The metabolic rewiring of cardiomyocytes is a widely accepted hallmark 
of heart failure (HF). These metabolic changes include a decrease in 
mitochondrial pyruvate oxidation and an increased export of lactate. We 
identify the mitochondrial pyruvate carrier (MPC) and the cellular 
lactate exporter monocarboxylate transporter 4 (MCT4) as pivotal nodes 
in this metabolic axis. We observed that cardiac assist device-induced 
myocardial recovery in chronic HF patients was coincident with increased
 myocardial expression of the MPC. Moreover, the genetic ablation of the
 MPC in cultured cardiomyocytes and in adult murine hearts was 
sufficient to induce hypertrophy and HF. Conversely, MPC overexpression 
attenuated drug-induced hypertrophy in a cell-autonomous manner. We also
 introduced a novel, highly potent MCT4 inhibitor that mitigated 
hypertrophy in cultured cardiomyocytes and in mice. Together, we find 
that alteration of the pyruvate-lactate axis is a fundamental and early 
feature of cardiac hypertrophy and failure.