Prevalence of Q-T Interval Dispersion in Type 1 Diabetes and Its Relation With Cardiac Ischemia

Abstract

OBJECTIVE -The interlead variation in duration of the Q-T interval on the surface electrocardiogram (Q-T interval dispersion [QTd]) has been shown to predict mortality in type 2 diabetic patients. We evaluated the prevalence of QTd prolongation in the EURODIAB population and its relation to corrected Q-T interval (QTc), sex, age, duration of diabetes, blood glucose control, and complications.RESEARCH DESIGN AND METHODS -A total of 3,042 type 1 diabetic patients were studied. QTc was calculated according to the Bazett's formula; QTc Ͼ0.44 s was considered abnormally prolonged. QTd was calculated using the difference between the maximum and the minimum QTc in any thoracic lead. QTd Ͼ0.080 s was considered abnormally prolonged.RESULTS -The prevalence of an increased QTd was 7%. A significant relation was observed between QTd prolongation and diastolic blood pressure (P Ͻ 0.05). A higher prevalence of QTd prolongation was observed in patients with ischemic heart disease (P ϭ 0.004), whereas no relationship was observed with retinopathy, albumin excretion rate, or measures of somatic and autonomic neuropathy. QTc and QTd were significantly related (P ϭ 0.001); however, a proportion of patients with normal QTd showed a prolonged QTc (Ͼ0.44 s).CONCLUSIONS -In patients with type 1 diabetes, QTd is associated with ischemic heart disease and diastolic blood pressure but not neuropathy. Although QTd is statistically related to duration of QTc, increased QTd and increased QTc identify different patients, and their predictive value deserves prospective evaluation. Diabetes Care 25:702-707, 2002T he Q-T interval in the electrocardiogram (ECG) reflects the total duration of ventricular myocardial depolarization and repolarization. It has been shown that a prolonged Q-T interval is associated with sudden death and poor survival in healthy subjects (1) and in a variety of clinical conditions, including newly diagnosed type 2 diabetes (2), nephropathy (3), and type 1 diabetes (4,5).The observation that the Q-T interval exhibits a certain degree of spatial variability on the epicardial surface (6) has led to the hypothesis that differences in the duration of the Q-T interval between ECG leads may reflect heterogeneity in recovery of excitability (7). Based on the evidence that nonuniform repolarization provides a substrate for the development of malignant ventricular arrhythmias (8), variation in the duration of the Q-T interval has been advocated as a more predictive marker of arrhythmias and mortality than the maximum duration of the Q-T interval (9).The interlead variation in duration of the Q-T interval on the surface ECG has been referred to as Q-T interval length dispersion or Q-T dispersion (QTd). It has been shown that the QTd is predictive of mortality in normal subjects and different groups of patients. Increased QTd has been described in patients with recent myocardial infarction (10), long Q-T syndrome (9,11), heart failure (12), and hypertrophic cardiomyopathy (13). Furthermore, QTd has been related to arrhythmia and ...

Effects of metoprolol on QT interval and QT dispersion in Type 1 diabetic patients with abnormal albuminuria

“…Bedside cardiovascular autonomic function tests are less sensitive in detecting impaired sympathovagal function than spectral analysis methods [27,28]. This may explain the discrepancy in results, as others have found no relation, when using bedside tests, between QTc interval dispersion and autonomic neuropathy measurements [8,25].…”

“…In non-diabetic hypertensive patients an increased QTc dispersion is presumed to be related to left ventricular hypertrophy [23]. In addition, an association between QTc dispersion and ischaemic heart disease has been shown in non-diabetic [24] and in diabetic [8,25] patients. Abnormal albuminuria is a strong predictor of cardiovascular disease and although none of the patients in the present study showed symptoms or signs of cardiovascular disease, the difference in test results between patients with normal and abnormal albuminuria may reflect a more pronounced (although subclinical) myocardial ischaemic disease and/or ventricular hypertrophy in the latter group.…”

“…The EURODIAB IDDM study found that increased QTc interval and increased QT dispersion identified different patients, as the former was related to autonomic neuropathy and the latter was associated with ischaemic heart disease and diastolic blood pressure [25]. In studies of patients with hypertension, QT dispersion has been related to left ventricular hypertrophy [23].…”

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

“…Clinically, there are several inherited and acquired conditions, including diabetes,4, 5, 9, 10, 12, 13 that are characterized by prolongation of the QT interval, a factor that enhances the incidence of ventricular arrhythmia and sudden cardiac death 14. 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.…”

“…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.…”