Cooling with near-freezing saline improves efficacy of cool-tip radiofrequency catheter ablation Eduardo Back Sternick, MD, PhD, FHRS, Luiz Márcio Gerken, MD, Ricardo Baeta Scarpelli, MD, Frederico Correa Soares, MD From the Arrhythmia and Electrophysiology Unit, Biocor Instituto, Nova Lima, Brazil. Introduction It is estimated that nearly 20% of outflow tract ventricular arrhythmias have an epicardial origin. 1 Careful assess- ment of the 12-lead ECG can be of value in recognizing patients with idiopathic outflow tract arrhythmia. 2 The most frequent site of focal epicardial perivascular ven- tricular arrhythmia appears to be the junction of the distal great cardiac vein and the proximal anterior interventric- ular vein. 3 These veins are in close anatomic proximity to major coronary arteries, such as the circumflex and left anterior descending artery, 4 and there is potential risk of coronary artery injury. 5 Nonetheless, radiofrequency catheter ablation in this setting can be performed within the coronary venous system in most patients using either regular 6–9 or cool-tip catheters 10 as well as cryoablation with low risk of complications. 11 We report the case of a patient with idiopathic perivas- cular ventricular arrhythmia in whom conventional cool- tip catheter ablation within the great cardiac vein was ineffective. Successful ablation was accomplished after a very cold saline solution was used. Therefore, we intro- duce the concept of cool-tip ablation using very cold saline solution. Case report A 48-year-old woman with palpitations due to frequent monomorphic ventricular premature beats (VPBs; Figure 1) and progressive reduction of left ventricular ejection frac- tion (0.49 at admission) was admitted for catheter ablation. No reason for left ventricular dysfunction other than the occurrence of frequent VPBs was noted. Twenty-four– hour Holter monitoring showed 15.445 VPBs (18% of daily beats) with three episodes of nonsustained ventricular tachycardia (maximum of four beats). Electrophysiologic study and ablation procedures During electrophysiologic study, three morphologies of VPBs were identified; one of the morphologies was the most preva- lent by far (Figure 1). Maximum deflection index was 0.59 (suggestive of epicardial origin). 3 Careful mapping of the right and left ventricular outflow tracts and of the aortic cusps yielded no early ventricular activation, which was found at the distal great cardiac vein (Figures 2 and 3). A first attempt at ablation was made using a standard 4-mm-tip ablation catheter, but impedance rise precluded radiofrequency current delivery. During the same procedure, we also tried a 3.5-mm cool-tip ablation catheter (ThermoCool, Biosense Webster, Diamond Bar, CA, USA) coupled with an automatic pump connected to a radiofrequency generator (Stockert, Cool-Flow pump, Bio- sense Webster, Division of Johnson & Johnson). However, even with flow of 60 mL/min, the maximum power achieved was 16 W, which was not enough to suppress VPBs. We made many attempts, titrating power output delivery in stepwise increments of 2 to 3 W, but without success. A second proce- dure was undertaken using percutaneous pericardial access, but the proximity of the catheter tip to the proximal part of the left anterior descending coronary artery precluded delivery of ra- diofrequency current. The patient then underwent a third pro- cedure. After the ablation site was carefully selected (Figures 2 and 3), achievement of optimal power delivery inside the great cardiac vein once again was hampered by impedance rise. At this point, as a last resort (cryoablation would have been an option but was not available), we hypothesized that using a very cold saline infusion possibly could enhance the cooling effect of the irrigated-tip catheter and allow a higher power output. Saline solution temperature measurements Temperature measurements were made using a temperature monitoring probe with three sensors (Sensitherm, FIAB-St. Jude Medical, Florence, Italy) that usually is used for esoph- ageal temperature monitoring. Temperature measurements of the 500 mL of 0.9% saline solutions were made using the temperature probe placed inside a small stainless-steel re- cipient. Measurements were made 1 minute (T 1 ) and 5 minutes (T 5 ) after the recipient was filled with the saline solution (50 mL) in order to assess spontaneous rewarming of the cold saline solution in the laboratory. Ambient tem- perature in the laboratory was 21.5°  0.1°C. Temperatures KEYWORDS Cold saline; Cool-tip catheter; Idiopathic ventricular tachycar- dia; Monomorphic ventricular premature beat; Radiofrequency catheter ablation ABBREVIATION VPB = ventricular premature beat (Heart Rhythm 2010;7: 983–986) Address reprint requests and correspondence: Dr. Eduardo Sternick, Rua Correias 281/301, CEP 30315-340, Belo Horizonte, MG, Brazil. E-mail address: eduardosternick@terra.com.br. (Received February 9, 2010; Accepted March 18, 2010.) 1547-5271/$ -see front matter © 2010 Heart Rhythm Society. All rights reserved. doi:10.1016/j.hrthm.2010.03.022