STAT3 participates in protection against myocardial infarction (MI), cardiac ischemia/reperfusion (I/R) injury, and peripartum cardiomyopathy (PPCM) by reducing apoptosis, increasing the expression of survival proteins, protecting mitochondrial respiration and metabolism, and delaying mitochondrial permeability transition pore (mPTP) opening. The gene discussed is STAT3; the disease is peripartum cardiomyopathy.