Vascular Calcification in End-Stage Renal Disease

Among patients with end-stage renal disease (ESRD), low leg bone mineral density (BMD) has been linked to more significant vascular calcification, according to research published in the Journal of Bone Mineral Metabolism.

Abdul Rashid Qureshi, MD, of the Karolinska Institutet at Karolinska University Hospital in Stockholm, Sweden, and colleagues conducted a prospective cohort study of adult patients with ESRD. A total of 66 patients were assessed to determine the link between low BMD, coronary artery calcium (CAC) scores, and signs of vascular calcification.

The study cohort (median age 45 years; 68% male) was divided into 2 subgroups based on patients’ median total body BMD (tBMD); 26% of patients had a T-score between −1.0 and −2.5 (osteopenia) and 7% had a T-score ≤ −2.5 (osteoporosis). Patients with lower-than-median tBMD scores (≤1.127 g/cm²; n=33) were more often women with lower BMI, lean BMI, creatinine and phosphate, and higher levels of cholesterol, high-density lipoprotein cholesterol, 25(OH)-vitamin D, and 1,25(OH)₂-vitamin D compared with patients with higher-than-median tBMD scores.

Of the patients who underwent coronary artery calcification measurements — assessed via CT scan — 28% had CAC scores of >100 AUs. The researchers reported “no clinically meaningful significant differences” in demographic or biochemical traits between patients who did and did not undergo CT scans.

Of the patients who were examined, 31% had calcification scores of 2 or 3, indicating moderate to extensive vascular calcification. Significant differences in gender, albumin, calcium, and systolic blood pressure were noted among patients who underwent vascular biopsy vs those who did not. The investigators found that leg and pelvic BMD measurements (1.25 vs 1.03 g/cm²; P =.01 and 0.99 vs 0.87 g/cm²; P =.01, respectively) were “significantly lower” in patients with extensive vascular calcification; arm and femoral neck BMD measurements were not significantly higher or lower among patients with extensive vs no or moderate vascular calcification (0.80 vs 0.75 g/cm²; P =.07 and 0.93 vs 0.84 g/cm²; P =.06, respectively).

After adjusting for age and gender, the analysis showed that higher BMD in arms (odds ratio [OR]: 0.25; 95% CI, 0.07-0.93; P =.04) and legs (OR: 0.33; 95% CI, 0.13-0.87, P =.03) could be linked to extensive vascular calcification. Additionally, CAC scores differed based on the patient’s degree of vascular calcification, with significantly higher CAC scores found in patients with extensive vascular calcification (score 3).

“Although BMD and [vascular calcification] have been shown to be pathogenically connected, the pathogenic mechanism(s) remain unclear,” the researchers wrote. “There is no consensus as to which specific bone location should be used for measurement of BMD when studying relationships between BMD and [vascular calcification].”

Study Limitations

• Due to the observational nature of the study, no conclusions regarding causality can be drawn.
• Due to selection bias criteria, these findings cannot be applied to other groups of patients with ESRD.
• Use of CT scan for CAC measurement does not allow researchers to differentiate between medial and intimal calcification.

Disclosures: Dr Lindholm is an employee of Baxter Healthcare.

Reference

Chen Z, Sun J, Haarhaus M, et al. Bone mineral density of extremities is associated with coronary calcification and biopsy-verified vascular calcification in living-donor renal transplant recipients [Published online December 2, 2016]. J Bone Miner Metab. doi:10.1007/s00774-016-0788-1