The main finding of the present study was that
HbA1c and DM duration were significantly associated
with the presence of fQRS on ECG and increased
fQRS-T angle in DM patients, even in the absence of
clinically evident CVDs. These results suggest that
both ECG parameters may be useful to demonstrate
and monitor the subclinical myocardial damage in
DM patients without established CVDs.
Diabetes mellitus causes significant changes in the
physiological properties of the myocardium that leads
myocardial fibrosis and diabetic cardiomyopathy,[2,3]
and CVD is the major cause of mortality in patients
with type 2 DM.[1,23] Of note, ECG has a crucial role
in the monitoring of diabetic cardiomyopathy and
ECG alterations detected in the clinical follow-up
of DM patients are associated with both clinical and
subclinical myocardial involvement, and significantly
predict adverse cardiovascular events.[5-8] However,
little is known regarding the relationship of clinical
and glycemic parameters with fQRS and fQRS-T
angle in asymptomatic patients with type 2 DM.
The fQRS is a depolarization abnormality that is an
ECG sign of myocardial fibrosis and damage and
is an independent predictor of future cardiovascular
events in a wide variety of patients with and without
CVD.[9-11,24-26] More importantly, fQRS is significantly
associated with subclinical myocardial fibrosis,
deteriorated cardiac functions, and adverse events
in DM patients even in the absence of apparent
CVD.[17,18,27,28] Additionally, as a sign of ventricular
repolarization heterogeneity, increased fQRS-T
angle is a predictor of abnormal cardiac functions
and is associated with adverse cardiovascular events
independent of underlying cardiovascular status.[12,13]
Moreover, increased fQRS-T angle is significantly
associated with diabetic cardiomyopathy and adverse cardiovascular events in DM patients.[19] In this
context, both ECG parameters seem to be useful in
the monitoring of diabetic cardiomyopathy and to
demonstrate the early-stage myocardial fibrosis and
damage before the emergence of manifest CVD in
patients with DM.
The HbA1c level is a sign of mean blood
glucose concentrations over the preceding three
months, considered as a cardiovascular risk factor
and is significantly associated with cardiovascular
complications and adverse cardiovascular events in
patients with DM.[1,8] More importantly, hyperglycemia
and HbA1c is the leading cause of ECG abnormalities
in patients with DM.[5,8] However, little is known
regarding the relationship of HbA1c with fQRS and
fQRS-T angle in DM patients without known CVD.
The results of our study demonstrated that HbA1c
was an independent predictor of fQRS on ECG and
increased fQRS-T angle and we found a significant
positive correlation between HbA1c levels and both
ECG parameters. Therefore, our results suggest that
fQRS and fQRS-T angle may be useful ECG findings
to demonstrate the hyperglycemia related subclinical
myocardial damage in the early phase of diabetic
cardiomyopathy before the occurrence of clinically
evident CVD. Additionally, DM duration is usually
considered as a cardiovascular risk factor and is
significantly associated with diabetic cardiomyopathy
and future cardiovascular events in asymptomatic
patients with type 2 DM independent of coexisting risk
factors.[8,29] Nevertheless, the impact of DM duration
on ECG parameters has not been well described yet.
In the present study, we demonstrated that prolonged
DM duration was the most powerful predictor of
presence of fQRS on ECG and increased fQRS-T
angle in DM patients without known CVD. In this
context, both ECG parameters may be considered as
the ECG signs of prolonged DM duration related
subclinical diabetic cardiomyopathy. Hence, fQRS
and fQRS-T angle may have a significant association
with prolonged hyperglycemia and DM duration and
may be useful in the monitoring of subclinical diabetic
cardiomyopathy.
Nonetheless, there are some limitations in this
study. The main limitation was the lack of data
regarding the clinical events. However, this study was
not a follow-up study and the association of both ECG
parameters with cardiovascular events is well described
in previous studies. Also, the clinical importance
of our findings needs to be investigated in further studies to demonstrate whether effective treatment of
DM leads disappearance of fQRS or narrowing in the
fQRS-T angle. Finally, the absence of confirmation of
subclinical myocardial fibrosis with cardiac magnetic
resonance imaging is another limitation.
In conclusion, type 2 DM confers a significant
increase in the risk of CVD and CVD is the leading
cause of mortality in DM patients. The ECG has
an important role in the monitoring of diabetic
cardiomyopathy and demonstrating the cardiovascular
involvement in patients with type 2 DM. Our study
results demonstrated that glycemic parameters HbA1c
and DM duration were significantly associated with
fQRS and increased fQRS-T angle in type 2 DM
patients without manifest CVDs. Therefore, both
ECG parameters may be useful in the monitoring
glycemic status and cardiovascular involvement in
type 2 DM patients without known CVDs.
Ethics Committee Approval: The study protocol
was approved by the Tokat Gaziosmanpaşa University
Clinical Research Ethics Committee (date: 25.06.2020,
no: 20-KAEK-151). The study was conducted in accordance
with the principles of the Declaration of Helsinki.
Patient Consent for Publication: A written informed
consent was obtained from each patient.
Data Sharing Statement: The data that support the
findings of this study are available from the corresponding
author upon reasonable request.
Author Contributions: Idea/concept, data collection
and/or processing, writing the article: M.E.; Design, control/
supervision, analysis and/or interpretation, literature review,
critical review: M.E., A.Ç.
Conflict of Interest: The authors declared no conflicts
of interest with respect to the authorship and/or publication
of this article.
Funding: The authors received no financial support for
the research and/or authorship of this article.