Thermal mapping of right ventricular outflow tract tachycardia

Catheter ablation for ventricular tachycardia following surgical treatment of pulmonary stenosis with intact ventricular septum

AIMS

This study was aimed to report the characteristics and treatment of ventricular tachycardia (VT) following surgical treatment of pulmonary stenosis with intact ventricular septum.

METHODS AND RESULTS

Five patients underwent radiofrequency catheter ablation for sustained monomorphic left bundle branch block (LBBB) type VT who previously underwent surgical treatment of pulmonary stenosis. Except stimulation, voltage and activation mapping was performed using three-dimensional (3D) electro-anatomic mapping and ablation was applied accordingly. Four VTs were induced during EP study. Two VTs were focal and the earliest activity was targeted in the right ventricular apex (RVA). The other two VTs were reentrant and the critical isthmus located in the mid-lateral wall and anterior wall of right ventricle, respectively. Ablation abolished all inducible VTs in four patients. In the patient whose VT was non-inducible, radiofrequency (RF) energy was delivered to the RVA where pacing mapping matched the clinical VT. One focal VT recurred 60 months after the initial RF ablation. Repeat mapping and ablation was performed and no VT recurred over a 24-month period.

CONCLUSIONS

The mechanism of VT following surgical treatment of pulmonary stenosis can be either focal or reentrant. Ablation of this subgroup of VT is feasible.

Multiple multisite low-temperature and low-power radiofrequency currents for the induction of atrioventricular nodal reentry tachycardia in non-inducible patients

AIMS

Some patients with documented episodes of paroxysmal supraventricular tachycardia (PSVT) do not have inducible tachycardia during the electrophysiological study. In this study, we describe how multiple low-temperature, low-power radiofrequency (RF) currents in the atrioventricular (AV) junction region can increase the rate of the induction of atrioventricular nodal reentrant tachycardia (AVNRT) in non-inducible cases.

METHOD

We enrolled 31 consecutive patients (mean age = 50.9 ± 11.9 years; 5 [16.1 %] male) who presented with documented clinical PSVT in superficial electrocardiography but had non-inducible arrhythmia in the electrophysiology laboratory despite applying different stimulation protocols. We delivered low-power (25 W), low-temperature (45 °C) RF currents into the AV junction region to induce AVNRT.

RESULTS

Arrhythmia was induced in 20 (64.5 %) patients, and it was non-sustained in 3 (9.6 %) patients. RF current was delivered into the posterior region near the coronary sinus ostium and midseptal region. RF ablation target in inducible patients was the non-inducibility of the AVNRT at the end of the procedure, while the target in the non-inducible patients was slow pathway ablation with no antegrade conduction over the slow pathway. During the follow-up period, none of the patients (either with inducible or non-inducible arrhythmia) had recurrence of AVNRT.

CONCLUSION

Multiple low-power, low-temperature RF current application into the AV junction region is a more effective method for the induction of AVNRT in comparison with a single current use into the slow pathway.

The significance of repetitive ventricular responses induced by radiofrequency energy application for idiopathic left ventricular tachycardia

In radiofrequency (RF) ablation for idiopathic left ventricular tachycardia (ILVT), the termination of tachycardia during RF ablation is considered a hallmark of success. However, in cases of patients with difficulty of induction of ventricular tachycardia (VT), the evaluation of procedural success can be problematic. We have observed thermal responses reflected as ventricular rhythm change to RF energy delivered on sinus rhythm for ILVT. We therefore describe the significance of repetitive ventricular responses. The study subjects were 11 ILVT patients for whom RF energy was delivered during sinus rhythm because of difficulty in re-induction of tachycardia. During each energy delivery, we focused on the occurrence of repetitive ventricular responses especially exhibiting a similar morphology to clinical VT. The repetitive ventricular responses were noted in 10 of 11 patients. Two patients received a second procedure due to the recurrence of ILVT. The mean follow-up period was 36.2+/-12.8 months. The clinical course of the remaining patients was favorable and without recurrence of ILVT. Based on the favorable clinical outcomes, ablation-induced repetitive ventricular responses with similar QRS morphology to clinical ILVT are useful markers for selecting an ablation site and could be used as an additional mapping method, termed as "thermal mapping".