Non-invasive vascular assessment in the foot with diabetes: sensitivity and specificity of the ankle brachial index, toe brachial index and continuous wave Doppler for detecting peripheral arterial disease.

BACKGROUND & AIMS: Non-invasive lower limb vascular assessment in people at risk of peripheral arterial disease (PAD) including those with diabetes is crucial. There is evidence that standard assessment techniques such as the ankle-brachial index (ABI) may be less effective in people with diabetes. However there is limited evidence for other frequently used tests including continuous wave Doppler (CWD), and the toe-brachial index (TBI). The aim of this study was to determine the sensitivity and specificity of, ABI, CWD and TBI in a population with, and without diabetes. METHODS: Participants with and without diabetes who met current guidelines for vascular screening were recruited, and CWD waveforms, an ABI and a TBI were obtained from the right lower limb. Diagnostic accuracy was determined using colour duplex ultrasound (CFDU). Receiver operating characteristic curves were calculated. RESULTS: 117 participants were recruited, seventy-two with diabetes and forty-five without diabetes. CWD had the highest sensitivity in people with diabetes (74%) and without (84%). CWD also had the highest specificity in people with diabetes (74%) and without (84%) compared to both TBI and ABI. In participants with diabetes, the ABI was a poor test, area under the curve: 0.58 (p=0.27). CONCLUSIONS: CWD waveform is more likely to detect significant PAD compared to ABI and TBI in people with and without diabetes.

Sensitivity and Specificity of the Toe-Brachial Index for Detecting Peripheral Arterial Disease: Initial Findings.

OBJECTIVES: The toe-brachial index (TBI) is an alternative to the ankle-brachial index (ABI) in screening for peripheral arterial disease (PAD); however, there is limited evidence comparing their diagnostic accuracy. This study compared the diagnostic accuracy of the ABI and TBI in a population at risk of PAD. METHODS: The sensitivity and specificity of the ABI and TBI were determined by color duplex sonography. Receiver operating characteristic (ROC) analysis was performed. RESULTS: A total of 119 participants were recruited (75 male and 44 female). The sensitivity for PAD was highest for the TBI (71%; ABI, 45%), and the specificity was highest for the ABI (93%; TBI, 78%). Receiver operating characteristic analysis indicated that the TBI (ROC area, 0.77; P = .0001) had greater clinical efficacy for diagnosis of PAD than the ABI (ROC area, 0.65; P = .005). CONCLUSIONS: In specific populations, the TBI may have greater clinical efficacy than the ABI for diagnosis of PAD.

Customized fenestrated endovascular graft repair of abdominal aortic aneurysm with concomitant horseshoe kidney.

The occurrence of an abdominal aortic aneurysm (AAA) with horseshoe kidney (HSK) is an uncommon but complex surgical problem. This report outlines three such cases, the particular issues encountered and how customized endovascular grafts were successfully used to overcome them. Case one shows an accessory renal artery arising from the left common iliac artery, case two shows a right accessory renal artery from the AAA sac and case three has the right renal artery coming off the distal abdominal aorta within the sac. Across three patients, each graft had a single custom fenestration, which preserved a total of three major vessels with no change in renal function. Customized endografts are a viable tool to preserve aberrant vessels and thus renal mass in AAA and HSK. Customized endografts require an extensive work-up and are currently expensive to fabricate. However they are rapidly evolving as a mainstream tool in vascular surgery and provide a solution in cases of aberrant visceral vasculature.

Geometry of phase separation.

We study the domain geometry during spinodal decomposition of a 50:50 binary mixture in two dimensions. Extending arguments developed to treat nonconserved coarsening, we obtain approximate analytic results for the distribution of domain areas and perimeters during the dynamics. The main approximation is to regard the interfaces separating domains as moving independently. While this is true in the nonconserved case, it is not in the conserved one. Our results can therefore be considered as a "first-order" approximation for the distributions. In contrast to the celebrated Lifshitz-Slyozov-Wagner distribution of structures of the minority phase in the limit of very small concentration, the distribution of domain areas in the 50:50 case does not have a cutoff. Large structures (areas or perimeters) retain the morphology of a percolative or critical initial condition, for quenches from high temperatures or the critical point, respectively. The corresponding distributions are described by a cA-tau tail, where c and tau are exactly known. With increasing time, small structures tend to have a spherical shape with a smooth surface before evaporating by diffusion. In this regime, the number density of domains with area A scales as A1/2 , as in the Lifshitz-Slyozov-Wagner theory. The threshold between the small and large regimes is determined by the characteristic area A approximately t2/3. Finally, we study the relation between perimeters and areas and the distribution of boundary lengths, finding results that are consistent with the ones summarized above. We test our predictions with Monte Carlo simulations of the two-dimensional Ising model.

