Deirdre Cassidy

Revisiting the risks of MRI with Gadolinium based contrast agents—review of literature and guidelines

Gadolinium based contrast agents (GBCA) have been linked to the occurrence of nephrogenic systemic fibrosis (NSF) in renal impaired patients. The exact interaction between the various different available formulations and occurrence of NSF is not completely understood, but has been postulated. This association has triggered public health advisory bodies to issue guidelines and best practice recommendations on its use. As a result, the reported incidence of NSF, as well as the published use of GBCA-enhanced magnetic resonance imaging in renal impairment, has seen a decline. Understanding of the events that led to these recommendations can increase clinical awareness and the implications of their usage. We present a review of published literature and a brief overview of practice recommendations, guidelines and manuals on contrast safety to aide everyday imaging practice.Teaching Points• Low risk gadolinium based contrast agents should be the choice in renal insufficiency.• Higher doses have been linked to NSF development. Doses should be as low as possible.• Clear documentation of date,dose and type of formulation used should be noted.• Post-scan dialysis should be arranged as soon as possible and feasible.• Pre-existing inflammatory state is a risk factor;liver insufficiency is not a contraindication.

Systematic review of drug eluting balloon angioplasty for arteriovenous haemodialysis access stenosis

Background Native or prosthetic arteriovenous (AV) fistulas are preferred for permanent haemodialysis (HD) access. These are marked with circuit steno-occlusive disease leading to dysfunction or even failure. Late failure rates have been reported as high as 50%. Standard angioplasty balloons are an established percutaneous intervention for HD access stenosis. Reported restenosis rates remain high and practice guidelines recommend a wide 6-month primary patency (PP) of at least 50% for any intervention. Neointimal hyperplasia is one of the main causes for access circuit stenosis. Drug eluting balloon (DeB) angioplasty has been proposed as an alternative intervention to reduce restenosis by local drug delivery and possible inhibition of this process. Purpose To systematically assess the reported efficacy and safety of DeB angioplasty in percutaneous management of prosthetic and autologous HD access stenosis. Methods Protocol for the review was developed following the PRISMA-P 2015 statement. An electronic database (Medline, EMBASE, Clinical Trials.gov and Cochrane CENTRAL) search was conducted to identify articles reporting on the use of DeB intervention in HD AV access. Backward and forward citation search as well as grey literature search was performed. The MOOSE statement and PRISMA 2009 statement were followed for the reporting of results. Data from the included studies comparing DeBs with non-DeBs were pooled using a random effects metaanalysis model and reported separately on randomised and non-randomised studies. Results Six studies reported on 254 interventions in 162 participants (mean 27 ± 10 SD). The pooled mean and median duration of follow-up was 12 and 13 months (range 6-24 months). These comprised two randomised control trials (RCTs) and four cohort studies. Participants mean age was 64 ± 5 years and 61% were male. Target lesions (TLs) ranged from under 2 mm to 5.9 mm and 51 were reported as de novo stenosis. Device failure described as wasting of the DeB was reported in two studies (55% and 92.8%). At 6 months TL PP was reported between 70% to 97% for DeBs in the RCTs and cohort studies, and 0% to 26% for non-DeBs. TLs treated with DeBs were associated with a higher primary patency at 6 months as compared to non-DeB balloons (RCTs: odds ratio [OR] 0.25, 95% CI 0.08 to 0.77 and I2 = 19%, cohort studies: OR 0.10, 95% CI 0.03 to 0.31 and an I2 = 20%). No procedure-related major or minor complications were reported. Conclusions Current literature reports DeBs as being safe and may convey some benefit in terms of improved rate of restenosis when used to treat AV access disease. However, this body of evidence is small and clinically heterogeneous. A large multicentre RCT may help to clarify the role of DeBs in the percutaneous treatment of AV HD access stenosis.

