Importance of Cardiovascular Autonomic Dysfunction in IDDM Subjects With Diabetic Nephropathy

Diabetic nephropathy (DNP) is associated with increased cardiovascular mortality. This may be contributed to by associated cardiovascular autonomic dysfunction (CAD). The aim of this study was to investigate the prevalence of CAD in patients with insulin-dependent diabetes mellitus (IDDM) at different stages of DNP. We studied patients with incipient DNP (group 1, n = 10), overt DNP (group 2, n = 20), renal insufficiency (group 3, n = 27), and end-stage renal failure (group 4, n = 12) and compared them with 30 IDDM patients without clinical signs of DNP (group 5) and with 17 nondiabetic controls (group 6). All groups were matched for age and diabetic groups were matched for duration of diabetes. Assessments of CAD included beat-to-beat variation during forced respiration, heart-rate response to standing, heart-rate response to Valsalva maneuver, basal heart rate, and blood pressure response to standing. Clinical evaluation included assessment of the history and an examination for peripheral polyneuropathy. We found mean impairment of heart-rate variation during respiration, in response to Valsalva maneuver, and in heart-rate response to standing in all diabetic groups compared with nondiabetic controls (P < .01). Heart-rate responses differed significantly between patients with renal insufficiency (groups 3 and 4) and with other patient groups (group 5; P < .01). CAD was shown to be more prevalent in patients with DNP, more so as DNP progresses. To some extent, it is already present in the early stages of DNP. CAD may be a contributory factor for increased cardiovascular mortality in patients with DNP. Patients with incipient DNP should be followed prospectively, with respect to CAD, to further elucidate their relationship and the impact on cardiovascular mortality.