Comparing aortic stiffness in kidney transplant recipients, hemodialysis patients, and patients with chronic renal failure

Free-Breathing Three-Dimensional Isotropic-Resolution MR sequence for simultaneous vessel wall imaging of bilateral renal arteries and abdominal aorta: Feasibility and reproducibility

PURPOSE

Many diseases can simultaneously involve renal arteries and the adjacent abdominal aorta. The study proposed a free-breathing three-dimensional (3D) isotropic-resolution MR sequence for simultaneous vessel wall imaging of bilateral renal arteries and adjacent abdominal aorta.

METHODS

A respiratory triggered isotropic-resolution sequence which combined the improved motion-sensitized driven-equilibrium (iMSDE) preparation with the spoiled gradient recalled (SPGR) readout (iMSDE-SPGR) was proposed for simultaneous vessel wall imaging of renal arteries and abdominal aorta. The proposed iMSDE-SPGR sequence was optimized by positioning spatial saturation pulses (i.e. REST slabs) elaborately to further alleviate respiratory and gastrointestinal motion artifacts and selecting appropriate first-order gradient moment (m₁ ) of the iMSDE preparation. Thirteen healthy subjects and thirteen patients with renal artery stenosis (RAS) underwent simultaneous vessel wall imaging with the optimized iMSDE-SPGR sequence at 3.0T. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and morphology of renal arterial wall and aortic wall were measured. Reproducibility of intra-observer, inter-observer and scan-rescan (n = 13 healthy subjects) in measuring SNR, CNR and morphology was evaluated. For the reproducibility test, the agreement was determined using intraclass correlation coefficients (ICC) and the differences were compared using paired-t test or non-parametric Wilcoxon test when appropriate. Bland-Altman plots were used to calculate the bias between observers and between scans.

RESULTS

The proposed iMSDE-SPGR sequence was feasible for simultaneous vessel wall imaging both in the healthy subjects and the patients. The sequence showed good to excellent inter-observer (ICC:0.615-0.999), excellent intra-observer (ICC:0.801-0.998) and scan-rescan (ICC:0.768-0.998) reproducibility in measuring morphology, SNR and CNR. There were no significant differences in SNR, CNR and morphology measurements between observers and between scans (all P>0.05). Bland-Altman plots showed small bias in assessing SNR, CNR and morphology.

DATA CONCLUSION

The proposed free-breathing 3D isotropic-resolution iMSDE-SPGR technique is feasible and reproducible for simultaneous vessel wall imaging of bilateral renal arteries and adjacent abdominal aorta. This article is protected by copyright. All rights reserved.

A Systematic Review and Meta-analysis of Nonpharmacologic-based Interventions for Aortic Stiffness in End-Stage Renal Disease

Introduction

Increased carotid-femoral pulse wave velocity (cf-PWV) in end-stage renal disease (ESRD) indicates enhanced aortic stiffness and mortality risk. We conducted a systematic review and meta-analysis of nonpharmacologic interventions in adults with ESRD to determine their effects on cf-PWV, systolic blood pressure (SBP), and intervention-associated adverse events.

Methods

MEDLINE, EMBASE, and EBM databases were searched. Study screening, selection, data collection, and methodological quality assessments were performed by 2 independent reviewers. Pooled-effect estimates from mean differences and 95% confidence intervals (CIs) were calculated using random effect models.

Results

A total of 2166 subjects with ESRD from 33 studies (17 randomized; 16 nonrandomized) were included. Four intervention-comparator pairs were meta-analyzed. Quality of evidence ranged from very low to moderate. Kidney transplantation decreased cf-PWV (−0.70 m/s; CI: –1.3 to −0.11; P = 0.02) and SBP (−8.3 mm Hg; CI: −13.2 to −3.3; P < 0.001) over pretransplantation. In randomized trials, control of fluid overload by bio-impedance reduced cf-PWV (−1.90 m/s; CI: −3.3 to −0.5); P = 0.02) and SBP (−4.3 mm Hg; CI: −7.7 to −0.93); P = 0.01) compared with clinical assessment alone. Cross-sectional studies also demonstrated significantly lower cf-PWV and SBP in normovolemia compared with hypervolemia (P ≤ 0.01). Low calcium dialysate decreased cf-PWV (−1.70 m/s; CI: −2.4 to −1.0; P < 0.00001) without affecting SBP (−1.6 mm Hg; CI: −8.9 to 5.8; P = 0.61). Intradialytic exercise compared with no exercise reduced cf-PWV (−1.13 m/s; CI: −2.2 to −0.03; P = 0.04), but not SBP (+0.5 mm Hg; CI: −9.5 to 10.4); P = 0.93).

Conclusions

Several nonpharmacologic interventions effectively decrease aortic stiffness in ESRD. The impact of these interventions on cardiovascular outcomes and mortality risk reduction in ESRD requires further study.

