Characterization of high-power and very-high-power short-duration radiofrequency lesions performed with a new-generation catheter and a temperature-control ablation mode.

INTRODUCTION: High-power short-duration (HPSD) has been proposed to shorten procedure times while maintaining efficacy and safety. We evaluated the differences in size and geometry between radiofrequency lesions obtained with this method and conventional ones. METHODS AND RESULTS: Twenty-eight sets of 10 perpendicular radiofrequency applications were performed with two commercially available catheters: a temperature-controlled HPSD catheter (QDot-Micro) and a conventional power-controlled catheter (Thermocool SmartTouch) on porcine left ventricle. Different power settings (35, 40, 50, and 90 W), contact force (CF; 10 and 20 g), ablation index (AI; 400 and 550), and application times were combined to create conventional (35-40 W), HPSD (50 W) and very-high-power short-duration (VHPSD; 90 W) lesions, that were cross-sectioned and measured. About 4-s VHPSD lesions were smaller, shallower, and thinner than HPSD performed with the QDot-Micro catheter in any scenario of CF or AI (61 ± 7.8 mm3 , 6.1 ± 0.3 mm wide, and 2.9 ± 0.1 mm deep with 10 g; 72.2 ± 0.5 mm3 , 6.8 ± 0.3 mm wide, and 2.9 ± 0.2 mm deep with 20 g). Conventional and HPSD lesions performed with the temperature-controlled catheter were generally bigger, deeper, and wider than the ones obtained with the power-controlled catheter, as well as more consistent in size. This was especially true with the lower CF and AI scenario, while differences were less notable with other setting combinations. CONCLUSION: VHPSD lesions performed with QDot-Micro catheter were smaller than any other lesions, which is especially attractive for posterior left atrial wall ablation. On the contrary, conventional-powered and HPSD lesions performed with this catheter were equally sized (or even bigger with lower CF and AI objectives), as well as more consistent in size, which would guarantee transmurality in other locations.

Wireless Ultrasound Guidance for Femoral Venous Cannulation in Electrophysiology: Impact on Safety, Efficacy, and Procedural Delay.

BACKGROUND: Ultrasound (US) guidance increases safety and efficacy in vascular cannulation and is considered the standard of care. However, barriers including workflow interference and the need to be assisted by a second operator limit its adoption in clinical routine. The use of wireless US (WUS) may overcome these barriers. The aim of this study was to assess the impact of a novel WUS probe during its initial implantation in an electrophysiology (EP) laboratory. METHODS: Thirty-six patients requiring femoral venous cannulation for EP procedures were included in this single center, prospective, observational study, comparing WUS guidance with the anatomical landmark approach. The primary endpoint was time to successful cannulation. Secondary endpoints included rate of unsuccessful punctures, accidental arterial punctures, and workflow interference. RESULTS: Compared with anatomical landmark approach, WUS guidance significantly reduced mean time to successful cannulation (87.3 ± 94.3 vs 238.1 ± 294.7 seconds, P < 0.01). Workflow interference was predominantly nonexistent or mild and decreased after the first three weeks of use. In addition, WUS guidance improved safety and efficacy, reducing the rate of accidental arterial punctures (0.02 ± 0.1 vs 0.25 ± 0.5 arterial punctures per cannulation, P < 0.05) and unsuccessful attempts (0.26 ± 0.8 vs 1.75 ± 2.1 attempts per cannulation, P < 0.01). CONCLUSIONS: WUS guidance resulted in faster, safer, and more effective femoral venous cannulation than the anatomical landmark approach without adding significant workflow interference. The application of wireless technology in this setting contributed to overcoming some of the barriers preventing a more widespread clinical use of US guidance.

Characterization of the impact of catheter-tissue contact force in lesion formation during cavo-tricuspid isthmus ablation in an experimental swine model.