Experimental test of curvature-driven dynamics in the phase ordering of a two dimensional liquid crystal.

We study electric field driven deracemization in an achiral liquid crystal through the formation and coarsening of chiral domains. It is proposed that deracemization in this system is a curvature-driven process. We test this prediction using the recently obtained exact result for the distribution of hull-enclosed areas in two-dimensional coarsening with nonconserved scalar order parameter dynamics [J. J. Arenzon et al., Phys. Rev. Lett. 98, 145701 (2007)]. The experimental data are in very good agreement with the theory. We thus demonstrate that deracemization in such bent-core liquid crystals belongs to the Allen-Cahn universality class, and that the exact formula, which gives us the statistics of domain sizes during coarsening, can also be used as a strict test for this dynamic universality class.

Endovascular abdominal aortic aneurysm repair in patients with common iliac artery aneurysms--Initial experience with the Zenith bifurcated iliac side branch device.

OBJECTIVE: To present our initial experience with the Zenith bifurcated iliac side branch device that preserves internal iliac artery flow whilst excluding aorto-iliac aneurysms. METHODS: Between November 2005 and October 2006, data was prospectively collected on 8 patients in whom this device was used; 2 aorto-bi-iliac aneurysms, 3 aorto-uni-iliac aneurysms, 1 solitary common iliac aneurysm, 1 distal type 1 endoleak, and 1 internal iliac aneurysm. RESULTS: No mortality or major complications resulted from use of this device. The median fluoroscopy time was 53 minutes (range 38 to 105) and a median of 102 g of iodine (range 84 to 130) as contrast were used. One patient required a blood transfusion and only one of the eight side branches occluded. There has been no endoleak related to the device in the median follow-up period of 6 months (1 to 14 months). CONCLUSION: This device provides an alternative for the management of patients with aorto-iliac aneurysms that is safe and less complex than, previously described, hybrid procedures that preserve internal iliac flow.

Exact results for curvature-driven coarsening in two dimensions.

We consider the statistics of the areas enclosed by domain boundaries ("hulls") during the curvature-driven coarsening dynamics of a two-dimensional nonconserved scalar field from a disordered initial state. We show that the number of hulls per unit area that enclose an area greater than A has, for large time t, the scaling form Nh(A,t)=2c/(A+lambdat), demonstrating the validity of dynamical scaling in this system, where c=1/8pisquare root 3 is a universal constant. Domain areas (regions of aligned spins) have a similar distribution up to very large values of A/lambdat. Identical forms are obtained for coarsening from a critical initial state, but with c replaced by c/2.

Statistics of critical points of Gaussian fields on large-dimensional spaces.

We calculate the average number of critical points of a Gaussian field on a high-dimensional space as a function of their energy and their index. Our results give a complete picture of the organization of critical points and are of relevance to glassy and disordered systems and landscape scenarios coming from the anthropic approach to string theory.

Domain growth morphology in curvature-driven two-dimensional coarsening.

We study the distribution of domain areas, areas enclosed by domain boundaries ("hulls"), and perimeters for curvature-driven two-dimensional coarsening, employing a combination of exact analysis and numerical studies, for various initial conditions. We show that the number of hulls per unit area, n_{h}(A,t)dA , with enclosed area in the interval (A,A+dA) , is described, for a disordered initial condition, by the scaling function n_{h}(A,t)=2c_{h}(A+lambda_{h}t);{2} , where c_{h}=18pi sqrt[3] approximately 0.023 is a universal constant and lambda_{h} is a material parameter. For a critical initial condition, the same form is obtained, with the same lambda_{h} but with c_{h} replaced by c_{h}2 . For the distribution of domain areas, we argue that the corresponding scaling function has, for random initial conditions, the form n_{d}(A,t)=2c_{d}(lambda_{d}t);{tau'-2}(A+lambda_{d}t);{tau'} , where c_{d} and lambda_{d} are numerically very close to c_{h} and lambda_{h} , respectively, and tau'=18791 approximately 2.055 . For critical initial conditions, one replaces c_{d} by c_{d}2 and the exponent is tau=379187 approximately 2.027 . These results are extended to describe the number density of the length of hulls and domain walls surrounding connected clusters of aligned spins. These predictions are supported by extensive numerical simulations. We also study numerically the geometric properties of the boundaries and areas.

