John Michael Criley, the cardiologist known to colleagues and patients as J. Michael Criley, who gave mitral valve prolapse its name and helped bring lifesaving emergency care to the streets of Los Angeles, died on June 15, 2026. He was 95 and had long made his home in Palos Verdes Estates, California.

Born on May 23, 1931, Criley earned his medical degree at Stanford University School of Medicine and went east to train at Johns Hopkins, where he completed a residency on the storied Osler Service and a fellowship in cardiology before directing the hospital's cardiac catheterization laboratories. He then returned to his native California, joining the faculty of the UCLA School of Medicine and beginning a relationship with Harbor-UCLA Medical Center in Torrance that would span more than four decades, including roughly twenty years leading its cardiology division, according to the EMS Museum.

It was at Harbor-UCLA that Criley made one of the contributions for which he is most remembered. Studying the heart's mitral valve, he showed that a long-misunderstood finding was caused not by an aneurysm of the valve leaflet but by its displacement, and he gave the condition the name by which it is now universally known: mitral valve prolapse. He was equally inventive in the science of resuscitation, discovering cough CPR and, working with Drs. James Niemann and John Rosborough, helping define how both coughing and manual chest compression move blood selectively toward the brain. The American College of Cardiology credited him with explaining the functional anatomy that reshaped how clinicians understand the heart.

Perhaps his most public legacy began in 1969, when Criley helped found the Los Angeles County paramedic program. It started modestly, with eighteen county firefighters and six city firefighters reporting to Harbor General Hospital to learn skills that had until then belonged only to physicians. Convinced that trained civilians could deliver coronary care before a patient ever reached the hospital, Criley worked with County Supervisor Kenneth Hahn to win political backing, including from Governor Ronald Reagan, for the Wedworth-Townsend Act that allowed paramedics to operate across jurisdictional lines. The model that grew out of that effort became a template for emergency medical services across the country.

A gifted teacher as well as a researcher, Criley spent more than half a century at the bedside and the lectern. Over the years he trained more than two hundred cardiologists and taught cardiology to well over six thousand medical students, residents and nurses, building interactive multimedia teaching programs in three languages and co-founding Blaufuss Medical Multimedia with his sons Stuart and David. He published more than a hundred research papers and helped write two cardiology textbooks, as documented by EurekAlert. In 2016 the American College of Cardiology recognized him with its Distinguished Teacher Award, citing his "innovative, outstanding teaching characteristics and compassionate qualities."

John Michael Criley leaves a legacy measured in both ideas and lives. The vocabulary he helped create still guides cardiologists at the bedside, the resuscitation insights he pursued still inform how clinicians respond to a stopping heart, and the paramedic system he championed has carried hope to countless families in their most frightening moments. Through the physicians he mentored and the students he inspired, his patient, exacting devotion to understanding the human heart continues to ripple outward, a quiet reminder that careful teaching can save as many lives as any single discovery.