I have had type 1 diabetes for 28 years, my control is reasonable (last hemoglobin A1c was 7.4%), and except for more and more problems with recognizing hypoglycemia and some microalbuminuria, I am doing okay. However, recently I noticed that my heart rate at rest rarely goes below 90 (it used to be between 60 and 70). What is this?

The autonomic nervous system has control of the pacemaker of the heart. There is a sympathetic innervation and a parasympathetic innervation. When neuropathy occurs, one of the manifestations can be loss of parasympathetic innervation into the pacemaker of the heart. This leaves an individual with unopposed sympathetic innervation and an increased resting heart rate.

Other things to check would include an electrocardiogram, in order to rule out a primary irregular heart rhythm. I would also make sure you do not have any silent injury to the heart from undiagnosed coronary artery disease. This can be screened with an electrocardiogram but would be better tested by performing an exercise stress test. Another thing to rule out is hyperthyroidism.

JTL