Comment: This emergency medicine review course recommends a 6 step process when evaluating tachycardia. Here are some general guidelines: FIRST, plan on being stupid, due to the high stress and chaos. So SECOND, have a mantra: IV, O2, Monitor, Advanced Airway, defibrillator. THIRD: is the patient stable (you have some time to try meds) or unstable (electricity)? FOURTH: are p-waves present? FIFTH: regular or irregular? If irregular, typically atrial tachycardia and treat by blocking the AV node (beta blockers, calcium channel blockers, digoxin). SIXTH: narrow or wide? If narrow (<0.12 ms QRS = 3 small squares), rhythm is supraventricular (block the node). If narrow, it's not V-tach (usually, but still must consider narrow complex VT). NARROW REGULAR: adenosine first, consider diltiazem second (2.5 mg/min up to 50 mg); if unstable: electricity 50J then double 2nd time. NARROW IRREGULAR: adenosine won't hurt but will need a long acting blocker of the AV nodes, e.g. diltiazem 10 mg slow IVP and if tolerates, repeat; possibly amiodarone; if unstable cardiovert. WIDE REGULAR NO P-WAVES: treat as if VT (cardiovert) unless *proven* otherwise. Could be SVT with a bundle branch block (adenosine won't hurt but condition is rare). Can try amiodarone if stable. Unstable = cardiovert starting at 100J then double 2nd time. WIDE IRREGULAR: typically afib with bundle branch; all complexes look the same; treat with AV node blockade. BUT be wary regarding possible afib with WPW because treatment is entirely different (do not block AV node). These rhythms can be very fast; QRS complexes are not consistent in appearance (they are bizarre). Cardiovert, possibly try procainamide. Ask - do you have history of WPW?. More common in the young. If you are not sure, then cardiovert. WPW (short PR, delta wave). Always, look closely for p-waves (their presence may indicate another cause of tachycardia, e.g. cocaine, sepsis).
Some key points: Cardiovert patients with a pulse, otherwise defibrillate. Unstable patients get electricity. Try meds in stable patients. As a general guideline, irregular rhythms are atrial, narrow QRS atrial (but consider aberrant conduction) and for these rhythms block the atrial node. Wide complex regular rhythms typically ventricular (but consider atrial tachycardia with aberrant conduction). HippoEM 2014 a (retrieved Feb, 2014).
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