Contact Force Values Research Articles

Impact of electrode tip shape on catheter performance in cardiac radiofrequency ablation.

The role of catheter tip shape on the safety and efficacy of radiofrequency (RF) ablation has been overlooked, although differences have been observed in clinical and research fields. The purpose of this study was to analyze the role of electrode tip shape in RF ablation using a computational model. We simulated 108 RF ablations through a realistic 3-dimensional computational model considering 2 clinically used, open-irrigated catheters (spherical and cylindrical tip), varying contact force (CF), blood flow, and irrigation. Lesions are defined by the 50°C isotherm contour and evaluated by means of width, depth, depth at maximum width, and volume. Ablations are deemed as safe, critical (tissue temperature >90°C), and pop (tissue temperature >100°C). Tissue-electrode contact is less for the spherical tip at low CF but the relationship is inverted at high CF. At low CF, the cylindrical tip generates deeper and wider lesions and a 4-fold larger volume. With increasing CF, the lesions generated by the spherical tip become comparable to those generated by the cylindrical tip. The 2 tips feature different safety profiles: CF and power are the main determinants of pops for the spherical tip; power is the main factor for the cylindrical tip; and CF has a marginal effect. The cylindrical tip is more prone to pop generation at higher powers. Saline irrigation and blood flow effect do not depend on tip shape. Tip shape determines the performance of ablation catheters and has a major impact on their safety profile. The cylindrical tip shows more predictable behavior in a wide range of CF values.

Dynamic parameter estimation method of impact between bourrelet and barrel based on experimental value correction

The impact between bourrelet and barrel often involves material, geometric, and boundary condition nonlinearities. In the process of dynamic parameter estimation, the parameter iteration is highly sensitive to the initial value. Different initial values will lead to great differences in iteration time and estimation results. Therefore, an experimental method to fast acquire the initial value is established and applied to the dynamic parameter estimation of impact between bourrelet and barrel. According to the contact force model between bourrelet and barrel, the estimation method of dynamic parameters is established. The relationship between contact time and impact velocity in the contact force model is analyzed, and an impact test system is established to accurately measure the contact time and velocity. The dynamic parameters obtained from the inverse solution are used as the initial values in the estimation calculation process. The dynamic parameters are obtained by the linearization estimation and the theoretical initial value are compared respectively. The convergence time of dynamic parameters is shortened by about 1/3, and the relative error of the return value of contact force is about 5%, which improves the solution accuracy of dynamic parameters of impact for complex contacting surfaces.

Flexible, durable, and washable triboelectric yarn and embroidery for self-powered sensing and human-machine interaction

The novel combination of textiles and triboelectric nanogenerators (TENGs) successfully achieves self-powered wearable electronics and sensors. However, the fabrication of Textile-based TENGs remains a great challenge due to complex fabrication processes, low production speed, high cost, poor electromechanical properties, and limited design capacities. Here, we reported a new route to develop Textile-based TENGs with a facile, low-cost, and scalable embroidery technique. 5-ply ultrathin enameled copper wires, low-cost commercial materials, were utilized as embroidery materials with dual functions of triboelectric layers and electrodes in the Textile-based TENGs. A single enameled copper wire with a diameter of 0.1 mm and a length of 30 cm can produce over 60 V of open-circuit voltage and 0.45 µA of short circuit current when in contact with polytetrafluoroethylene (PTFE) fabric at the frequency of 1.2 Hz and the peak value of contact force of 70 N. Moreover, the triboelectric performance of enameled copper wire after plasma treatment can be better than that without plasma treatment, such as the maximum instantaneous power density can reach 245 μW/m which is ∼ 1.5 times as much as the untreated wire. These novel embroidery TENGs possess outstanding triboelectric performance and super design capacities. A 5 × 5 cm2 embroidery sample can generate an open-circuit voltage of 300 V and a short circuit current of 8 μA under similar contact conditions. The wearable triboelectric embroidery can be employed in different parts of the wear. A self-powered, fully fabric-based numeric keypad was designed based on triboelectric embroidery to serve as a human-machine interface, showing good energy harvesting and signal collection capabilities. Therefore, this study opens a new generic design paradigm for textile-based TENGs that are applicable for next-generation smart wearable devices.

