Quality of glycemic control has significant impact on myocardial mechanics in type 1 diabetes mellitus

Type 1 Diabetes and Cardiovascular Health

Type 1 diabetes (T1D) is associated with an increased risk of cardiovascular disease (CVD). CVD occurs much earlier in people with T1D than in the general population, and several risk factors have been identified some of which are modifiable. Risk prediction models and imaging tests to detect early signs of CVD have not been extensively validated. Strategies to promote cardiovascular health (CVH) in T1D include identifying risk factors, early treatment to achieve CVH targets, and improving the education of health care providers and people with T1D.

Glycemic Status and Myocardial Strain by Cardiac MRI in Patients With ST-Segment Elevation Myocardial Infarction

BACKGROUND

It is uncertain how various degree of glycemic status affect left ventricular (LV) myocardial strain in ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PPCI).

PURPOSE

To investigate the relationship of glycemic status and myocardial strain in STEMI patients.

STUDY TYPE

Prospective cohort study.

POPULATION

282 STEMI patients with cardiac magnetic resonance imaging 5 ± 2 days post-PPCI. Patients were divided into three groups based on the level of glycated hemoglobin A1c (HbA1c) (group 1: HbA1c < 5.7%; group 2: 5.7% ≤ HbA1c < 6.5%; group 3: HbA1c ≥ 6.5%).

FIELD STRENGTH/SEQUENCE

3.0-T; late gadolinium enhancement, balanced steady-state free precession cine sequence, black blood fat-suppressed T2-weighted.

ASSESSMENT

LV function, myocardial strain, and infarct characteristics (infarct size, microvascular obstruction, and intramyocardial hemorrhage) were compared among the three groups by one-way analysis of variance (ANOVA) or Wilcoxon rank sum test. Intraobserver and interobserver reproducibility of LV myocardial strain was evaluated.

STATISTICAL TESTS

ANOVA or Wilcoxon rank sum test, Pearson chi-square or Fisher's exact test, Spearman's correlation analyses and multivariable linear regression analysis. A two-tailed P value <0.05 was considered statistically significant.

RESULTS

Infarct characteristics were similar among the three groups (P = 0.934, P = 0.097, P = 0.533, respectively). Patients with HbA1c ≥ 6.5% had decreased LV myocardial strain compared with HbA1c 5.7%-6.4%, as evidenced by global radial (GRS), global circumferential (GCS), and global longitudinal (GLS) strain. However, no significant differences in myocardial strain were observed between patients with HbA1c 5.7%-6.4% and HbA1c < 5.7% (P = 0.716; P = 0.294; P = 0.883, respectively). After adjustment for confounders, HbA1c as a continuous variable (beta coefficient [β] = -0.676; β = 0.172; β = 0.205, respectively) and HbA1c ≥ 6.5% (β = -3.682; β = 0.552; β = 0.681, respectively) were both independently associated with decreased GRS, GCS, and GLS.

DATA CONCLUSION

Patients with uncontrolled blood glucose (categorized in group HbA1c ≥ 6.5%) had worse myocardial strain. The level of HbA1c appeared to be independently associated with decreased myocardial strain in STEMI patients.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 2.

Determinants of the heart rate variability in type 1 diabetes mellitus

Background

Evaluation of heart rate variability (HRV) detects the early subclinical alterations of the autonomic nervous system. Thus, impaired HRV is the earliest subclinical marker of cardiac autonomic neuropathy (CAN) in type 1 diabetes mellitus (T1DM).

Objectives

We aimed to explore the HRV parameters in asymptomatic T1DM patients and compare them with the results obtained in healthy subjects. Potential associations between HRV parameters and the established risk factors for CAN and cardiovascular diseases were also investigated.

Methods

Seventy T1DM patients (38 ± 12 years, 46 females) and 30 healthy subjects were enrolled into the study. For HRV analysis, beat-to-beat heart rate was recorded for 30 min. The less noisy 5-min segment of the recording was analyzed by Bittium Cardiac Navigator HRV analysis software. Time domain, frequency domain, and nonlinear indices were calculated.

Results

Regarding ratio of low to high frequency component (LF/HF), no differences were found between the two populations (p = 0.227). All the further, time domain, frequency domain, and nonlinear HRV indices were significantly lower in T1DM patients (each p < 0.001). In multiple linear models, disease duration remained the only independent predictor of LF/HF ratio (p = 0.019). HbA1c was found to be significant independent predictor of all further time domain (SDNN, p < 0.001; rMSSD, p < 0.001), frequency domain (VLF, p < 0.001; LF, p = 0.002; HF, p = 0.006; Total Power, p = 0.002), and nonlinear indices (SD1, p = 0.006; SD2, p = 0.007), alone, or in combination with other factors, such as age or body mass index.

Conclusion

Asymptomatic T1DM patients have significantly reduced overall HRV as compared with healthy subjects, indicating subclinical CAN. Quality of the glycemic control is important determinant of HRV among T1DM patients. This relationship is independent of other risk factors for CAN or cardiovascular diseases.