Noncontact mapping of small pulmonary artery potentials preceding ectopy from the right ventricular outflow tract

Idiopathic right ventricular tachycardia typically originates from the right ventricular outflow tract (RVOT). However, it also may originate from above the pulmonic valve. We describe a patient with a 2-year history of symptoms of palpitations associated with premature ventricular contractions (PVCs) in whom radiofrequency catheter ablation at the PVC exit site in the lateral RVOT failed despite the presence of several favorable criteria. However, using a multiple electrode array catheter, we demonstrated above the pulmonic valve clear evidence of low-amplitude preceding electrical activity ("blue ghost") that swept 3 cm inferolaterally over 20 ms to the previously identified lateral RVOT exit. Catheter mapping even at 128x gain demonstrated only very-low-amplitude potentials at this site, and pacing was unable to capture the ventricle from this region. However, ablation at this site immediately terminated the arrhythmia, and the patient has remained PVC-free after 1 year. This case supports the existence of previously hypothesized myocardial sleeves above the pulmonary valve that may be responsible for RVOT tachycardia and shows that they can be detected using noncontact mapping.