RVOT Ventricular Tachycardia
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RVOT Ventricular Tachycardia represents up to 10% of all Ventricular Tachycardias. Episodes usually begin between ages 20-40 years old and NSVT is frequent compromising 60-92% of the cases. Associated with no clearly defined structural heart disease. Patients usually present with palpitations that are occur with caffeine intake, stress, exercise (during or in recovery), or Hormonal triggers.
- Tachycardia is due to cAMP mediated triggered activity.
- Are usually adenosine sensitive.
- In more than 80% of the cases, the QRS is LBBB with an inferior axis.
- The diagnosis is one of exclusion and ARVD must be ruled out. Sarcoidosis can also mimic RVOT VT
- MRI abnormalities can be seen in RVOT
- Long term prognosis is excellent and sudden death is rare
- Be certain to discontinue anti-arrhythmic agents for a minimum of five half lives prior to procedure.
- You may need up to 10 mcg of Isoproterenol Aminophylline, Phenylephrine or Epinephrine infusion to initiate VT. Also sedation may suppress the VT.
- Only 1/3 initiated with programmed stimulation and may need to use burst pacing.
- When VT or PVCs occur record for future reference for pacemapping.
- To map advance the catheter to the Pulmonic Valve (area with no electrograms) most originate at the septal portion of the RVOT.
- Pacemap must be an identical match.
Free Wall Versus Septal
- To differentiate RV free wall versus septum use the inferior leads which are typically broader (QRS > 140ms)
- R wave notching in the inferior leads
- Lead V3 R/S Ratio < 1
Anterior (Leftward) Versus Posterior (Rightward)
- Look at Lead I. Large positive R or qR wave signifies posterior (rightward) location and a negative QS signifies an anterior site. Middle sites are isoelectric.
Caudal (> 2 cm from PV) Versus Cranial
- VT arising with 2 cm of the pulmonary valve near the His bundle virtually always has a negative QRS in lead aVL
- To signifiy epicardial a ratio of time to R wave peak to total QRS duration greater tham 0.54 is a useful indicator
- Ablation at successful sites tends to be only moderately early 10-60 msec pre before QRS onset
- Pacemapping adds little additional precision to sites based on 3D activation mapping.
- Fractionated potentials and diatolic potentials are rarely seen.
- The vast majority of RVOT VT, both septal (70-80%) and free wall (20-30%) originates 1-2cm beneath the pulmonary valve. It may also originate from the proximal pulmonary artery above the valve.
- Use 4 mm tip with temp control mode at 40-50W at 55 degrees for 60 seconds.
- Termination at successful sites generally occurs within 10 seconds with acceleration of the tachycardia then general slowing.
- Acute procedural success is 93% with a 5% recurrence rate
- Consider prexcited antidromic right sided tachycardias.
- A small number of RVOTs may originate in the epicardium near the AIV.
- Utility of the 12-lead electrocardiogram in localizing the origin of right ventricular outflow tract tachycardia. Ram L. Jadonath, MD, David S. Schwartzman, MD, Mark W. Preminger, MD, Charles D. Gottlieb, MD, and Francis E. Marchlinski, MD. A~ HEART J 1995;130:1107-13.