Efficacy of the Ulnar-Basilic Arteriovenous Fistula for Hemodialysis: A Systematic Review

BACKGROUND The fistula first initiative has promoted arteriovenous fistulas (AVFs) as the vascular access of choice. To preserve as many future access options as possible, multiple guidelines advocate that the most distal AVF possible should be created in the first place. Generally, snuff box and radiocephalic (RC) are accepted and well-described sites for AVFs; however, the forearm ulnar-basilic (UB) AVF is seldom used or recommended. The aim of this study is to assess and systematically review the evidence base for the creation of the UB fistula and to critically appraise whether more attention should be given to this site. METHODS Electronic databases were searched for studies involving the creation of UB fistulas for dialysis in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The primary outcomes for this study were 1-year primary and secondary patency rates. Secondary outcomes were rates of hemodialysis access-induced distal ischemia (HAIDI) and infection. RESULTS After strict inclusion and/or exclusion criteria by 2 reviewers, 8 studies were included in our review. Weighted-pooled data reveal 1-year primary patency rate for UB AVFs of 53.0% (95% confidence interval [CI]: 40.1-65.8%) with a secondary patency rate of 72.0% (95% CI: 59.2-83.3). HAIDI and infection rates were low. CONCLUSIONS Our review has shown that the UB AVF may be a viable alternative when a RC AVF is not possible, and dialysis is not required urgently. It has adequate 1-year primary and secondary patency rates and extremely low risk of HAIDI. While it may be more challenging for both surgeons and dialysis nurses to make it a successful vascular access it offers a further option of distal access which may be overlooked.

Whole-body cardiovascular MRI for the comparison of atherosclerotic burden and cardiac remodelling in healthy South Asian and European adults.

Objective: To determine the feasibility of using whole-body cardiovascular MRI (WB-CVMR) to compare South Asians (SAs)—a population known to have a higher risk of cardiovascular disease (CVD) but paradoxically lower prevalence of peripheral arterial disease—and Western Europeans (WEs). Methods: 19 SAs and 38 age-, gender- and body mass index-matched WEs were recruited. All were aged 40 years and over, free from CVD and with a 10-year risk of CVD <20% as assessed by the adult treatment panel (ATP) III risk score. WB-CVMR was performed, comprising a whole-body angiogram (WBA) and cardiac MR (CMR), on a 3-T MRI scanner (Magnetom® Trio; Siemens, Erlangen, Germany) following dual-phase injection of gadolinium-based contrast agent. A standardized atheroma score (SAS) was calculated from the WBA while indexed left ventricular mass and volumes were calculated from the CMR. Results: SAs exhibited a significantly lower iliofemoral atheroma burden (regional SAS 0.0 ± 0.0 vs 1.9 ± 6.9, p = 0.048) and a trend towards lower overall atheroma burden (whole-body SAS 0.7 ± 0.8 vs 1.8 ± 2.3, p = 0.1). They had significantly lower indexed left ventricular mass (46.9 ± 11.8 vs 56.9 ± 13.4 ml m−2, p = 0.008), end diastolic volume (63.9 ± 10.4 vs 75.2 ± 11.4 ml m−2, p=0.001), end systolic volume (20.5 ± 6.1 vs 24.6 ± 6.8 ml m−2, p = 0.03) and stroke volume (43.4 ± 6.6 vs 50.6 ± 7.9 ml m−2, p = 0.001), but with no significant difference in ejection fraction, mass-volume ratio or global functioning index. These differences persisted after accounting for CVD risk factors. Conclusion: WB-CVMR can quantify cardiac and atheroma burden and can detect differences in these metrics between ethnic groups that, if validated, may suggest that the paradoxical high risk of CVD compared with PVD risk may be due to an adverse cardiac haemodynamic status incurred by the smaller heart rather than atherosclerosis. Advances in knowledge: WB-CVMR can be used to stratify and compare disease between ethnicities.

