• In asystole, there is sinus arrest and no pacemaking activity of any of the automaticity foci (i.e. atria, AV junction, ventricles).
• As a result of no electrical activity, there is a flat line shown on ECG.
• Fine ventricular fibrillation might also present as a flat line.
• Occasionally, there will be escape beats or rhythm from other automaticity foci (ie. atria, AV junction, ventricles) creating a “brady-asystolic pattern" (e.g. junctional escape rhythm or ventricular escape rhythm).
• In pulseless electrical activity (PEA), the heart stops pumping due to problems arising from outside of the conduction system.
• Major causes of PEA include (5Hs & 5Ts):
Hypovolemia
Hypoxemia
Hyperkalemia
Hypothermia
Hydroden ions (acidemia)
Thrombosis (myocardial infarction)
Thromboembolism (pulmonary embolism)
Tamponade
Tension pneumothorax
Tablets/Toxins
• ECG might show normal sinus rhythm or benign arrhythmia.
• In fatal tachyarrhythmia, there are erratic, asynchronous depolarizations of ventricular myocardial cells leading to inefficient contraction of the global heart hence little/ no cardiac output.
• ECG shows ventricular fibrillation that occurs either spontaneously or follows runs of ventricular tachycardia.
