Visualization of electrographic flow fields of increasing complexity and detection of simulated sources during spontaneously persistent AF in an animal model.

Background: Mapping algorithms have thus far been unable to localize triggers that serve as drivers of AF, but electrographic flow (EGF) mapping provides an innovative method of estimating and visualizing in vivo, near real-time cardiac wavefront propagation. Materials and Methods: One-minute unipolar EGMs were recorded in the right atrium (RA) from a 64-electrode basket catheter to generate EGF maps during atrial rhythms of increasing complexity. They were obtained from 3 normal, animals in sinus rhythm (SR) and from 6 animals in which persistent AF which was induced by rapid atrial pacing. Concurrent EGF maps and high-resolution bipolar EGMs at the location of all EGF-identified sources were acquired. Pacing was subsequently conducted to create focal drivers of AF, and the accuracy of source detection at the pacing site was assessed during subthreshold, threshold and high-output pacing in the ipsilateral or contralateral atria (n = 78). Results: EGF recordings showed strong coherent flow emanating from the sinus node in SR that changed direction during pacing and were blocked by ablation lesions. Additional passive rotational phenomena and lower activity sources were visualized in atrial flutter (AFL) and AF. During the AF recordings, source activity was not found to be correlated to dominant frequency or f wave amplitude observed in concurrently recorded EGMs. While pacing in AF, subthreshold pacing did not affect map properties but pacing at or above threshold created active sources that could be accurately localized without any spurious detection in 95% of cases of ipsilateral mapping when the basket covered the pacing source. Discussion: EGF mapping can be used to visualize flow patterns and accurately identify sources of AF in an animal model. Source activity was not correlated to spectral properties of f-waves in concurrently obtained EGMs. The locations of sources could be pinpointed with high precision, suggesting that they may serve as prime targets for focal ablations.

Electrographic flow mapping for atrial fibrillation: theoretical basis and preliminary observations.

Ablation strategies remain poorly defined for persistent atrial fibrillation (AF) patients with recurrence despite intact pulmonary vein isolation (PVI). As the ability to perform durable PVI improves, the need for advanced mapping to identify extra-PV sources of AF becomes increasingly evident. Multiple mapping technologies attempt to localize these self-sustained triggers and/or drivers responsible for initiating and/or maintaining AF; however, current approaches suffer from technical limitations. Electrographic flow (EGF) mapping is a novel mapping method based on well-established principles of optical flow and fluid dynamics. It enables the full spatiotemporal reconstruction of organized wavefront propagation within the otherwise chaotic and disorganized electrical conduction of AF. Given the novelty of EGF mapping and relative unfamiliarity of most clinical electrophysiologists with the mathematical principles powering the EGF algorithm, this paper provides an in-depth explanation of the technical/mathematical foundations of EGF mapping and demonstrates clinical applications of EGF mapping data and analyses. Starting with a 64-electrode basket catheter, unipolar EGMs are recorded and processed using an algorithm to visualize the electrographic flow and highlight the location of high prevalence AF "source" activity. The AF sources are agnostic to the specific mechanisms of source signal generation.

Adalimumab in the treatment of cardiac sarcoidosis: Single center case series and narrative literature review.

Background: Tumor necrosis factor (TNF) inhibitors have been used in the treatment of cardiac sarcoidosis, infliximab being the most commonly used. We have previously reported a case of effective treatment of cardiac sarcoidosis using adalimumab. Objective: To describe our experience of using adalimumab in the treatment of cardiac sarcoidosis. Methods: We conducted a retrospective study to evaluate patients with cardiac sarcoidosis who received adalimumab treatment at the University of Illinois Health between 2011 and 2022. The outcome was evaluated by assessing safety, tolerability, and ability to taper systemic corticosteroids therapy following initiation of adalimumab. Results: Seven patients met the inclusion criteria. Clinical responses to adalimumab were universally positive. Corticosteroid therapy was discontinued in five patients and the dose was reduced in two patients. Furthermore, adalimumab was well tolerated, and no adverse events were reported. Conclusion: Adalimumab was safe and well-tolerated in seven patients with cardiac sarcoidosis seen at our medical center and exhibited corticosteroid-sparing effects. Our observation further warrants large prospective studies to evaluate the safety and efficacy of adalimumab in the treatment of cardiac sarcoidosis.

Determination of single cryoablation outcome within 30 to 60 seconds of freezing based on ice impedance.

