24 Apr Diabetes: Nocturnal Hypoglycemia and Risk of Cardiac Arrhythmias
MedicalResearch.com: What are the main findings of the study?
Prof. Heller: We explored the potential to hypoglycaemia to cause cardiac arrhythmias since we have previously shown that a low glucose can alter the electrocardiogram. We had a hypothesis that alterations in heart rhythm or ectopic beats might contribute to cardiac mortality and in part explain the association between intensive diabetic therapy and increased mortality. We therefore undertook continuous glucose monitoring and 12 lead EKG monitoring for a period of 5 days in individuals with Type 2 diabetes at increased CV risk. We found that hypoglycaemia was fairly common and that nocturnal episodes in particular, were generally marked by a pattern whereby glucose levels dropped to low levels for some hours during which patients slept. These periods of hypoglycemia were associated with a high risk of marked slow heart rates (bradycardia) accompanied by ectopic beats. Our data suggest that this was due to overactivity of the vagus nerve. We have therefore identified a mechanism which might contribute to increased mortality in individuals with Type 2 diabetes and high CV risk during intensive insulin therapy.
MedicalResearch.com: Were any of the findings unexpected?
Prof. Heller: We were surprised to see how common, prolonged episodes of hypoglycaemia were in these patients with type 2 diabetes and that these were symptomatic (i.e. patients slept through them) although such a pattern has been described in people with type 1 diabetes, particularly children. We also didn’t expect to see these very slow heart rates during nocturnal hypoglycaemic episodes.
MedicalResearch.com: What should clinicians and patients take away from your report?
Prof. Heller: There should be no undue cause of alarm among patients. These slow heart rates while a cause for concern, were not in this study associated with any very serious heart rhythms. However it does suggest that even those with standard insulin therapy and who are not aiming for intensive glucose targets should be aware of the risk of running low overnight (particularly if they have known cardiovascular disease), perhaps check their blood glucose in the middle of the night every now and then and work with their doctor to either change insulin dose timing or type to minimize the risk of prolonged episodes of hypoglycemia overnight.
Clinicians responsible for the care of insulin treated patients with type 2 diabetes need to be more aware of the potential for prolonged nocturnal episodes of hypoglycemia at night to check for it and alter therapy to reduce the risk especially for those who have known CV disease.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Prof. Heller: More research of this type needs to be undertaken, with larger numbers, perhaps with Holter monitoring to see how common these abnormal heart rates and rhythms are occurring in people with type 2 diabetes at CV risk. More studies of the effect of hypoglycaemia on nerve function affecting the heart (autonomic nervous system) should also be undertaken, particularly in patients with diabetes.