Pre-Transplant Assessment of Vascular Calcification as a Risk Factor of Mortality, Graft Loss, and Cardiovascular Events in Renal Transplant Recipients

Systematic, Pretransplant Screening by Aortoiliac CT Angiography: Impact on Surgical Decision-making and Clinical Outcomes

Background

Aortoiliac screening before kidney transplantation is suggested by some guidelines to select patients for transplantation and to assist surgical planning. We investigated the clinical outcomes of systematic screening for aortoiliac disease in potential kidney transplant candidates.

Methods

In this observational study, 470 potential kidney transplant candidates underwent aortoiliac computed tomography angiography. Patients were characterized by the presence of peripheral artery disease and calcification of iliac arteries and aortoiliac arteries. The risk of graft loss and graft function at 1 y posttransplant were examined and clinical decisions based on the vascular findings were assessed.

Results

Clinically diagnosed peripheral artery disease was present in 66 patients (14%), circular calcifications in 101 patients (21%), and aortoiliac stenosis in 77 patients (16%). In 326 patients undergoing kidney transplantation, circular calcification or aortoiliac stenosis was not associated with an increased risk of graft loss (P = 0.45 and P = 0.28) or estimated glomerular filtration rate (P = 0.23 and P = 0.76) at 1 y posttransplant. When evaluated for transplantability, clinical decision-making based on vascular findings was recorded in 67 of 429 patients (16%), including rejection for transplantation in 7 patients (2%) and laterality for surgical implantation in 52 patients (12%).

Conclusions

Systematic screening by aortoiliac computed tomography angiography may assist in surgical planning but seems of limited clinical value in assessing the risk of future graft loss and graft function in patients undergoing kidney transplantation.

Ipsilateral Aorto-Iliac Calcification is Not Directly Associated With eGFR After Kidney Transplantation: A Prospective Cohort Study Analyzed Using a Linear Mixed Model

Aorto-iliac calcification (AIC) is a well-studied risk factor for post-transplant cardiovascular events and mortality. Its effect on graft function remains unknown. The primary aim of this prospective cohort study was to assess the association between AIC and estimated glomerular filtration rate (eGFR) in the first year post-transplant. Eligibility criteria were: ≥50 years of age or ≥30 years with at least one risk factor for vascular disease. A non-contrast-enhanced CT-scan was performed with quantification of AIC using the modified Agatston score. The association between AIC and eGFR was investigated with a linear mixed model adjusted for predefined variables. One-hundred-and-forty patients were included with a median of 31 (interquartile range 26-39) eGFR measurements per patient. No direct association between AIC and eGFR was found. We observed a significant interaction between follow-up time and ipsilateral AIC, indicating that patients with higher AIC scores had lower eGFR trajectory over time starting 100 days after transplant (p = 0.014). To conclude, severe AIC is not directly associated with lower post-transplant eGFR. The significant interaction indicates that patients with more severe AIC have a lower eGFR trajectory after 100 days in the first year post-transplant.

Gender-Related Differences in Chronic Kidney Disease-Associated Vascular Calcification Risk and Potential Risk Mediators: A Scoping Review

Vascular calcification (VC) involves the deposition of calcium apatite in vascular intima or media. Individuals of advanced age, having diabetes mellitus or chronic kidney disease (CKD) are particularly at risk. The pathogenesis of CKD-associated VC evolves considerably. The core driver is the phenotypic change involving vascular wall constituent cells toward manifestations similar to that undergone by osteoblasts. Gender-related differences are observed regarding the expressions of osteogenesis-regulating effectors, and presumably the prevalence/risk of CKD-associated VC exhibits gender-related differences as well. Despite the wealth of data focusing on gender-related differences in the risk of atherosclerosis, few report whether gender modifies the risk of VC, especially CKD-associated cases. We systematically identified studies of CKD-associated VC or its regulators/modifiers reporting data about gender distributions, and extracted results from 167 articles. A significantly higher risk of CKD-associated VC was observed in males among the majority of original investigations. However, substantial heterogeneity exists, since multiple large-scale studies yielded neutral findings. Differences in gender-related VC risk may result from variations in VC assessment methods, the anatomical segments of interest, study sample size, and even the ethnic origins of participants. From a biological perspective, plausible mediators of gender-related VC differences include body composition discrepancies, alterations involving lipid profiles, inflammatory severity, diversities in matrix Gla protein (MGP), soluble Klotho, vitamin D, sclerostin, parathyroid hormone (PTH), fibroblast growth factor-23 (FGF-23), and osteoprotegerin levels. Based on our findings, it may be inappropriate to monotonously assume that male patients with CKD are at risk of VC compared to females, and we should consider more background in context before result interpretation.