AIMS: Catheter-tissue contact is critical for effective lesion creation. The objective of this study was to determine in an experimental swine model the pathological effects of cavo-tricuspid isthmus ablation using two systems that provide reliable measures of the pressure at the catheter tip during radiofrequency ablation procedures. METHODS AND RESULTS: We performed the procedure in eight pigs in our experimental electrophysiology laboratory after right femoral vein dissection and insertion of a 12 Fr. introducer during general anaesthesia and endotracheal intubation. The target contact force during the applications was <10 grs. (axial or lateral), 10-20, 20-30, and >30 grs. in two pigs each. The power was set at 40 W and maximum target temperature at 45°C. We performed a radiofrequency line dragging from the tricuspid valve to the inferior vena cava in the eight pigs. Euthanasia of the animals was carried out a week after the procedure and a pathological examination of the lesions was performed. In the endocardial macroscopic analysis the extent of lesions, presence of thrombus, transmurality, and endothelial rupture was assessed. External surface was examined searching for transmural lesions. The mean contact force applied was 18.7 ± 8.4 grs. and the mean depth of the lesions was 3.6 ± 2 mm. Lesions were never transmural with average forces <10 grs., and the mean depth was very low (0.75 mm). To achieve transmural lesions contact forces of at least 20 grs. were required. We found a positive correlation (r = 0.85, P < 0.05) between the average force during the applications and depth of the lesions. CONCLUSION: When ablating the cavo-tricuspid isthmus in a swine model, contact forces of at least 20 grs. are required to achieve transmural lesions. Catheter-tissue contact is critical for effective lesion creation. This information is important for improving ablation efficacy.

Subjective identification and ablation of drivers improves rhythm control in patients with persistent atrial fibrillation. The CHAOS-AF study.

INTRODUCTION AND OBJECTIVES: The optimal approach for persistent atrial fibrillation (AF) ablation remains unknown. In patients with persistent AF, we compared an ablation strategy based on pulmonary vein isolation (PVI) plus ablation of drivers (PVI+D), with a conventional PVI-only approach performed in a 1:1 propensity score-matched cohort. METHODS: Drivers were subjectively identified using conventional high-density mapping catheters (IntellaMap ORION, PentaRay NAV or Advisor HD Grid), without dedicated software, as fractionated continuous or quasicontinuous electrograms on 1 to 2 adjacent bipoles, which were ablated first; and as sites with spatiotemporal dispersion (the entire cycle length comprised within the mapping catheter) plus noncontinuous fractionation, which were only targeted in patients without fractionated continuous electrograms, or without AF conversion after ablation of fractionated continuous electrograms. Ablation included PVI plus focal or linear ablation targeting drivers. RESULTS: A total of 50 patients were included in each group (61±10 years, 25% women). Fractionated continuous electrograms were found and ablated in 21 patients from the PVI+D group (42%), leading to AF conversion in 7 patients. In the remaining 43 patients, 143 sites with spatiotemporal dispersion plus noncontinuous fractionation were targeted. Globally, AF conversion was achieved in 21 patients (42%). The PVI+D group showed lower atrial arrhythmia recurrences at 1 year of follow-up (30.6% vs 48%; P=.048) and at the last follow-up (46% vs 72%; P=.013), and less progression to permanent AF (10% vs 40%; P=.001). CONCLUSIONS: Subjective identification and ablation of drivers, added to PVI, increased 1-year freedom from atrial arrhythmia and decreased long-term recurrences and progression to permanent AF.

Cardiac resynchronization therapy: do patient selection and implant practice vary depending on the volume a center handles?

BACKGROUND: The annual volume of implants may condition and determine many aspects of cardiac resynchronization therapy (CRT). METHODS: After the Spanish centers performing CRT were identified, data were recorded voluntarily by each implantation team from September 2010 to September 2011. RESULT: A total of 88 implanter centers were identified, and of these 85 (96.5%) answered the questionnaire. In total, 2,147 device implantations were reported, comprising 85% of the Eucomed's overall estimate for the same period, which was 2,518 implantations. Centers handling a higher volume of implants have a higher percentage of patients referred from other centers and more indications in patients over 80 years of age, with atrial fibrillation (AF), right bundle branch block, and unspecific disorders of intraventricular conduction. These high-volume centers stimulate more frequently in patients with very wide QRS > 200 ms. Lower-volume centers select more classic patients for resynchronization, whereas higher-volume centers increase the rate of patients with AF and prior cardiac stimulation (upgrade). Implant duration is shorter for higher-volume centers, which also perform implants in patients with congenital heart disease. By contrast, there are no significant differences in terms of heart disease, device type (pacemaker or defibrillator), implant techniques, achieved optimal site location, or complications. CONCLUSIONS: High-volume centers perform CRT more frequently in elderly patients, mostly with AF and other alternative implants. No significant differences were found between the complications reported by high-volume centers and those reported by low-volume centers.

