The Effect of Ablation Electrode Length and Catheter Tip to Endocardial Orientation on Radiofrequency Lesion Size in the Canine Right Atrium

Abstract

Although the determinants of radiofrequency lesion size have been characterized in vitro and in ventricular tissue in situ, the effects of catheter tip length and endocardial surface orientation on lesion generation in atrial tissue have not been studied. Therefore, the dimensions of radiofrequency lesions produced with 4-, 6-, 8-, 10-, and 12-mm distal electrode lengths were characterized in 26 closed-chested dogs. The impact of parallel versus perpendicular catheter tip/endocardial surface orientation, established by biplane fluoroscopy and/or intracardiac echocardiography, on lesion dimensions was also assessed. Radiofrequency voltage was titrated to maintain a steady catheter tip temperature of 75 degrees C for 60 seconds. With a perpendicular catheter tip/tissue orientation, the lesion area increased from 29 +/- 7 mm2 with a 4-mm tip to 42 +/- 12 mm2 with the 10-mm tip, but decreased to 29 +/- 8 mm2 with ablation via a 12-mm tip. With a parallel distal tip/endocardial surface orientation, lesion areas were significantly greater: 54 +/- 22 mm2 with a 4-mm tip, 96 +/- 28 mm2 with a 10-mm tip and 68 +/- 24 mm2 with a 12-mm tip (all P < 0.001 vs perpendicular orientation). Lesion lengths and apparent volumes were larger with parallel, compared to perpendicular tip/tissue orientations, although lesion depth was independent of catheter tip length with both catheter tip/tissue orientations. Electrode edge effects were not observed with any tip length. Direct visualization using intracardiac ultrasound guidance was subjectively helpful in insuring an appropriate catheter tip/tissue interface needed to maximize lesion size. Although atrial lesion size is critically dependent on catheter tip length, it is more influenced by the catheter orientation to the endocardial surface. This information may also be helpful in designing electrode arrays for the creation of continuous linear lesions for the elimination of complex atrial tachyarrhythmias.

Analysis of Catheter-Tip (8-mm) and Actual Tissue Temperatures Achieved During Radiofrequency Ablation at the Orifice of the Pulmonary Vein

“…14 -22 With larger electrode sizes, the tip surface area exposed to the circulating blood increases, resulting in convective heat loss and tip cooling. 22 The process is similar to cooling produced by saline-irrigated tips. 15 Despite the use of these catheter designs in clinical practice, few data exist regarding the in vivo efficacy and safety.…”

Remote Magnetic Catheter Navigation for Cavotricuspid Isthmus Ablation in Patients With Common-Type Atrial Flutter

“…15 It is well appreciated, however, that adequate lesion formation with large ablation electrodes requires a sufficient electrode to tissue surface area of contact. 26 In consideration of the anatomic complexity of the CTI, significant force often must be exerted to the catheter tip to embed the ablation electrode parallel oriented within the tissue and to thereby increase the area of contact for energy transfer. Earlier studies demonstrated that the maximal endocardial force that is exerted by the RMN-assisted magnetic catheter is generally lower than that applied by CON-controlled ablation catheters.…”

Apical thrombus associated with left ventricular apical ballooning

“…As the penetration of these catheters was limited, the quantification of RFCA lesions was restricted to superficial lesions in the neighbourhood of the ICE catheter. [19][20][21] Recently, a new phased array ICE catheter with better tissue penetration, in a deflectable device, has become available. Some investigators examined RFCA lesions detected by the phased array ICE.…”