[3] In his career he made a multitude of contributions published in peer review journals, and was the cardiologist to the Shah of Iran and his family and later to Ayatollah Khomeini until 1980.

[failed verification][6] From 1970 to 1974, as Professor of Cardiology at the University of California, Davis School of Medicine, Massumi continued research in the new field of electrophysiology, contributing over 40 original papers published in peer-reviewed journals.

Simultaneously, as Professor and Chief of the Department of Cardiology at Tehran University, Massumi laid the groundwork for an up-to-date teaching center which, to this day, continues to produce qualified cardiologists.

The pupils that Massumi has trained at the University of Tehran have become among the most respected cardiologists in Iran and have been the driving force in building ultra-modern cardiac centers in several major cities in the nation.

Into his 80s he continued to publish articles, as recently as October 2010 at the age of 84,[12] making him a successful contributor to the academic body of knowledge in the field for seven decades.