A measure of global longitudinal strain (GLS) was far more predictive of mortality than left ventricular ejection fraction (LVEF) in a study of 4,172 patients with acute heart failure, demonstrating its potential as a new standard technique.
“Myocardial strain is based on the speckle-tracking method and can be used for the objective and reliable assessment of systolic function,” wrote lead author Jin Joo Park, MD, PhD, and colleagues in the Journal of the American College of Cardiology. “It is a simple and feasible method, with excellent reproducibility, and is a strong independent prognostic factor for outcomes in patients with HF, independently of LVEF.”
To compare the predictive value of GLS versus LVEF, the researchers divided their cohort into three groups for each measurement. Reduced ejection fraction was defined as LVEF less than 40 percent, midrange ejection fraction covered the range between 40 and 50 percent and preserved ejection fraction included everything at 50 percent or above. Mildly reduced strain encompassed all patients with GLS above 12.6 percent, severely reduced strain included patients with 8.0 percent GLS or lower and moderately reduced strain covered everything between those two categories.
Park et al. reported similar five-year mortality rates across the LVEF categories: 41 percent for heart failure with reduced ejection fraction (HFrEF), 38 percent for heart failure with midrange ejection fraction (HFmrEF) and 39 percent for heart failure with preserved ejection fraction (HFpEF). But for GLS, reduced levels of strain were strongly associated with mortality: 34 percent for mildly reduced GLS, 38 percent for moderately reduced GLS and 49 percent for severely reduced GLS.
After adjusting for multiple variables, the researchers found each 1 percent increase in GLS was associated with a 5 percent decrease in a patient’s mortality risk. LVEF wasn’t significantly associated with mortality after multivariable adjustment.
“If the medical community has ignored previous reports about the prognostic value of GLS, this paper should help convince those who are still in doubt,” wrote Kristina H. Haugaa, MD, PhD, and Lars A. Dejgaard, MD—both with Oslo University Hospital, Norway—in a related editorial.
“The design of the study and the number of included patients allow us to conclude that GLS is now ready to be implemented in daily clinical work and in the guidelines for diagnosis, monitoring, and assessment of prognosis in patients when cardiac function matters.”
The editorialists said GLS could be particularly helpful in guiding the management of HFpEF because GLS is reduced in those cases but ejection fraction isn’t.
“It is essential to differentiate between the terms systolic function and EF, which are not synonymous and not interchangeable,” they wrote. “In hearts with mildly reduced function, EF is not sensitive enough to detect dysfunction. The fact that 84 percent of patients with preserved EF in the study by Park et al. had reduced GLS highlights that GLS quantifies ‘invisible’ HF with good precision and is strongly linked to prognosis.”
Haugaa and Dejgaard said in the case of HFrEF, ejection fraction is still prognostic and there is little incremental value for GLS. But using both tests in routine practice could help address all forms of acute heart failure, they noted.
“We still need EF and do not anticipate the fall of a giant,” Haugaa and Dejgaard wrote. “However, a tool is needed to assess the mild reduction in cardiac function found in a large subset of patients with HF and here GLS is an excellent candidate.”
Park et al. said the GLS technique demonstrated “high feasibility,” pointing to the 98 percent success rate with which the analysts at the core laboratory measured GLS. However, they pointed out the study only included patients with acute heart failure, so it is unknown whether their findings would translate to those with chronic heart failure.
Also, it is too early to say how GLS classification may impact treatment decisions.
“This new concept needs extensive validation in further clinical trials and practice, but it may also explain some of the paradoxical phenomena observed in HF management,” Lee and colleagues wrote. “Further investigation to identify patient subgroups that may respond to medical therapy is required.”