Case Series of Ventricular Tachycardia Ablation With Pulsed-Field Ablation: Pushing Technology Further (Into the Ventricle).

Three cases of ventricular tachycardia ablation with pulsed-field ablation technology performed at 2 separate centers are reported, highlighting the advantages and disadvantages of this tool inside the ventricle: its dependence on proximity rather than contact makes it useful in sites with poor stability, while the speed of application and large scope of action provided by commercially available catheters could help with ablating large diseased areas of endocardium in a fast and hemodynamically well-tolerated fashion. However, lesion depth could be insufficient for guaranteeing efficacy in preventing ventricular tachycardias originating at an epicardial site, even in the right ventricle.

Impact of power and contact force on index-guided radiofrequency lesions in an ex vivo porcine heart model.

PURPOSE: Lesion size index (LSI) and ablation index (AI) are markers of lesion quality that incorporate power, contact force (CF) and time in a weighted formula to estimate lesion size. Although accurate predicting lesion depth in vitro, their precision in lesion size estimation has not been well established for certain power and CF settings. We conducted an experimental ex vivo study to analyse the effect of power and CF in size and morphology of ablation lesions in a porcine heart model. METHODS: Twenty-four sets of 10 perpendicular epicardial radiofrequency applications were performed with two commercially available catheters (TactiCath, Sensor Enabled; and SmartTouch) on porcine left ventricle submerged in 37 °C saline, combining different power (25, 30, 35, 40, 50 and 60 W) and CF (10 and 20 g) settings, and aiming at a lower (LSI/AI of 5/400) or higher (LSI/AI of 6/550) index. After each application, lesions were cross-sectioned and measured. RESULTS: Four hundred eighty lesions were performed. For a given target index and CF, significant differences in lesion volume and depth with different power were observed with both catheters, generally with smaller lesions using higher power. Lesions performed with CF of 10 g were particularly smaller with TactiCath compared to SmartTouch; lesions with CF of 20 g aiming a low LSI/AI were, however, bigger; lesions with CF of 20 g aiming a high LSI/AI were similar. In general, high-power lesions were wider and shallower than low-power lesions, especially with SmartTouch. CONCLUSION: Size and morphology of index-guided radiofrequency lesions varied significantly with different power and CF settings.

Ivabradine for chronic heart rate control in persistent atrial fibrillation. Design of the BRAKE-AF project.

INTRODUCTION AND OBJECTIVES: Ivabradine is an inhibitor of the If channel, the main determinant of the pacemaker function of the sinus node. The drug has been approved for the treatment of angina and heart failure. There is some evidence of its role as an inhibitor of atrial-ventricular node (AVN) conduction. The aim of the BRAKE-AF project is to assess ivabradine use for rate control in atrial fibrillation (AF). METHODS: A multicenter, randomized, parallel, open-label, noninferiority phase III clinical trial will be conducted to compare ivabradine vs digoxin in 232 patients with uncontrolled permanent AF despite beta-blockers or calcium channel blockers. The primary efficacy endpoint is the reduction in daytime heart rate measured by 24-hour Holter monitoring at 3 months. This clinical trial will be supported by an electrophysiological study of the effect of ivabradine on the action potential of the human AVN. To do this, an experimental model will be used with Chinese hamster ovarium cells transfected with the DNA encoding the expression of the t channels involved in this action potential and recording of the ionic currents with patch clamp techniques. RESULTS: New data will be obtained on the effect of ivabradine on the human AVN and its safety and efficacy in patients with permanent AF. CONCLUSIONS: The results of the BRAKE-AF project might allow inclusion of ivabradine within the limited arsenal of drugs currently available for rate control in AF. CLINICAL TRIAL REGISTRATION: http://www.clinicaltrials.gov. Identifier: NCT03718273.

