Technology is rapidly advancing in detecting subclinical heart disease at a much earlier stage. Global heart strain, better known as Left Ventricular Global Longitudinal Strain (LV-GLS) is such an example. It utilizes speckle tracking imaging of transthoracic echocardiography.
LV-GLS identifies left ventricular dysfunction at its embryo before the ejection fraction has declined, a definition of heart failure. Investigators have tested it in a variety of heart anomalies, including ischemic, atherosclerotic, viral, hypertrophic, and dilated myopathies.
Authors applied LV-GLS technology to adults with type 2 diabetes. Retrospectively, they followed about 400 diabetes patients for six years and documented their all-cause mortality.
The article defined abnormal global heart strain when LV-GLS measurement was greater than two positive standard deviations (>-17%). All-cause mortality was significantly higher, by 2.8-fold, in adults with abnormal LV-GLS versus those with normal LV-GLS.
Prospective research would need to validate these results in outcome-driven interventional randomized clinical trials. I anticipate positive results and wide-spread use of LV-GLS technology in the future.
Fortunately, we have SGLT-2 inhibitors as a unique class of medication that could potentially treat and manage patients with diabetes and abnormal heart strain.
GT
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American J Cardiology
Retrospective Cohort
September 2019
Left ventricular (LV) global longitudinal strain (GLS) can detect subclinical myocardial systolic dysfunction in individuals with diabetes.
The present study investigates the clinical usefulness and incremental net benefit of identifying subclinical myocardial systolic dysfunction in individuals with diabetes. A cohort of 397 type 2 diabetic individuals was followed up for the occurrence of all-cause mortality.
Clinical and echocardiographic data of diabetic patients were assessed retrospectively. LV GLS was evaluated on transthoracic echocardiography using speckle tracking imaging. Subclinical LV systolic dysfunction was defined as LV GLS > −17.0% from 104 healthy volunteers recruited from the community.
A total of 178 (44.8%) diabetic individuals had evidence of subclinical LV systolic dysfunction and 46 (11.6%) died during follow-up. The presence of subclinical LV systolic dysfunction was independently associated with all-cause mortality on follow-up (HR 2.83, p = 0.004).
Diabetic individuals without subclinical LV systolic dysfunction had similar survival as the general population (standardized mortality ratio 0.94, 95% CI 0.52 to 1.58). Decision curve analysis showed identification of subclinical LV systolic dysfunction and quantification of LV GLS provided an incremental net clinical benefit at risk stratifying patients for risk of death at 5 years.
In conclusion, subclinical LV systolic dysfunction is independently associated with all-cause mortality in diabetic patients. Decision curve analyses suggest use of LV GLS and identification of subclinical LV systolic dysfunction is clinically useful, and provided incremental net clinical benefit for diabetic individuals.
More from the publication
Diabetes mellitus is the most common endocrinological disease in the world and its presence portends an increased risk for the subsequent development of cardiovascular disease, heart failure, and death.
Echocardiographic techniques such as 2-dimensional (2D) speckle tracking global longitudinal strain analysis permits early identification of subclinical left ventricular (LV) systolic dysfunction despite preserved LV ejection fraction (EF) in asymptomatic type 2 diabetic individuals. However, limited data exist on the prevalence and prognostic implications of subclinical LV systolic dysfunction with preserved LVEF in diabetic population. Thus, we conducted a multicenter study aimed to:
- Evaluate the prevalence of subclinical LV systolic dysfunction with preserved LVEF in type 2 diabetic individuals by using 2D speckle tracking global longitudinal strain cut-off value derived from normal healthy volunteers; and
- Determine the prognostic implications of subclinical LV systolic dysfunction in type 2 diabetic patients and compare it with the general population; and
- Determine the clinical usefulness and incremental net benefit of identifying subclinical LV systolic dysfunction on echocardiography.
