Catheter Contact Research Articles

Design and Analysis of MEMS-Based Sensors Toward Measuring Catheter Contact Forces

A contact force sensor is a critical clinical unit while performing cardiac ablation procedures. The success rate of these procedures is determined by the effective contact between the tip and the heart tissues. Using a miniaturized, susceptible tri-axial force sensor in the cardiac ablation catheter is quintessential to determine the force acting on the tip accurately. This paper discusses the design, fabrication, and comparison of two MEMS-based force sensors that can potentially be integrated with the catheter tip for better sensitivity. The working principle, shape (ring-type), and outer dimensions of both the sensors are similar, with a strategically positioned narrow rectangular cavity in the second sensor. Finite element analysis is performed to validate the performances of both sensors with the experimental results. The experiments show that sensor 2 (with the rectangular cavity on bridges) has <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 1.84\times $ </tex-math></inline-formula> higher sensitivity than sensor 1 (bridges with no rectangular cavity). The results demonstrate the possibility of integrating the sensor with the catheter tip for measuring catheter contact force.

Establishing Safe Working Parameters for Radiofrequency Ablation In Vitro Using Acoustic Sensing, Probability Mapping, and Catheter Contact Angle.

Surgical quality and safety in radiofrequency catheter ablation (RFA) are critical in arrhythmia procedures. Steam pops, in particular, are potentially catastrophic events that must be avoided; otherwise, they may cause significant damage to the myocardium. This study aimed to evaluate the effect of applied RFA inclination angle and tissue contact parameters on the ablated volume and “steam pop” formation. An ex vivo model consisting of a viable ovine myocardium, an ablation catheter, and a circulating warmed 0.9% NaCl saline solution was used. RFA was conducted while controlling for contact force, electrical power, ablation time, flow rate, irrigation, and catheter tip angle. Irrigation was delivered to the catheter tip manually when indicated. Acoustic transducers were included in the setup to detect preliminary acoustic signals. A total dataset of 567 measurements was taken. Benign precursory signals (hissing and lower-intensity “pops”) were detected by acoustic sensors preceding the occurrence of “steam pops.” Furthermore, a Pearson coefficient of r = 0.809 with P < .01 was shown to exist between the acoustic intensity of a “steam pop” and the ablated lesion volume. RFA powers of 25 and 30 W with a duration of 20 s induced more “steam pops” than ablation powers of ≤20 W with a duration of ≥30 s. There was also an increased probability of “steam pop” formation with the use of a non-irrigated catheter tip, as compared to an irrigated catheter tip. A more acute catheter angle increased the lesion size at powers of 20 and 25 W (r = −0.568 and r = −0.653, both P < .05, respectively). There is a potential benefit of using acoustic sensing as a warning before the occurrence of “steam pops.” Varying power, duration, and catheter tip angle will generate different ablation sizes and need to be tailored to individual needs and procedures.

