in healthy volunteers were also evaluated. Methods: During a 12-month period, 11 symptomatic limbs in 8 patients with a mean age of 29 years were referred with suspected PAES and enrolled consecutively. The popliteal artery was studied preoperatively with DUS in rest and during active plantar flexion. The popliteal artery was explored in all symptomatic limbs, and the intraoperative findings served as gold standard. Additionally, the popliteal arteries in 11 healthy volunteers (22 limbs) were evaluated with DUS during rest and plantar flexion. Results: Intraoperative findings confirmed PAES in all 11 symptomatic limbs in accordance with the preoperative DUS examination. Surgical release of the popliteal artery was performed in 11 limbs. At a median follow-up of 15 months, all 11 limbs were free of ischemic symptoms and regained normalized popliteal flow on DUS. In the 22 symptom-free limbs, DUS showed normal popliteal flow during both rest and plantar flexion. Conclusions: In this series of patients with surgically confirmed PAES, we found preoperative DUS to have perfect agreement with the intraoperative findings in diagnosing PAES. The applicability of the method seems to be emphasized by the restoration of popliteal flow and relief of arterial insufficiency after surgical release in all patients, and by the fact, that none of the healthy volunteers were able to compress the popliteal artery during plantar flexion.