Evaluating lesion integrity with diamond temp system

Abstract Background Pulmonary vein (PV) isolation by temperature-controlled (TC) radiofrequency ablation (RFA) is regaining popularity due to tissue-temperature feedback from thermocouples attached at the distal tip. The Diamond Temp (DT) ablation catheter system is uniquely able to monitor real time tissue temp during RFAs. The DT catheter tip has a 1.1 mm split tip electrode, allowing precise bipolar pacing during RFA. Loss of capture (LOC) with High output pacing (HOP) has been considered a surrogate to assess lesion transmurality [1]. This study evaluated the utility of DT catheter distal pacing to achieve durable lesions. Standard guidelines for TC ablation recommend achieving target tissue-temperature of 60ºC to produce durable lesions. The purpose of this study was to assess whether LOC is achieved at target tissue-temperature of 60ºC. Objective Pacing during ablation from distal tip micro electrode of the DT catheter and observing the time it takes for LOC at different segments around pulmonary veins. First pass isolation (FPI) percentage was also collected. Methods While target enrollment for this prospective study is 50 patients, these preliminary findings are based on analysis of the first 15 patients enrolled, all of whom had symptomatic, drug-refractory paroxysmal AF. Point-by-point RF lesions were delivered around ipsilateral PVs, divided into 4 segments: superior, inferior, anterior, and posterior. Ablation was performed in a TC mode with max temp setting of 60°C and max power of 50 watts. HOP was performed prior to start of ablation and discontinued once LOC was observed. Time taken to LOC around all 4 segments of PVs were recorded. Intracardiac echocardiography (ICE) was used to guide contact and monitor lesion formation. Results Overall mean time to LOC was 3.32 sec. Anterior sites exceeded this mean. Inferior, superior, and posterior sites generally had shorter times. 92.53% of locations achieved LOC within 2-5 sec of ablation. The right anterior PV had the longest time at 3.73 sec, exceeding the overall mean of 3.32 sec. All patient achieved FPI. Conclusion Reaching target therapeutic temp of 60°C alone may not be sufficient to achieve LOC around PVs. Ablation duration of 4 sec led to LOC in 92.53% of lesions. Certain anatomical regions like anterior locations required prolonged ablation time. Tissue thickness on ICE correlated directly with time required to LOC. This analysis shows that TC ablation with DT is effective; however, a therapeutic stable temperature of 60°C for at least 4 sec may be needed to achieve durable lesions around PVs. Tissue thickness on ICE and stability of temperature appear to be independent variables affecting duration prior to LOC.