Introduction
Outflow tract ventricular arrhythmias (OTVA) are the commonest form of
ventricular arrhythmia in patients with structurally normal hearts (1).
Arising from either the right or left ventricle, they are often benign,
but can be associated with debilitating symptoms and ventricular
dysfunction (2). Indications for ablation include drug refractory
symptoms or high ectopic burdens (>10%) resulting in
either left ventricular dilatation or systolic dysfunction.
Prior to OTVA ablation, predicting the site of origin (SOO) of the
arrhythmia can inform patient consent and facilitate appropriate
procedural planning. ECG algorithms have been devised to assist in these
differentiating SOO and have varying degrees of success (3).
Unfortunately, the algorithms can be complex, considered measurements
are required, and results may be limited by incorrect lead positioning
or due to population variations in cardiac orientation.
Behaviour of OTVA over a 24-hour period has not yet been studied as a
discriminator of SOO, although consistency of ectopic burden has
previously been shown to be associated with cardiomyopathy (4).
We propose an alternative approach to morphology based parameters, using
OTVA variability across a 24-hour period to predict SOO. This is an
attractive prospect given the easy availability of ambulatory monitors
and their near ubiquitous role in the investigation of patients with
OTVA.