In 1967, he became assistant professor in the department of medicine and head of the coronary artery disease research group at the University of Pisa. In 1979 he was appointed professor of cardiovascular medicine at the Royal Postgraduate Medical School of the
University of London and director of cardiology at
Hammersmith Hospital. In 1991 he returned to Italy, where he became professor of cardiology at the
Università Cattolica del Sacro Cuore in Rome and director of cardiology at the
Agostino Gemelli University Polyclinic. From 2002 to 2008, he was a professor of cardiology at the
Vita-Salute San Raffaele University and director of the cardio-thoracic and vascular department at the
San Raffaele Hospital, both in
Milan. He served on the editorial board of the
New England Journal of Medicine. During his time in Pisa he pioneered the use of
radioactive tracers, and later developed methods using
positron emission tomography to study both blood flow and energy use in the heart. In Pisa he made the first clinical observations of angina as a primary complaint, not caused by excessive myocardial oxygen demand. He also demonstrated the role of
coronary artery spasm in
variant angina. His proof, using double
crossover studies, that nitrates prevent coronary artery spasm provided the first convincing evidence for the now-widespread clinical use of coronary
vasodilators as
anti-ischemic drugs. He further elucidated the mechanisms by which coronary artery spasm occurs in variant angina after moving to London. While at the Hammersmith Hospital, he also showed that there were differences among patients with chronic
stable angina in the
degree of exertion at which chest pains occurred. Moreover, that variability was caused by
narrowing of the arteries in combination with
vasomotor tone, but the two factors interacted in a different way than was observed in variant angina. In other studies, he demonstrated that
vasoconstriction and
thrombosis are jointly responsible for ischemic attacks in patients with acute
myocardial infarction or
unstable angina. He also identified
adenosine as a major chemical mediator of ischemic cardiac pain. With his group in Rome, he developed a hypothesis of dispersed coronary microvascular dysfunction in angina patients with normal coronary angiograms, investigated the mechanisms of angina in patients with
microvascular angina, and made fundamental contributions towards identifying the processes by which
inflammation causes heart attacks in unstable angina. After moving to Milan, he continued his clinical research using newer techniques such as
nuclear magnetic resonance and
computer tomography to explore cardiac and coronary function. Maseri described his primary research interest as discovering what makes one patient different from another. In the final stage of his research career, he used the database of patients at the Fondazione per il Tuo Cuore to conduct research into individual paths to pathology. == Honours and awards ==