Ventricular arrhythmias associated with long QT interval as a predictor of sudden cardiac death in patients with coronary heart disease and type 2 diabetes mellitus

Aim. To determine the prognostic value of blood glucose level changes in patients with coronary heart disease and type 2 diabetes from the perspective of their impact on the duration of QT interval and type of cardiac arrhythmias.

Methods. The study involved 101 patients of 50 years or older with a diagnosis of ischemic heart disease (stable angina, II-III functional class) and healthy volunteers. Synchronous monitoring of ECG and blood glucose measuring were performed in all surveyed patients.

Results. The average duration of QT interval in patients with coronary heart disease and type 2 diabetes was significantly higher than in patients with coronary heart disease without diabetes and in the control group. Glycaemia less than 4 mmol/L and more than 12 mmol/L and high glycemic variability (mean amplitude of glycemic excursion more than 5 mmol/L) increase the risk of QT prolongation and dangerous ventricular arrhythmias. In patients with ischemic heart disease and type 2 diabetes premature ventricular contractions (PVCs) of high grade are detected more often compared to patients without diabetes mellitus and healthy individuals. In patients with coronary heart disease and type 2 diabetes with episodes of glycaemia below 4 mmol/L prevalence of PVCs of high grade is higher than that of patients with glycaemia 4,1 to 11,9 mmol/L.

Conclusion. Patients with coronary heart disease and type 2 diabetes with blood glucose levels below 4 mmol/L and above 12 mmol/L and high glycemic variability have an increased risk of arrhythmogenic sudden cardiac death.