Complex sentence: Johnson's health was poor, and he had suffered a serious heart attack in 1955 while serving in the U.S. Senate; indeed, he died on January 22,1973, only two days after the new presidential term would have concluded.
Split into simpler sentences: Johnson's health was poor, and he had suffered a serious heart attack in 1955 while serving in the U.S. Senate. Indeed, he died on January 22,1973, only two days after the new presidential term would have concluded.