Influence of geometric parameters of crankshaft-planetary reducer on cyclograph of work of contact pairs

Background. Crank-planetary reducers (CPR) have a number of advantages: compactness, high load capacity, high structural rigidity, to name a few. At the same time, there is no regulated methodology for their kinematic and force calculation, which limits theirdevelopment and mass production. The creation of effective methods for calculating these reducers to improve their performance at the design stage is of great practical importance.Objective. The aim of this work is to develop an analytical method for calculating the angle of pressure and the contact force in contact pairs “satellite hole – pin of output link” of the CPR depending on the angle between the cranks of its crankshaft (V-shaped),number of satellites and number of pins. Based on the developed method, check the possibility of designing a CPR with arbitrary values of these parameters and investigate their impact on the cyclogram of contact pairs and the associated maximum value of contact force, taking into account the nonlinearity of materials’ deformation.Methods. At the first stage, based on the formulas of analytical geometry, the possibility of theoretical implementation of CPR with an arbitrary value of the angle between the crankshaft cranks, the number of satellites and the number of pins of the output link is shown.The values of pressure angles in the contact pairs “satellite hole – pin of output link” are analysed and on the basis of the received results the cyclogram of work of leading pairs is calculated. In the second stage, using the principle of possible displacements, the formula for calculating the contact force in the leading contact pairs is written as a function of the input shaft rotation angle. When calculating thecontact force, a nonlinear model of material deformation was used.Results. An analytical method for constructing a cyclogram of the contact pairs of a CPR and the contact forces calculation was developed depending on the geometric parameters of the reducer. The possibility of theoretical implementation of reducers with arbitrary value of the angle between the crankshaft cranks, the number of satellites and the number of output link’s pins is shown Conclusions. The dependence of the contact force is obtained as a rotation angle function, the number of satellites and the numberof source pins. With a constant number of simultaneously active leading contact pairs and, accordingly, a uniform load transfer between them, the law of change in the contact force per cycle is similar to parabolic. Otherwise, the change in the contact force per cycle is quite complex. The obtained results can be used in the refined calculation of the efficiency of the CPR and in making various design decisions at the design stage

Atrial electrogram amplitude variability during atrial fibrillation ablation.

Variability of the bipolar atrial electrogram amplitude may affect voltage maps created during ablation procedures, and thus also the extent of ablations. Therefore, the aim of the study was to assess the beat-to-beat electrogram amplitude variability in the left atrium in patients undergoing atrial fibrillation ablation. In 11 patients undergoing ablation for atrial fibrillation, 362 mapping points were collected in two series. At each point, three consecutive beats were recorded and verified including the bipolar electrogram amplitude, contact force (CF), and orientation of the catheter tip. The repeatability and reproducibility of obtained measurements between consecutive beats and series were assessed by the Pearson correlation coefficient (r), the Bland-Altman test, repeatability coefficient (RC), relative standard deviation (RSD), and concordance correlation coefficient (CCC). A total of 1086 beats were analyzed. The correlation coefficient for bipolar atrial electrogram amplitude for the first two beats, and for the first and the third beats were 0.94 and 0.86, respectively. The average of differences between the first two beats and between the first and the third beats were 0.06and 0.13 mV with 95% limits of agreement (LoA)within ±0.98and ±1.74 mV, respectively. For CF values ≤5and ≥20 g, the 95% LoA were narrower compared to other CF rangesand were ±0.49and ±0.71 mV from the average value, respectively. When the analyzes were performed within the predefined ranges of bipolar electrogram amplitude: 0.05-1; 1-2; 2-3 mV, the 95% LoA were within ±0.33, ±0.98, and ±0.84 mV from the average value, respectively. RC and RSD were 1.41 mV and 20.8%, respectively. For repeated measurement between series,CCC ranged from 0.67 to 0.71 and the 95% LoA were within ±2.7 to 2.9 mV from the average value. Bipolar atrial electrogram amplitude recorded at a given site during ablation procedures is variable to an extent that may be clinically relevant. The magnitude of the observed variability is greater during remapping.

Masking Vibrations and Contact Force Affect the Discrimination of Slip Motion Speed in Touch.

