Abstract 1132: Early Detection of Cardiovascular Autonomic Neuropathy Using Exercise Testing in Patients with Type 2 Diabetes Mellitus
Cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes mellitus (DM2) is associated with higher mortality and sudden death. CAN is diagnosed using various maneuvers at rest (R) but not exercise (Ex). Hypothesis: In patients with DM2 without prior CAN, Ex testing will identify abnormal parasympathetic (PS) reactivation after Ex with abnormalities in repolarization dynamics. 13 DM2 subjects without peripheral neuropathy or CAN (9 male, age 56±9 yrs, HbA1c 6.4±0.7%, DM2 duration 6±4 yrs) and 20 controls (8 male, age 50±6 yrs) underwent 16 min submaximal bicycle Ex testing, with and without PS blockade with atropine 0.04mg/kg, followed by 45 min recovery (Rec). Norepinephrine levels (NE), RR, and QT intervals (to peak [QTp] and end [QTe] of T wave) were measured. PS effect in Rec was measured as ΔRR=difference between RR intervals with and without atropine. QT dispersion was measured as QTpe=Qte−QTp. DM2 subjects had higher heart rates at R (79±11 vs 70±3 bpm, p=0.03) and Rec (p<0.0001) but not at peak Ex (132±24 bpm vs 123±10 bpm). In DM2, ΔRR was lower during Rec (p<0.0001; Figure⇓). DM2 had lower HRR (10.1±4.9 vs 14.8±4.4 bpm, p=0.02) and NE was consistently higher at R, Ex, and Rec (Peak NE 1508±473 vs 1073±348 pg/mL, p=0.01). There was no difference in QTc, but QTpe was consistently smaller in DM2 during R, Ex, and Rec (p<0.01)-45 min QTpe 64±8 ms vs 72±14 ms. Ex testing in DM2 uncovers autonomic abnormalities earlier than standard CAN testing. Given the associated effects on cardiac repolarization dynamics, further work is necessary to elucidate its prognostic significance and whether early interventions are warranted.