Thomas Joseph O’Neill IV, MD, PhD (T.J.) is an academic cardiologist and physician-scientist specializing in advanced heart failure and transplant cardiology. He currently serves as an Attending Physician in Advanced Heart Failure at the Harrington Heart & Vascular Institute within University Hospitals Health System in Cleveland, Ohio, and is an Associate Professor of Medicine at Case Western Reserve University. He also holds a leadership role as Associate Program Director of the Cardiovascular Medicine Fellowship at CWRU/UH.

Dr. O’Neill completed his undergraduate studies at Dartmouth College, earning a Bachelor of Arts in Biophysical Chemistry. He went on to pursue combined medical and doctoral training at the University of Virginia, where he earned both his MD and PhD in Molecular Physiology. His doctoral research focused on the role of bone marrow–derived cells in hypoxia-mediated angiogenesis and arteriogenesis, contributing to a deeper understanding of vascular biology and repair mechanisms.

Following medical school, Dr. O’Neill completed his Internal Medicine residency and Cardiovascular Disease fellowship at the University of North Carolina at Chapel Hill. He then pursued subspecialty training in Advanced Heart Failure and Transplant Cardiology at the University of Pennsylvania.

Prior to his current appointment in Cleveland, Dr. O’Neill served as an Attending Physician in Advanced Heart Failure and Assistant Professor at Wake Forest School of Medicine, where he was actively involved in clinical care, research, and medical education as the associate director of the heart failure program. During his tenure, he contributed extensively to fellowship training, curriculum development, and multidisciplinary cardiovascular care.

Dr. O’Neill is board certified in Internal Medicine, Cardiovascular Disease, and Advanced Heart Failure and Transplant Cardiology. He is an active member of several professional heart failure cardiology and transplant societies, including being a Fellow of the American College of Cardiology 

Beyond that his clinical and research interests include immunosuppression related to heart transplant, frailty in the advanced heart failure population. interactions between arrhythmia and heart failure. invasive hemodynamic assessment, and cardiopulmonary exercise testing with a number of local, regional and national presentations and publications in these areas.