Multiple cues contribute to the discrimination of slip motion speed by touch. In our previous article, we demonstrated that masking vibrations at various frequencies impaired the discrimination of speed. In this article, we extended the previous results to evaluate this phenomenon on a smooth glass surface, and for different values of contact force and duration of the masking stimulus. Speed discrimination was significantly impaired by masking vibrations at high but not at low contact force. Furthermore, a short pulse of masking vibrations at motion onset produced a similar effect as the long masking stimulus, delivered throughout slip motion duration. This last result suggests that mechanical events at motion onset provide important cues to the discrimination of speed.

Моделирование напряженно-деформируемого состояния контактирующих поверхностей торца ролика и борта кольца конического роликоподшипника

The tapered roller bearings serviceability is significantly affected by contact conditions between the roller ends and the ring flange. In this regard, the actual task is to determine influence of the contacting surfaces geometric shape on the value of the limiting contact force, where the contact spot boundary reaches the boundary of the contacting end surfaces area projecting on each other, and formation of the oil film between them becomes impossible. The stress-strain state was simulated by the finite element method in the CAE ANSYS software package making it possible to adequately evaluate the complex geometry and describe in detail all the features of this contact. The contact pressure fields obtained as a result of the finite element calculations allowed determining the limiting contact force values depending on the value of the contacting ends reduced curvature.

Evaluation of the influence of pantograph cracks on contact forces in the interaction between pantograph and catenary

Pantograph-catenary (P-C) systems operating under cracks would induce potential risks to railways. Previous relevant research efforts lack consideration of the dynamic characteristics of P-C systems under crack damages. A rigid-flexible P-C coupling model with pantograph cracks for a metro line is developed in this study. The evolution law of P-C contact forces under the condition of cracked propagation is described, and the influence of speed, uplift force, span length, and pullout value arrangement on P-C contact force and the sensitivity of crack influence are explored. Results show that the dispersion of contact force values decreases continuously upon the existence and expansion of cracks on the pantograph. Proper selection of operating conditions is advised because of the sensitivity differences of the five influencing factors indicates. Metro trains should not be operated at 100 km/h for the rail section with an 8 m-span catenary, and further inspections on the pantograph should be scheduled for trains operating over 100 km/h. The uplift force should be adjusted to the 90-100 N range. The 8 m span length is suggested in a metro catenary, and the splayed arrangement of pullout value is recommended as a priority when the situation allows.

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.

Impact of contact force on local impedance measurements in different atrial locations

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860974 Regions with pathologically altered substrate have been identified as potentially responsible for atrial fibrillation and atrial flutter maintenance. Also, real time feedback on lesion formation especially in those critical areas is a challenge. The LOCALIZE trial has shown significant value of the usage of the local impedance (LI) drop as a real time indicator during ablation for durable lesion formation. In these procedures, a decrease of 10-20% of the initial LI value is used as a marker of successful ablation. Also known is the fact that low electrode-tissue contact force is associated with ineffective lesion formation, whereas a high value can lead to an increased risk of steam pop. The IntellaNavSTABLEPOINT catheter offers both, LI and contact force, as a novel combined technique to characterize the process of lesion formation. Additionally, LI values are expected to distinguish between healthy and scar tissue independently from the atrial rhythm, which can improve the understanding of underlying substrate, even more, when corrected for an eventual lack of contact by combining it with contact force. This study aims to: (1) evaluate the relationship between contact force and LI; (2) characterise the contact force during local impedance mapping depending on the wall region of the left atrium (LA). Patients undergoing LA ablation with the STABLEPOINT catheter were included in this analysis. Contact force and LI data were recorded in four different healthy anatomical points in the LA, two in the anterior wall, and two in the posterior wall, using manually controlled contact force values between 0 g and the saturation point (70 g). When possible, additional points in scar regions were recorded. Data were exported and processed to correlate each LI measurement with the corresponding contact force. Due to the susceptibility of raw LI recordings to oscillations, moving average approach was considered. The clinical cohort comprised ten patients with a mean age of 61 years, one female. De-Novo ablations as well as redo procedures were included. Measurements at different contact force values yielded a non-linear relationship between contact force and LI. Median value of the difference between the moving average LI measurement and the LI bloodpool value were calculated at the anterior and posterior walls of the LA at contact force values from 5 to 40 g (5 g step size). Comparing the LI values at each segment, measurements differ significantly (Mann-Whitney U-test for unpaired samples) between the anterior and the posterior wall of the LA, with an ascending trend. Scar points showed a globally lower curve. Results from this preliminary study showed that LI and contact force are non-linearly dependent and it differs between anterior and posterior atrial walls, as well as between healthy and pathological substrate. Further investigations in a larger clinical cohort will analyse the LI variability to set an optimal contact force technique during LI mapping.

