Faculty Bibliography

Background: Micra is a leadless VVI pacemaker implanted in the right ventricle with an embedded 3-axis accelerometer (ACC) to provide rate response. As any ACC placed in or at the surface of the heart can detect cardiac cycle events, we tested the detection of the atrial contraction signal with the Micra ACC to provide AV synchronous (AVS) pacing. Objective: To sense atrial contractions from a Micra ACC signal and provide AVS pacing in a patient with intact sinus node and AV block(AVB). Methods: Custom software was designed to identify four distinct segments of the ACC signal (fgure) that corresponded to isovolumic contraction and mitral/tricuspid valve closure (A1), aortic/pulmonic valve closure (A2), passive ventricular flling (A3), and atrial contraction (A4). A rate smoothing feature was implemented to maintain AVS during intermittent A4 undersensing. AVS was assessed during a 30-minute resting period using continuous recording of device telemetry and ECG. AVS was defned as a P-wave visible on surface ECGs followed by a ventricular event (VP or VS) <=300 ms. Results: The software was temporarily downloaded into a Micra that was implanted for 23 months in a 79-year-old female with 3rd degree AVB. Of 1933 recorded P-waves, sensitivity of A4 signal was 92.0%, and rate smoothing improved the rate of AVS to 96.9%. No ACC oversensing was observed as there were no A4 events not related to an atrial contraction. Median heart rate was 64 bpm [IQR: 62, 66] and median PR interval was 117 ms [IQR: 111, 128]. Conclusion: AVS pacing is feasible using cardiac acceleration associated with atrial contraction from leadless pacemaker implanted in the RV. [Figure Presented]

Background: Biophysical markers of effective lesion formation during radiofrequency (RF) ablation include impedance decline, stable catheter-tissue contact and local unipolar electrogram change suggesting lesion transmurality The interactions between these factors as well as the implications of lesion sequence are not well understood. Objective: To analyze the impact of catheter stability and lesion sequence on markers of lesion formation during atrial fbrillation (AF) ablation. Methods: Sequential or time-spaced paired RF lesions with goal force-time integral (FTI) 400 gs were placed in prespecifed locations in 20 patients undergoing frst time RF ablation for paroxysmal AF. Custom developed software (MATLAB, Mathworks, USA) was used to extract and analyze lesion data, and 3D catheter position sampled at 60Hz from the CARTO3 mapping system (Biosense Webster, Inc.). All cases were performed using jet ventilation and irrigated force-sensing catheters. Results: 282 ablation lesions were studied, with mean FTI 410.8+/-18.2 gs. Mean impedance decline was greater for the frst lesion in a given pair, 13.6+/-7.9OMEGA vs. 10.7+/-4.6OMEGA, (p < 0.01). Compared to time-spaced lesions, sequential lesions resulted in signifcantly smaller impedance decline (9.8+/-3.8OMEGA vs. 11.8+/-5.2OMEGA, p<0.01), but increased probability of achieving transmurality, as evident by unipolar signal change (68% vs 42% p=0.01). Mean catheter excursion for a single lesion was 0.67+/-0.54mm and maximal catheter excursion was 1.64+/-1.3mm. Ablation catheter spatial stability was found to be inversely related to both amplitude (rho=0.51, p<0.0001) and maximal rate (dI/dT) of impedance decline (rho=0.32, p<0.0001). Conclusion: Lesion sequence and catheter spatial stability were major modifers of impedance change and unipolar electrographic evidence of lesion transmurality during RF ablation. Sequential ablation resulted in transmural lesions more frequently, despite lesser impedance decline. In contrast to previously reported positive association between contact-force and impedance decline, increased ablation catheter spatial stability was associated with lesser impedance decline

BACKGROUND:Micra is a leadless pacemaker that is implanted in the right ventricle and provides rate response via a 3-axis accelerometer (ACC). Custom software was developed to detect atrial contraction using the ACC enabling AV synchronous pacing. OBJECTIVE:To sense atrial contractions from the Micra ACC signal and provide AV synchronous pacing. METHODS:The MASS/MASS2 early feasibility studies showed intracardiac accelerations related to atrial contraction can be measured via ACC in the Micra leadless pacemaker. MARVEL was a prospective multicenter study designed to characterize the closed-loop performance of an AV synchronous algorithm downloaded into previously implanted Micra devices. AV synchrony (AVS) was measured during 30-minutes of rest and during VVI pacing. AVS was defined as a P-wave visible on a surface ECG followed by a ventricular event <300ms. RESULTS:A total of 64 patients completed the MARVEL study procedure at 12 centers in 9 countries. Patients were implanted with a Micra for a median of 6.0 months (range: 0-41.4). High-degree AV block was present in 33 patients while 31 had predominantly intrinsic conduction during the study. Average AVS during AV algorithm pacing was 87.0% (CI: 81.8%-90.9%); 80.0% in high-degree block patients and 94.4% in patients with intrinsic conduction. AVS was significantly greater (P<0.001) during AV algorithm pacing compared to VVI in high-degree block patients while AVS was maintained in patients with intrinsic conduction. CONCLUSION/CONCLUSIONS:Accelerometer-based atrial sensing is feasible and significantly improves AV synchrony in patients with AV block and a single-chamber leadless pacemaker implanted in the right ventricle.