Contact force guided radiofrequency current application at developing myocardium

Catheter contact is akey determinantfor lesion size in radiofrequency catheter ablation (RFA). Monitoring of contact force (CF) during RFA has been shown to improve efficacy of RFA in experimental settings as well as in adult patients. Coronary artery narrowing after RFA has been described in experimental settings as well as in children and adults and may be dependent from catheter contact. The value of CF monitoring concerning these issues has not been systematically studied yet. Value of high versus low CF during RFA in piglets was studied to assess lesion size and potential coronary artery involvement mimicking RFA in small children. RFA with continuous CF monitoring was performed in 24 piglets (median weight 18.5 kg) using a 7 F TactiCath Quartzradiofrequency (RF) ablation catheter (Abbott). A total of 7 lesions were induced in each animal applying low (10-20 g) or high (40-60 g) CF. RF energy was delivered with a target temperature of 65°C at 30 W for 30 s. Coronary angiography was performed prior and immediately after RF application. Animals were assigned to repeat coronary angiography followed by heart removal after 48 h (n = 12) or 6 months (n = 12). Lesions with surrounding myocardium were excised, fixated, and stained. Lesion volumes were measured by microscopic planimetry. A total of 148 RF lesions were identified in the explanted hearts. Only in the subset of lesions at the AV annulus 6 month after ablation, lesion size and number of lesions exhibiting transmural extension were higher in the high CF group compared to low CF. In all other locations CF had no impact on lesion size and mural extension after 48 h as well as after 6 months. Additional parameters such as lesion size index and force time integral were also not related to lesion size. Coronary artery damage was present in two animals after 48 h and in one after 6 months and was not related to CF. In our experimental setting, lesion size in piglets was not related to catheter CF. Transmural extension of the RF lesions involving the layers of the coronary arteries was frequently noted irrespective of CF. Coronary artery narrowing was present in 3/24 animals and was not related to CF. In infants and toddlers, low CF (10-20 g) may be of adequate effect. Impact of CF monitoring during conventional RF ablation in children requires further investigation.

Pulsed-field ablation: Computational modeling of electric fields for lesion depth analysis.

BackgroundPulsed-field ablation (PFA) is an emerging and promising nonthermal technology for cardiac ablation. The effective applied voltage to achieve adequate irreversible myocardial injury is not well studied. The pulsed-field strength remains independent of tissue contact; therefore, PFA is assumed to be an ablation technology, not mandating the need for tissue contact.ObjectiveDetermine the effect of applied voltage and distance to surface on depth of myocardial injury using PFA.MethodsA computational model was developed and validated based on extracted data from in vivo studies to examine the effect of different applied voltages and the impact of distance between the catheter and endocardial surface on the depth of irreversible myocardial injury using PFA.ResultsThe depth of lesions created by PFA are dose-dependent, and there is a direct correlation between applied PFA voltages and depth of irreversible myocardial injury. The minimum applied voltage of PFA required to create a lesion deeper than 1 mm is 300 volts. The catheter-tissue contact plays a pivotal role in determining lesion depth. With optimal catheter contact in the absence of trabeculation, the minimal applied energy required to achieve a 3-mm-deep lesion is 700 volts. A minor increase in the catheter-tissue distance of 1–2 mm doubles the minimum required applied voltage, increasing it to 1500 volts.ConclusionPFA is an important new technology that is proposed to be more efficacious and safer than currently used thermal ablation. Here we demonstrate the impact of dose dependence and the need for maintaining tissue contact during ablation.

Visualizable vs. standard, non-visualizable steerable sheath for pulmonary vein isolation procedures: randomized, single-center trial

Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction Steerable sheaths are frequently used to improve catheter contact during pulmonary vein isolation (PVI) procedures. A new type of visualized (by electroanatomical mapping system) steerable sheath has become available in clinical treatment. Purpose We aimed to compare procedural data of visualizable vs. non-visualizable steerable sheath assisted PVI procedures of patients with atrial fibrillation (AF). Methods In this single-center randomized study, we enrolled a total of 58 consecutive patients who underwent PVI due to AF. In 30 patients, the procedures were performed using non-visualizable steerable sheath (Group 1), while we used visualizable steerable sheath for PVI in 28 cases (Group 2). Results Compared to Group 1, using the visualizable sheath significantly reduced total fluoroscopy time (267 ± 145 s vs. 197 ± 74 s; p=0.03), fluoroscopy dose (26.2 ± 24.7 mGy vs. 16.7 ± 16.1 mGy; p=0.04) and left atrial procedure time (72.1 ± 18.7 min vs. 61.4 ± 18.9 min; p=0.05). Total ablation time (1158 ± 347 s vs. 1067 ± 196 s; p= 0.28), number of radiofrequency pulses (78 ± 19 vs. 77 ± 32; p=0.81) and total procedure time (117.7 ± 30.0 min vs. 105.0 ± 21.4 min; 0.09) did not differ between the two groups. No major complications occurred in either group. Conclusion Using visualizable steerable sheath for PVI procedures can reduce fluoroscopy exposure and left atrial procedure time compared to standard, non-visualizable steerable sheath in patients undergoing PVI procedures.

