What is the clinical evidence from this study?

Study design: Case-Control. Population: Type 2 Diabetes Mellitus (n=130). Intervention: Cardiac autonomic neuropathy vs. Without cardiac autonomic neuropathy. Primary outcome: QT dispersion (QTd) (p=0.02).

November 19, 2020Open Access

The relationship between QT interval indices with cardiac autonomic neuropathy in diabetic patients: a case control study

Key Result

In patients with type 2 diabetes, cardiac autonomic neuropathy was associated with significantly higher QT maximum, QT mean, and QT dispersion compared to those without the condition.

Study Design

Type

Case-Control (n=130)

Multicenter

Structured PICO

Population

130 adults aged 18-75 years with type 2 diabetes mellitus, with and without cardiac autonomic neuropathy, evaluated in a case-control study.

Comparator

Type 2 diabetic patients without cardiac autonomic neuropathy

Outcome

QT interval indices including QT, QTc, QT min, QT max, QT mean, and QT dispersion (QTd) assessed from standard ECGsurrogate

In patients with type 2 diabetes, cardiac autonomic neuropathy is associated with higher QT max, QT mean, and QT dispersion, suggesting these indices may help identify autonomic dysfunction.

Main Result

Absolute Event Rate: 69% vs 58%

p-value: p=0.02

Limitations

Single center study with a small number of patients, reducing external validity.
Sample size was calculated for QTc and may not be sufficient to examine the relationship of other indices to CAN.
QT intervals were measured manually, introducing potential operator error.
Other factors affecting QT interval, such as electrolyte imbalances, were not evaluated.

Abstract

BACKGROUND: Long QT interval (QT) and abnormal QT dispersion (QTd) are associated with sudden death. The relationship between cardiac autonomic neuropathy (CAN) and QT indices in type 2 diabetic patients were investigated. METHODS: Totally 130 diabetic subjects (mean age 50.87 ± 13.9 years) were included (70 individuals with and 60 individuals without CAN). All participants had sinus cardiac rhythm. The patients who had diseases or take drugs that cause orthostatic hypotension (OH), cardiac arrhythmia and QT prolongation were excluded. After interview and examination, standard and continuous ECG was taken in supine position with deep breathing and standing up position. CAN diagnosis was based on Ewing's tests. QT, QT corrected (QTc), minimum QT (QT min), maximum QT (QT max) and mean ± SD of QT (QT mean) and QTd were assessed from standard ECG. QTc was calculated by Bazett's formula from V2 lead. QTc > 440 ms in men and QTc > 460 ms in women and QTd > 80 ms were considered abnormal. RESULTS: In patients with CAN, 21.5% were symptomatic. The prevalence of abnormal QTc and QTd was 11.3% and 28.7%, respectively. There was no significant difference between the patients with or without CAN in terms of long QTc and abnormal QTd. However, the mean ± SD of QT max, QT mean and QTd was higher in the patients with CAN (P value < 0.03). The used cut points for QTc and QTd have high specificity (79% for both) and low sensitivity (30% and 37%, respectively). To use QTc and QTd as screening test for CAN in T2DM patients, the cutoff points 380 and 550 ms are suggested, respectively. CONCLUSION: The prevalence of asymptomatic CAN was 3.7 times that of symptomatic CAN. In patients with CAN the QT max, QT mean and QTd were higher than those without CAN. There was no association between CAN and long QTc and abnormal QTd.

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