Faculty Bibliography

Electrocardiogram (ECG) acquisition is increasingly widespread in medical and commercial devices, necessitating the development of automated interpretation strategies. Recently, deep neural networks have been used to automatically analyze ECG tracings and outperform physicians in detecting certain rhythm irregularities¹. However, deep learning classifiers are susceptible to adversarial examples, which are created from raw data to fool the classifier such that it assigns the example to the wrong class, but which are undetectable to the human eye^2,3. Adversarial examples have also been created for medical-related tasks^4,5. However, traditional attack methods to create adversarial examples do not extend directly to ECG signals, as such methods introduce square-wave artefacts that are not physiologically plausible. Here we develop a method to construct smoothed adversarial examples for ECG tracings that are invisible to human expert evaluation and show that a deep learning model for arrhythmia detection from single-lead ECG⁶ is vulnerable to this type of attack. Moreover, we provide a general technique for collating and perturbing known adversarial examples to create multiple new ones. The susceptibility of deep learning ECG algorithms to adversarial misclassification implies that care should be taken when evaluating these models on ECGs that may have been altered, particularly when incentives for causing misclassification exist.

Measurement of the concentration of hippurate in the inferior vena cava and renal blood samples performed in 13 subjects with normal or near-normal serum creatinine concentrations confirmed the prediction that endogenous hippurate was cleared on a single pass through the kidney with the same avidity as that reported for infused para-amino hippurate. This suggests that a timed urine collection without infusion would provide a measure of effective renal plasma flow. Comparison of the arteriovenous concentration differences for a panel of protein-bound solutes identified solutes that were secreted by the renal tubule and solutes that were subjected to tubular reabsorption.

OBJECTIVES/OBJECTIVE:We report performance of a leadless ventricular pacemaker with automated, enhanced accelerometer-based algorithms to provide atrioventricular (AV) synchronous pacing. BACKGROUND:Despite many advantages, leadless pacemakers are currently only capable of single-chamber ventricular pacing. METHODS:The prospective Micra Atrial tRacking using a Ventricular accELerometer (MARVEL) 2 study assessed the performance of an automated, enhanced accelerometer-based algorithm downloaded for up to 5 hours in patients with AV block implanted with a Micra leadless pacemaker. The primary efficacy objective was to demonstrate the superiority of the algorithm to provide AV synchronous (VDD) pacing versus VVI-50 pacing in patients with sinus rhythm and complete AV block. The primary safety objective was to demonstrate that the algorithm did not result in pauses or heart rates >100 bpm. RESULTS:Overall, 75 patients from 12 centers were enrolled and received a software download of the accelerometer-based algorithm to their leadless pacemakers. Among the 40 patients with sinus rhythm and complete AV block included in the primary efficacy objective analysis, the percentage of patients with ≥70% AV synchrony at rest was significantly greater with VDD pacing than with VVI pacing (95% vs. 0%, P<0.001). The mean %AV synchrony increased from 26.8% (median 26.9%) during VVI pacing to 89.2% (median 94.3%) during VDD pacing. There were no pauses or episodes of pacing-induced tachycardia reported during VDD pacing in all 75 patients. CONCLUSION/CONCLUSIONS:Accelerometer-based atrial sensing with an automated, enhanced algorithm significantly improved AV synchrony in patients with sinus rhythm and AV block implanted with a leadless ventricular pacemaker.

BACKGROUND:Optimal ablation technique, including catheter-tissue contact during atrial fibrillation (AF) radiofrequency (RF) ablation, is associated with improved procedural outcomes. We used a custom developed software to analyze high-frequency catheter position data to study the interaction between catheter excursion during lesion placement, lesion-set sequentiality, and arrhythmia recurrence. METHODS:A total of 100 consecutive patients undergoing first-time RF ablation for paroxysmal AF were analyzed. Spatial positioning of the ablation catheter sampled at 60 Hz during RF application was extracted from the CARTO3 system (Biosense Webster Inc, USA) and analyzed using custom-developed MATLAB software to determine precise catheter spatial 3D excursion during RF ablation. The primary end point was freedom from atrial arrhythmia lasting longer than 30 seconds after a single ablation procedure. RESULTS:At 1 year, 86% of patients were free from recurrent arrhythmia. There was no significant difference in clinical, echocardiographic, or ablation characteristics between patients with and without recurrent arrhythmia. Analyzing 15,356,998 position data points revealed that lesion-set sequentiality and mean lesion catheter excursion were predictors of arrhythmia recurrence. Analyzing arrhythmia recurrence by mean single-lesion catheter excursion (excursion >2.81 mm) and by sequentiality (using 46% of lesions with interlesion distance >6 mm as cutoff) revealed significantly increased arrhythmia recurrence in the higher excursion group (23% vs 6%, P = .03) and in the less sequential group (24% vs 4%, P = .02). CONCLUSIONS:Ablation lesion sequentiality measured by catheter interlesion distance and catheter stability measured by catheter excursion during lesion placement are potentially modifiable factors affecting arrhythmia recurrence after RF ablation for AF.

