SP341
EFFECTS OF DECLINE IN RENAL FUNCTION ON CARDIAC AND VASCULAR AUTONOMIC CONTROL IN PATIENTS WITH CKD 4-5

Introduction and Aims: Increased risk of arrhythmias and lack of nocturnal blood pressure dipping, both due to loss of autonomic function, play an important role in the increased cardiovascular morbidity and mortality in patients with CKD. The aim of this study was to analyse the effects of a decline in GFR on vascular and cardiac autonomic function, as determined by heart rate variability (HRV) indices and nocturnal blood pressure dipping, in patients with CKD 4 -5.

Methods: Data was obtained from 123 patients (45 women, 78 men; age 66±14 years) with CKD 4-5, who volunteered to participate in the study. GFR was measured with iohexol clearance. Time domain indexes of HRV, as standard deviation of N-N intervals (SDNN) and root mean square of N-N intervals (rMSSD), were measured with 24-hour Holter ECG. Nocturnal dipping was measured with 24-hour ambulatory blood pressure monitoring.

Results: The measured GFR was 22.5±8.6ml/min/1.73 sqm. Multivariable regression analysis revealed a significant association between GFR < 31ml/min/1.73 sqm and SDNN (p=0.01), a marker of sympathovagal balance, after sex, age and diabetes mellitus had been accounted for. Moreover, a significant association between nocturnal systolic blood pressure dipping and GFR <16ml/min/1.73 sqm (p=0.03) was found.

Both SDNN and nocturnal systolic blood pressure dipping showed curvilinear relationships with GFR. The effect of diabetes mellitus on SDNN corresponded to a decline in GFR from 30 to 12 ml/min/1.73 sqm. The effect of diabetes mellitus on nocturnal systolic blood pressure dipping corresponded to a decline in GFR from 30 to 8 ml/min/1.73 sqm.

Conclusions: Autonomic neuropathy seems to occur gradually in CKD with cardiac sympathetic overdrive and loss of vagal control appearing as patients reach CKD 4 and loss of nocturnal systolic blood pressure dipping as patients reach CKD 5.

An earlier deterioration is observed in diabetic patients.

These defined thresholds have clinical implications. They can serve as markers for introducing interventions that influence cardiovascular morbidity and mortality in the different stages of CKD.