SARS-CoV2 infection leads to cardiac injury and dysfunction in 20-30% of hospitalized patients and higher rates of mortality in patients with pre-existing cardiovascular disease. Inflammatory factors released as part of the 'cytokine storm' are thought to play a critical role in cardiac dysfunction in severe COVID-19 patients. Here we use human cardiac organoid technology combined with high sensitivity phosphoproteomics and single nuclei RNA sequencing to identify inflammatory targets inducing cardiac dysfunction. This new pipeline allowed rapid progress and identification of putative therapeutics. We identify a novel interferon-gamma driven BRD4 (bromodomain protein 4)-fibrosis/iNOS axis as a key intracellular mediator of inflammation-induced cardiac dysfunction. This axis is therapeutically targetable using BRD4 inhibitors, which promoted full recovery of function in human cardiac organoids and prevented severe inflammation and death in a cytokine-storm mouse model. The BRD inhibitor INCB054329 was the most efficacious, and is a prime candidate for drug repurposing to attenuate cardiac dysfunction and improve COVID-19 mortality in humans.