Source : Webster's Revised Unabridged Dictionary (1913)

Asystole \A*sys"to*le\, n. [Pref. a- not + systole.] (Physiol.)
   A weakening or cessation of the contractile power of the
   heart.

Source : WordNet®

asystole
     n : absence of systole; failure of the ventricles of the heart
         to contract (usually caused by ventricular fibrillation)
         with consequent absence of the heart beat leading to
         oxygen lack and eventually to death [syn: {cardiac arrest},
          {cardiopulmonary arrest}]