The R-R interval study is a simple, affordable test of the vagus nerve, and it should be part of your intial diabetes physical examination. It is performed like an ordinary EKG, but with only 3 leads.
The vagus nerve is the main control of the “automatic pilot” nervous functions, including heart rate and digestion. It can be injured by chronic high blood sugar, causing reduced stomach activity (gastroparesis), rapid heart rate and erection problems. Fortunately it can recover from normalizing your blood sugar.
The R-R Study tests the variation in your heart rate between inhaling and exhaling. It is a good indicator of blood sugar complications, especially gastroparesis, and more importantly, it shows improvement after aggressive blood sugar control. I usually perform it once on all new patients and later after 12-18 months.