Before Dr. William Ganz helped develop a more flexible catheter, intimate examinations of the heart were performed by inserting a relatively stiff plastic catheter into a large artery, such as in the groin.

Dr. William Ganz, who survived a Nazi labor camp to become an internationally recognized cardiologist who co-invented the Swan-Ganz catheter for monitoring heart conditions and who was one of the first physicians to use clot-busting enzymes to open blocked arteries that cause heart attacks, died Tuesday night of natural causes. He was 90. Ganz “changed the life of millions through his significant contributions to medicine,” said his colleague, Dr. P.K. Shah, director of the cardiology division at Cedars-Sinai Heart Institute, “but he never lost sight of the importance of family and friends. He has left us a rich and enviable legacy.”

The Swan Ganz catheter is inserted into an artery and then the balloon tip is wedged into narrow blood vessels near the heart in order to measure blood pressure. The catheter is actually inserted into a vein and the balloon is inflated in the small vessels of the lung to read an indirect measure of the pressure in the left atrium of the heart. Also, the obituary said that his son Dr. Peter Ganz is a cardiologist at Harvard Medical School. He is now chief of cardiology at San Francisco General Hospital.

Before Ganz’s work, such intimate examinations of the heart were performed by inserting a relatively stiff plastic catheter into a large artery, such as in the groin, and carefully guiding it to the heart using a fluoroscope, a time-consuming and occasionally dangerous process. In 1970, Ganz and H.J.C. “Jeremy” Swan of Cedars-Sinai Medical Center developed the idea of placing an inflatable balloon at the tip of a more flexible catheter. Once inserted into the artery, pressure from blood flowing toward the heart pushed it along, directing it to the heart. Although external guidance was still necessary, the procedure was faster and safer. The balloon also wedged the device into narrow blood vessels near the heart to allow blood pressure to be measured.

Ganz later said he got the idea by watching sailboats. He also developed devices to attach to the catheters to measure blood pressure and other characteristics of blood flow. The catheter and the devices are now used by physicians worldwide.

Ganz also played a key role in the development of thrombolysis, in which enzymes are injected into the bloodstream to break down clots that block the vessels. He demonstrated that such enzymes would work in animals; then, in 1982, he and Shah conducted the first clinical trials in humans. That technique is also now used worldwide, although it has been supplanted in many cases by balloon angioplasty, in which a balloon-tipped catheter is used to flatten the clot and restore blood flow.

William Ganz was born in 1919 in the small town of Kosice in what is now the Republic of Slovakia. An honor student and soccer player in high school, he enrolled in the Charles University School of Medicine in Prague in 1937. When the Nazis occupied Czechoslovakia two years later, the students were all dispersed to their regions of origin. Kosice was only a few miles from the Hungarian border, and the Jewish Ganz was interned at a Hungarian labor camp. He was scheduled to be sent to Auschwitz in 1944, but, as he told Swan, “I refused the offer and instead went underground.” He returned to Charles University after the war and graduated at the top of his class in 1947.

He worked in Czechoslovakia for nearly 20 years but grew disillusioned with Communist orthodoxy. In 1966, he ostensibly took his wife and two sons on a vacation to Italy, a privilege reserved for only a few. Upon reaching Vienna, he applied for an entry visa to the United States. Because he had relatives in Los Angeles, he was allowed to enter, and contacts got him a position at Cedars, where he spent the rest of his career. His wife, Magda, died in 2005. He is survived by his two sons, Dr. Tomas Ganz, a pulmonologist at UCLA, and Dr. Peter Ganz, a cardiologist at Harvard Medical School; and five grandchildren.

By Thomas H. Maugh II of the L.A. Times