QT interval prolongation during spontaneous episodes of hypoglycaemia in type 1 diabetes: the impact of heart rate correction

Abstract

Aims/hypothesis Prolongation of the heart rate corrected QT interval (QTc) is seen during episodes of hypoglycaemia in type 1 diabetes. We studied the relationship between spontaneous hypoglycaemia and the QT interval and hypothesised that the choice of heart rate correction affects the observed change in QTc. Methods Twenty-one participants with type 1 diabetes (aged 58±10 years with duration of diabetes 34±12 years) had continuous glucose and ECG monitoring for 72 h. QT and RR intervals were measured during hypoglycaemia (blood glucose or continuous glucose measurements ≤3.5 mmol/l) and compared with euglycaemia (5-12 mmol/l). QT intervals were measured using the semi-automated tangent method from signal-averaged ECG and corrected using Bazett's formula, Fridericia's formula, the nomogram method and a linear subject-specific method.Results Hypoglycaemia was present in 14 participants. With Bazett's formula, QTc changed significantly from euglycaemia to hypoglycaemia (422±30 vs 432±33 ms; p=0.02). Heart rate, QT intervals and QTc corrected with formulas other than Bazett's were not associated with a significant change (p= 0.07-0.29). During hypoglycaemia, significantly lower values of QTc compared with the subject-specific method were seen for Fridericia's formula (p=0.02) and the nomogram method (p=0.04). Conclusions/interpretation Spontaneous hypoglycaemia was associated with a modest increase in QTc. Bazett's formula resulted in overcorrection of QTc while both Fridericia's formula and the nomogram method undercorrected the QTc compared with the subject-specific method during hypoglycaemia. The results may indicate that the use of a fixed heart rate correction formula can lead to misleading results in investigations of spontaneous hypoglycaemia.

Vital Signs, QT Prolongation, and Newly Diagnosed Cardiovascular Disease During Severe Hypoglycemia in Type 1 and Type 2 Diabetic Patients

“…Recently, several studies have reported an association between hypoglycemia and QT prolongation (11)(12)(13), which reflects abnormal cardiac repolarization and may be a marker of increased mortality in T1DM patients (32). The results of the current study demonstrated that not only T1DM patients but also many T2DM patients exhibited an abnormal QT prolongation during severe hypoglycemia.…”

“…1. The median GCS scores in the T1DM and T2DM group were 12 (9-14) and 11 (7)(8)(9)(10)(11)(12)(13)(14), respectively (Fig. 1A).…”

“…Serious conditions can be anticipated during severe hypoglycemia based on previous case reports (7,8), observational studies (4)(5)(6), and small interventional studies in which patients experienced mild to moderate hypoglycemia (9,10). Moreover, recent studies have suggested an association between hypoglycemia and prolongation of the QT interval (11)(12)(13). However, various aspects of the actual conditions and complications that occur during severe hypoglycemia remain unclear.…”

Diurnal Differences in Risk of Cardiac Arrhythmias During Spontaneous Hypoglycemia in Young People With Type 1 Diabetes

“…The Bazett formula corrects intervals to a rate of 60 bpm and tends to result in overcorrection at high heart rates and undercorrection at lower heart rates. Nevertheless, it is generally considered a reasonably accurate correction in the setting of hypoglycemia (36). In our study we detected a mean QTc prolongation of 5 ms during nocturnal hypoglycemia and 12 ms during daytime hypoglycemia in comparison with matched euglycemia.…”

Glutathione oxidation unmasks proarrhythmic vulnerability of chronically hyperglycemic guinea pigs

“…This distinction is important because unlike rodents, patients with t1DM do not exhibit heart rate corrected QT-interval prolongation in the absence of confounding factors, such as diabetic ketoacidosis (24) or spontaneous hypoglycemia (11). Clinically, these additional stimuli are required to unmask pathological QT-interval prolongation in patients with t1DM (11,14,17,24).More importantly, most EP studies in t1DM have been performed in animal models that exhibited highly artificial rises (Ͼ300%) in blood glucose levels that are well beyond what is commonly encountered in patients with diabetes (20,33,36,40,46). Such extreme levels of hyperglycemia, which are known to affect ion channels, preclude the direct translation of some of these earlier findings to humans.…”