title: Determination of lesion size by ultrasound during radiofrequency catheter ablation.
abstract: The catheter tip temperature that is used to control the radiofrequency generator output poorly correlates to lesion size. We, therefore, evaluated lesions created in vitro using a B-mode ultrasound imaging device as a potential means to assess lesion generation during RF applications non-invasively. Porcine ventricular tissue was immersed in saline solution at 37 degrees C. The catheter was fixed in a holder and positioned in a parallel orientation to the tissue with an array transducer (7.5 MHz) app. 3 cm above the tissue. Lesions were produced either in a temperature controlled mode with a 4-mm tip catheter with different target temperatures (50, 60, 70 and 80 degrees C, 80 W maximum output) or in a power controlled mode (25, 50 and 75 W, 20 ml/min irrigation flow) using an irrigated tip catheter. Different contact forces (0.5 N, 1.0 N) were tested, and RF was delivered for 60 s. A total of 138 lesions was produced. Out of these, 128 could be identified on the ultrasound image. The lesion depth and volume was on average 4.1 +/- 1.6 mm and 52 +/- 53 mm3 as determined by ultrasound and 3.9 +/- 1.7 mm and 52 +/- 55 mm3 as measured thereafter, respectively. A linear correlation between the lesion size determined by ultrasound and that measured thereafter was demonstrated with a correlation coefficient of r = 0.87 for lesion depth and r = 0.93 for lesion volume. We conclude that lesions can be assessed by B-mode ultrasound imaging.
authors.affiliation: Medtronic Bakken Research Center, Maastricht, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Awad
authors.forename: O
authors.initials: O
authors.lastname: Eick
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation*; D004452:Echocardiography / Q000295:instrumentation*; D006352:Heart Ventricles / Q000473:pathology / Q000601:surgery*; D066298:In Vitro Techniques; D016014:Linear Models; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013552:Swine; D013696:Temperature