Influence of catheter orientation on local impedance parameters during radiofrequency delivery in AF ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Recently, a novel contact force (CF) sensing catheter able to measure local tissue impedance (LI) providing a measure of tissue characteristics has become available for clinical use. Purpose We sought to evaluate the influence of catheter contact angle on LI and CF parameters in consecutive atrial fibrillation ablation cases. Methods Consecutive pts undergoing radiofrequency catheter (RFC) ablation of AF from the CHARISMA registry were included. A novel ablation catheter (IntellaNav Stablepoint catheter) with dedicated algorithm (DirectSense) was used to measure LI at the distal electrode of this catheter. Each targeted spot was characterized in terms of RF delivery time, catheter contact angle, baseline LI and subsequent LI drop during ablation at different levels of CF (&amp;lt;5g, 5-19g and ≥20g). RFC ablations were performed at ≥45 watts. Data are reported as mean±SD. Results A total of 4193 point ablations performed around PVs from 54 cases of AF ablation were analyzed (57% paroxysmal, 85% de novo). The LI was 157±17Ω prior to ablation and 137±14Ω after ablation (p&amp;lt;0.0001, absolute LI drop of 22±8Ω). The CF was 12.5±8g and the RFC delivery time was 8.8±4s. The LI drop increased as CF increased (ranging from 18.9±7Ω for CF&amp;lt;5g to 24.8±7Ω for CF≥20g, p&amp;lt;0.0001) as well as RFC delivery time decreased (ranging from 12.7±4s for CF&amp;lt;5g to 6.6±4s for CF≥20g, p&amp;lt;0.0001). The LI drop at perpendicular orientations was significantly lower than at parallel orientations (19.5±8Ω vs 23.4±8Ω, p&amp;lt;0.0001) and RFC delivery time was higher (9.6±5s vs 8.4±4s, p&amp;lt;0.0001). This trend was confirmed among different level of CF both for LI drop and RFC delivery time. Figure Conclusions In this experience, the magnitude of the LI drop at perpendicular orientation were significantly lower than at parallel orientation and RFC delivery time was greater in parallel instances than in perpendicular instances. Thus, perpendicular RF ablations required longer RF applications and produced weaker LI decreases that parallel lesions, suggesting that catheter orientation may have critical role in RF delivery for ablation.

PO-661-04 THE ASSOCIATION BETWEEN INTRAPROCEDURAL IMPEDANCE DROP AND ATRIAL FIBRILLATION ABLATION SUCCESS USING CARTO DATA LINKED TO ELECTRONIC HEALTH RECORD DATA

Greater impedance drop during radiofrequency catheter ablation (RFA) reflects greater catheter contact with atrial tissue, which contributes to durable lesion formation. The role of impedance drop in influencing ablation success is not fully understood.

The correlation between local impedance drop and catheter contact in clinical pulmonary vein isolation use

