Echocardiographic lesion characteristics associated with successful ablation of inappropriate sinus tachycardia

Introduction: Catheter ablation of inappropriate sinus tachycardia has prov en difficult. Despite the use of intracardiac echocardiography to help dire ct radiofrequency (RF) application to the anatomic target of the superolate ral crista terminalis (CT), multiple RF lesions often are required, Further more, the characteristic echo-anatomic changes with RF application associat ed with a reduction in heart rate have not been defined. A characteristic e cho signature, if present, may facilitate the ablation process. The purpose of this retrospective study was to define the echocardiographic characteri stic changes associated with effective RF ablation for inappropriate sinus tachycardia. Methods and Results: Detailed intracardiac echocardiographic imaging charac terization of the superolateral CT was performed before and at the time of successful heart rate reduction. Using on-line videotape intracardiac echoc ardiography (9 MHz, 9 French), changes in wail thickness and echodensity at the CT lesion site were assessed at baseline, after each BF lesion, and wi th the lesion that produced heart rate reduction in 17 patients (age 32 +/- 9 years; 15 women) with inappropriate sinus tachycardia. In all patients, RF ablation was anatomically based and targeted only the superolateral CT. RF lesions were created using 20 to 50 W for up to 2 minutes using an 8-mm tip electrode. Successful heart rate reduction (greater than or equal to 20 beats/min) was achieved in 15 of 17 patients and required 41 +/- 31 RF app lications (range 5 to 110, median 40). Effective RF (reduced heart rate) wa s observed starting with the 34th +/- 24th lesion (range 3rd to 86th, media n 25th). After effective RF, CT wall thickness was increased (11.4 +/- 3.1 mm vs 7.7 +/- 2.4 mm at baseline) and wall swelling expanded to adjacent su perior vena cava, but the degree of thickening was not specific for effecti ve RF associated with heart rate reduction. Importantly, we noted echodensi ty changes reaching directly to the epicardiun with the development of a li near low echodensity or echo-free space at the time of effective RF resulti ng in heart rate reduction. In two patients without effective heart fate re duction, echodensity changes never reached the epicardium. No complications (superior vena cava-right atrial junction orifice narrowing > 50% or peric ardial effusion) of RF were identified. Conclusion: An echocardiographically guided anatomic approach to RF ablatio n of inappropriate sinus tachycardia is safe and effective. A characteristi c echocardiographic signature suggesting transmural/ epicardium damage appe ars to be present at the time of successful heart rate reduction and may se rve as an appropriate guide for directing additional RF when using this ana tomic echocardiographically based approach.