Optimal catheter-tissue contact value for ablation of ventricular arrythmias originating from the left ventricular papillary muscles

Abstract Funding Acknowledgements Type of funding sources: None. Background Good catheter-tissue contact is mandatory to create effective ablation lesions. The minimal contact force (CF) value for successful ablation of arrhythmias originating from the left ventricle (LV) was reported at the 8-10 g level, however, optimal CF values for ablation of arrhythmias arising from papillary muscles (PM) are not known. Purpose To determine optimal CF value for ablation of arrhythmias from LV PM. Methods Twenty-four consecutive patients (mean age 57,9 ± 11,9 years, 16 males) who from May 2017 to June 2020 underwent ablation of premature ventricular complexes (PVC) originating from LV PM were included. The primary endpoints were an acute procedural success (total elimination of PVC) and long-term success (median 27 months). Ablation was performed with the use of the CARTO electro-anatomical system and intracardiac echocardiography (ICE). Results Acute success – complete abolition of PVC, was obtained in 23 (96%) patients. The fluoroscopy time was 3,9 ± 3,5 min and the procedure duration was 114,8 ± 38 min. The mean number of applications was 8,74 ± 6,78 and the mean application time - 518,5 ± 437,25 sec. The mean CF during successful ablations was 3,1 ± 1,5 g, with 3 ± 1,1 g and 3,18 ± 1,8 g for anterolateral and posteromedial PM, respectively (p= 0,809975). The mean CF during one unsuccessful ablation was 3 g. At control Holter ECG, the mean PVC burden in all patients was reduced from 28,36 ± 14,48 % to 2,42 ± 2 %: in the anterolateral PM group from 18 ± 8 % to 2,6 ± 2 % (p= 0,005415) and in the posteromedial PM group - from 34,8 ± 13,7 % to 1,7 ± 1,3 % (p= 0,012694). During long-term follow-up (median 27, IQR 17-34) there was one recurrence among 23 patients who had acutely successful procedures. Conclusion The values of CF for successful ablation of PVC originating from LV PM are lower than those for ablation in other parts of LV. The values slightly exceeding 3 g seem to be sufficient to achieve ablation success.

Electrode tissue coupling is a new main determinant of RF lesion creation, experience from a cardiac animal model

Abstract Funding Acknowledgements Type of funding sources: None. Background Radiofrequency (RF) current is a classic ablation technology used in the EP lab. By now it is assumed that RF lesion size is mainly determined by RF power, duration and contact force. This ex vivo animal model study shows that a new parameter - "electrode tissue coupling" (ETC) - plays an additional major role in RF lesion creation. The ETC level describes the amount of electric contact between the RF electrode and cardiac tissue: In minor ETC levels, only the distal electrode connects to tissue. In full ETC levels, the whole RF electrode is embedded in cardiac tissue. Methods RF-lesions were created using an ex vivo porcine cardiac model. The experimental setup consisted of a saline-filled container, a dispersive electrode, a heated thermostat and a circulation pump to imitate in vivo conditions. Global impedance was kept at 120 Ohm as well as the temperature at 37°C. RF-lesions were created using identic values of RF duration and contact force. A RF power of 20W, 30W, 40W, and 50W was used. The ETC levels were systematically varied between minor and full coupling. All parameters (power, temperature, global and local impedance, contact force, ETC, lesion size) were measured constantly during application of RF-current, enabling real-time correlation of RF parameters and lesion size. Results In total, 1923 measurements during application of RF-current were analyzed. In ETC III (full tissue coupling), lesions became significantly wider and deeper. In 20W ablations, lesion diameters were significantly (1.68 fold) larger when applying ETC III instead of ETC I. This relation was found in variations of RF parameters (Table 1). Interestingly, baseline local impedance and local impedance drop showed a high correlation with selected ETC levels. The average baseline local impedance in ETC I was 207.2 Ohm, compared to 267.3 Ohm in ETC III (p < 0.01). Discussion In addition to by now known parameters (power, duration, contact force), electrode tissue coupling is a main determinant of lesion size. Higher ETC levels result in higher amounts of RF current going into adjacent tissue instead of current dissipation into the blood pool. In clinical practice, the ETC level can be predicted by baseline local and global impedance. Observation of these parameters should become clinical practice during RF ablation.

