Double chamber and branch discrimination V = A

VT2 in the V=A branch Both discriminants (morphology and onset of arrhythmia) are consistent with VT

SVT in the V=A branch Both discriminants (morphology and onset of arrhythmia) are consistent with SVT

Points to remember

• In the presence of 1/1 tachycardia, various diagnoses are possible (VT with retrograde conduction, sinus tachycardia, 1/1 atrial tachycardia, junctional tachycardia).
• In the V=A branch, two discriminants are used: morphology and onset of arrhythmia; these two criteria function in the same way as described for single-chamber discrimination; they may or may not be associated: “One of” or “All” criteria; on recent platforms, the initial cavity criterion has replaced abrupt onset as the nominal criterion.
• It is a different algorithm that also analyzes the sudden onset, but in a different way than the old sudden onset alone present in the single chamber; in fact, the analysis of the onset alone (sudden or gradual) allowed for the discrimination of sinus tachycardias but not atrial tachycardias; the analysis of the initial cavity allows this limitation to be addressed.
• The arrhythmia onset/initial cavity discriminant analyzes both the atrial and ventricular channels, assessing whether there was a sudden onset in both cavities and whether the arrhythmia began in the atrium or ventricle.
• if the onset of arrhythmia is considered gradual, the discriminant favors SVT; if the onset is considered sudden and the initial cavity is the atrium, the discriminant favors SVT; if the onset is considered sudden and the initial cavity is the ventricle, the discriminant favors VT
• the first tracing corresponds to VT with 1:1 retrograde conduction; the tachycardia starts on a premature ventricular complex; the two discriminants (morphology and onset of arrhythmia) favor VT; indeed, the appearance of the ventriculograms is clearly different in tachycardia compared to sinus rhythm, and the onset of tachycardia is abrupt with a first premature ventricular complex
• the second trace corresponds to a well-defined episode of sinus tachycardia; the two discriminating factors (morphology and onset of arrhythmia) are consistent with SVT; the gradual acceleration followed by deceleration are consistent with a diagnosis of sinus tachycardia
• The third trace corresponds to a clearly distinguished episode of atrial tachycardia; the two discriminating factors (morphology and onset of arrhythmia) point to SVT; indeed,the appearance of the ventriculograms is clearly similar in tachycardia compared to sinus rhythm, the onset of tachycardia is sudden with a first premature atrial complex; the tachycardia stops spontaneously on a ventricle