Local impedance (LI) drop during radiofrequency (RF) application is monitored to assess the lesion formation. Recently, a novel ablation catheter has been introduced to clinical setting, which is capable of monitoring LI and catheter contact parameters including contact force (CF) and contact angle (CA). This study aimed to clarify the correlation between LI drop and catheter contact parameters. This prospective study included 15 paroxysmal atrial fibrillation (AF) patients who underwent initial pulmonary vein isolation (PVI). First-pass encircling point-by-point PV ablation was performed by using a 4.5-mm irrigated ablation catheter, with monitoring LI, CF, and CA. RF energy was applied for 30 s at each site with 30 W. Stable ablation points were analyzed to examine the correlation between LI drop and catheter contact parameters. Among 903 ablation points, 499 stable ablation points (55.2%) were analyzed. CA showed good correlation with LI drop (ρ = 0.418, p < .001). Maximum CF, minimum CF, average CF, and initial CF all showed weak correlation with LI drop (ρ = 0.201, p < .001; ρ = 0.224, p < .001; ρ = 0.258, p < .001; and ρ = 0.212, p < .001, respectively). Multivariate analysis demonstrated that CA was an independent factor of LI drop among the catheter contact parameters (β = 0.139, 95% CI = 0.111-0.167, p < .001). The LI drop in the blocked segments was significantly higher than that in the electrical conduction gap segments (27.3 ± 9.8 vs. 19.6 ± 6.4 Ω, p < .001) CONCLUSION: In clinical PVI use, both CF and CA were correlated with LI drop. More parallel CA could induce higher LI drop, which may lead to effective lesion formation.

Impact of catheter contact angle on lesion formation and durability of pulmonary vein isolation

PurposeThis study is aimed to evaluate the impact of catheter contact angle on lesion formation and durability of pulmonary vein isolation (PVI).MethodsBoth in vitro experiment and retrospective observational study were conducted. For in vitro experiment, radiofrequency lesions were created on explanted swine hearts in three different catheter contact angles (0°, 45°, and 90°). In the retrospective observational study, we assessed patients who had undergone repeat catheter ablation due to atrial fibrillation recurrence after initial PVI. When pulmonary vein (PV) reconnection was observed, we analyzed the previous ablation points within and without the gap area. The gap areas were where ablation had changed the PV activation sequence or eliminated the PV potential in the repeat session.ResultsIn the in vitro experiment, lesion width was the smallest (5.3 ± 0.4 mm) in perpendicular contact compared to 0° (vs 5.8 ± 0.5 mm, p = 0.040) and 45° (vs 6.4 ± 0.4 mm, p < 0.001). In the retrospective observational study, we assessed 666 tags of 16 patients with PV reconnections, and 60 tags were in the gap area. Tags in the gap area had longer interlesion distance (odds ratio [OR] 1.49, p < 0.001), greater contact force variability (OR 1.03, p = 0.008), and higher rate of perpendicular contact (OR 3.26, p < 0.001) on multivariate analysis.ConclusionsPerpendicular contact was associated with a smaller lesion and higher rate of PV reconnection.

Catheter contact angle influences local impedance drop during radiofrequency catheter ablation: Insight from a porcine experimental study with 2 different LI‐sensing catheters

Local impedance (LI) can indirectly measure catheter contact and tissue temperature during radiofrequency catheter ablation (RFCA). However, data on the effects of catheter contact angle on LI parameters are scarce. This study aimed to evaluate the influence of catheter contact angle on LI changes and lesion size with two different LI-sensing catheters in a porcine experimental study. Lesions were created by the INTELLANAV MiFi™ OI (MiFi) and the INTELLANAV STABLEPOINT™ (STABLEPOINT). RFCA was performed with 30 W and a duration of 30 s. The contact force (CF) (0, 5, 10, 20, and 30 g) and catheter contact angle (30°, 45°, and 90°) were changed in each set (n = 8 each). The LI rise, LI drop, and lesion size were evaluated. The LI rise increased as CF increased. There was no angular dependence with the LI rise under all CFs in the MiFi. On the other hand, the LI rise at 90° was lower than at 30° under 5 and 10 g of CF in STABLEPOINT. The LI drop increased as CF increased. Regarding the difference in catheter contact angles, the LI drop at 90° was lower than that at 30° for both catheters. The maximum lesion widths and surface widths were smaller at 90° than at 30°, whereas there were no differences in lesion depths. The LI drop and lesion widths at 90° were significantly smaller than those at 30°, although the lesion depths were not different among the 3 angles for the MiFi and STABLEPOINT.

