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.