CONFLICT OF INTEREST J.A. reports institutional grants from Bristol-Myers Squibb/Pfizer and Boehringer Ingelheim. Z.H. reports lecture fees from Boehringer Ingelheim, Bristol-Myers Squibb, Pfizer and Roche Diagnostics; consulting fees from Boehringer Ingelheim, Bristol-Myers Squibb, Meda, Merck Sharp & Dohme, Pfizer, and Roche Diagnostics; research grants from the Swedish Society for Medical Research [S17-0133] and the Swedish Heart-Lung Foundation . J.L. reports institutional research grant from Bristol-Myers Squibb/Pfizer. J.H.A. reports institutional research grants Bayer, Bristol-Myers Squibb, CryoLife, Ferring, US Food & Drug Administration, US National Institutes of Health, and XaTek, and consulting fees/honoraria from AbbVie, Bayer, Bristol-Myers Squibb, CryoLife, Pfizer, Portola, and XaTek. B.G. is a data safety monitoring board member at Boston Scientific, the Cardiovascular Research Foundation, Janssen Research & Development, Mount Sinai Morningside, Teva Pharmaceutical Industries, and MyoKardia; reports consulting fees from Coretherapix SLU, Janssen Scientific Affairs, and Sirtex Medical; personal fees from Kowa Research Institute and Medtronic. C.B.G. reports research grants and consulting/speaker fees from Bristol-Myers Squibb, Janssen Pharmaceutica Products, L.P., Novartis Pharmaceutical Company, Pfizer, and Boehringer Ingelheim; research grants from AKROS, Apple, AstraZeneca, Daiichi-Sankyo, US Food & Drug Administration, GlaxoSmithKline, and Medtronic Foundation; consulting/speaker fees from Abbvie, Abiomed, Anthos Therapeutic, LLC, Bayer Corp US, Boston Scientific Corp, CeleCor Therapeutics, Correvio, Espero BioPharma, Medscape, Medtronic Inc., Merck, National Institutes of Health, NovoNordisk, Philips, Rhoshan Pharmaceuticals, and Roche Diagnostics. M.H. reports as an employee of Bristol-Myers Squibb he received salary and company stock as compensation. J.H. has nothing to report. E.M.H. reports grant from Janssen; consultant/advisory board fees and honoraria from Boehringer Ingelheim; consultant/advisory board fees from Medtronic and Roche; honoraria from Bristol-Myers Squibb. R.D.L. reports institutional research grant and consulting fees from Bristol-Myers Squibb, GlaxoSmithKline, Medtronic, Pfizer, and Sanofi; consulting fees from Bayer, Boehringer Ingelheim, Daiichi Sankyo, Merck, and Portola. J.J.V.McM. reports fees to his institute for work on clinical trials, consulting and other activities from Alnylam, Amgen, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Cardurion, Cytokinetics, Dal-Cor, GlaxoSmithKline, Ionis, KBP Biosciences, Novartis, Pfizer, and Theracos; personal fees from Abbott, Alkem Metabolics, Eris Lifesciences, Hikma, Ionis, Lupin, ProAdWise Communications, Sun Pharmaceuticals, and Servier. J.O. reports fees to his institution from AstraZeneca, Boehringer Ingelheim, Bayer, Bristol-Myers Squibb, Daiichi Sankyo, Pfizer, Portola, Roche Diagnostics, and Sanofi. A.S. reports institutional research grants from AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb/Pfizer, GlaxoSmithKline, and Roche Diagnostics; consulting fees from Olink Proteomics. L.W. reports institutional research grants, consultancy fees, lecture fees, and travel support from Bristol-Myers Squibb/Pfizer, AstraZeneca, GlaxoSmithKline, and Boehringer Ingelheim; institutional research grants from Merck & Co and Roche; holds two patents involving GDF-15.