Computational Analysis of Mapping Catheter Geometry and Contact Quality Effects on Rotor Detection in Atrial Fibrillation.

Atrial fibrillation (AF) is the most common cardiac arrhythmia and catheter mapping has been proved to be an effective approach for detecting AF drivers to be targeted by ablation. Among drivers, the so-called rotors have gained the most attention: their identification and spatial location could help to understand which patient-specific mechanisms are acting, and thus to guide the ablation execution. Since rotor detection by multi-electrode catheters may be influenced by several structural parameters including inter-electrode spacing, catheter coverage, and endocardium-catheter distance, in this study we proposed a tool for testing the ability of different catheter shapes to detect rotors in different conditions. An approach based on the solution of the monodomain equations coupled with a modified Courtemanche ionic atrial model, that considers an electrical remodeling, was applied to simulate spiral wave dynamics on a 2D model for 7.75 s. The developed framework allowed the acquisition of unipolar signals at 2 KHz. Two high-density multipolar catheters were simulated (Advisor™ HD Grid and PentaRay®) and placed in a 2D region in which the simulated spiral wave persists longer. The configuration of the catheters was then modified by changing the number of electrodes, inter-electrodes distance, position, and atrial-wall distance for assessing how they would affect the rotor detection. In contact with the wall and at 1 mm distance from it, all the configurations detected the rotor correctly, irrespective of geometry, coverage, and inter-electrode distance. In the HDGrid-like geometry, the increase of the inter-electrode distance from 3 to 6 mm caused rotor detection failure at 2 mm distance from the LA wall. In the PentaRay-like configuration, regardless of inter-electrode distance, rotor detection failed at 3 mm endocardium-catheter distance. The asymmetry of this catheter resulted in rotation-dependent rotor detection. To conclude, the computational framework we developed is based on realistic catheter shapes designed with parameter configurations which resemble clinical settings. Results showed it is well suited to investigate how mapping catheter geometry and location affect AF driver detection, therefore it is a reliable tool to design and test new mapping catheters.

Relationship between luminal esophageal temperature and volume of esophageal injury during RF ablation: In silico study comparing low power-moderate duration vs. high power-short duration.

To model the evolution of peak temperature and volume of damaged esophagus during and after radiofrequency (RF) ablation using low power-moderate duration (LPMD) versus high power-short duration (HPSD) or very high power-very short duration (VHPVSD) settings. An in silico simulation model of RF ablation accounting for left atrial wall thickness, nearby organs and tissues, as well as catheter contact force. The model used the Arrhenius equation to derive a thermal damage model and estimate the volume of esophageal damage over time during and after RF application under conditions of LPMD (30 W, 20 s), HPSD (50 W, 6 s), and VHPVSD (90 W, 4 s). There was a close correlation between maximum peak temperature after RF application and volume of esophageal damage, with highest correlation (R2 = 0.97) and highest volume of esophageal injury in the LPMD group. A greater increase in peak temperature and greater relative increase in esophageal injury volume in the HPSD (240%) and VHPSD (270%) simulations occurred after RF termination. Increased endocardial to esophageal thickness was associated with a longer time to maximum peak temperature (R2 > 0.92), especially in the HPSD/VHPVSD simulations, and no esophageal injury was seen when the distances were >4.5 mm for LPMD or >3.5 mm for HPSD. LPMD is associated with a larger total volume of esophageal damage due to the greater total RF energy delivery. HPSD and VHPVSD shows significant thermal latency (resulting from conductive tissue heating after RF termination), suggesting a requirement for fewer esophageal temperature cutoffs during ablation.

