The Study Of The Characteristics Of 12-Lead Electrocardiogram During Pacing In Different Sites In Right Ventricular Outflow Tract

The Study of the Charactristics of 12-Lead Electrocardiogram During Pacing in Different Sites in Right Ventricular Outflow TractObjective:The right ventricular outflow tract septum and free wall are common locations of origin for the idiopathic right ventricular outflow tract tachycardias.The origin of tachycardias should be more preciously localized in order to guide the radiofrequency catheter ablation.Methods:The patient population included 30 idiopathic right ventricular outflow tract tachycardias patients,a detailed magnetic electroanatomic map of right ventricular outflow tract was constructed in sinus rhythm,then pace mapping was performed from anterior,mid,and posterior sites along the septum and free wall of right ventricular outflow tract.12-lead electrocardiograms were simultaneously recorded.Results:(1) The contour of the R wave in the inferior leads was helpful in differentiating septal and free-wall locations in RVOT.R waves from free-wall sites demonstrated characteristic"notching",which was uncommon in R waves from septal locations.Nocthing of the R waves was seen in 84 of 90 free-wall sites (93%) and in only 15 of 90 septal locations (16%),and difference was statistic significance (P<0.001) (2) The height of the R wave in leadⅡat septal sites for all 30 patients was 1.8±0.4mv,1.7±0.4mv,1.7±0.5mv; The height of the R wave in leadⅡat free-wall sites for all 30 patients was 1.3±0.5mv,1.1±0.3mv,1.2±0.3mv and the difference was significance (P<0.05)(3) The duration of the QRS wave in leadⅡat septal sites for all 30 patients was 110.5±4.7ms,115.1±6.5ms,100.1±5.0ms; The duration of the QRS wave in leadⅡat free-wall sites for all 30 patients was 143.1±3.7ms,141.3±3.1ms,150.3±4.1ms.The difference was statistic significance (P<0.05)(4) The duration of the QRS wave in lead II was another useful index in differentiating septal and free-wall locations.If QRS durations in lead II were prolonged(> 140ms), the origin was likely to be the free-wall sites. The sensitivity was 93.3%,the specificity was 90%,the positive predictive value was 90.3%,the negative predictive value was 93.1%.(5)The QRS morphology in lead I was another useful index. If the QRS morphology in lead I showed QS type,the origin was likely to be the septal sites.The sensitivity was 70%,the specificity was 96.7%,the positive predictive value was 95.5%,the negative predictive value was 76.3%; If the QRS morphology in lead I showed R type,the origin was likely to be the free-wall sites. The sensitivity was 76.7%,the specificity was 83.3%,the positive predictive value was 89.3%,the negative predictive value was 78.2%. (6) Pacing in anterior,middle and posterior sites of RVOT,the QRS complex in lead V3 had a characteristic pattern. R type QRS complex occurred in lead V3 when pacing in anterior sites.The sensitivity was 75%,the specificity was 77.5%,the positive predictive value was 62.5%,the negative predictive value was 86%; rS type QRS complex occurred in lead V3 when pacing in posterior sites. The sensitivity was 70%,the specificity was 92.5%,the positive predictive value was 82.3%,the negative predictive value was 86%.Conclusion:The Carto system can help to overcome the limitations of fluoroscopy and can further refine the relationship between the localization of the anatomic site of origin and specific 12-lead electrocardiogram features.