Sudden cardiac death is often the first manifestation of arrhythmogenic cardiomyopathy (AC), given the lack of markers to predict disease progression. A study in Science Translational Medicine reports that the myocardial levels of enzymes involved in ketone metabolism are increased in patients with AC, in agreement with the hypothesis that metabolic markers of increased fatty acid oxidation (FAO), such as those involved in ketone production and utilization, might provide clues for the diagnosis of AC. Specifically, the plasma levels of the ketone body β-hydroxybutyrate (β-OHB) were higher among probands than in healthy volunteers and correlated with the occurrence of major adverse cardiac events. Furthermore, plasma β-OHB concentration increased progressively with disease severity, supporting its use as a clinical marker of adverse disease progression in both patients with AC and their asymptomatic relatives.