P86
Differences in Augmentation Index Between Different aetiologies of Chronic
Kidney Disease
Thilini Abeygunaratne, Darren Green, Jim Ritchie, Diana Chiu, Philip A. Kalra.
Salford Vascular Research Group, University of Manchester, United Kingdom.
Background
Chronic kidney disease (CKD) is associated with increased vascular stiffness. This
can be defined by pulse wave velocity and augmentation index (AIx), is
independently associated with all cause mortality and cardiovascular mortality. This
study aims to consider if AIx varies by cause of CKD.
Method
360 patients with AIx measured by pulse wave analysis were selected from the
Chronic Renal Insufficiency Standards Implementation Study (CRISIS) study, a
prospective study of outcome in patients with CKD 3-5. Primary cause of CKD was
assigned by notes review. Heart rate adjusted AIx was assessed against primary
disease as a binary variable (above/below median) using the Chi-squared test and as a
continuous variable using student’s t-test.
Results
At the time of AIx measurement meanSD age was 6612 years, eGFR 3014
ml/min/1.73 m2. 65% of patients were male. 27% had diabetic nephropathy, 13% IgA
nephropathy, 14% autosomal dominant polycystic kidney disease (ADPKD) and 46%
renovascular/hypertensive renal disease. Median AIx was 24.
For each primary disease a different proportion of patients had a measured AIx above
the median - diabetes 36%, IgA 55%, APKD 65% and vascular 53%, p between
groups = 0.004.
When individual primary diseases were compared to the other primary disease in
combination the most significant differences was observed using diabetic nephropathy
as the referent (36% vs. 52% above median AIx p=0.003). This difference persisted
when AIx was considered as a continuous variable (218 vs. 249 p=0.001). Patients
with diabetic nephropathy were generally comparable to the remainder of the study
population: age 54 vs.57 years p=0.9, systolic blood pressure, 134 22mmHg vs.
13521 mmHg p=0.6; diastolic blood pressure 689 mmHg vs. 7111 mmHg p=0.02,
despite having a lower eGFR 2611 ml/min/1.73 m2 vs. 3316 ml/min/1.73 m2,
p<0.001.
Discussion
The study suggests primary disease may confound measurements of vascular stiffness
in CKD. Also, a major confounder that would need to be considered is the effect of
different classes of drugs. Further study is required to validate this finding.