It is well recognized that LVEF is a poor marker for identifying myocardial dysfunction as it remains well preserved until significant impairment of longitudinal, circumferential and radial deformations. Depending on the echocardiographic modality used, the prevalence of myocardial dysfunction in diabetics ranged from 21-63%.
In the present study, up to 45% of diabetic individuals had evidence of subclinical LV systolic dysfunction as defined by 2D speckle tracking LV global longitudinal strain. This was identical to a previous publication by Holland et al.
Myocardial dysfunction in diabetics has a multifactorial pathophysiology. Proposed mechanisms include metabolic derangements, autonomic dysfunction, abnormal calcium homeostasis, endothelial dysfunction, altered structural proteins and interstitial fibrosis. As such, the diabetic myocardium has accentuated cellular damage, reduced structural and function reserve, and is more prone to future decompensation and eventual failure when exposed to adverse cardiac events.
This was highlighted in the seminal work by From et al that showed increased incidence of new-onset heart failure in diabetic patients with preclinical diastolic dysfunction. Although it is traditionally held that diastolic dysfunction precedes systolic dysfunction, recent work suggested that subclinical LV systolic dysfunction detected by LV global longitudinal strain may be the first sign of diabetic heart disease instead. Even though it is clear that prognosis is very poor once clinical heart failure is established, there is a paucity of research data on prognosis of the earlier subclinical dysfunction stage.
To our knowledge, only 2 previous publications have demonstrated adverse long-term prognosis associated with subclinical LV systolic dysfunction using LV global longitudinal strain.
- Holland et al included 230 diabetic patients and showed increased all-cause mortality and hospitalization in patients with subclinical LV systolic dysfunction compared with those with preserved LV global longitudinal strain.
- However, the primary outcome was primarily driven by hospitalization, and the causes of hospitalizations were unknown. Liu et al included 247 diabetic patients and showed that an impaired LV global longitudinal strain was associated with an increased incidence of cardiovascular events defined as a composite of acute coronary syndrome, cerebrovascular stroke, cardiovascular death and hospitalization for heart failure.
- In contrast, the present study is the largest to date to include 397 diabetic patients with a primary end-point of all-cause mortality. Not only did our results corroborate the previous 2 publications demonstrating similar adverse prognosis associated with subclinical LV systolic dysfunction, it is also first to show diabetic individuals with preserved LV systolic function had similar long-term survival rates as the general population.
In studies by Holland et al and Liu et al, the “incremental” prognostic value of LV global longitudinal strain were based on the Chi square change in the multivariable Cox model, which is a statistical measure of the overall model performance related to the concept of “goodness-of-fit” (i.e., a better model results in smaller distances between predicted and observed outcomes). However, it fails to inform the doctor and patient if the test is clinically useful.
In contrast, the use of a decision curve analysis in the present study illustrated the net clinical benefit of identifying subclinical LV systolic dysfunction and LV global longitudinal strain in diabetic individuals over the baseline prediction model (age, GFR, hemoglobin, and LV mass index) by incorporating the clinical consequences across a large range of all-cause mortality risk.
As the relative weights of benefits and harms in identifying subclinical LV systolic dysfunction in asymptomatic diabetic population will differ individually, the decision curve analysis allows the setting of individual patient’s thresholds for predicting the probability of death at 5 years.
- It showed that the identification of subclinical LV systolic dysfunction is only of incremental net clinical benefit if the risk of death at 5 years is between 10-50%.
- As for quantification of LV global longitudinal strain as a continuous variable, the incremental net clinical benefit is present if the risk of death at 5 years is between 8-70%.
- Therefore, the identification of subclinical LV systolic dysfunction provided superior net clinical benefit across a wide range of probabilities of death at 5 years.
Although the present study included healthy volunteers and diabetic individuals across 3 different institutions, all diabetic individuals were recruited from a single center. Subgroup analyses based on cardiovascular and noncardiovascular mortality were not available. Finally, by virtue of the study design, we did not evaluate the progression of subclinical LV systolic dysfunction over time. However, that research was previously reported by our group.