agonal heart rhythm agonal heart rhythm in medicine, an agonal heart rhythm is a variant of asystole. agonal heart rhythm is usually ventricular in origin. occasional p waves and qrs complexes can be seen on the electrocardiogram. the complexes tend to be wide and bizarre in morphological appearance. clinically, an agonal rhythm is regarded as asystole and should be treated equivalently, with cardiopulmonary resuscitation and administration of intravenous adrenaline. as in asystole, the prognosis for a patient presenting with this rhythm is very poor. sometimes this appears after asystole or after a failed resuscitation attempt. not to be confused with agonal respiration.