Excerpt from Consensus Statement on Ventricular Arrhythmia
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
Definitions:
Many terms have entered clinical usage to describe observations during mapping and ablation of VT. There has been substantial variation in the use of some terms by different investigators. The committee felt that these terms should be standardized to facilitate better understanding of methods, endpoints, and outcomes across centres
Clinical characteristics
- Clinical ventricular tachycardia (VT): VT that has occurred spontaneously based on analysis of 12-lead ECG QRS morphology and rate.
- There are many potential problems and assumptions with this designation as it is applied to inducible VT in the electrophysiology laboratory (see Endpoints for ablation section).
- Haemodynamically unstable VT causes haemodynamic compromise requiring prompt termination.
- Idiopathic VT is a term that has been used to indicate VT that is known to occur in the absence of clinically apparent structural heart disease.
- Idioventricular rhythm is three or more consecutive beats at a rate of 100/min that originate from the ventricles independent of atrial or AV nodal conduction.
- Incessant VT is continuous sustained VT that recurs promptly despite repeated intervention for termination over several hours.
- Non-clinical VT is a term that has been used to indicate a VT induced by programmed ventricular stimulation that has not been documented previously. This term is problematic because some VTs that have not been previously observed will occur spontaneously.262 It is recommended that this term can be avoided. Induced VTs with a QRS morphology that has not been previously observed should be referred to as ‘undocumented VT morphology’.
- Non-sustained VT terminates spontaneously within 30 s.
- Presumptive clinical VT is similar to a spontaneous VT based on rate and ECG or electrogram data available from ICD interrogation, but without the 12-lead ECG documentation of either the induced or spontaneous VT.
- Repetitive monomorphic VT: continuously repeating episodes of self-terminating non-sustained VT.378,462
- Sustained VT: continuous VT for 30 s or that requires an intervention for termination (such as cardioversion).
- Ventricular tachycardia: a tachycardia (rate 100/min) with three or more consecutive beats that originates from the ventricles independent of atrial or AV nodal conduction.
- VT storm is considered three or more separate episodes of sustained VT within 24 h, each requiring termination by an intervention.262,463
VT morphologies
- Monomorphic VT has a similar QRS configuration from beat to beat (Figure 1A). Some variability in QRS morphology at initiation is not uncommon, followed by stabilization of the QRS morphology.
- Multiple monomorphic VTs: refers to more than one morphologically distinct monomorphic VT, occurring as different episodes or induced at different times.
- 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 branch 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’.
- Focal VT has a point source of earliest ventricular activation with a spread of activation away in all directions from that site. The mechanism can be automaticity, triggered activity, or microreentry.
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1547-5271/$ -see front matter © 2009 Heart Rhythm Society and the European Heart Rhythm Association, a registered branch of the European Society of
Cardiology. Published by Elsevier, Inc. All rights reserved.
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