Association between mortality and abdominal aortic calcification and their progression in hemodialysis patients

Recent reports suggest that cardiovascular (CV) events are associated with vascular calcification (VC) on plain radiographs. Kidney Disease Improving Global Outcomes (KDIGO) recommends that lateral abdominal radiography can be used to detect the presence or absence of VC [1]. A previous report showed that an abdominal aortic calcification (AAC) score of Z7 on lateral abdominal radiography was well correlated with a coronary artery calcium score of Z100 on electron beam computed tomography [2]. Another report showed that the middle to highest tertile AAC score of Z5 was associated with an increased risk of CV events compared with the lowest tertile AAC score of o5 in dialysis patients [3]. Recently, Kwon et al [4] showed that an AAC score of 48 predicted higher mortality and CV events in hemodialysis patients. I fully understand the authors’ opinion to determine a cut-off value of 8 based on the data of mortality. However, optimal AAC score cutoff values for CV events should be slightly lower than cutoff values for mortality because CV events frequently occur and are an important issue related to morbidity, such as intradialytic hypotension in hemodialysis patients. The authors reported that AAC progression was found in 68% of patients with a follow-up duration of 3 years. VC on plain radiographs definitely progresses, and the progression of aortic calcification on plain radiographs is also related to an increased risk of mortality in dialysis patients. Approximately one-third of dialysis patients show VC progression on plain chest X-rays within 1–2 years compared to baseline [5]. To acquire more information regarding the harmful impact of AAC progression, I would like to suggest that the authors should precisely define AAC progression such as increases of AAC score and evaluate the risk of CV events or mortality according to AAC progression. Additionally, the authors proved that corrected serum calcium concentration was partially related to AAC progression. As the authors mentioned [4], evaluations of total calcium load and total dose of active vitamin D supplementation resolve the questions about the effect of calcium on AAC progression and help clinical practice. Nevertheless, this study supports that monitoring of VC progression by following plain radiography is a cost-effective tool for quality care of dialysis patients.