Diabetes affects the temporal dynamics of the repolarization properties of cardiomyocytes

The progressive changes in the repolarization phase of the action potential (AP) for isolated cardiomycytes from control and diabetic mice were tested on a set of 100 consecutive excitations at 2 Hz pacing rate. Each repolarization was normalized and fitted with a strictly decreasing function by using an original approach. The temporal properties of the repolarization function were automatically evaluated for the set of consecutive APs and the obtained indices were tested with linear regressions to define the dynamic characteristics of the repolarization over time. Specifically, whether the train of stimulations resulted in a stable pattern of APs or led to prolongation/shortening of the early and late repolarization phases was tested. In both control and diabetic groups prolongation and shortening of the AP were observed. Importantly, the progressive stimulation led to a faster late repolarization phase of the AP in the diabetic cells, as documented by a Wilcoxon signed rank test (p<;0.001). In contrast, AP indices for control myocytes were overall preserved over time. The dynamic changes of the AP profile in the diabetic group were restricted to the late repolarization phase, whereas the early phase behaved similarly for the two groups of cells. Thus, temporal dynamics of repolarization properties of cardiomyocytes are altered with diabetes.