More on wide complex tachycardias

From the ACLS Reference Textbook and Experienced Provider Manual (2003). Chapter 16: Stable Wide Complex Tachycardias:

“Electrical cardioversion is the definitive therapy for stable wide complex tachcyardia. It should be used immediately if the patient becomes unstable. It can avoid the potential complications resulting from the use of antiarrhythmic drugs, but its use may not always be feasible, desirable, or successful.

“Antiarrhythmic drugs require time to administer, and they have potential hypotensive, negative inotropic and proarrhythmic effects…”

“Most patients who develop ventricular rhythm disturbances have long-standing structural heart disease. Structural heart disease renders a patient at risk for adverse cardiac events during antiarrhythmic therapy. These adverse events include sudden arrhythmic death, unstable rhythms, stable tachycardias, and higher susceptibility to the proarrhythmic effects of antiarrhythmic agents.”

“[P]erhaps the most difficult [wide complex tachycardias] for the clinician to identify are supraventricular (SVT) or junctional tachycardias with aberrancy such as bundle branch blocks and intraventricular conduction delays…”

“Always obtain a 12-lead ECG before you provide any pharmacologic intervention for the stable patient. Repeat the 12-lead ECG after administering any antiarrhythmic and if the rhythm converts to a different rhythm. Review previous ECGs if they are available. A history of previous aberrant rhythms, accessory pathways, pre-existing bundle branch block, or rate-dependent bundle branch block suggests supraventricular aberrancy if the QRS morphology matches the QRS observed with the tachycardia.”

“The presence of a new-onset, stable, wide complex tachycardia, particularly one known to be present for more than an hour, inevitably raises the question, Is it ventricular tachycardia or supraventricular tachycardia with aberrancy? This ostensibly simple question merits detailed discussion.”

“Asked to inspect a series of wide-complex tachycardias and identify the rhythm as ventricular or supraventricular in origin, emergency and initial care providers respond incorrectly more than 50% of the time. Two “wrong answers,” or errors, are possible: the true rhythm is VT and the healthcare provider incorrectly assesses the rhythm as SVT with aberrancy, or the true rhythm is SVT with aberrancy and the provider assesses the rhythm as VT.

“Clearly, to minimize risk to the patient, the clinician must try to avoid making the error that would result in greatest potential harm to the patient. The guidelines have tried to prevent significant harm by introducing multiple places where the clinician must verify conclusions to detect diagnostic error. Specifically, the algorithm was constructed to reduce the risk of administration of verapamil to marginally stable patients with VT (if these patients are mistakenly diagnosed as having SVT with aberrancy); this mistake has been reported to be fatal.”

(Omitting a discussion about the difficulty in applying Wellens criteria and Brugada’s algorithm, the lack of validation, and the problem of interobserver agreement.)

“This debate has begun to acquire a patina of the esoteric because differentiating SVT with aberrancy from VT is not required in the ECC Guidelines 2000. To paraphrase the 1992-1999 guidelines, there are 2 rules for treating wide complex tachycardias of unknown type:

Rule 1: Treat all wide complex tachcyardias like VT.
Rule 2: Never forget Rule 1.”

I see nothing in the ECC Guidelines 2005 that contradicts this philosophy, and I don’t expect to see anything different in the ECC Guildelines 2010.

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