QT interval, corrected for heart rate, is associated with HbA1c concentration and autonomic function in diabetes. Issue 10 (21st February 2016)

• Record Type: Journal Article
• Authors: Stern, K.; Cho, Y. H.; Benitez‐Aguirre, P.; Jenkins, A. J.; McGill, M.; Mitchell, P.; Keech, A. C.; Donaghue, K. C.
• Is Part Of: Diabetic medicine. Volume 33:Issue 10(2016:Oct.)
• Page Start: 1415
• Page End: 1421
• Publication Date: 2016-02-21
• Subjects: Diabetes -- Periodicals; 616.462
• DOI: 10.1111/dme.13085
• Languages: English
• ISSNs: 0742-3071

Abstract

Abstract: Aims: To examine QT intervals corrected for heart rate (QTc) in adolescents with Type 1 diabetes compared with control subjects, and to determine associations with metabolic control and autonomic function. Methods: Resting electrocardiogram recordings of 142 adolescents with Type 1 diabetes [mean (sd ) age 15.3 (2.0) years, diabetes duration 9.0 (3.5) years, HbA1c 71 (17) mmol/mol or 8.7 (1.6)%] and 125 control subjects [mean (sd ) age 15.7 (2.5) years] were used to calculate QTc duration and derive mean heart rate and heart rate variability (HRV) values. Linear and logistic regression models were used to examine the associations between QTc, metabolic control and autonomic function (HRV and pupillary function). Results: QTc duration was not significantly different between subjects with Type 1 diabetes and control subjects (mean duration 392 vs 391 ms; P = 0.65). In the Type 1 diabetes group, QTc was positively associated with HbA1c [β = 4 (95% CI 2, 6); P < 0.001] and inversely associated with severe hypoglycaemic events [β = ‐10 (95% CI ‐20, ‐2); P = 0.01], less insulin/kg [β = ‐12 (95% CI ‐22, ‐2); P = 0.024] and less HRV. In the Type 1 diabetes group, QTc in the highest quintile (≥409 ms) vs quintiles 1–4 had more pupillary abnormalities (83 vs 56%; P = 0.03), lower pupillary maximum constriction velocity (4.8 vs 5.3 mm/s; P = 0.04), higher heart rate (78 vs 72 beats per min; P = 0.02) and lower HRV (standard deviation of mean NN intervals 4.0 vs 4.3 ms, P = 0.004 and root‐mean‐square difference of successive NN intervals 3.7 vs 4.1 ms; P = 0.004). Conclusions: Although there are concerns about hypoglycaemia in general in people with Type 1 diabetes, chronic hyperglycaemia, rather than intermittent hypoglycaemia, appears to be more deleterious to autonomic cardiac function, even in adolescence. Longer QTc was associated with higher HbA1c concentration, lower risk of hypoglycaemia and autonomic dysfunction. Longitudinal studies are warranted. What's new?: Longer QT interval corrected for heart rate (QTc) is associated with higher HbA1c concentration, less exogenous insulin and a lower rate of significant hypoglycaemia in adolescents with Type 1 diabetes. This is the first study to show significant associations between abnormal pupillometry, cardiac autonomic dysfunction and longer QTc interval in adolescents with Type 1 diabetes. A threshold of QTc > 409 ms in adolescents with Type 1 diabetes differentiates those most at risk of autonomic dysfunction, in addition to being female, having higher HbA1c, BMI and total cholesterol. Electrocardiogram screening to exclude long QTc syndromes and assess complication risk may be of value in routine complications assessment in young people with diabetes.