Can a thyroid hormone rebuild failing hearts?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Aged 18-80 years, male or female; * Confirmed diagnosis of ischemic HF with left ventricular ejection fraction (LVEF) ≤ 40% (measured by echocardiography within 1 month of Screening); * Stable symptoms; NYHA class II-III without recent admission (1 month) for acute decompensation; * Receiving guideline-based standard HF therapies at the maximum tolerated doses for \>1 month. Patients on other beta-blockers will be switched to metoprolol succinate at equivalent doses for 3 weeks. * Presence of ICD for \>1 month or implantable cardiac resynchronization therapy defibrillator (CRT-D) for \>3 months * Understand and sign the informed consent form. Exclusion Criteria: * LVEF \> 40%; * Unremitting atrial fibrillation during the screening period or clinically significant ventricular tachycardia (on ICD interrogation); * Non-ischemic HF including hypertrophic cardiomyopathy, peripartum or chemotherapy-induced cardiomyopathy, other non-ischemic cardiomyopathies, constrictive pericarditis, significant and uncorrected valvular heart disease (severe regurgitation or severe stenosis or valvular disease requiring surgery), congenital heart disease, primary pulmonary hypertension or secondary severe pulmonary hypertension (≥ 70 mmHg); large pericardial or pleural effusions; right heart failure due to lung disease; * Recent admission (1 month) for acute decompensated HF; * Angina pectoris, cerebrovascular accident, myocardial infarction, revascularization (PCI or other surgery), carotid artery or other large vessel surgery, or cardiac resynchronization therapy (CRT) implant within the past 3 months; * Planned revascularization within 6 months; * History of heart transplantation, use of ventricular assist device (VAD) or preparation for heart transplantation, VAD; * Liver dysfunction (bilirubin or alkaline phosphatase \> 2 times the upper limit of normal (ULN), aspartate aminotransferase or alanine aminotransferase \> 3 times the upper limit of normal), estimated glomerular filtration rate (eGFR) calculated using the Modification of Diet in Renal Disease Study (MDRD) method \< 30 ml/min/1.73 m2; * Systolic blood pressure \< 90 mmHg or \> 160 mmHg; * Blood K+ \< 3.2 mmol/L or \> 5.5 mmol/L; * Women of childbearing age who are planning to become pregnant within 2 years, and pregnant or lactating women; * Patients whose survival time is expected to be less than 6 months as judged by the investigator; * Those who have participated in any drug clinical trial within the previous 3 months; * Severe neurological disorders (Alzheimer's disease, progressive parkinsonism); * The subjects with a history of cancer that limits life expectancy to \<1 year; * Endocrine disorders include thyroid disease, thyroid replacement therapy, pheochromocytoma, thyromegaly, etc. * The subject, in the judgment of the Investigator, is unable to complete the study or to comply with the requirements of the study (for administrative or other reasons); * Prisoners; * Adults unable to consent;