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Nocturnal Hypoglycemia May Increase Arrhythmia Risk in Type 2 Diabetes
May 5, 2014 (Healio) Nocturnal hypoglycemia may be linked to bradycardia, atrial ectopic activity and other cardiac arrhythmia in patients with type 2 diabetes, according to recent study findings.
"What we've found is potentially important in explaining a possible mechanism by which low overnight blood sugars lead to prolonged, slow heart rates that could disturb blood flow to the heart, causing life-threatening heart attacks Simon Heller, DM, FRCP, professor of clinical diabetes and honorary consultant physician at Sheffield Teaching Hospitals NHS Foundation Trust in the United Kingdom, said in a press release. "While we expected to find some low overnight blood sugars, we were startled to find how extensively it was occurring overnight and that it was sometimes lasting for several hours. When this occurred, we also saw evidence of prolonged periods of very slow heart rate rhythms in patients."
This observational study included 25 patients recruited from diabetes outpatient clinics at Sheffield Teaching Hospitals. These participants were on insulin treatment for at least 4 years and had a history of cardiovascular disease and/or to additional CV risk factors, according to the study. After a baseline assessment, patients participated in 5 days of concurrent heart and continuous glucose monitoring.
Fourteen patients experienced at least one episode of hypoglycemia, 10 of which were nocturnal, but only three of which were reported as symptomatic. Researchers found that these nocturnal episodes were "prolonged" (170 ± 112 minutes vs. 62 ± 42 minutes for episodes during the day) and had a lower glucose nadir (1.9 ± 0.7 mmol/L vs. 2.8 ± 0.5 mmol/L) with undulating profiles, as opposed to a straight descent. The researchers attributed this undulation to "repeated counterregulatory attempts to resist the glucose-lowering effects of injected insulin."
Nocturnal heart rates dropped as low as 34 bpm and bradycardia was eightfold higher during nocturnal hypoglycemia (incident rate ratio [IRR]=8.42; 95% CI, 1.4-51.01). Atrial ectopic activity was almost fourfold higher during nocturnal hypoglycemia (IRR=3.98; 95% CI, 1.1-14.4). "The occurrence of bradycardia may be linked to increased vagal counteraction after sympathetic neural activation," the researchers wrote.
"Clinicians responsible for the care of patients using insulin to treat type 2 diabetes need to be more aware of the potential for prolonged nocturnal episodes of hypoglycemia at night," Heller said. "They need to check for it and alter therapy to reduce the risk, especially for those who have known history of cardiovascular disease."
In addition, the researchers suggested this could be linked to "dead-in-bed" syndrome seen in patients with type 1 diabetes.