Usefulness of pretransplant aortic arch calcification evaluation for kidney transplant outcome prediction in one year follow-up

Vascular calcification (VC) is linked to post-transplant cardiovascular events and hypercalcemia which may influence kidney graft function in the long term. We aimed to evaluate whether pretransplant aortic arch calcification (AoAC) can predict post-transplant cardiovascular or cerebrovascular events (CVEs), and to assess its association with post-transplant plasma calcium levels and renal function in one-year follow-up. Our single-center observational prospective study enrolled 37 kidney transplant recipients (KTR) without previous history of vascular events. Two radiologists evaluated pretransplant AoAC on chest X-ray as suggested by Ogawa et al. in 2009. Cohen’s kappa coefficient was 0.71. The mismatching results were repeatedly reviewed and resulted in consensus. Carotid-femoral (cfPWV) and carotid-radial pulse wave velocity (crPWV) was measured using applanation tonometry before and one year after transplantation. Patient clinical, biochemical data, and cardiovascular/CVE rate were monitored within 1 year. We found out that eGFR_1year correlated with eGFR_discharge and calcium based on hospital discharge data (β = 0.563, p = .004 and β = 51.360, p = .026, respectively). Multivariate linear regression revealed that donor age, donor gender, and recipient eGFR_discharge (R-squared 0.65, p = .002) better predict eGFR_1year than AoAC combined with recipient eGFR_discharge (R-squared 0.35, p = .006). During 1-year follow-up, four (10.81%) patients experienced cardiovascular events, which were predicted by PWV ratio (HR 7.549, p = .045), but not related to AoAC score (HR 1.044, p = .158). In conclusion, KTR without previous vascular events have quite low cardiovascular/CVE rate within 1-year follow-up. VC evaluated as AoAC on pretransplant chest X-ray together with recipient eGFR_discharge could be related to kidney function in one-year follow-up.

Serum osteoprotegerin is associated with pulse pressure in kidney transplant recipients

Pulse pressure (PP) reflects increased large artery stiffness, which is caused, in part, by arterial calcification in patients with chronic kidney disease. PP has been shown to predict both cardiovascular and cerebrovascular events in various patient populations, including kidney transplant (KTX) recipients. Osteoprotegerin (OPG) is a marker and regulator of arterial calcification, and it is related to cardiovascular survival in hemodialysis patients. Here we tested the hypothesis that OPG is associated with increased pulse pressure. We cross-sectionally analyzed the association between serum OPG and PP in a prevalent cohort of 969 KTX patients (mean age: 51 +/- --13 years, 57% male, 21% diabetics, mean eGFR 51 +/- 20 ml/min/1.73 m2). Independent associations were tested in a linear regression model adjusted for multiple covariables. PP was positively correlated with serum OPG (rho = 0.284, p < 0.001). Additionally, a positive correlation was seen between PP versus age (r = 0.358, p < 0.001), the Charlson Comorbidity Index (r = 0.232, p < 0.001), serum glucose (r = 0.172, p < 0.001), BMI (r = 0.133, p = 0.001) and serum cholesterol (r = 0.094, p = 0.003). PP was negatively correlated with serum Ca, albumin and eGFR. The association between PP and OPG remained significant after adjusting for multiple potentially relevant covariables (beta = 0.143, p < 0.001). We conclude that serum OPG is independently associated with pulse pressure in kidney transplant recipients.

Successful kidney transplantation ameliorates arterial stiffness in end-stage renal disease patients

PURPOSE

Successful kidney transplantation (KTx) can ameliorate bodily damage caused by end-stage renal disease (ESRD). Arterial stiffness (AS) is one of the critical factors that shorten the survival of patients due to cardiovascular events. KTx may reduce AS as well; however, this has not been investigated well. We therefore conducted a retrospective study using noninvasive pulse wave velocity (PWV), which is a useful index of aortic damage.

PATIENTS AND METHODS

Fifty-eight consecutive kidney recipients (34 men, 24 women) were enrolled in this study. Mean age at transplantation was 40.5 ± 12.3 years and the dialysis period was 73.1 ± 95.8 months. The brachial-ankle PWV was measured preoperatively and 6 months postoperatively. First, we investigated the relationship between the PWV and the other parameters related to AS. Second, we studied the pre- to posttransplant change in PWV to evaluate the amelioration of AS after successful KTx.

RESULTS

PWV showed significant positive correlations with age, systolic blood pressure (BP), diastolic BP, and abdominal aortic calcification index. After successful KTx, PWV significantly decreased (P < .01). In addition, systolic and diastolic BP significantly decreased (P < .01 and P < .05, respectively).

CONCLUSION

Successful KTx ameliorates AS in ESRD patients. This might explain the improved cardiovascular prognosis of ESRD patients who undergo KTx.

Vascular compliance in blood pressure

PURPOSE OF REVIEW

Vascular stiffening is a hallmark of the aging process. Improvements in the methods used to measure central stiffness, particularly applanation tonometry, and their use as therapeutic targets have generated great interest.

RECENT FINDINGS

Vascular stiffness is associated with increases in pulse pressure (PP), aortic augmentation index, and pulse wave velocity (PWV). This last has emerged as the gold standard for evaluation of vascular stiffness, as it is an independent predictor of coronary heart disease, stroke, and mortality. Angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and calcium-channel blockers with or without diuretics are all commonly used to ameliorate vascular stiffness; however, selective β-1 blockers (β-blockers) may actually worsen aortic PP and aortic augmentation index.

SUMMARY

Serial measurements of vascular stiffness, including PWV, augmentation index, and PP, may be especially beneficial in older patients to supplement brachial blood pressure. At present, given the lack of universally accepted normal values for vascular stiffness as measured by applanation tonometry, serial measurements over time may be more helpful than a single isolated value. In patients with suspected vascular stiffening, therapy should include inhibition of the renin-angiotensin-aldosterone system with ACE inhibitors or ARBs, calcium-channel blockers, and diuretics as needed to normalize blood pressure. β-Blockers should be reserved for patients with a history of myocardial infarction or congestive heart disease. It remains to be established whether β-blockers with vasodilator properties could improve the assessment of vascular compliance.