ATM and hypertrophy: To assess the influence of ATM haplodeficiency on post‐MI cardiac hypertrophy, we also performed wheat germ agglutinin staining, and the cross‐sectional cardiomyocyte area in ATM+/− mice was markedly larger than that in WT mice 28 days after MI (Figure S2B) and showed disarrayed collagen fiber alignment within the infarct zone in ATM+/− mice after MI (Figure S2C).