Cardiac arrest can happen to anyone, at any time without any warning. In fact, it is estimated that more than 356,000 sudden cardiac arrests happen outside of the hospital setting in the United States every year, and only less than 10% of the victims survive. Early recognition and timely intervention are critical for survival. One of the key interventions that can help save the life of someone in cardiac arrest is defibrillation, where an electric current is delivered to the heart to correct the heart rhythm. However, not all heart rhythms are shockable. In this article, we’ll explain what shockable and non-shockable rhythms are, what all the shockable rhythms are, what the two non-shockable rhythms are, and how to know if a rhythm is shockable or not.
What Are Shockable and Non-Shockable Rhythms?
When the heart is functioning normally, it beats in a regular pattern, pumping blood and oxygen effectively throughout the body. A heart rhythm is an electrical pattern that stimulates the heart muscle to contract and relax rhythmically. The heart has four chambers: the right atrium, the right ventricle, the left atrium, and the left ventricle. An electrocardiogram (ECG or EKG) is a test that can detect the electrical activity of the heart and produce a visual representation of the heart rhythm.
In the context of cardiac arrest, heart rhythms can either be shockable or non-shockable. Shockable rhythms are abnormal heart rhythms that can be corrected by defibrillation. Non-shockable rhythms are abnormal heart rhythms that cannot be corrected by defibrillation alone but require other interventions such as cardiopulmonary resuscitation (CPR) and advanced cardiac life support (ACLS) algorithms.
What Are All the Shockable Rhythms?
The two most common shockable rhythms are ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT). VF is a chaotic heart rhythm that results in an ineffective pumping action of the ventricles. VT is a rapid heart rhythm that originates in the ventricles and prevents the ventricles from filling properly, leading to reduced blood flow.
Other less common shockable rhythms include programed electrical stimulation (PES)-induced VT and sustained monomorphic VT in the setting of a reentry circuit.
What Are 2 Non-Shockable Rhythms?
The two most common non-shockable rhythms are asystole and pulseless electrical activity (PEA). Asystole is the total absence of electrical activity in the heart and is commonly referred to as a ‘flatline’. PEA is a rhythm that has electrical activity but does not result in a palpable pulse or blood pressure, and can be caused by a variety of factors such as hypoxia, hypovolemia, tension pneumothorax, or electrolyte imbalances.
How Do You Know If a Rhythm Is Shockable or Not?
The only way to determine if a rhythm is shockable or not is by performing an ECG or EKG. An ECG machine will display a visual representation of the heart rhythm, which can be interpreted to determine if the rhythm is shockable or non-shockable. If the rhythm is shockable, immediate defibrillation should be performed. If the rhythm is non-shockable, other interventions such as ACLS algorithms and medications should be initiated.
In summary, recognizing the type of heart rhythm is critical in determining the appropriate intervention. Shockable rhythms such as VF and VT require immediate defibrillation, while non-shockable rhythms such as asystole and PEA require other interventions such as CPR and ACLS algorithms. The use of defibrillation has significantly improved survival rates in cardiac arrest, and proper training and access to defibrillators can help increase the chances of a positive outcome.
References:
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