PTFE-covered self-expanding nitinol stents for the treatment of severe iliac and femoral artery stenoses and occlusions: final results from a prospective study.

PURPOSE: To evaluate the technical performance, safety, and 1-year clinical efficacy of polytetrafluoroethylene (PTFE)-covered nitinol stents in the treatment of atherosclerotic iliac and superficial femoral artery (SFA) disease. METHODS: The multicenter, prospective, nonrandomized COVENT study involved 98 patients (70 men; mean age 64+/-10 years) who received PTFE-covered nitinol stents in 107 arteries (60 iliac and 47 SFAs) after predilation. The average lesion length was 50 mm in the SFA and 45 mm in the iliac arteries. Postdilation was performed when necessary. Duplex ultrasound and ankle-brachial index (ABI) were performed at discharge and at 1, 6, and 12 months in follow-up. RESULTS: In total, 130 stents were placed successfully in 97 (99%) of 98 patients. One stent was misplaced during deployment and required subsequent surgical removal. The average stenosis grade was reduced from 98% to 6% in the SFAs and from 96% to 4% in the iliac arteries after covered stent placement. There was a significant rise of the mean ABI from 0.64 at baseline to 0.97 and 0.95 at 1 and 12 months, respectively (p<0.001). There were 7 primary covered stent occlusions (6.5% of 107 stented lesions: 3 not treated, 2 bypassed, 2 dilated or stented) and 5 (4.7%) recurrent in-stent occlusions (1 bypassed, 2 dilated, 2 untreated) during the 1-year follow-up. Primary patency rates were 92% at 6 months and 89.8% at 12 months for the entire cohort. Secondary patency rates were 98% and 95.6%, respectively. No statistically significant differences were observed in the primary patency rates for the SFAs (89.3% at both 6 and 12 months) versus the iliac arteries (94.3% at 6 months and 90.7% at 12 months). CONCLUSIONS: Primary implantation of PTFE-covered nitinol stents in the iliac and superficial femoral arteries is technically feasible, safe, and effective, with excellent 1-year patency.

Persistence exponents and the statistics of crossings and occupation times for Gaussian stationary processes.

We consider the persistence probability, the occupation-time distribution, and the distribution of the number of zero crossings for discrete or (equivalently) discretely sampled Gaussian stationary processes (GSPs) of zero mean. We first consider the Ornstein-Uhlenbeck process, finding expressions for the mean and variance of the number of crossings and the "partial survival" probability. We then elaborate on the correlator expansion developed in an earlier paper [G. C. M. A. Ehrhardt and A. J. Bray, Phys. Rev. Lett. 88, 070602 (2002)] to calculate discretely sampled persistence exponents of GSPs of known correlator by means of a series expansion in the correlator. We apply this method to the processes d(n)x/dt(n)=eta(t) with n>/=3, incorporating an extrapolation of the series to the limit of continuous sampling. We then extend the correlator method to calculate the occupation-time and crossing-number distributions, as well as their partial-survival distributions and the means and variances of the occupation time and number of crossings. We apply these general methods to the d(n)x/dt(n)=eta(t) processes for n=1 (random walk), n=2 (random acceleration), and larger n, and to simple diffusion from random initial conditions in one to three dimensions. The results for discrete sampling are extrapolated to the continuum limit where possible.

Survival probability of a ballistic tracer particle in the presence of diffusing traps.

We calculate the survival probability P(S)(t) up to time t of a tracer particle moving along a deterministic trajectory in a continuous d-dimensional space in the presence of diffusing but mutually noninteracting traps. In particular, for a tracer particle moving ballistically with a constant velocity c, we obtain an exact expression for P(S)(t), valid for all t, for d<2. For d> or =2, we obtain the leading asymptotic behavior of P(S)(t) for large t. In all cases, P(S)(t) decays exponentially for large t, P(S)(t) approximately exp(-theta t). We provide an explicit exact expression for the exponent theta in dimensions d< or =2 and for the physically relevant case, d=3, as a function of the system parameters.