PO-710-01 “ELECTRODE TISSUE COUPLING” IS A NEW MAIN DETERMINANT OF RF LESION CREATION - EXPERIENCE FROM A CARDIAC ANIMAL MODEL

Radiofrequency (RF) current is a classic ablation technology used in the EP lab. By now it is assumed that RF lesion seize is mainly determined by RF power, duration and contact force. This ex vivo animal model study shows that a new parameter - “electrode tissue coupling” (ETC) - plays an additional major role in RF lesion creation. The ETC level describes the amount of electric contact between the RF electrode and cardiac tissue: In minor ETC levels, only the distal electrode connects to tissue. In full ETC levels, the whole RF electrode is embedded in cardiac tissue. The aim of this study was to investigate the influence of ETC levels on RF-lesion size. RF-lesions were created using an ex vivo porcine cardiac model. The experimental setup consisted of a saline-filled container, a dispersive electrode, a heated thermostat and a circulation pump to imitate in vivo conditions. Global impedance was kept at 120 Ohm as well as the temperature at 37°C. RF-lesions were created using identic values of RF duration and contact force. A RF power of 20W, 30W, 40W, and 50W was used. The ETC levels were varied between minor and full coupling. All parameters (power, temperature, global and local impedance, contact force, lesion size) were measured during application of RF-current, enabling real-time correlation of RF parameters and lesion size. In total, 1923 measurements during application of RF-current were analyzed. In ETC III (full tissue coupling), lesions became significantly wider and deeper. In 20W ablations, lesion diameters were significantly (1.68 fold) larger when applying ETC III instead of ETC I. This relation was found in variations of RF parameters. Baseline local impedance and local impedance drop showed a high correlation with selected ETC levels. The average baseline local impedance in ETC I was 207.2 Ohm, compared to 267.3 Ohm in ETC III (p < 0.01). In addition to by now known parameters (power, duration, contact force), ETC is a main determinant of lesion size. Higher ETC levels result in higher amounts of RF current going into adjacent tissue instead of current dissipation into the blood pool. In clinical practice, the ETC level can be predicted by baseline local and global impedance. Observation of these parameters should become clinical practice during RF ablation.

High-Frequency, Low-Tidal-Volume Mechanical Ventilation Safely Improves Catheter Stability and Procedural Efficiency During Radiofrequency Ablation of Atrial Fibrillation

High-Frequency, Low-Tidal-Volume Mechanical Ventilation Safely Improves Catheter Stability and Procedural Efficiency During Radiofrequency Ablation of Atrial Fibrillation

A Simple Model to Predict Loads within Muscle-Tendon Complexes of the Shoulder during Fast Motions

The load scenario within the shoulder joint among its muscle–tendon complexes during fast motions is of interest, as it would allow an evaluation of critical, accident-like motions. To enhance knowledge, a modelling approach was carried out and compared to experimental data. Nine subjects were investigated while performing tasks that ranged from easy to demanding. Motions were (1) an easy lift of a small weight, (2) a push against a force measurement device, and (3) a gentle side fall against the immovable force measurement device. Extracted data were the kinematics of the right arm and the contact force on the elbow. A simple direct dynamics shoulder model actuated by Hill-type muscle models was arranged to simulate the three experimental motions. The Hatze-based activation of the muscle models was used without any further simulation of neural regulation. For fast motions, the simple shoulder model predicts well the shoulder angle or contact force values, and data fit well into the variability of the data measured experimentally. Because there was no implementation of more complex neural regulation, slow motions, as performed by the subjects, were, in part, not predicted by the shoulder model. Simple mechanisms can be described by the simple model: When activated, the larger deltoid muscle is able to protect the smaller supraspinatus muscle. Furthermore, in awkward conditions, the gentle side fall against an immovable device alone has enough momentum to damage small muscles.

Local impedance measurements during contact force-guided cavotricuspid isthmus ablation for predicting an effective radiofrequency ablation.