AIMS/OBJECTIVE:Patient selection is a key component of securing optimal patient outcomes with leadless pacing. We sought to describe and compare patient characteristics and outcomes of Micra patients with and without a primary pacing indication associated with atrial fibrillation (AF) in the Micra IDE trial. METHODS AND RESULTS/RESULTS:The primary outcome (risk of cardiac failure, pacemaker syndrome, or syncope related to the Micra system or procedure) was compared between successfully implanted patients from the Micra IDE trial with a primary pacing indication associated with AF or history of AF (AF group) and those without (non-AF group). Among 720 patients successfully implanted with Micra, 228 (31.7%) were in the non-AF group. Reasons for selecting VVI pacing in non-AF patients included an expectation for infrequent pacing (66.2%) and advanced age (27.2%). More patients in the non-AF group had a condition that precluded the use of a transvenous pacemaker (9.6% vs. 4.7%, P = 0.013). Atrial fibrillation patients programmed to VVI received significantly more ventricular pacing compared to non-AF patients (median 67.8% vs. 12.6%; P < 0.001). The overall occurrence of the composite outcome at 24 months was 1.8% with no difference between the AF and non-AF groups (hazard ratio 1.36, 95% confidence interval 0.45-4.2; P = 0.59). CONCLUSION/CONCLUSIONS:Nearly one-third of patients selected to receive Micra VVI therapy were for indications not associated with AF. Non-AF VVI patients required less frequent pacing compared to patients with AF. Risks associated with VVI therapy were low and did not differ in those with and without AF.

INTRODUCTION/BACKGROUND:A common complication of TAVR is development of conduction defects requiring pacemaker (PPM) implantation. These defects are not universally permanent. OBJECTIVE:To determine the incidence and predictors of persistent device dependency in patients with PPM implantation following TAVR with a self-expanding prosthesis. METHODS:Records of patients who underwent post-TAVR PPM implantation were reviewed. Patients with persistent complete AV block (AVBIII) one month post-TAVR were compared to those regaining conduction. RESULTS:Between September 2014 and March 2017, 485 patients underwent TAVR with a self-expanding prosthesis; 77 (15.9%) underwent PPM implantation for AVBIII. Device interrogation at one month was available for 61 patients (79%): 22 (36.1%) had resolution of AVBIII while 39 (63.9%) remained pacemaker-dependent. Pre-TAVR RBBB was more frequent in device-dependent patients (19 of 38, 50% vs 4 of 22, 18%; RR 2.75; p = 0.01). Device-dependence was associated with AVBIII as the first post-procedural rhythm (37 of 39, 95% vs 12 of 22, 55%; RR 1.74; p<0.0001), earlier implantation (median 1d, IQR: 0-1.5d vs 2d, IQR: 1.0-4.0d, p = 0.0004), and a shorter duration of hospitalization (median 3d, IQR: 2-3.5d vs 4d, IQR: 2-5.75d, p = 0.03). Pacemaker dependence was also associated with a higher prosthesis-to-LVOT diameter (1.45±0.11 vs 1.39±0.07; p = 0.02) and the lack of prior aortic valvuloplasty (5 of 39, 13% vs 8 of 22, 36%; RR 0.35; p = 0.03). CONCLUSIONS:In patients receiving a PPM following self-expanding TAVR, a long-term pacing requirement can be predicted from the timing of AV block, existing conduction-system disease, larger prosthesis-to-LVOT diameter, and the lack of aortic valvuloplasty. This article is protected by copyright. All rights reserved.

Recent improvements in 3D TEE post processing rendering techniques referred to as TrueVue (Philips Medical Systems, Andover, MA, USA). It allows for novel photorealistic imaging of cardiac structures including left atrial appendage (LAA) and its closure devices. Here we present TrueVue images of the LAA prior to and after LAA exclusion/occlusion using various percutaneous and surgical techniques. TrueVue may improve delineation of LAA anatomy prior to occlusion as well as visualization of occluder device position within the LAA.

PURPOSE OF REVIEW/OBJECTIVE:Atrial fibrillation is the most common arrhythmia worldwide and is a major risk factor for embolic stroke. For patients with atrial fibrillation who are unable to tolerate systemic anticoagulation, left atrial appendage (LAA) occlusion has been shown to mitigate stroke risk. In this article, we describe the vital role of the echocardiographer in intraprocedural guidance of percutaneous LAA occlusion procedures as well as in the pre- and post-procedure assessment of these patients. RECENT FINDINGS/RESULTS:A few percutaneously delivered devices for LAA exclusion from the systemic circulation are available in contemporary practice. These devices employ an either exclusive endocardial LAA occlusion approach, such as the Watchman (Boston Scientific, Maple Grove, MN) and Amulet (St. Jude Medical, Minneapolis, MN), or both an endocardial and pericardial (epicardial) approach such as the Lariat procedure (SentreHEART, Palo Alto, CA). Two- and three-dimension transesophageal echocardiography is critical for patient selection, procedure planning, procedural guidance, and ensuring satisfactory immediate as well as long-term LAA occlusion/exclusion efficacy. This review will provide an overview of the role of the echocardiographer in all aspects of LAA occlusion/exclusion procedures for the most commonly used commercially available devices in current practice.