Abstract
We present an illustrative case of a patient known with both supraventricular and ventricular tachycardias. Ventricular tachycardia was characterized by 1:1 retrograde ventriculo-atrial conduction and it was difficult to differentiate supraventricular and ventricular tachycardias that were stored by her cardiac resynchronization defibrillator. Left ventricular electrical delay could differentiate between both arrhythmias. This measurement could be included in future devices for enhanced specificity of ventricular tachycardia detection.
Patients with heart failure often present with both supraventricular (SVT) and ventricular tachycardias (VT). Inappropriate therapy from implantable cardioverter-defibrillators (ICDs) often occurs in patients with SVTs. Modern ICDs have several programmable features to reduce inappropriate therapy (antitachycardia pacing or shocks) and the incidence of such unwanted and potentially harmful treatments has decreased to 3% in 2 years1. Two of the commonly used discriminators that can differentiate SVT from VT are atrioventricular (AV) dissociation as assessed by the presence of more R waves than P waves and morphology of near-field or far-field electrograms. Morphology is a notoriously difficult parameter and sensitivity and specificity for VT depends on threshold programming2. AV dissociation shows a high specificity but sensitivity depends on the absence of retrograde ventriculo-atrial (VA) conduction and it cannot be used in the presence of supraventricular tachyarrhythmias such as atrial fibrillation1. As a new discriminator, timing of near-field and far-field electrograms has been suggested as a very specific but less sensitive discriminator of VT and SVT3.