Gregory M Marcus, M.D., M.A.S. is Professor of Medicine at the University of California, San Francisco (UCSF), Associate Chief of Cardiology for Research at UCSF Health, and the inaugural Endowed Professor of Atrial Fibrillation Research. His research is dedicated to understanding the fundamental causes of abnormal heart rhythms, identifying optimal therapeutic approaches for those arrhythmias, understanding the overall health effects of common exposures such as caffeine, alcohol, tobacco smoke, and cannabis, and using technology and wearable sensors to enhance health and the efficiency of patient-oriented research. He is one of the founders and continues to serve as one of the Principal Investigators of the world-wide, internet-based, Health eHeart Study, the NIH-funded national infrastructure to facilitate mobile health, called Eureka, and the COVID-19 Citizen Science Study. He runs several ongoing single-center and multi-center randomized, prospective trials, and frequently analyzes secondary datasets, including administrative data, NIH-funded cohort data, and data from wearables and sensors. Samples of the results of his original research include: elucidating relationships between race, ancestry, and atrial fibrillation; demonstrating the importance of common cardiac ectopy pertaining to atrial fibrillation and heart failure risk; characterizing the effects of alcohol on atrial fibrillation risk; describing relationships between coffee consumption and arrhythmia risk; performing the first study to show a smartwatch could detect atrial fibrillation; demonstrating that common left ventricular ablation procedures lead to brain emboli; demonstrating real-time effects of common exposures using randomized N-of-1 trial designs.

A graduate of UC, San Diego as a Philosophy major, he attended medical school at George Washington University. He completed his internship, residency, and served as Chief Medical Resident at Stanford. Subsequently, he completed his general cardiology and cardiac electrophysiology fellowships at UCSF. As part of an NIH-funded career development award, he then completed a Masters in Advanced Studies in Clinical Research at UCSF.