Introduction Objectives: The AutoMark feature of the EnSite PrecisionTM electroanatomical mapping system allows physicians to create RF ablation lesion markers automatically. Additionally, the lesion markers can be scaled and colored based on up to two metrics of the RF energy delivery including: RF energy, RF duration, impedance drop magnitude, impedance drop (%), average RF power, maximum RF power, average temperature, maximum temperature, average force, and maximum force. Data exploring the optimal use of the AutoMark feature for creating consistent lesions are currently lacking. This study seeks to determine which combinations of two AutoMark metrics yield the best prediction of lesion diameter. Methods: In 24 canines, ventricular focal lesions were created using a contact force sensing, irrigated, RF ablation catheter over a wide range of ablation conditions (20-50W, 5-40 g, 5-60 seconds). Animals were sacrificed, hearts explanted and stained with 1% TTC, and fixed in 10% formalin. Lesions were identified, photographed, and digitally measured. Pairs of AutoMark metrics were exhaustively explored to find optimal combinations of metrics and success criteria for predicting consistent lesion diameter. Results: A total of 228 lesions were created with 227 found at dissection (> 99%). Within the IFU recommended contact force range (10- 30 g, n = 167 lesions), the combinations of energy and impedance drop (%); energy and average power; and average power and impedance drop (%) provided accurate indications for predicting lesion diameter equal to or exceeding 8 mm. The combination of energy >=473 J and impedance drop >=14% resulted in 92.1% lesions with a diameter of at least 8 mm versus only 50% when one or both criteria were not met (P < 0.001). Similarly, energy >=473 J and average RF power >=27 W yielded 95.1% of lesions with a diameter of at least 8 mm versus only 44.6% when one or both criteria were not met (P < 0.001). When RF power was at least 29 W and impedance drop was at least 14%, 100% of the lesions had a diameter of at least 8 mm versus only 54.4% when one or both criteria were not met (P < 0.001). Conclusions: The size and color of lesion markers placed using the AutoMark feature assisted in the identification of lesions of a desired dimension in this acute, preclinical model. Clinical use of theAutoMark featuremay facilitate creation of efficacious lesions

Background: Micra is a leadless single chamber VVIR pacemaker implanted in the right ventricle (RV) with a 3-axis accelerometer (ACC) capable of sensing heart motion. A method to detect the atrial contraction from the ACC may enable AV synchronous pacing in a single chamber ventricular leadless pacemaker. Purpose: To measure intracardiac accelerations via the ACC signal in subjects implanted with a ventricular leadless pacemaker. Methods: The Micra Accelerometer Sensor Studies (MASS and MASS2) were prospective non-randomized, multi-center clinical research studies designed to characterize the ACC signal in subjects with implanted Micra devices. Subjects in sinus rhythm (SR) were preferentially enrolled. Custom software was downloaded into the device to enable continuous telemetry of ACC and EGM waveforms to an ambulatory recorder. Surface ECG, RV EGM, and ACC recordings were collected during in-office recordings with posture and exercise tests. Results: Seventy-five subjects were enrolled, of which 66 were in SR, 9 were in AF. Mean age was 74612 years. Mean time since implant was 13.6 months (range: 0 to 35.5 months). For SR subjects without AVB or frequent ventricular pacing (n=39): four distinct segments of the ACC were identified (Figure) and characterized corresponding to: isovolumic contraction and mitral/tricuspid valve closings (A1), aortic/pulmonic valve closing (A2), early passive ventricular filling (A3), and atrial contraction generating active filling (A4). The mean peak-to-peak A4 amplitude for SR subjects was measured for each posture/axis combination (Table). The A4 amplitude in Axis 2 was significantly larger than Axis 1 and 3 (p < 0.05). Axis 2 is longitudinal to the device body, while Axis 1 and 3 are radial. The A4 amplitude was lowest while Standing, (p<0.05 vs. Left Side, Right Side, and Supine). Conclusion: Intracardiac accelerations related to the atrial contraction can be measured via a 3-axis accelerometer within a ventricular leadless pacemaker. Sensing of atrial contraction from the ventricle may provide a method for AV synchronous pacing

Atrial fibrillation is the most common arrhythmia worldwide and is a major risk factor for embolic stroke. In this article, the authors describe the crucial role of two- and three-dimensional transesophageal echocardiography in the pre- and postprocedural assessment and intraprocedural guidance of percutaneous left atrial appendage (LAA) occlusion procedures. Although recent advances have been made in the field of systemic anticoagulation with the novel oral anticoagulants, these medications come with a significant risk for bleeding and are contraindicated in many patients. Because thromboembolism in atrial fibrillation typically arises from thrombi originating in the LAA, surgical and percutaneous LAA exclusion/occlusion techniques have been devised as alternatives to systemic anticoagulation. Currently, surgical LAA exclusion is typically performed as an adjunct to other cardiac surgical procedures, which limits the number of eligible patients. Recently, several percutaneously delivered devices for LAA exclusion from the systemic circulation have been developed, some of which have been shown in clinical trials to reduce the risk for thromboembolism. These devices use an either purely endocardial LAA occlusion approach, such as the Watchman and Amulet procedures, or both an endocardial and a pericardial (epicardial) approach, such as the Lariat procedure. In the Watchman and Amulet procedures, a transseptally delivered structure composed of nitinol is placed in the LAA orifice, thereby excluding the LAA from the systemic circulation. In the Lariat procedure, a magnet link is created between a transseptally delivered endocardial wire and epicardially delivered pericardial wire, followed by epicardial suture ligation of the LAA.

Aims: THERMOCOOL SMARTTOUCH(R) SF Catheter is a new contact-force (CF)-sensing catheter with 56-hole porous tip designed for improved cooling and reduced fluid delivery compared with a standard 6-hole open-irrigated catheter. The SMART SF study examined the periprocedural safety, acute effectiveness, and procedural efficiency of the catheter for drug-refractory symptomatic paroxysmal atrial fibrillation (PAF) ablation. Methods and results: The prospective, open-label, non-randomized SMART-SF was conducted at 17 US sites. Circumferential pulmonary vein (PV) isolation was performed with confirmation of entrance block in all PVs. Stable ablation sites were identified using CARTO VISITAG Module. Primary adverse events (AEs;