A defibrillator is a medical device that delivers a controlled electrical shock to the heart. Its purpose is to interrupt abnormal electrical activity and allow the heart’s natural pacemaker to resume a normal, effective rhythm. This intervention is often life-saving in emergency situations, acting as a crucial tool in the immediate response to sudden cardiac arrest.
When a Defibrillator is Used
A defibrillator is used for specific life-threatening heart rhythms. The primary conditions necessitating defibrillation are ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT). In ventricular fibrillation, the heart’s electrical activity becomes chaotic and disorganized, causing the ventricles to quiver instead of contract effectively.
Pulseless ventricular tachycardia involves a very rapid heartbeat, preventing the heart from adequately filling with blood, resulting in no detectable pulse. Both rhythms lead to sudden cardiac arrest because they prevent blood from circulating to the brain and other vital organs. A defibrillator analyzes the heart’s electrical rhythm and will only advise a shock if one of these “shockable” rhythms is detected. It is not used for a flat-line (asystole) rhythm or if the patient is conscious and has a pulse.
How the Shock Affects the Body
When a defibrillator delivers a shock, it sends a powerful electrical current through the body. This electrical discharge momentarily stops all chaotic electrical activity within the heart. The aim is to create a brief electrical standstill, allowing the heart’s natural pacemaker, typically the sinoatrial node, to re-establish a coordinated rhythm.
The physiological impact is immediate. The entire body experiences a sudden, forceful muscle contraction, which can cause the patient to arch or convulse briefly. Individuals requiring defibrillation are typically unconscious due to lack of blood flow to the brain, so they do not feel the pain. In rare instances, the shock can cause minor skin burns or superficial tissue damage at the site where the electrode pads are applied.
Immediate Steps After Defibrillation
Immediately following a defibrillator shock, certain actions are emphasized. If the heart has not resumed a normal rhythm, chest compressions (CPR) should be resumed without delay. This continuation of CPR is important because the heart may still be in an ineffective rhythm or may take time to restart pumping blood efficiently.
Automated External Defibrillators (AEDs) often re-analyze the heart rhythm after a set period, typically two minutes of CPR, to determine if another shock is necessary. During the shock delivery, all bystanders and operators must ensure they are not touching the patient, and a clear verbal warning like “clear” is given. Environmental precautions are also important, including moving the patient away from water or flammable materials. After the emergency, the patient requires ongoing medical care and transport to a hospital for further assessment and treatment.