EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias: Developed in a partnership with the European Heart Rhythm Association (EHRA), a Registered Branch of the European Society of Cardiology (ESC), and the Heart Rhythm Society (HRS); in collaboration with the American College of Cardiology (ACC) and the American Heart Association (AHA)
Downloaded from Polymorphic VT has a continuously changing QRS configuration from beat to beat indicating a changing ventricular activation sequence ( Figure 1C ). Pleomorphic VT has more than one morphologically distinct QRS complex occurring during the same episode of VT, but the QRS is not continuously changing ( Figure 1B ). Right and left bundle branch block-like-VT configurations: terms used to describe the dominant deflection in V1, with a dominant R-wave described as 'right bundle
... block-like' and a dominant S-wave as 'left bundle branch block-like' configurations. This terminology is potentially misleading as the VT may not show features characteristic of the same bundle branch block-like morphology in other leads. Unmappable VT does not allow interrogation of multiple sites to define the activation sequence or perform entrainment mapping; this may be due to: haemodynamic intolerance that necessitates immediate VT termination, spontaneous or pacing-induced transition to other morphologies of VT, or repeated termination during mapping. Ventricular flutter is a term that has been applied to rapid VT that has a sinusoidal QRS configuration that prevents identification of the QRS morphology. It is preferable to avoid this term, in favour of monomorphic VT with indeterminant QRS morphology. Mechanisms Scar-related reentry describes arrhythmias that have characteristics of reentry and originates from an area of myocardial scar identified from electrogram characteristics or myocardial imaging. Large reentry circuits that can be defined over several centimetres are commonly referred to as 'macroreentry'.