A-48 year old presents with history of precordial chest pain. He has BP of 80/60 mm of Hg. EKG shows wide QRS complex with no preceding P waves and a rate of 112/min. The most immediate step to the management of this patient would be
Correct Answer: DC electrical cardioversion
Description: Delivery of direct current (DC) shocks to the hea has long been used successfully to conve abnormal hea rhythms back to normal sinus rhythm. In 1775, Abildgaard repoed using electricity to both induce and revive a hen from lifelessness. Beck was the first physician to use DC defibrillation on a human to treat ventricular fibrillation (VF, vfib) in a 14-year-old during cardiac surgery in 1947. Fifteen years later, Lown applied synchronized DC shocks to the hea to conve atrial fibrillation (AF, afib) and ventricular tachycardia (VT, vtach) to normal sinus rhythm. Cardioversion is defined as a "synchronized DC discharge, and does not apply to ventricular defibrillation or to the pharmacologic reversion of arrhythmias." It is typically used to terminate life-threatening or unstable tachycardic arrhythmia (unstable ventricular and supraventricular rhythms) in patients who still have a pulse but who are hemodynamically unstable. The DC electrical discharge is synchronized with the R or S wave of the QRS complex. Synchronization in the early pa of the QRS complex avoids energy delivery near the apex of the T wave in the surface electrocardiogram (ECG), which coincides with a vulnerable period for induction of ventricular fibrillation. The peak of the T wave represents the terminal poion of the refractory state when adjacent hea fibers are in differing states of repolarization. Ref Harrison 20th edition pg 1515
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