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Ablation of haemodynamically unstable right ventricular outflow tract ventricular tachycardia guided by non-contact mapping
  1. J W H Fung,
  2. H C K Chan,
  3. J E Sanderson
  1. jesanderson{at}

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A 60 year old man presented with recurrent near syncope preceded by fast palpitation for six months. Investigations showed normal left and right ventricles. Programmed electrical stimulation (PES) was able to induce clinical arrhythmia of cycle length 250 ms with left bundle branch block pattern and inferior axis, suggesting right ventricular outflow tract (RVOT) ventricular tachycardia (VT). Blood pressure dropped to 60/40 mm Hg during tachycardia with notable dizziness. Overdrive pacing was successful in terminating the arrhythmia. The clinical arrhythmia was not under satisfactory control by antiarrhythmic treatment and he agreed to have ablative therapy. The non-contact Ensite catheter (Endocardial Solution Inc) was positioned in the RVOT via the left femoral vein with guide wire lined up from RVOT to pulmonary artery across pulmonary valve (PV). The geometry of the RVOT was established during sinus rhythm with location of PV, His bundle, right ventricular apex, and tricuspid annulus. VT was induced again by PES with concurrent non-contact activation mapping. VT was rapidly terminated by overdrive pacing because of low blood pressure.

Activation mapping information during the brief period of VT was recorded. The earliest focus of activation during VT was located at the lateral wall of RVOT below PV and propagation of depolarisation wavefront was displayed in a colour coded format with white colour denoting the earliest site (0 ms) (below left). With the Ensite navigational guide, two radiofrequency energy applications were delivered by the roving catheter to the target focus (“white patch”) during sinus rhythm. The earliest activation site of RVOT during sinus rhythm after radiofrequency ablation was at His bundle (below right). The procedure was successful and there was no recurrence without any antiarrhythmic treatment. This case illustrates that non-contact mapping can greatly facilitate ablative therapy for haemodynamically unstable arrhythmia.

Isochronal map of patient during sinus rhythm after successful ablation in lateral projection. The two dark patches just below the pulmonary valve (PV) represent the radiofrequency ablation lesions (L). The colour coded format is identical to that of other figure. During sinus rhythm, earliest activation of RVOT was at the level of the His bundle denoted as NSR (white colour) in the map.

Isochronal map of patient during right ventricular tract (RVOT) ventricular tachycardia in lateral projection. White denotes the area of earliest activation (0 ms); red denotes the area depolarised 20 ms later than the white area; green and blue denote the areas depolarised 40 and 60 ms later than the white area.