Rhythm Recognition (ECG)
Fast, correct rhythm identification decides which arm of the algorithm you follow. This chapter separates shockable from non-shockable arrest rhythms and reviews the tachy- and brady-rhythms you must recognize.
Shockable vs. non-shockable arrest rhythms
The most consequential decision in a pulseless patient is whether the rhythm is shockable. Ventricular fibrillation (a chaotic, disorganized waveform) and pulseless ventricular tachycardia (a rapid, wide, regular complex without a pulse) are shockable — defibrillation is the definitive treatment. Asystole (a confirmed flat line) and pulseless electrical activity (an organized-appearing rhythm with no pulse) are non-shockable and are treated with CPR, epinephrine, and correction of reversible causes. Confirm asystole in more than one lead so you do not mistake fine VF or a disconnected lead for a flat line.
Reading the perfusing tachy- and brady-rhythms
For a patient WITH a pulse, first sort by QRS width and regularity. A narrow (< 0.12 s), regular tachycardia is usually SVT; a wide (≥ 0.12 s) tachycardia is treated as ventricular tachycardia until proven otherwise. Regularity and the presence or absence of P waves help distinguish atrial fibrillation, atrial flutter, and sinus tachycardia. On the slow side, recognize sinus bradycardia and the AV blocks (first-degree, Mobitz I, Mobitz II, and third-degree/complete block), because high-grade blocks are more likely to need pacing than atropine alone.
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