Abstract 12300: Impact of Catheter Contact Angle on Local Impedance Drop and Lesion Size Using the INTELLANAV STABLEPOINT Ablation Catheter: Insight From a Porcine Experimental Study

Background: Local impedance (LI) at a distal tip of the ablation catheter can indirectly measure tissue temperature during radiofrequency catheter ablation (RFCA). LI decreases by RFCA, and a degree of LI drop is correlated with lesion size. However, data on the effects of catheter contact angle on LI parameters were scarce. This study aimed to evaluate the influence of catheter contact angle on LI change and lesion size in a porcine experimental model. Methods: Lesions were created on porcine myocardial left ventricles by the LI and Contact force(CF)-sensing ablation catheter (INTELLANAV STABLEPOINT™). Radiofrequency ablation was performed with a power of 30 watts and a duration of 30 seconds. CF (0, 5, 10, 20, and 30g) and catheter contact angle (30°, 45°, and 90°) were changed in each set (total 120 lesions, n=8 each). LI rise by catheter contact, LI drop by RF application, and lesion size (lesion width, surface width, and lesion depth) were evaluated. Results: The values of LI rise increased as CF increased. Regarding the difference of catheter angles, LI rise with 90° was lower than those with 30°. The LI drop also increased as CF increased in all contact angles. The LI drop with 90° was lower than those with 30° in CF 5, 10, 20, and 30 g, respectively. Maximum lesion width and surface width were smaller in 90° than those in 30°, whereas there were no differences in maximum lesion depth except for CF 5g. The approximate curves were well fitted with a quadratic equation in all angles on LI drop vs. maximum lesion width, and lesion depth. Conclusion: Under the same CF, the values of LI drop and lesion width in 90° were significantly lower than those in 30° despite lesion depths were not different among the three angles. LI drop correlates with lesion width and lesion depth at any angle, which may be a good predictor of lesion size.

Catheter contact angle influences local impedance drop during radiofrequency catheter ablation: insight from a porcine experimental study

Abstract Background Local impedance (LI) at a distal tip of the ablation catheter can indirectly measure catheter contact and tissue temperature during radiofrequency catheter ablation (RFCA). LI decreases by RFCA, and a degree of LI drop is correlated with lesion size. However, data on the effects of catheter contact angle on lesion size and LI drop were scarce. This study aimed to evaluate the influence of catheter contact angle on lesion size and LI drop in a porcine experimental study. Methods Lesions were created on porcine myocardial left ventricles by the LI-sensing ablation catheter (IntellaNav MiFi OI®). Contact force (CF) was measured using pressure to current transducer (load cell). Radiofrequency ablation was performed with a power of 30 Watt and a duration of 30 seconds. CF (0g, 5g, 10g, 20g, and 30g) and catheter angle (30°, 45°, and 90°) were changed in each set (total 120 lesions, n=8 each). LI rise, LI drop by RF application, and lesion size (maximum lesion width, maximum surface width, and maximum lesion depth) were evaluated. Results There was no angular dependence in LI rise in all CF. The values of LI rise increased as CF increased. The LI drop also increased as CF increased in all contact angles. Regarding the difference of catheter angles, LI drop with 90° was lower than those with 30° and 45°in CF 10g, 20g, and 30g, respectively. Maximum lesion width and surface width were larger in 30° and 45° than those in 90°, whereas there were no differences in maximum lesion depth. Conclusion LI drop in 90° were significantly lower than those in 45° and 30°. Although lesion depths were not different among the three angles, the absolute values of LI drop were different. Caution should be exercised to comprehend the LI drop with catheter angles. Funding Acknowledgement Type of funding sources: None.

Catheter contact area strongly correlates with lesion area in radiofrequency cardiac ablation: an ex vivo porcine heart study

