Prognosticating with Left Ventricular Global Longitudinal Strain – A New Opportunity for Cardiac Anesthesiologists

Left ventricular (LV) ejection fraction lacks sensitivity for identifying subclinical LV impairment from subendocardial longitudinal fiber disease, which may not affect LV ejection fraction measurements.¹ LV strain is an echocardiographic measure of myocardial function capable of quantifying longitudinal, radial, and circumferential contractions.² LV longitudinal strain is extensively used in the outpatient setting to predict outcomes in patients with valvular heart disease,³ cardiomyopathies,⁴ or undergoing anthracycline chemotherapy⁵ with a normal LV ejection fraction. Are cardiac anesthesiologists missing out on this vital parameter?

We read with interest the retrospective study of Kang et al.⁶ that demonstrated the incremental prognostic value of LV longitudinal strain in patients with preserved LV ejection fraction as a predictor of all-cause mortality after isolated coronary artery bypass graft surgery. Left ventricular function was categorized as 'preserved LV ejection fraction and preserved longitudinal strain,' 'preserved LV ejection fraction but impaired longitudinal strain,' and 'reduced LV ejection fraction ' (with impaired longitudinal strain by default).⁶ As expected, mortality was highest in the cohort with impaired LV function. In the two cohorts with normal LV ejection fraction, longitudinal strain demonstrated a linear relationship with postoperative mortality (hazard ratio of 1.13 per % increase in LV strain > -15.5%, 95% CI 1.09-1.18, P<0.001).⁶ Postoperative survival was greater in patients with normal ejection fraction and preserved compared with impaired longitudinal strain (90.0% vs. 84.6%, p=0.002).⁶

The results suggest that LV longitudinal strain is valuable in stratifying risk in cardiac surgery patients, especially those with normal LV ejection fraction. We commend the authors of this pivotal study for their insightful work. Patients identified preoperatively to have decreased LV strain may benefit from afterload reduction and catecholamine suppression.⁷ Whether these findings may also be extended intraoperatively to affect anesthetic management in patients with American College of Cardiology/American Heart Association Stage A heart failure (i.e. subtle LV systolic dysfunction and preserved ejection fraction) is unresolved.⁸ LV strain may be capable of detecting subtle impairments in LV systolic function before any reduction in LV ejection fraction becomes apparent.² The benefit of obtaining LV strain may influence decision-making after bypass in patients with “normal LV systolic function" defined by ejection fraction alone. Specifically, the greater sensitivity of LV strain may allow anesthesiologists to more proactively initiate LV support, particularly in patients with subclinical subendocardial fiber failure, but this hypothesis remains to be tested.⁹ The current study identified patients with atrial fibrillation, regional wall motion abnormalities, and moderate-severe mitral regurgitation as those who had impaired LV strain despite normal LV ejection fraction.⁶ These patients and those with heart failure with preserved LV ejection fraction may benefit from intraoperative LV strain analysis because LV ejection fraction alone insufficiently prognosticates the acute declines in LV function during or after surgery, as evidenced by the poorer all-cause postoperative mortality compared to non-heart failure patients.⁷