Novelty Statement. (i) The present study shows the efficacy and safety of treatment with angiotensin converting enzyme (ACE) inhibitors in patients with cardiovascular autonomic neuropathy (CAN), especially in patients with type 2 diabetes mellitus at early stages of the disease, in whom coronary heart disease and hypertension are much more common than in type 1 diabetes mellitus. Here, ACE is linked to type 1 diabetes mellitus.