Leslie was born on July 8, 1934 in New York City. Growing up in Brooklyn, he lived with his parents, Murray and Rose, and his older sister, Elayne, on the corner of Washington Ave and Montgomery Street directly across from the Brooklyn Botanic Gardens. Ebbets Field was just around the corner and Les was fascinated with seeing the Brooklyn Dodgers on the field. His formative years were spent at Public School 241. Just a short trolley ride south, down famous Flatbush Avenue, was his high school, Erasmus Hall.
In the early 1950’s, Les left Brooklyn to attend college at the University of Illinois and then went on to Chicago Medical School where he graduated in 1959 with a specialty in cardiology. In Chicago, he met and married the love of his life, Rita Posen. They moved to Washington DC, where Les continued his post graduate training at DC General Hospital. Following his commission in the US Navy, Les spent the next five years at the US Naval Hospital in Philadelphia. Rita and Les settled down in Southern New Jersey to raise a family in Cherry Hill and then Haddonfield.
After his service as an officer in the Navy, he was an attending physician and Director of the Cardiac Care Unit at Thomas Jefferson University Hospital as well as a professor of medicine and the Director of the Cardiac Care Unit and Cardiac Physiology Research Lab at Jefferson Medical College. After leaving Thomas Jefferson University Hospital, he became Director of the Cardiac Catheterization Laboratory at Bryn Mawr Hospital and the Director of Cardiovascular Services at Our Lady of Lourdes Hospital. In addition, he was a consultant at Pennsylvania Hospital, Bryn Mawr Hospital and Underwood Memorial Hospital for many years. Leslie was board certified by the National Board of Medical Examiners, American Board of Internal Medicine and Subspecialty Board of Cardiovascular Disease.
Leslie is survived by his wife, Rita, of 65 years, daughters Catherine Landrum and Carolyn Manchel (Robert) and son John Wiener (Marybeth), as well as six grandchildren, Emily and Paige Landrum, Alexandra and Leah Manchel and Ryan and Jack Wiener.