Electrocardiographic Repolarization Complexity and Abnormality Predict All-Cause and Cardiovascular Mortality in Diabetes

Abstract

Type 2 diabetes is associated with increased risk of cardiovascular (CV) and all-cause mortality. Although electrocardiographic measures of repolarization abnormality and complexity stratify risk in the general population, their prognostic value in diabetes has not been well characterized. Digital electrocardiogram (ECG) readings were acquired for 994 American Indians with type 2 diabetes. ST segment depression (STD) >50 V and rate-corrected QT interval (QTc) >460 ms were examined as measures of repolarization abnormality. The principal component analysis (PCA) of the ratio of the second to first eigenvalues of the T-wave vector (PCA ratio) (>32.0% in women and >24.6% in men) was examined as a measure of repolarization complexity on the ECG. After a mean follow-up of 4.7 ؎ 1.0 years, there were 56 CV deaths and 155 deaths from all causes. In univariate analyses, STD, QTc, and the PCA ratio predicted CV and all-cause mortality. T he surface electrocardiogram (ECG) remains the most widely used noninvasive method for cardiovascular (CV) risk assessment. Abnormalities of ventricular repolarization on the ECG, such as ST segment depression (STD) and QT interval prolongation, are well-established markers of mortality risk in the general population (1-6). ECG measures of the heterogeneity or complexity of ventricular repolarization have been implicated in the genesis of ventricular arrhythmias and also associated with adverse prognosis (6 -14). A number of surface ECG approaches to analysis of repolarization heterogeneity have been proposed, including QT dispersion (6,9,12), T-wave morphology analyses (9,10,13), and principal component analysis (PCA) of the T-wave vector loop (11,14), a spatial measure of T-wave complexity that avoids many of the theoretical and practical limitations of simple QT dispersion and improves prediction of CV death (11,14). However, these repolarization abnormalities may be strongly correlated with one another (11), and whether they provide independent prognostic information when examined together remains unclear.Diabetes is an established risk factor for CV disease and is associated with an increased risk of both all-cause and CV mortality (15)(16)(17)(18)(19). The increasing prevalence of type 2 diabetes, earlier onset of diabetes, and aging of the population will result in an increasing prevalence of diabetesinduced CV disease (18,19), suggesting that accurate noninvasive identification of diabetic individuals at high risk may play a role in the development of more effective preventive strategies for decreasing diabetes-related CV risks (19). Although increased QT interval and QT dispersion have been implicated as possible ECG predictors of CV and all-cause mortality in several small type 2 diabetic cohorts (20 -22), the prognostic value of the QT interval has not been examined in an unselected type 2 diabetic population, and the prognostic value of STD and the more accurate PCA ratio have not been assessed in diabetes. Therefore, the present study examined the value of repolarization abn...

Reduction in Kv Current Enhances the Temporal Dispersion of the Action Potential in Diabetic Myocytes: Insights From a Novel Repolarization Algorithm

“…Moreover, increased dispersion of ventricular repolarization occurs in diabetic patients5, 6, 7, 8, 10 with an important implication on propensity to develop electrical disturbances 4, 13, 15, 16. To test the possibility that prolonged electrical recovery with hyperglycemia was associated with increased repolarization variability and rhythm disturbances, the degree of temporal dispersion of myocardial repolarization and susceptibility to develop arrhythmias were quantified.…”

“…Prolongation of the QT interval and increased dispersion of repolarization have been observed in the diabetic population,4, 5, 6, 7, 8, 9, 10 and these variables, together with intervening comorbidities,11 represent critical substrates for the occurrence of electrical disturbances 4, 12, 13, 14, 15, 16, 17. But whether alterations at the cellular level contribute to protracted electrical recovery and repolarization variability with diabetes remain to be determined.…”

Usefulness of QT-interval parameters for cardiovascular risk stratification in type 2 diabetic patients with arterial hypertension

“…Future efforts should focus on new, more reliable and precise methods of assessing ventricular repolarization complexity and abnormalities, such as spatial T-wave axis deviation, 35 descriptors of T-wave morphology 36 or principal component analysis of T-wave vector, 37 as well as on intervention studies to verify whether these repolarization abnormalities could be modified to decrease cardiovascular risk.…”

Incidence and Risk Factors of Prolonged QTc Interval in Type 1 Diabetes

“…he QT interval on the electrocardiogram reflects the total duration of ventricular myocardial depolarization and repolarization, and when corrected for heart rate (QTc) it is predictive of all-cause and cardiovascular mortality in apparently healthy people (1) as well as in people with various conditions, including diabetes (2)(3)(4)(5)(6). Therefore, measurement of QTc has been proposed as a simple and noninvasive method for the assessment of cardiovascular risk in the clinical setting (2,7).…”