Transcatheter Ablation of Ventricular Tachycardia Arising From Left Ventricular Outflow Tract. In Two Patients With Arrhythmogenic Ventricular Dysplasia.

Pozzer Domingo Luis; Reyes Ignacio.

Department of Arrhytmias
Institute of Cardiology Juana F. Cabral
Corrientes, Argentina.

Abstract
Introduction
Objectives
Material and Methods
Results
Discussion
Conclusions

Abstract
Introduction: Ventricular tachycardia (VT) originating from left ventricular outflow tract (LVOT) is uncommon
Objectives: We report two patients with VT arising from left ventricular outflow tract, with arrhythmogenic ventricular dysplasia, who underwent catheter ablation.
Methods: Both patients had recurrent episodes of symptomatic, non-sustained monomorphic ventricular tachycardia, refractory to medical therapy. QRS configuration during VT showed an inferior axis and monophasic R waves in all precordial leads. One patient had inducible sustained VT with isoproterenol infusion in a previous EPS. One patient had arrhythmogenic right and left ventricular dysplasia and the other had arrhythmogenic right ventricular dysplasia. Definitive diagnosis was made by magnetic resonance imaging (MRI) which showed the presence of focal fatty replacement of myocardium and wall thinning.
Results: Both patients underwent catheter ablation in order to give relief VT. Early potentials were mapped during VPS or non sustained ventricular episodes in both patients. Successful ablation sites were located at LVOT in both patients. No antiarrythmic therapy was administered, and no recurrence was observed during 4 and 10 month follow-up period respectively. There were no acute or long term complications.
In conclusion, LVOT non-sustained VT, may be related with bi-ventricular or right ventricular structural abnormalities detected by MRI, suggesting arrythmogenic ventricular dysplasia, and may be successfully ablated by RF therapy .

Top

Introduction:

Ventricular tachycardias that originate in the right and left ventricle outflow tract, has rarely been associated with structural alterations of the heart. Different studies demonstrated that catheter therapy in this patients have high rate of success. However, there is little information about radiofrecuency therapy in tachycardias originating from the left ventricle outflow tract.

Objectives:

The present paper was conduced in order to report two patients with VT arising from left ventricular outflow tract, with arrhythmogenic ventricular dysplasia, who underwent catheter ablation.

A 27 and 43 years-old females with recurrent episodes of symptomatic, non-sustained monomorphic ventricular tachycardia, refractory to medical therapy. One of them had a previous episode of syncope, several years ago, and she had inducible sustained VT with isoproterenol infusion during an EPS at that time. QRS configuration during VT (Figure 1) showed an inferior axis and monophasic R waves in all precordial leads. Ventricular function measured by echocardiography was normal in both patients. One patient had arrhythmogenic right and left ventricular dysplasia and the other had arrhythmogenic right ventricular dysplasia. Dysplasia diagnosis was made through magnetic resonance imaging (MRI) which showed the presence of focal fatty replacement of myocardium and wall thinning (Figure 2 and 3).

Fig. 1:  ECG of 12 leads, non-sustained ventricular tachycardia episodes are observed,
with axis deviated to the right, and R positive waves in precordial leads.

Fig. 2: NMRI, sagittal view, involvement of RVOT is observed (arrow).

Fig. 3: NMRI, transversal view, the vertebral column is
observed behind, and in the anterior area,
involvement of the anterior side and the RV's
point are observed (arrow).

Top

Mapping and ablation procedure:

Catheters were inserted through the right femoral vein, under fluoroscopic guidance, to registered His activity or stimulated as needed, and to mapped the right ventricle outflow tract. Through the right femoral artery, another catheter was introduced for mapping and radiofrecuency ablation in the left ventricle.
Both catheters, were placed on each side of the septum, in the right and left outflow tract. Both patients undergone a mapping procedure during VPC or non sustained ventricular tachycardias episodes in the right ventricle outflow tract and in the left ventricular outflow tract. Procedural success was defined as the absence of all spontaneous with and without isoproterenol infusion.

Top

Results:

Pace mapping was not made. Early potentials (Figure 4), were found the left ventricle outflow tract, Catheter ablation attempts based on this mapping information were immediately successful in both cases, without complications (Figure 5). No antiarrythmic therapy was administered, Holter monitoring as well as many ECGs, were carried out and no recurrence was observed during a 4 months and 10 months-follow-up period respectively (Figure 6). There were no acute or long term complications.

Fig. 4: Catheter ablation detects a ventricular potential with scant precocity
during mapped ventricular extrasystoles in the LVOT, as it can be
observed in the figure, the potential of the RVOT is tardive.

Fig. 5: During application of RF, interruption of ventricular ectopic activity is observed.

Fig.6: ECG of 12 leads post ablation, the patient did not present
any kind of ventricular activity again during follow up.

Top

Discussion:

Classically, outflow tract tachycardias, were reported as idiopathic, however a deeper evaluation, including an MRI scan, which can show evidence of associated structural abnormalities.
Thus, MRI scan can be used in order to identify focal fatty replacement of myocardium. These abnormalities, were associated with the diagnosis of arrhythmogenic right ventricular dysplasia, although the fatty tissue can be a normal variant of the myocardium.
The ventricular dysplasia, involved mainly the right ventricle, and less and smaller proportion the left one. Many times, ventricular tachycardia often show to be sustained at high rate and not well tolerated, with inadequate response to pharmacological therapy. Ventricular tachycardias morphology in ECG, typically shows a positive QRS complex lead 1, and left branch bundle block pattern, the QRS axis frequently is frequently normal, but it can show right shift when it originates in the outflow tract, or left shift when its originates in the posterior region or near the right ventricle apex.
ECG configurations consistent with tachycardias sites on the septal aspect of the RVOT have a precordial R wave transition at lead V3 or later, and tachycardias from LVOT have a monophasic R waves in all precordial leads precordial.
These reported cases, show findings that strongly support a dysplasic envolvement of the right ventricle in one patient and bi-ventricular in the second patient.

Conclusion:

LVOT non-sustained VT, may be related with bi-ventricular or right ventricular structural abnormalities detected by MRI, suggesting that arrhythmogenic ventricular dysplasia, may be successfully ablated by RF therapy.

Top