24 Assessment of the effects of technique on pulmonary arterial pulse wave velocity measurement

Aim The flow-area (QA) technique allows measurement of pulse wave velocity (PWV) from a single phase contrast slice. However in the pulmonary circulation reflected waves arrive during systole and may cause erroneous measurements using this technique. The aim of the study was to compare three post-processing calculations, one of which avoids the reflected wave, and the other which corrects for it, on the measurement of pulmonary PWV and its reproducibility. Materials and methods 10 young healthy volunteers (YHV) (30% male, mean age 31.5 ± 7.6) and 20 older healthy volunteers (OHV) (45% male, mean age 60.2 ± 4.0) underwent MRI using phase contrast sequences through the main pulmonary artery (MPA), right pulmonary artery (RPA) and left pulmonary artery (LPA). Measurements were repeated at 6 months in the YHV cohort and on the same visit in the OHV cohort. QA PWV was calculated using three techniques: QATrad = ΔQ/ΔA; QA3 = ΔQ/ΔA (using only the first three datapoints in the reflectionless upstroke); and QAInv = √(∑ΔA2/∑ΔQ2). Results QATrad produced significantly higher results than QA3 (p < 0.001) and QAInv (p < 0.001), whilst there was no difference between QA3 and QAInv (p = 0.41). In scan-rescan reproducibility, QAInv yielded improved precision over QATrad and QA3: mean (SD) of PWV differences = −0.46 (0.98) ms−1, 0.05 (0.88) ms−1, and 0.01 (0.63) ms−1 for the QATrad, QA3, and QAInv of the MPA respectively; 0.17 (0.43), 0.19 (0.83) and 0.06 (0.25) ms−1 for the QATrad, QA3, and QAInv of the RPA respectively; and −0.29 (0.31), −0.01 (0.39) and −0.06 (0.32) ms−1 for the QATrad, QA3, and QAInv of the LPA respectively (see Figure 1). Conclusion Calculations which account for wave reflections yield lower PWV than those that don’t suggesting significant confounding effects from these early reflected waves. Combining a phase contrast sequence acquisition through the right pulmonary artery with a post processing technique to account for wave reflections yields the most reproducible measurements of pulmonary PWV. Abstract 24 Figure 1 Bland-Altman plots comparing interscan PWV repeatability using the 3 techniques in the 3 pulmonary arterial locations

15 Epicardial fat in diabetes mellitus and cardiovascular disease measured using cardiac magnetic resonance imaging: a summit substudy

Background Ectopic fat stored in the epicardium has previously been associated with coronary heart disease. However the role of type-2 diabetes mellitus (T2DM) in epicardial fat deposition has not been well explored. This study compares the volume of epicardial and paracardial fat in a T2DM cohort with and without cardiovascular disease (CVD) and matched non-diabetic cohorts. Methods A cohort of 158 participants were categorised into one of 4 groups: 1-T2DM with CVD; 2-T2DM without CVD; 3-CVD without T2DM; 4-Healthy controls. Measurements were performed on 4 chamber cardiac magnetic resonance (CMR) images using Segment (v2.0-R4339 (http://segment.heiberg.se). Epicardial adipose tissue (EAT) was defined as fat within the visceral pericardium while paracardial adipose tissue (PAT) was defined as fat out with the parietal pericardium. Results In total, 148 participants completed the MRI study protocol (61% male, 64 ± 8.2 years). EAT was highest in those with CVD without diabetes (15.2 ± 6.6 cm2), followed by those with T2DM and CVD (14.3 ± 6.4 cm2), then those with T2DM only (13.1 ± 4.6 cm2) with healthy controls having the lowest EAT (10.8 ± 5.0 cm2) (F = 3.5, p = 0.016). No difference between the groups was observed for PAT (F = 2.1, p = 0.1). Post-hoc analysis showed only the non-diabetic CVD group to have significantly higher EAT than the healthy controls with no other significant differences between the groups. These differences persisted when accounting for differences in BMI between the groups (ANCOVA F = 2.9, p = 0.038). Conclusion EAT was higher in non-diabetics with CVD, but not in T2DM with or without CVD. This suggests EAT may play a greater role in CVD in non-diabetics than those with T2DM.