Echocardiographic lesion characteristics associated with successful ablation of inappropriate sinus tachycardia

Catheter ablation of inappropriate sinus tachycardia has proven difficult. Despite the use of intracardiac echocardiography to help direct radiofrequency (RF) application to the anatomic target of the superolateral crista terminalis (CT), multiple RF lesions often are required. Furthermore, the characteristic echo-anatomic changes with RF application associated with a reduction in heart rate have not been defined. A characteristic echo signature, if present, may facilitate the ablation process. The purpose of this retrospective study was to define the echocardiographic characteristic changes associated with effective RF ablation for inappropriate sinus tachycardia.

Detailed intracardiac echocardiographic imaging characterization of the superolateral CT was performed before and at the time of successful heart rate reduction. Using on-line videotape intracardiac echocardiography (9 MHz, 9 French), changes in wall thickness and echodensity at the CT lesion site were assessed at baseline, after each RF lesion, and with 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 (> or = 20 beats/min) was achieved in 15 of 17 patients and required 41 +/- 31 RF applications (range 5 to 110, median 40). Effective RF (reduced heart rate) was observed starting with the 34th +/- 24th lesion (range 3rd to 86th, median 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 superior vena cava, but the degree of thickening was not specific for effective RF associated with heart rate reduction. Importantly, we noted echodensity changes reaching directly to the epicardium with the development of a linear low echodensity or echo-free space at the time of effective RF resulting in heart rate reduction. In two patients without effective heart rate reduction, echodensity changes never reached the epicardium. No complications (superior vena cava-right atrial junction orifice narrowing >50% or pericardial effusion) of RF were identified.

An echocardiographically guided anatomic approach to RF ablation of inappropriate sinus tachycardia is safe and effective. A characteristic echocardiographic signature suggesting transmural/epicardium damage appears to be present at the time of successful heart rate reduction and may serve as an appropriate guide for directing additional RF when using this anatomic echocardiographically based approach.