Asystole means there is no ventricular activity.  In most cases, this is a lethal arrhythmia with no electrical or mechanical activity.

ECG Interpretation:


  • Is the rhythm regular or irregular?
    • No rhythm


  • What is the rate?
    • There is no rate, so no other rate findings apply

P Wave

  • Are they present?
    • In some cases, a small P wave can sometimes be seen, but it’s not followed by any other waveforms. In rare cases, this can mean that the atrial pacemaker may be trying to send an impulse but has no ventricular reaction.  
    • No other P wave findings apply.

PR Interval

  • There is no P wave, so there is not a PR interval


  • Is the QRS interval less than 0.12 seconds?
    • There are no QRS complexes, so no other QRS questions apply

Cardiac Interpretation

Because there is no myocardial, electrical, or mechanical activity, there is no pulse and no circulation of blood.  This is most commonly seen after a time of untreated or unconverted ventricular fibrillation.

Though asystole is most commonly seen after extended untreated sudden cardiac arrest, it can also be caused by:

  • Hypothermia
  • Hyper or hypokalemia
  • Hypoxia
  • Hydrogen ions, which means acidosis
  • Toxins
  • Cardiac tamponade
  • Tension pneumothorax
  • Pulmonary or coronary thrombosis