Utility of a Simplified Iliac Artery Calcium Scoring System to Guide Perioperative Management for Renal Transplantation

Non-contrast computed tomography scans of the abdomen and pelvis (CTAP) are often obtained prior to renal transplant to evaluate the iliac arteries and help guide surgical implantation. The purpose of this study was to describe the association of iliac calcification scores with operative and clinical outcomes using a simplified scoring system. A retrospective review of 204 patients who underwent renal transplant from 1/2013 to 11/2014 and who had a CTAP within 3 years prior to transplant was performed. Data were collected from the electronic medical record. Common iliac artery (CIA) and external iliac artery (EIA) calcification on CTAP were assessed using a simple scoring system. Descriptive statistics, logistic regression, and survival analyses were performed. A total of 204 patients were included in the analysis. The mean age was 57.4 ± 11.2 years and 134/204 (66%) were men. Nineteen patients (9%) had a history of peripheral artery disease (PAD), 78 (38%) had coronary artery disease, and 22 (11%) had a previous cerebrovascular accident (CVA). Patients with severe right EIA plaque morphology were significantly more likely to require arterial reconstruction compared to those without severe plaque (3/14[21%] 4/153 [3%], p = 0.03). Eleven patients (5%) had one or more amputations (toe, foot, or transtibial) following transplant. In UV logistic regression, severe EIA plaque morphology (OR 8.1, CI 2.2–29.6, p = 0.002) and PAD (OR 10.7, CI 2.8–39.9, p = 0.0004) were associated with increased odds of amputation. In the MV model containing both variables, EIA plaque morphology (OR 4.4, CI 0.99–18.3, p = 0.04) and PAD (OR 6.3, CI 1.4–26.4, p = 0.01) remained independently associated with increased odds of amputation. Over a median follow up of 3.3 years (IQR 2.9–3.6), 21 patients (10%) had post-operative major adverse cardiac events (MACE, defined as myocardial infarction, coronary intervention, or CVA), and 23 patients died (11%). In unadjusted Kaplan Meier analysis, CIA plaque (p = 0.00081) and >75% CIA length calcification (p = 0.0015) were significantly associated with MACE. Plaque burden in the EIA is associated with increased need for intra-operative arterial reconstruction and post-operative lower extremity amputations, while CIA plaque is associated with post-operative MACE. Assessment of CIA and EIA calcification scores on pre-transplant CT scans in high risk patients may guide operative strategy and perioperative management to improve clinical outcomes.

Prognostic Value of Abdominal Aortic Calcification: A Systematic Review and Meta-Analysis of Observational Studies

Background The prognostic importance of abdominal aortic calcification (AAC) viewed on noninvasive imaging modalities remains uncertain. Methods and Results We searched electronic databases (MEDLINE and Embase) until March 2018. Multiple reviewers identified prospective studies reporting AAC and incident cardiovascular events or all-cause mortality. Two independent reviewers assessed eligibility and risk of bias and extracted data. Summary risk ratios (RRs) were estimated using random-effects models comparing the higher AAC groups combined (any or more advanced AAC) to the lowest reported AAC group. We identified 52 studies (46 cohorts, 36 092 participants); only studies of patients with chronic kidney disease (57%) and the general older-elderly (median, 68 years; range, 60-80 years) populations (26%) had sufficient data to meta-analyze. People with any or more advanced AAC had higher risk of cardiovascular events (RR, 1.83; 95% CI, 1.40-2.39), fatal cardiovascular events (RR, 1.85; 95% CI, 1.44-2.39), and all-cause mortality (RR, 1.98; 95% CI, 1.55-2.53). Patients with chronic kidney disease with any or more advanced AAC had a higher risk of cardiovascular events (RR, 3.47; 95% CI, 2.21-5.45), fatal cardiovascular events (RR, 3.68; 95% CI, 2.32-5.84), and all-cause mortality (RR, 2.40; 95% CI, 1.95-2.97). Conclusions Higher-risk populations, such as the elderly and those with chronic kidney disease with AAC have substantially greater risk of future cardiovascular events and poorer prognosis. Providing information on AAC may help clinicians understand and manage patients' cardiovascular risk better.

Aorto-Iliac Artery Calcification and Graft Outcomes in Kidney Transplant Recipients

While the association of vascular calcification with inferior patient outcomes in kidney transplant recipients is well-established, the association with graft outcomes has received less attention. With this dual-centre cohort study, we aimed to determine the clinical impact of recipient pre-transplant aorto-iliac calcification, measured on non-contrast enhanced computed tomography (CT)-imaging within three years prior to transplantation (2005-2018). We included 547 patients (61.4% male, age 60 (interquartile range 51-68) years), with a median follow-up of 3.1 (1.4-5.2) years after transplantation. The aorto-iliac calcification score (CaScore) was inversely associated with one-year estimated-glomerular filtration rate (eGFR) in univariate linear regression analysis (standard β -3.3 (95% CI -5.1 to -1.5, p < 0.0001), but not after adjustment for potential confounders, including donor and recipient age (p = 0.077). In multivariable Cox regression analyses, a high CaScore was associated with overall graft failure (p = 0.004) and death with a functioning graft (p = 0.002), but not with death-censored graft failure and graft function decline. This study demonstrated that pre-transplant aorto-iliac calcification is associated with one-year eGFR in univariate, but not in multivariable linear regression analyses. Moreover, this study underlines that transplantation in patients with a high CaScore does not result in earlier transplant function decline or worse death censored graft survival, although ongoing efforts for the prevention of death with a functioning graft remain essential.