Percutaneous treatment of long superficial femoral artery occlusive disease: efficacy of the Hemobahn stent-graft.

PURPOSE: To assess the efficacy of the Hemobahn stent-graft in the percutaneous treatment of long occlusive lesions of the superficial femoral artery (SFA). METHODS: Fifty-nine limbs in 54 patients (42 men; mean age 73.3+/-8.2 years, range 55.2-91.3) with 59 symptomatic SFA occlusions >10 cm in length were selected for percutaneous treatment with the Hemobahn stent-graft. The treated SFA was assessed for patency and degree of stenosis by color-flow duplex ultrasound prior to discharge and at 1, 3, and 6 months and yearly thereafter. The actuarial life-table method was used to derive primary and secondary patency rates. RESULTS: Primary technical success was achieved in 56 (95%) of 59 limbs on an intention-to-treat basis (2 access and 1 device failures). In the first 30 days, 4 (6.8%) stent-graft thromboses and 5 (8.5%) minor technical difficulties occurred. Up to 1 year, there were 15 (25.4%) primary occlusions, 7 (11.9%) of which were associated with restenosis. Cumulative primary patencies were 88%, 67%, and 58% at 1, 6, and 12 months, respectively; secondary patencies were 92%, 82%, and 73% at the same intervals. There was no statistically significant difference (p<0.05) in patency (primary or secondary) with respect to presenting symptoms, lesion length, stent-graft length, or distal runoff. CONCLUSIONS: Symptomatic long occlusive lesions of the SFA treated percutaneously with the Hemobahn stent-graft achieved good outcomes initially with a low complication rate. Primary and secondary patencies were similar to those reported for open synthetic femoropopliteal bypass procedures.

Iatrogenic vertebral arteriovenous fistula treated with a hemobahn stent-graft.

PURPOSE: To illustrate the utility of color flow duplex ultrasound (CFDU) in the diagnosis and stent-graft treatment of a rare arteriovenous fistula (AVF) involving the vertebral artery and vein. CASE REPORT: An iatrogenic AVF involving the right vertebral artery and vein was diagnosed in a 45-year-old man using CFDU. Treatment was recommended due to the large volume of blood shunted through the fistula and the associated loud bruit. Endoluminal treatment involved deployment of a covered stent within the vertebral artery to exclude the fistula. Postoperative CFDU confirmed the success of the treatment. CONCLUSIONS: CFDU can be utilized to accurately diagnose unusual lesions, such as AVFs involving the vertebral artery. The technique is also useful in planning treatment and monitoring the durability of stent-grafts implanted to obliterate this type of defect.

Persistence of manifolds in nonequilibrium critical dynamics.

We study the persistence probability P(t) that, starting from a random initial condition, the magnetization of a d'-dimensional manifold of a d-dimensional spin system at its critical point does not change sign up to time t. For d'>0 we find three distinct late-time decay forms for P(t): exponential, stretched exponential, and power law, depending on a single parameter zeta=(D-2+eta)/z, where D=d-d' and eta,z are standard critical exponents. In particular, we predict that for a line magnetization in the critical d=2 Ising model, P(t) decays as a power law while, for d=3, P(t) decays as a power of t for a plane magnetization but as a stretched exponential for a line magnetization. Numerical results are consistent with these predictions.

Formal solution of a class of reaction-diffusion models: reduction to a single-particle problem.

We consider the trapping reaction A+B-->B in space dimension d0 or B, in d=2.

Exact asymptotics for one-dimensional diffusion with mobile traps.

We consider a diffusing particle, with diffusion constant D', moving in one dimension in an infinite sea of noninteracting mobile traps with diffusion constant D and density rho. We show that the asymptotic behavior of the survival probability, P(t), satisfies lim([-ln(P(t)]/sqrt[rho2Dt]=4/sqrt[pi], independent of D'. The result comes from obtaining upper and lower bounds on P(t), and showing that they coincide asymptotically. We also obtain exact results for P(t) to first order in D(')/D for an arbitrary finite number of traps.