BackgroundAn ablation catheter capable of contact force (CF) and local impedance (LI) monitoring (IntellaNav StablePoint, Boston Scientific) has been recently launched. We evaluated the relationship between the CF and LI values during radiofrequency catheter ablation (RFCA) along the cavotricuspid isthmus (CTI).MethodsFifty consecutive subjects who underwent a CTI‐RFCA using IntellaNav StablePoint catheters were retrospectively studied. The initial CF and LI at the start of the RF applications and mean CF and minimum LI during the RF applications were measured. The absolute and percentage LI drops were calculated as the difference between the initial and minimum LIs and 100 × absolute LI drop/initial LI, respectively.ResultsWe analyzed 602 first‐pass RF applications. A weak correlation was observed between the initial CF and LI (r = 0.13) and between the mean CF and LI drops (r = 0.22). The initial LI and absolute and percentage LI drops were greater at effective ablation sites than ineffective ablation sites (median, 151 vs. 138 Ω, 22 vs. 14 Ω, and 14.4% vs. 9.9%; p < .001), but the initial and mean CF did not differ. At optimal cutoffs of 21 Ω and 10.8% for the absolute and percentage LI drops according to the receiver‐operating characteristic analysis, the sensitivity, and specificity for predicting an effective ablation were 57.4% and 88.9% and 80.0%, and 61.1%, respectively.ConclusionsThe effective sites during the CF‐guided CTI‐RFCA had greater initial LI and LI drops than the ineffective sites. Absolute and percentage LI drops of 21 Ω and 10.8% may be appropriate targets for an effective ablation.

Study and failure analysis of Zero-Backlash high precision roller Enveloping reducer

In this study, the analysis method combining multi-body dynamics (MBD) and finite element analysis (FEA) is used to study the transmission failure of the Zero-Backlash High Precision Roller Enveloping Reducer (ZHPRER). A dynamic model of the reducer is first constructed using the MBD method, and the correctness of the model is verified through experiment. The model is then applied to calculate the change in the contact force of the reducer during the meshing period under different speeds and loads. Finally, the maximum value of contact force in the meshing period of different working conditions is used as a boundary condition, and the weak position in the transmission process is analyzed by the FEA. At the same time, the validity of the FEA model is verified by an overload test. The results show that, within the rated load, the failure mode of the transmission is the fracture of the inner ring assembly shaft caused by fatigue damage or the fatigue deformation or cracking of the worm gear assembly hole. The change in speed and load significantly impacts its fatigue life. When the rated load is exceeded, the failure mode of the transmission is manifested by crushing of the outer ring, rolling bodies, and cracking of the worm gear assembly hole.

Concomitant real-time measurement and correlation of contact force to baseline local impedance and local impedance drops in RF ablation of left and right atrial procedures

