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KEY POINTS
Biphasic waveform cardioversion is safe and equally effective as monophasic cardioversion, using much lower energy with reduced post-shock complications such as cardiac dysfunction, dysrhythmias, and skin burns.
Defibrillation or unsynchronized cardioversion is indicated in any patient with pulseless VT/VF or unstable polymorphic VT, where synchronized cardioversion is not possible.
Synchronized cardioversion is utilized for the treatment of persistent unstable tachyarrhythmia in patients without loss of pulse. Amongst this category, AF remains the most frequently encountered.
In critically ill patients, unstable supraventricular tachyarrhythmias benefit from individualized therapy such as inotrope and vasopressor support, antiarrhythmic medications or mechanical ventilation and not necessarily electrical cardioversion as the first treatment.
It is important to become familiar with the cardioversion device available, the appropriate energy settings and the correct placement of the paddles to ensure effective and timely shock administration.
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The incidence of cardiac arrhythmias in critically ill patients has been shown to be considerable, ranging from less than 50% in trauma patients to more than 90% in those admitted with a primary cardiac illness.1 In the ICU, the most common arrhythmias are atrial fibrillation (AF) and ventricular tachycardia (VT).2 These arrhythmias vary in their presentation from incidental findings on telemetry to symptomatic episodes with profound compromise in cardiac and pulmonary function. Rapid diagnosis and critical interventions are important as these arrhythmias cause hemodynamic instability, prolong ICU length of stay, and increase morbidity and mortality.2,3
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Electrical current or shocks delivered to the chest to terminate ventricular fibrillation (VF) was first reported in the 1950s.4 Today, defibrillation is an established component of the Advanced Cardiovascular Life Support (ACLS) algorithm for pulseless VT/VF. The delivery of an electrical shock results in simultaneous depolarization of the myocardium making the heart refractory to the ongoing disordered electrical activity. This allows for the interruption of the underlying malignant rhythm and reestablishment of the normal electrical rhythm of the heart.5,6
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In the case of tachyarrhythmias where the rhythm is organized and the patients have a palpable pulse, an electrical shock is given as a synchronized cardioversion. Cardioversion refers to the delivery of an electrical shock that is timed to the peak of the R wave on the EKG. This synchronization ensures that the electrical stimulation occurs only during the refractory period of the cardiac cycle minimizing the risk of iatrogenic arrhythmias. The literature on cardioversion can be confusing as many alternate terms such as external cardioversion, synchronized cardioversion, DC cardioversion, and transthoracic DC cardioversion are used interchangeably.
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Traditionally monophasic waveform cardioverters were used until the introduction of biphasic waveform cardioversion in the mid-1990s. Increasingly more cardioverters in the ICU are biphasic. Biphasic waveform cardioversion is safe and as equally effective as monophasic cardioversion, using much lower energy with reduced post-shock complications such as cardiac dysfunction, dysrhythmias, and skin burns.7,8...