heart attack vs pale rider

heart attack

noun
  • Death or failure. 

  • An acute myocardial infarction, sometimes fatal, caused by the sudden occurrence of coronary thrombosis, which obstructs the blood supply to the heart and leads to necrosis of heart muscle tissue. 

pale rider

noun
  • Death, the Grim Reaper or angel of death; and one of the Four Horsemen of the Apocalypse. 

How often have the words heart attack and pale rider occurred in a corpus of books? (source: Google Ngram Viewer )