OR7. Validation study: Association between aortoseptal angulation on echocardiography with the origin of outflow tract ventricular arrhythmias

Background Radiofrequency ablation (RFA) has become therapeutic modality with high success rate for outflow tract ventricular arrhythmia (OTVA). Determining the origin of OTVA before ablation is important to choose the appropriate approach, avoiding multiple complications, and saving fluoroscopy time. ECG-based criteria is a method that has been widely used to predict the origin of OTVA, but it oftenly has inconsistent diagnostic value. Previous study showed that aortoseptal angulation by echocardiography might be beneficial to predict the origin of OTVA. We need to validate the result in a prospective manner. Objective To validate the association between aortoseptal angulation measurements by echocardiography and OTVA origin. Methods A validation of diagnostic study involving patients VTs/PVCs with the ECG’s morphology of LBBB and inferior axis who underwent RFA therapy. An echocardiography examination was held before RFA therapy. Aortoseptal angulation is measured on parasternal long axis (PLAX)view to measure the angle between the aortic root and interventricular septum. The origin of OTVA was determined by mapping during RFA. Results There were 41 subjects with a mean age of 44.7±12.6 years. Majority of subjects were patients with right OTVA (n = 34, 82.9%). The mean aortoseptal angulation of the left OTVA 127.2±2.8 was significantly smaller than the right OTVA 136.7±5.7(p < 0.001). An angle below 129.2o has 71.4% sensitivity and 85.29% specificity to predict an LVOT origin. Conclusion This validation study proved that aortoseptal angulation measurement by echocardiography <129,2o is a valid diagnostic tool to differentiate left OTVA origin with OR 10,1.