Evaluation of a standardized approach using optimized and contiguous RF applications for electrical isolation of the superior vena cava.

The superior vena cava (SVC) is well described as one of the most common non-pulmonary vein (PV)-triggers for atrial tachyarrhythmias (ATA). In our study we evaluated a standardized approach for electrical isolation of the SVC from the right atrium using a horseshoe-shaped lesion set with optimized and contiguous ostial RF lesions. The results are promising, demonstrating a very high rate of acute SVC isolation in a safe and time efficient manner (mostly less than 10 min).

Biosense Webster's QDOT Micro™ radiofrequency ablation catheter.

The QDOT Micro™ catheter (Biosense Webster, Inc., CA, USA) is a new radiofrequency ablation catheter based on the SmartTouch SF™ (Biosense Webster, Inc.). It combines diffuse external irrigation with six thermocouples located within the outer metal shell and three additional microelectrodes in a 3.5 mm-tip contact force radiofrequency catheter. This article focuses on the different characteristics of the catheter, which incorporates the ability of high power delivery, irrigation flow control based on temperature sensing through the six thermocouples and the generation of microelectrograms. An outline of its performance in preclinical and clinical setting is presented, showing promising results, especially concerning procedural efficiency and short-term safety. Additional studies need to confirm long-term effectiveness, and durability studies should evaluate whether superiority on a lesion quality level can be achieved.

Lay abstract Radiofrequency (RF) energy is the most widely used type of energy in the field of catheter ablation, an invasive treatment for heart rhythm disorders. In patients with atrial fibrillation (AF; the most frequent type of problem with the rhythm of the heart), catheter ablation aims at delivering RF energy around the pulmonary veins (PVs). PVs have been shown to contain AF triggers. Catheter ablation results in electrical isolation of the PV, making them less likely to trigger AF. The latest technical developments resulted in better success rate of the procedure (up to 90% success rate after 1 year follow-up) without increasing complication rates. During the last decade, the catheter used to isolate the PV has improved a lot and includes now contact force measurement in addition to the delivery mechanism for RF energy and can record the local electrical activity. The newly developed QDOT Micro™ catheter (Biosense Webster, Inc., CA, USA), presented in this article, combines different aspects of further technical development. These include the integration of smaller electrodes, resulting in higher local electrical signal resolution, more accurate feedback of local tissue temperature during the procedure and the ability to use higher RF power which reduces the RF delivery time and therefore reduced the duration of the procedure. An outline of its performance in preclinical and clinical setting is presented in this paper. These studies have shown promising results, especially concerning procedural efficiency and short-term safety. However, additional studies need to confirm long-term treatment success and potential superiority in comparison with other ablation approaches.

Left Ventricular End-Systolic Dimension and Outcome in Patients With Heart Failure Undergoing Percutaneous MitraClip Valve Repair for Secondary Mitral Regurgitation.

Recent MitraClip heart failure (HF) trials suggest that baseline left ventricular (LV) remodeling may be critical for patient selection. We, therefore, investigated whether baseline LV remodeling affects safety, efficacy, and clinical outcomes in HF patients with symptomatic secondary mitral regurgitation (MR) undergoing percutaneous mitral valve repair using MitraClip. LV remodeling was assessed by LV end-systolic dimension index (LVESDi) on transthoracic baseline echocardiography. Early and late outcome was reported using Mitral Valve Academic Research Consortium-criteria. A total of 107 consecutive HF patients (73 ± 10 years, 70% male) who underwent MitraClip intervention for secondary MR were studied. The study population was stratified by median LVESDi between nonadvanced (<28 mm/m², n = 49) and advanced LV remodeling (≥28 mm/m², n = 58). Both groups had similar acute procedural success, in hospital bleeding and nonbleeding complications and significant improvement in MR severity and symptoms, sustained up to 36 months (all p >0.05). LVESDi, but not LV end-diastolic diameter index nor LV ejection fraction, independently related to HF hospitalization (hazard ratio 1.11, 95% confidence interval 1.05 to 1.16, p <0.001) and mortality (hazard ratio 1.11, 95% confidence interval 1.06 to 1.17, p <0.001). At 1 and 3 years, survival free of HF hospitalization was higher in patients without versus with advanced LV remodeling (89% vs 66% and 65% vs 37%, p = 0.002) and mortality was lower (9% vs 24% and 36% vs 47%, p = 0.074), respectively. Annual HF hospitalization rate only decreased in the nonadvanced LV remodeling group (-43%, p = 0.025). Advanced LV remodeling, assessed by LVESDi, in HF patients who underwent MitraClip therapy does not influence therapeutic safety nor efficacy, but implies increased HF hospitalization and mortality risk. This parameter may be valuable for MitraClip therapy patient selection.

'CLOSE'-Guided Pulmonary Vein Isolation and Changes in Local Bipolar and Unipolar Atrial Electrograms: Observations from the EP Lab.

BACKGROUND: 'CLOSE'-guided pulmonary vein isolation (PVI) is a point-by-point, contact force (CF)-guided radiofrequency (RF) approach aiming to enclose the PVs with contiguous RF lesions by targeting strict criteria for interlesion distance and ablation index (AI). We characterized real-time changes in bipolar (B-EGMs) and unipolar electrograms (U-EGMs) during AI-targeted RF delivery. METHODS: EGM changes during 56 RF applications in 7 patients with paroxysmal atrial fibrillation (AF) undergoing 'CLOSE'-guided PVI were studied. CF-guided RF was delivered with 35W targeting an AI of 400 at posterior and 550 at anterior wall. 336 B-EGMs and 336 U-EGMs before, during and after RF delivery were analyzed with their RF characteristics. Amplitude of the B-and U-EGM and morphology of the U-EGM were measured at each 5-second step using custom-made software. RESULTS: We observed a significant reduction in B-EGM amplitude (0.43 [IQR=0.25, 0.55] to 0.11 [0.07, 0.22] mV, p<0.001) and U-EGM amplitude (0.57 [0.40, 0.87] to 0.22 [0.10, 0.34] mV, p<0.001) within 5 seconds, after which no more changes were observed. Impedance drop was 18.3±1.1Ω. Loss of the unipolar terminal S-wave occurred in 59% of applications. There was no correlation between U-EGM morphology changes and RF characteristics. CONCLUSION: In AI-guided RF delivery there is a significant reduction in EGM amplitude within 5 seconds. Loss of the unipolar terminal S wave occurred in 59% of applications and was not related to RF characteristics suggestive of adequate lesion formation. These findings suggest that there is a limited value in monitoring electrograms to further optimize 'CLOSE'-guided PVI.