Indoxyl Sulfate, Cardiac Biomarkers, and Left Ventricular Wall Thickening in Cats with Chronic Kidney Disease

Factors associated with left ventricular wall thickening (LVWT) in cats with chronic kidney disease (CKD) remain unclear. This prospective observational study compared renal variables, systolic blood pressure (SBP), echocardiographic measurements, cardiac biomarkers, and uremic toxins in 31 cats: 12 with CKD without LVWT, 8 with CKD and LVWT, and 11 healthy controls. LVWT was defined as IVSd and/or LVPWd ≥ 6 mm in at least two of three examinations. IRIS stage distribution did not differ between the CKD groups (p = 1.000). Urea, creatinine, and phosphorus concentrations were higher in both CKD groups than in controls but were similar between CKD groups. SBP, NT-proBNP, and cardiac troponin I concentrations were highest in the CKD-LVWT group (p < 0.001). Plasma indoxyl sulfate concentrations were significantly higher in the CKD-LVWT group than in both other groups, whereas serum p-cresyl sulfate concentrations did not differ between CKD groups. However, SBP was markedly higher in the CKD-LVWT group and represents a major potential confounder. However, because SBP was also higher in the CKD-LVWT group and reliable multivariable adjustment could not be performed, the independent contribution of indoxyl sulfate could not be determined. The observed association may have been influenced by systemic hypertension, CKD stage, antihypertensive treatment and adherence, and other potential confounders and should not be interpreted as independent or causal.