The idea of treating heart diseases with thyroid hormones (THs) has been around for over 60 years, but has never been proven or disproven. Many things have contributed to this open question, including: (1) lack of financial incentive; (2) negative effects of several influential clinical studies that actually used an overdose of TH analogs rather than actual THs; and (3) lack of a proven TH treatment/monitoring protocol than can be safely translated to humans. Nonetheless, a growing body of pre-clinical and clinical evidence suggests that we should be asking the following question- “How many of your symptoms are due to the diagnosed heart disease and how many are due to low cardiac tissue TH levels?” Those who have not kept up with recent evidence may be surprised by what we have learned recently. In particular, it now appears that heart diseases in general may trigger low cardiac tissue T3 levels, a condition that by itself has been shown to cause heart failure. THs offer the promise of improving ventricular contraction and relaxation, improving coronary blood flow, inhibiting atherosclerosis, and new results suggest that restoration of cardiac tissue THs may even reduce the incidence of arrhythmias in heart diseases.