The following are key points to remember about this article on assessing left ventricular (LV) systolic function: from ejection fraction (EF) to strain analysis:

1. LVEF, defined as the ratio of LV stroke volume to LV end-diastolic volume, is one of the most frequently measured variables in clinical practice. However, LVEF is an imperfect measure of LV contractility, affected also by preload, afterload, heart rate, and LV geometry.
2. LVEF can be measured using radionuclide imaging, contrast angiography, echocardiography, and cardiac magnetic resonance (CMR) imaging. Nuclear methods have poor temporal resolution, which can lead to underestimation of LVEF. Contrast angiography and one- or two-dimensional echocardiography require manual contouring resulting in limited accuracy and reproducibility. Published normal ranges for LVEF have varied between techniques.
3. Myocardial strain is a dimensionless variable representing the change in length between two points over the cardiac cycle, and can be quantified using echocardiography or CMR tissue tracking. Regional strain is less reproducible; whereas peak global strain is more consistent, supporting the use of global longitudinal strain (GLS) in clinical practice. However, GLS varies based on techniques, modalities, vendors, and software.
4. Guidelines for the management of patients with heart failure (HF) use subtypes based on cutoffs of LVEF: reduced LVEF (HFrEF, LVEF <40%), mid-range LVEF (HFmrEF, 40-50%), and preserved LVEF (HFpEF, LVEF >50%). However, LVEF is not static, and therapies might not be optimally determined solely based on LVEF.
5. GLS might better stratify risk among patients with HFpEF and HFrEF, and also can be useful in the diagnosis of specific etiologies of HF (including amyloidosis). Among patients with HFrEF, GLS also can be useful in helping select patients most likely to benefit from cardiac resynchronization therapy.
6. Among patients with aortic stenosis, LVEF can be preserved despite abnormal LV contractility. There is growing evidence that patients with severe aortic stenosis and LVEF 50-60% have a higher rate of adverse outcomes compared to patients with LVEF >60%. A meta-analysis suggests that impaired LV GLS despite LVEF >50% is associated with reduced survival.
7. Among patients with aortic regurgitation, impaired LV GLS might be an earlier marker of LV decompensation than are current guideline measures of LV enlargement or LV dysfunction based on reduced LVEF.
8. Among patients with primary mitral regurgitation, ejection of blood into the low-pressure left atrium can mask LV systolic dysfunction despite a normal LVEF. Contractile reserve on exercise and LV GLS might allow for earlier detection of early stage but clinically significant LV systolic dysfunction.
9. LV GLS is useful to detect future cardiotoxicity among patients receiving cardiotoxic chemotherapy, and to detect subclinical LV systolic dysfunction among family members of patients with heritable cardiomyopathies.

Clinical Topics: Arrhythmias and Clinical EP, Cardio-Oncology, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Valvular Heart Disease, Implantable Devices, Acute Heart Failure, Interventions and Imaging, Interventions and Structural Heart Disease, Angiography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging, Mitral Regurgitation

Keywords: Amyloidosis, Angiography, Aortic Valve Insufficiency, Aortic Valve Stenosis, Cardiac Resynchronization Therapy, Cardiomyopathies, Cardiotoxicity, Diagnostic Imaging, Echocardiography, Gadolinium, Heart Failure, Heart Valve Diseases, Magnetic Resonance Imaging, Mitral Valve Insufficiency, Stroke Volume, Systole, Ventricular Function, Left

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