PurposeOur previous study confirmed that not only force but also the catheter contact angle substantially impacted the contact area and its morphology. Therefore, in this study, we aimed to further investigate the relationship between the catheter contact area and the dimensions of the ablation lesion area as a function of catheter contact angle and force in radiofrequency catheter ablation.MethodsThe radiofrequency catheter ablation test was performed for 5 contact angles and 8 contact forces at a fixed ablation time of 30 s. The initial impedance was 92.5 ± 2.5 Ω, the temperature during ablation was 30 °C, and the power was 30 W. The irrigation rate during ablation was set to 17 mL/min. Each experiment was repeated 6 times.ResultsThe catheter contact area showed a strong correlation with the ablation lesion area (r = 0.8507). When the contact area was increased, the lesion area also increased linearly in a monotonic manner. The relationships between catheter contact force and ablation lesion area and between catheter contact force and ablation lesion depth are logarithmic functions in which increased contact force was associated with increased lesion area and depth. The catheter contact angle is also an important determinant of the lesion area. The lesion area progressively increased when the contact angle was decreased. In contrast, the lesion depth progressively increased when the contact angle was increased.ConclusionsThe catheter contact area was strongly correlated with the ablation lesion area. Additionally, catheter contact force and contact angle significantly impacted the dimensions of the lesion in radiofrequency catheter ablation procedures.

Cryoablation to improve catheter stability and ablation success in the right atrioventricular groove

Catheter instability can limit ablation success of arrhythmia substrates at the right atrioventricular groove. We describe cases where cryoablation improved catheter stability, enabling ablation success. Methods and resultsFour patients with supraventricular tachycardia (SVT) substrates at the right atrioventricular groove had radiofrequency ablation procedures limited by poor catheter contact. Cryoablation offered improved catheter stability, and all four patients achieved acute ablation success using cryoablation. Three patients had long-term success and one patient later required repeat radiofrequency ablation. ConclusionsFor patients with arrhythmia substrates at the right atrioventricular groove, cryoablation may be a useful adjunctive technique in cases with catheter instability.

Simple periprocedural precautions to reduce Doppler microembolic signals during AF ablation

BackgroundDoppler microembolic signals (MES) occur during atrial fibrillation ablation despite of permanent flushed transseptal sheaths, frequent controls of periprocedural coagulation status and the use of irrigated ablation cathetersPurposeTo investigate the number and type of MES depending on the procedure time, prespecified procedure steps, the activated clotting time (ACT) during the ablation procedure and the catheter contact force.MethodsIn a prospective trial, 53 consecutive atrial fibrillation patients underwent pulmonary vein isolation by super-irrigated “point-by-point” ablation. All patients underwent a periinterventional, continuous transcranial Doppler examination (TCD) of the bilateral middle cerebral arteries during the complete ablation procedure.ResultsAn average of 686±226 microembolic signals were detected by permanent transcranial Doppler. Thereby, 569±208 signals were differentiated as gaseous and 117±31 as solid MES. The number of MES with regard to defined procedure steps were as follows: gaseous: [transseptal puncture, 26 ± 28; sheath flushing, 24±12; catheter change, 21±11; angiography, 101±28; mapping, 9±9; ablation, 439±192; protamine administration, 0±0]; solid: [transseptal puncture, 8±8; sheath flushing, 9±5; catheter replacement, 6±6; angiography, not measurable; mapping, 2±5; ablation, 41±22; protamine administration, 0±0]. Significantly less MES occurred with shorter procedure time, higher ACT and the use of tissue contact force monitoring.ConclusionThe current study demonstrates that during atrial fibrillation ablation using irrigated, “point-by-point” RF ablation, masses of microembolic signals are detected in transcranial ultrasound especially in the period of RF current application. The number of MES depends on the total procedure time and the reached ACT during ablation. The use of contact force monitoring might reduce MES during RF ablation.

