Background: The left ventricular ejection fraction (LVEF) is the most commonly used measure describing pumping efficiency, but it is heavily dependent on loading conditions and therefore not well-suited to study pathophysiologic changes. The novel concept of echocardiography-derived myocardial work (MyW) overcomes this disadvantage as it is based on LV pressure-strain loops. We tracked the in-hospital changes of indices of MyW in patients admitted for acute heart failure (AHF) in relation to their recompensation status and explored the prognostic utility of MyW indices METHODS AND RESULTS: We studied 126 patients admitted for AHF (mean 73 ± 12 years, 37% female, 40% with a reduced LVEF [<40%]), providing pairs of echocardiograms obtained both on hospital admission and prior to discharge. The following MyW indices were derived: global constructive and wasted work (GCW, GWW), global work index (GWI), and global work efficiency. In patients with HF with reduced ejection fraction with decreasing N-terminal prohormone B-natriuretic peptide levels during hospitalization, the GCW and GWI improved significantly, whereas the GWW remained unchanged. In patients with HF with preserved ejection fraction, the GCW and GWI were unchanged; however, in patients with no decrease or eventual increase in N-terminal prohormone B-natriuretic peptide, we observed an increase in GWW. In all patients with AHF, higher values of GWW were associated with a higher risk of death or rehospitalization within 6 months after discharge (per 10-point increment hazard ratio 1.035, 95% confidence interval 1.005-1.065)., Conclusions: Our results suggest differential myocardial responses to decompensation and recompensation, depending on the HF phenotype in patients presenting with AHF. The GWW predicted the 6-month prognosis in these patients, regardless of LVEF. Future studies in larger cohorts need to confirm our results and identify determinants of short-term and longer term changes in MyW., Competing Interests: Declaration of Competing Interest Floran Sahiti receives financial support from IZKF Würzburg (MD/PhD program scholarship). Caroline Morbach reports a research cooperation with the University of Würzburg and Tomtec Imaging Systems funded by a research grant from the Bavarian Ministry of Economic Affairs, Regional Development and Energy, Germany, speakers honorarium from Amgen and Tomtec, a travel grant from Orion Pharma and Alnylam, and participation in Advisory and Patient Eligibility Boards sponsored by AKCEA, Alnylam, Pfizer, and EBR Systems outside the submitted work. Carsten Henneges has nothing to disclose. Ulrich Stefenelli has nothing to disclose. Nina Scholz has nothing to disclose. Vladimir Cejka has nothing to disclose. Judith Albert has nothing to disclose. Peter U. Heuschmann reports grants from the German Ministry of Research and Education, European Union, Charité – Universitätsmedizin Berlin, Berlin Chamber of Physicians, German Parkinson Society, University Hospital Würzburg, Robert Koch Institute, German Heart Foundation, Federal Joint Committee (G-BA) within the Innovationfond, University Hospital Heidelberg (within RASUNOA-prime; RASUNOA-prime is supported by an unrestricted research grant to the University Hospital Heidelberg from Bayer, BMS, Boehringer-Ingelheim, Daiichi Sankyo), grants from Charité – Universitätsmedizin Berlin (within Mondafis; Mondafis is supported by an unrestricted research grant to the Charité from Bayer), from University Göttingen (within FIND-AF randomized; FIND-AF randomized is supported by an unrestricted research grant to the University Göttingen from Boehringer Ingelheim), outside the submitted work. Georg Ertl reports significant honoraria for trial leadership from Abbott, and Novartis; has been a consultant for Abbott, Boehringer Ingelheim, Novartis, ResMed, and Vifor (modest); and received significant grant support from Boehringer Ingelheim, Thermo Fisher, Siemens Healthineers, Vifor, and Federal Ministry of Education and Research. Stefan Frantz reports research grants from the German Ministry of Education and Research. He received honoraria from and was on advisory boards for AMGEN Europe, AstraZeneca, Bayer Vital, Boehringer Ingelheim, Bristol-Meyers Squibb GmbH, Daiichi Sankyo, MSD, Novartis, Pfizer, Sanofi, Servier, Vifor. Christiane Angermann reports honoraria for trial leadership from Abbott, Boehringer Ingelheim, and Novartis; has been a consultant for Abbott, Boehringer Ingelheim, Novartis, ResMed, Springer, and Vifor; and received significant grant support from Boehringer Ingelheim, Thermo Fisher, Siemens Healthineers, Vifor, Competence Network Heart Failure, Würzburg, and the Federal Ministry of Education and Research. Stefan Störk reports research grants from the German Ministry of Education and Research, European Union, University Hospital Würzburg; participation in Data Safety Monitoring or Event Adjudication in studies sponsored by Roche and Medtronic; participated on Advisory Boards for Novartis, Bayer, Boehringer Ingelheim, Thermo-Fisher, and Boston Scientific; principal investigator in trials (co-) sponsored by Boehringer Ingelheim, Novartis, and Bayer; and received speaker honoraria from Boehringer Ingelheim, Servier, Novartis, Astra-Zeneca, Pfizer, Bayer, and Thermo-Fisher, outside the submitted work., (Copyright © 2021 Elsevier Inc. All rights reserved.)