Mitral-Aortic Flow Reversal in Cardiac Resynchronization Therapy: Coupling With Ejection and Impact of Variations in Atrioventricular Delay.

BACKGROUND: Flow entering the left ventricle is reversed toward the outflow tract through rotating reversal flow around the mitral valve. This was thought to facilitate early ejection, but had not been proved to date. We hypothesized that perfect coupling between reversal and ejection flow would occur at optimal atrioventricular delay (AVD), contributing to its hemodynamic superiority, and evaluated its applicability for AVD optimization. METHODS AND RESULTS: Forty consecutive patients with cardiac resynchronization therapy underwent intracardiac flow analysis and AVD optimization. Reversal and ejection flow curves were studied. The presence and duration of reversal-ejection discontinuity were assessed for all programmed AVD. Reproducibility of each optimization method was evaluated through interobserver variability. Discontinuity between reversal and ejection flow was observed in all patients with longer than optimal AVD, increasing linearly with excess duration in AVD (linear R2=0.976, P<0.001). Longer discontinuities implied progressive decreases in pre-ejection flow velocity in the left ventricular outflow tract, with consequent loss of flow momentum. The equation optimal AVD=programmed AVD-[1.2(discontinuity duration)]+4 accurately predicted optimal AVD. Short AVD systematically compromised reversal flow because of premature ejection. Agreement over optimal AVD was superior when assessed by flow reversal method (intraclass correlation coefficient =0.931; P<0.001) over both iterative and aortic velocity-time integral methods. CONCLUSIONS: Perfect coupling between mitral-aortic flow reversal and ejection flow in the left ventricle occurs at optimal AVD. As a result, full blood momentum in the outflow tract is used to facilitate early ejection. This can be measured and provides a new method for AVD optimization.

Cross-sectional study of cardiac resynchronization therapy in Spain. Indications, implant techniques, optimization and follow-up.

INTRODUCTION AND OBJECTIVES: A cross-sectional study of cardiac resynchronization therapy use in Spain was performed to analyze problems with indications, implantation, and patient follow-up. METHODS: Spanish cardiac resynchronization therapy implanter centers were identified, then the department members were surveyed and the data were recorded by each implantation team. RESULTS: Eighty-eight implanter centers were identified; of these, 85 (96.6%) answered the survey. A total of 2147 device implantations were reported, comprising 85.6% of the overall number of 2518 implantations estimated by the European Confederation of Medical Suppliers Associations for the same period. The reported implantation rate was 46 per million inhabitants versus an estimated implantation rate of 51 per million (European average, 131). Cardiac resynchronization therapy devices accounted for 84% of implantations, and upgrades to previously implanted devices, 16%. The majority of cardiac resynchronization therapy devices were implanted in men (70.7%). The mean age was 68 (12) years, and the mean left ventricular ejection fraction was 26.4% (5%). Most patients (67%) were in New York Heart Association functional class III. The group of patients for whom cardiac resynchronization therapy was indicated according to the latest update of the guidelines was significant: 17.3% among New York Heart Association class II patients and more than 21.6% among patients with atrial fibrillation. In all, electrophysiologists accounted for 73.8% of implanters, followed by surgeons, accounting for 21.4%. CONCLUSIONS: The latest update of the guidelines is being progressively implemented in Spain, according to data obtained in patients in New York Heart Association class II or with atrial fibrillation. Nevertheless, the number of cardiac resynchronization therapy device implants is still well below the European average.

[Progress in cardiac electrophysiology and arrhythmias]. / Novedades en electrofisiología cardiaca y arritmias.

This article provides a commentary on some of the most significant research on cardiac arrhythmias published during the last year. Publications were selected for their clinical importance or because they report on improvements in the invasive techniques used in cardiac electrophysiology.