The prognosis of kidney transplant recipients with aorto-iliac calcification: a systematic review and meta-analysis

The prognosis of kidney transplant recipients (KTR) with vascular calcification (VC) in the aorto-iliac arteries is unclear. We performed a systematic review and meta-analysis to investigate their survival outcomes. Studies from January 1st, 2000 until March 5th, 2019 were included. Outcomes for meta-analysis were patient survival, (death-censored) graft survival and delayed graft function (DGF). Twenty-one studies were identified, eight provided data for meta-analysis. KTR with VC had a significantly increased mortality risk [1-year: risk ratio (RR) 2.19 (1.39-3.44), 5-year: RR 2.28 (1.86-2.79)]. The risk of 1-year graft loss was three times higher in recipients with VC [RR 3.15 (1.30-7.64)]. The risk of graft loss censored for death [1-year: RR 2.26 (0.58-2.73), 3-year: RR 2.19 (0.49-9.82)] and the risk of DGF (RR 1.24, 95% CI 0.98-1.58) were not statistically different. The quality of the evidence was rated as very low. To conclude, the presence of VC was associated with an increased mortality risk and risk of graft loss. In this small sample size, no statistical significant association between VC and DGF or risk of death-censored graft loss could be demonstrated. For interpretation of the outcomes, the quality and sample size of the evidence should be taken into consideration.

Incidental Coronary Artery Calcification Seen on Low-Dose Computed Tomography Is a Risk Factor for Obstructive Coronary Artery Disease in Patients Undergoing Liver Transplant

Incidental arterial calcification (Ca) on low-dose computed tomography (CT) prior to liver transplant (LT) may help identify those at risk for obstructive coronary artery disease (CAD). A single-center retrospective study of 358 consecutive patients who had undergone LT was performed. Of the 296 patients who met inclusion criteria, 193 patients (65.2%) had CT Ca. Aortic Ca was seen in 116 (39.2%), coronary Ca in 141 (47.6%), and peripheral Ca in 8 patients (2.7%). Patients with coronary Ca were assigned ordinal coronary artery Ca scores and classified as mild, moderate, and severe. All-cause mortality was higher in patients with Ca in any location (14.5% vs 6.8%, P = .05). Of the patients who underwent coronary angiography, those with obstructive CAD were more likely to have aortic and coronary Ca than patients with nonobstructive or no CAD (85.7% vs 50.0%, P = .02 and 92.9% vs 37.9%, P = < .001, respectively). Severe coronary artery Ca scores were more frequent in patients with obstructive CAD (35.7% vs 0%, P < .001). Any severity coronary Ca had an odds ratio of 11.57 (95% CI, 1.61-244.92; P = .04) for obstructive CAD. In conclusion, incidental coronary Ca seen on low-dose CT is a risk factor for obstructive CAD in patients undergoing LT.

Abdominal aorta and pelvic artery calcifications on plain radiographs may predict mortality in chronic kidney disease, hemodialysis and renal transplantation

PURPOSE

Vascular calcification is common in chronic kidney disease (CKD) and predicts poor patient outcomes. While computed tomography is the gold standard for evaluation of vascular calcification, plain radiograph offers a simpler and less costly alternative. The calcification of abdominal aorta, iliac and femoral arteries has been evaluated by plain radiograph, but the data on their outcome predictabilities are still limited. The present study investigated the role of abdominal aortic calcification (AAC) and pelvic arterial calcification (PAC) in predicting overall morality in non-dialysis CKD stages 2-5 (CKD 2-5), maintenance hemodialysis (HD) and long-term kidney transplant (KT) patients.

METHODS

Four hundred and nineteen patients were included. Lateral abdominal and pelvic radiographs were obtained. The degree of AAC and PAC was evaluated according to the methods described previously by Kaupplia et al. and Adragao et al. Patients were followed prospectively for 5 years.

RESULTS

AAC and PAC scores correlated well with the correlation coefficients of 0.442 for CKD 2-5, 0.438 for HD and 0.586 for KT (p < 0.001). Patients with AAC score > 6 or PAC score > 1 were older, showed higher prevalence of DM and had higher serum phosphate and PTH but lower serum albumin and eGFR. A more severe degree of AAC was associated with an increase in KT duration, whereas a more severe degree of PAC was associated with worsening kidney function and prolonged dialysis vintage. Kaplan-Meier survival curves revealed AAC score > 6 as a significant predictor of all-cause mortality in CKD 2-5 but not in HD or KT, whereas PAC score > 1 was a significant predictor of all-cause mortality in all three populations. After adjusting for age, the predictability of AAC was lost, whereas PAC remained an independent predictor of mortality in all three populations. Adjustments for cardiovascular and CKD risk factors including age, gender, BMI, DM, serum albumin, calcium and phosphate attenuated the predictability of PAC in HD but not in CKD 2-5 or KT patients.

CONCLUSION

PAC was better than AAC in predicting mortality in CKD, HD and KT patients.