Sympathectomy also results in reduced heart rate variability

"Cardiovascular autonomic neuropathy (CAN) is the most prominent focus because of the life-threatening consequences and the availability of direct tests of cardiovascular autonomic function.. .CAN results from damage due to the autonomic nerve fibers that innervate the heart and blood vessels and results in abnormalities in heart rate control and vascular dynamics. Reduced heart variation is the earliest indicator of CAN."

"CAN is the most studied and clinically important form of DAN. Meta-analyses of published data demonstrate that reduced cardiovascular autonomic function as measured by heart rate variability (HRV) is strongly associated with an increased risk of silent myocardial ischemia and mortality. The determination of the presence of CAN is usually based on a battery of autonomic function tests..."

TECHNICAL REVIEW: Standard of Care - Diabetic Autonomic Neuropathy

Aaron I. Vinik, MD, PHD; Braxton D. Mitchell, PHD
Raelene E. Maser, PHD; Roy Freeman, MD