asystole vs heart failure

asystole

noun
  • Absence of systole; failure of the heart to contract. 

heart failure

noun
  • The cessation of the heartbeat; cardiac arrest. 

  • The chronic inability of the heart to pump a sufficient amount of blood throughout the body, leading to a pooling of blood and shortness of breath. 

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