A novel local impedance algorithm and contact force sensing to guide high power short duration radiofrequency ablation is efficient and safe for circumferential pulmonary vein isolation

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Local impedance (LI) drop can predict sufficient lesion formation during radiofrequency ablation (RF). Recently, a novel ablation catheter technology able to measure LI and contact force has been made available for clinical use. High power short duration (HPSD) RF ablation has been shown to be feasible for atrial fibrillation (AF) ablation with short procedure time. We used LI drop and plateau formation to guide duration of 50 Watt RF power applications for circumferential pulmonary vein isolation (PVI). Methods Consecutive patients with indication for de novo AF ablation (n = 32, age 65 ± 10 years) with paroxysmal (n = 16) or persistent (n = 16) AF underwent ultra high density 3D mapping of the left atrium and catheter ablation. Thereafter, ipsilateral PV encircling with 50 Watt RF-applications targeting an interlesion distance of ≤ 6mm and a contact force of 10-30g was performed. Duration of HPSD RF application between 7-15s was guided by impedance drop &amp;gt;20 Ohm and plateau formation of LI. Further ablation strategy was left to the investigator’s discretion. Esophageal temperature measurement was performed using a three thermistor catheter with temperature cut off 39.0°C. In case of temperature rise or very near esophageal contact to the circumferential line, RF application time was shortened to 7s. Patients underwent adenosine testing after PVI. Previously we performed all types of AF ablation using an LI guided HPSD ablation without contact force measurement capability in 80 patients. Results Complete PVI was achieved in all pts with only 13.5 ± 4.3 min cumulative RF application duration and an ablation procedure duration of 46.5 ± 10.4 min with the novel LI measuring catheter. First-pass isolation of ipsilateral veins was achieved in 75% of circles. Recurrence of PV conduction during waiting period (20min) and adenosine testing occured in 25% of circles, and was reablated in most patients with a single spot of HPSD application. Using 94 ± 36 RF application per patient, mean maximum LI drop was 23.6 ± 4.0 Ohm. Reconnected fibers were associated with low LI drop due to instability of contact in most cases due to breathing in case of difficult sedation of the patients. No serious complications occurred in all 32 pts using HPSD with the novel contact force catheter design. Conclusion Guiding of HPSD RF ablation by LI is highly efficient and safe. A novel local impedance algorithm in combination with contact force sensing enable short PVI times with low early recurrence of PV conduction. Prediction of permanent lesions seems possible and the only limitation seems to be unstable RF catheter contact due patients breathing. Follow up have to be waited.

Biofilm and catheter-related bloodstream infections.

Careful attention to detail and adherence to procedure guidelines when inserting and managing intravascular catheters has decreased the incidence of catheter-related bloodstream infections (CRBSIs). In order to limit these, health professionals must understand the underlying microbiology. Biofilms can explain the clinical findings most often seen with CRBSIs, yet they are poorly understood within medicine. Bacteria growing on solid surfaces such as a catheter are predominantly in biofilm phenotype, with a group of genes active that allow the bacteria to be tolerant to antiseptics and antibiotics by producing a self-secreted protective matrix. It is unclear whether it is planktonic seeding or small fragments of biofilm breaking off into the bloodstream that eventually results in the acute infection. The literature identifies four routes for microbes to adhere to a catheter and start biofilm formation: catheter contact, catheter insertion, catheter management and non-catheter-related sources. Routine clinical culture methods are inadequate to fully identify microbes producing catheter biofilm and/or bloodstream infection, therefore DNA methods may be required to diagnose CRBSIs. Treatment is removal and reinsertion of the catheter in a different site when possible. However, antibiofilm strategies can be employed to try to salvage the catheter. The use of high-dose antiseptics or antibiotics for long durations inside the catheter and hub (antibiotic/antiseptic lock) can suppress biofilm enough to reduce the seeding of the blood below a level where the patient's immune system can prevent bloodstream infection.

POS-618 INTERMITTENT PNEUMATIC COMPRESSION PROMOTES PRE-SURGERY CEPHALIC VEIN DILATION

Arteriovenous fistulas (AVF) are the preferred for hemodialysis access with suitable (2.0-2.5 mm) veins. AVF maturation has been poor globally and often leads to increased catheter contact time and costs. Intermittent compression of upper arm veins may aid in forearm vein dilation pre-surgery to assist in AVF placement and maturation with size expectations.