Mahmood Mirhoseini

Dr. Mahmood ("Sid") Mirhoseini, M.D., practitioner and pioneer in cardiothoracic and cardiovascular surgery, died in Oak Creek, Wisconsin, on March 13, 2026.

Mahmood was born in Joupar, Kerman, Iran, on February 25, 1930, to Ata Mirhosseini and Turan Zandipour. He was the eldest of nine children.

Mahmood immigrated to the United States in 1957 with a Fulbright Scholarship to train in general surgery at Jewish Hospital (Mercy Health) in Cincinnati, OH. There, he met and married his first wife, Judith Hyser. Subsequent training in vascular surgery was completed at the University of Manitoba. His first practice was established in Athens, WI, followed by Medford, WI. In the late 1960s, he trained in cardiothoracic surgery at Marquette Medical School and was among the first to perform open heart bypass surgery in Milwaukee. With the family's move to Wausau, WI, in 1969, Dr. Mirhoseini brought open heart surgery to the area.

Dr. Mirhoseini moved his surgical practice to Milwaukee, WI, in the mid-1970s and was re-married to Mary Cayton, a nurse and physician assistant. Over the next 30 years, they wrote more than one hundred scientific papers on cardiac and thoracic subjects, and spoke at world-wide conferences and symposiums. Most notably, they developed the Transmyocardial Laser Revascularization (TMLR) procedure for open heart surgery, a technique, which uses a laser to create channels into the heart muscle to improve blood flow. TMLR offered new hope to patients who had diffuse heart disease or were otherwise ineligible for bypass surgery. Their ongoing research resulted in eight U.S. patents and six international patents.

Dr. Mirhoseini never retired. After he stopped performing surgery, he transitioned to research with a colleague and, as recently as 2023, obtained another patent for improved laser technology for TMLR that also uses AI for analyzing patient-related data.

Although medicine was always the focus of his life, Mahmood was also an avid reader and passionate about world history, Persian poetry, and music. He was a lifelong learner, with special interests in chemistry, nanotechnology, and quantum physics. In his final years, he found great joy in spending time with his great-granddaughters, who in turn loved seeing "Papa."

Even though he emigrated from Iran to the U.S. as a young man, Mahmood never forgot his homeland. He spoke often of Iran's rich history and physical beauty. In his last decades, he returned to Iran for periods to teach medical and surgical residents in Tehran.

Mahmood is survived by his children Andrea Chiroff, Greenfield, WI; David (Nadine) Mirhoseini, Morgantown, WV; Laura Mirhoseini, Franklin, WI; and Krista (Rory) Mirhoseini, Tavira, Portugal; stepdaughter Jill Cayton, Germantown, WI; grandchildren Callie, Katherine, Griffin, Madeline, Maeve, Sarah, Hannah Rose, and Holly; great-grandchildren Ada, Sloane, and Elena; and siblings Mustafa (Saeideh), Homah (Darush), Morteza (Shahrzad), Simin, Hossein (Mahshid), and Hassan (Forogh), niece Mina Mirhoseini, and many other nieces and nephews.

He was preceded in death by his parents, daughter Sheila Helm, brother Mohammad ("Saleh"), sister Mahin, wife Mary, former wife Judith, great-grandson Theo Schlicht, and son-in-law James Chiroff.

A private family service was held. Remembrances may be made to the American Heart Association or Project Bubaloo, a nonprofit organization dedicated to supporting research for congenital heart disease, which took the life of Dr. Mirhoseini's great-grandson, Theo.