Dr. Mathisen is the Distinguished Hermes C. Grillo Professor of Surgery at the Harvard Medical School after serving 25 years as Chief of Thoracic Surgery at the Massachusetts General Hospital. He did his general surgery and cardiothoracic training at the Massachusetts General Hospital. He spent two years in the Surgery Branch of the National Cancer Institute of Health in Bethesda, Maryland.
He has written over 450 manuscripts and chapters and five books. He is past Chairman of Thoracic Residency Review Committee, past President of the Thoracic Surgery Directors Association, former Chief of Thoracic Surgery and former Program Director of the MGH Cardiothoracic Surgery Residency. He is past President of the Society of Thoracic Surgeons, Director of the American Board of Thoracic Surgery and Counselor of the European Association of Cardiothoracic Surgery.