Abstract Introduction Radiofrequency (RF) ablation is performed in various arrhythmias. Still, arrhythmia recurrence is a challenging problem, not only in atrial fibrillation (AF). One reason for arrhythmia recurrence is suspected to be due to remaining gaps. Measurement of local impedance (LI) and change of LI during RF application can be used as a predictor and surrogate for successful ablation. Another tool, used for the last couple of years, estimating sufficient tissue contact is provided by catheters with real-time contact force (CF) measurement. The new INTELLANAV STABLEPOINT™ catheter by Boston Scientific was recently introduced combing both strategies. We sought to investigate the parallel measurement and correlation of LI and CF in real-time during left atrial (LA) and right atrial (RA) procedures. Methods We included the first n=20 patients who underwent LA ablation for AF or atypical atrial flutter and n=7 patients who underwent RA procedures for atrial flutter or atrial tachycardia and analysed retrospectively procedural data. For every RF delivery RF duration, CF, baseline LI, minimal LI, LI drop, as well as minimal LI and LI drop after 5 and 10 sec was documented. Only RF deliveries with stable contact (ablation without delay) were included. We then correlated baseline LI to LI drop (maximum, after 5 sec, after 10 sec) and to the documented CF at baseline. Results A total of 27 procedures was analysed. In total, 777 RF deliveries (663 in LA, 114 in RA) were documented with a mean RF duration of 21.7 sec. Mean baseline LI was 148.4 Ω, minimal LI 130.6Ω, LI after 5 sec 135.0 Ω and LI after 10sec 132.5 Ω. Mean complete LI drop was 17.8 Ω (13.4 Ω after 5 sec, 15.8 Ω after 10 sec). Mean CF was 15.5g. We could see a significant positive correlation between average CF and LI drop (p&amp;lt;0.01) (figure 1A), as well as between average CF and LI drop after 5 sec (p&amp;lt;0.01) and after 10 sec (p&amp;lt;0.01). Also, for baseline LI we could see a significant strong positive correlation to LI drop (p&amp;lt;0.001) (figure 1B), LI drop after 5 sec (p&amp;lt;0.001) and after 10 sec (p&amp;lt;0.001). Baseline LI did not correlate to average CF. Baseline LI was significantly higher in RA, when compared to LA (152.5Ω vs. 147.7Ω; p&amp;lt;0.05). LI drop did not differ between RA and LA procedures (17.8Ω vs. 17.7Ω), whereas mean RF duration per RF application was significantly longer in LA compared to RA procedures (22.8sec vs. 15.3sec; p&amp;lt;0.001) and applied CF was also higher in LA compared to RA procedures (16.0Ω vs. 12.8Ω; p&amp;lt;0.001). Conclusion Parallel real-time measurement of LI and CF is providing further insights into ablation biophysics. Based on these results the CF values might provide a prediction of subsequent lesion formation. A combination with LI measurement seems to be useful to prevent insufficient lesions, predisposing to gap formation and associated with arrhythmia recurrence, but also to potentially guarantee a higher safety by visualizing the applied CF and consecutive LI drop. Funding Acknowledgement Type of funding sources: None. Figure 1

Probabilistic Oblique Impact Analysis of Functionally Graded Plates – A Multivariate Adaptive Regression Splines Approach

Purpose: To investigate the probabilistic low-velocity impact of functionally graded (FG) plate using the MARS model, considering uncertain system parameters. Design/methodology/application: The distribution of various material properties throughout FG plate thickness is calculated using power law. For finite element (FE) formulation, isoparametric elements with eight nodes are considered, each component has five degrees of freedom. The combined effect of variability in material properties such as elastic modulus, modulus of rigidity, Poisson’s ratio, and mass density are considered. The surrogate model is validated with the FE model represented by the scatter plot and the probability density function (PDF) plot based on Monte Carlo simulation (MCS). Findings: The outcome of the degree of stochasticity, impact angle, impactor’s velocity, impactor’s mass density, and point of impact on the maximum value of contact force (CFmax ), plate deformation (PDmax), and impactor deformation (IDmax ) are determined. A convergence study is also performed to determine the optimal number of the constructed MARS model’s sample size. Originality/value: The results illustrate the significant effects of uncertain input parameters on FGM plates’ low-velocity impact responses by employing a surrogate-based MARS model.

In vivo biophysical characterization of very high power, short duration, temperature-controlled lesions.

A very high-power short-duration (vHPSD) strategy of radiofrequency (RF) ablation aims to minimize conductive heating and increase resistive heating. This study aimed to clarify the contribution of contact force (CF) and temperature and their interrelationship in making an adequate lesion with the vHPSD catheter. We enrolled 46 consecutive patients undergoing first catheter ablation for atrial fibrillation (AF). The vHPSD ablation was performed applying 90 W, for 4 s, with an irrigation of 8ml/min. During an application, an impedance drop (ID) ≥10 Ω was regarded as an adequate lesion formation. The mean procedural time was 95 ± 15 min. First-pass isolation was reached in 89% of patients and at the end of the procedure all pulmonary veins were isolated. No steam pop nor procedural complication occurred. A total of 3829 qualified RF points were analyzed and the median values of ID, CF and maximum temperature were respectively 10.6 (IQR 8.6-13.1) Ohm, 9 (5.8-13.8) g, 46.8 (44.1-49.8) °C. The mean ID significantly increased in parallel with the increasing CF as well as with the increasing maximum temperature. In the multivariable analysis only the CF and the maximum temperature were independent predictors of ID. From receiver operating characteristic curve analysis, a CF of 8g and a maximum temperature of 47°C are the optimal cutoff discriminatory value for adequate lesion formation. The vHPSD ablation is highly effective and safe. The CF and the maximum temperature are independent predictors of adequate lesion formation assessed by means of ID.