Complex sentence: Without the backing of the Commission, DiGregorio's claims to the family leadership lost credibility and, after suffering a heart attack, his faction was briefly headed by Paul Sciacca before slowly disappearing from New York's underworld.
Split into simpler sentences: Without the backing of the Commission, DiGregorio's claims to the family leadership lost credibility. After DiGregorio suffered a heart attack, his faction was briefly headed by Paul Sciacca before slowly disappearing from New York's underworld.