["The Journal of Physiology, Volume 604, Issue 13, Page 5493-5511, 1 July 2026. ", "\nAbstract figure legend Impact of Omecamtiv Mecarbil (OM) on in‐silico models of heart failure. A mathematical electromechanical model of human ventricular tissue is used to simulate the effects of OM in heart failure with reduced ejection fraction (HFrEF). Multiple mechanical features are quantified and it is observed that, despite the increase in systolic contraction, an increase of diastolic contraction and a prolonged twitch duration can compromise cardiac mechanics. In addition, augmented heart rates are an unsafe condition. Simulations results can help explain the failure of clinical trials. Created in BioRender. Mora, M. (2025) https://BioRender.com/3tk6jd4\n\n\n\n\nAbstract\nHeart failure is a cardiac pathology characterized by causing myocardial dysfunction. The need to improve current pharmacotherapy for patients with heart failure has encouraged the development of more promising compounds. Currently, the amount of experimentation required during the early phases of drug development to assess safety and efficacy is costly, but computer simulations can help accelerate the process. In the present study, we performed computer simulations to investigate the electromechanical effects of the sarcomeric drug omecamtiv mecarbil on cardiac tissue. We used a cellular human electromechanical model to develop a concentration‐dependent numerical model for the pharmacological compound based on previous experimental evidence. It was then implemented on a ventricular slab to extrapolate cellular activity to myocardial tissue scale, and heart failure with reduced ejection fraction conditions was reproduced. In silico results reveal that omecamtiv mecarbil can correct the depressed active force developed by failing myocytes and make the slab contract to the same extent as in healthy conditions. However, additional changes involving contraction times and diastolic function, measured as the time to active tension peak and baseline slab stretch, respectively, can compromise the pumping capacity of the heart. After exploring drug effects at different heart rates, results show that elevated stimulation frequencies (2 Hz), together with overdoses (omecamtiv mecarbil > 0.8 µm), are the main factors reducing fractional shortening and leading to loss of function. We demonstrate that electromechanical simulation results can provide a better understanding of the mechanism of action of a drug and facilitate the redirection of future investigations.\n\n\n\n\n\n\n\n\n\n\nKey points\n\nA new pipeline to assess the efficacy of inotropic drugs based on computational electromechanical models is described.\nOmecamtiv mecarbil increases developed force in failing cardiac tissue.\nUndesirable effects on diastolic function and contraction duration override the positive effects.\nFast heart rates and elevated omecamtiv mecarbil doses aggravate cardiac dysfunction.\n\n\n\n"]