BACKGROUND: A direct indicator of effective pulmonary vein isolation (PVI) based on early ice formation is presently lacking. OBJECTIVE: The initial impedance rise within 30 to 60 seconds (sec) of single cryoablation relating to ice on the distal surface of the cryoballoon could; predict effective PVI with early termination, the need for prolonging the cryoablation, or failure to achieve effective ablation. METHODS: Impedance measurements were taken between two ring electrodes, at the anterior balloon surface and at the shaft behind the balloon. Ice covering the anterior ring leads to impedance rise. Single cryoablation (eight animals, 37 veins) was applied for 90 to 180 sec. Cryoapplication was terminated if the impedance reached ≥500 Ω. Impedance levels at ≤60 sec of cryoablation were divided into three groups based on the characteristics of the impedance rise. PVI was confirmed acutely and at 45 ± 9 days recovery by electrophysiology mapping and histopathology. RESULTS: At 60 sec of freezing, an impedance rise of 34.1 ± 15.2 Ω (13-50 Ω) and slope of the impedance rise (measured during 15-30 sec of cryoapplication) less than 1 Ω/sec resulted in failed PVI. An impedance rise of 104.4 ± 31.5 Ω (76-159 Ω) and slope of 2 Ω/sec resulted in 100% PVIs. An impedance rise of 130.9 ± 137.8 Ω (40-590 Ω) and slope of 10 Ω/sec resulted in 100% PVIs with early termination at 90 sec. CONCLUSION: The efficacy of single cryoablation can be defined within 30 to 60 sec based on ice impedance. Three unique impedance profiles described in this investigation are associated with the uniformity and thickness of the ice buildup on the anterior surface of the balloon. One cryoablation with an adequate impedance rise is needed for successful outcomes.

Characteristics of Ice Impedance Recorded From a Ring Electrode Placed at the Anterior Surface of the Cryoballoon: Novel Approach to Define Ice Formation and Pulmonary Vein Isolation.

BACKGROUND: The success of cryoablation of the pulmonary vein isolation (PVI) is dependent on transmural and circumferential ice formation. We hypothesize that rising impedance recorded from a ring electrode placed 2 mm from the cryoballoon signifies ice formation covering the balloon surface and indicates ice expansion. The impedance level enables titration of the cryoapplication time to avoid extracardiac damage while ensuring PVI. METHODS AND RESULTS: In 12 canines, a total of 57 pulmonary veins were targeted for isolation. Two cryoapplications were delivered per vein with a minimum of 90 and maximum of 180-second duration. Cryoapplication was terminated on reaching a 500 Ω change from baseline. Animals recovered 38±6 days post-procedure, and veins were assessed electrically for isolation. Heart tissue was histologically analyzed. Extracardiac structures were examined for damage. PVI was achieved in 100% of the veins if the impedance reached 500 Ω in <90 seconds with freeze time of 90 seconds. When 500 Ω was reached >90 to 180 seconds (142.60±29.3 seconds), 90% PVI was achieved. When the final impedance was between 200 and 500 Ω with 180 seconds of freeze time, PVI was achieved in 86.8%. For impedance of <200 Ω, PVI was achieved in 14%. No extracardiac damage was recorded. CONCLUSIONS: Impedance rise of 500 Ω at <90 seconds with freeze time of 90 seconds resulted in 100% PVI. Impedance measurements from the nose of the balloon is a direct measure of ice formation on the balloon. It provides real-time feedback on the quality of the ablation and defines the cryoapplication termination time based on ice formation, limiting ice expansion to extracardiac tissues.

Novel dyeless and fluoro-less approach to cryoballoon pulmonary vein occlusion assessment.

BACKGROUND: Pulmonary vein (PV) occlusion is essential for PV isolation (PVI) using the cryoballoon. Currently occlusion is arbitrarily determined using fluoroscopy and contrast media. This study aimed to create an objective measure without utilizing excessive fluoroscopy and using no contrast media. OBJECTIVE: To ensure PV occlusion without fluoroscopy and contrast dye. METHODS: In 4 in vivo hearts 113 PV occlusions were tested with a 50% cold dye saline mix at 4°C. Occlusions were rated Good, Fair, and Poor by dye dissipation seen via fluoroscopy and correlated to temperature profiles recorded concurrently. Using these temperature profiles and no dye, cryoablations were placed in 12 additional hearts (56 unique veins, 126 occlusions). Two 180-second cryoablation applications were placed per vein with occlusion testing in between. PVI was defined by electrophysiology mapping, gross pathology, and histology after ≥4 weeks recovery. RESULTS: Dye results were as follows: With Good, Fair, and Poor the maximal postinjection PV temperature dropped (ΔT) by 6.2 ± 4.2°C, 5.1 ± 3.7°C, and 2.4 ± 2.0°C. At 5 seconds post nadir temperature, injection temperature recovered 18% ± 14%, 36% ± 23%, and 50% ± 33%. Console thaw time to 0°C was 11.5 ± 4.8 seconds, 8.5 ± 2.1 seconds, and 4.3 ± 1.3 seconds. Success rate for PVI was 100%, 97%, and 0%. With no dye: ΔT: 7.7 ± 4.4°C, 5.8 ± 5.0°C, and 3.4 ± 2.3°C; % recovery at 5 seconds: 15% ± 12%, 31% ± 23%, 45% ± 30%; thaw time to 0°C: 11.9 ± 4.8 seconds, 10.5 ± 5.2 seconds, 6.0 ± 2.8 seconds; success rate: 97%, 91%, and 10%. CONCLUSION: PV occlusion profile determination using 4°C cold saline injection is an effective approach to define the occlusion grade. Quality occlusions correlate strongly with PVI success.

Relationship between lesion formation and electrophysiological responses using catheters equipped with mini-electrodes in chronic atrial fibrillation.

BACKGROUND: The study focuses on the electrophysiological changes associated with lesion formation using 4.5-mm irrigated and 8-mm standard catheters equipped with mini-electrodes (MEs) positioned circumferentially on the tip. OBJECTIVE: The aim of the study was to test the relationship between the maximal electrogram (EGM) reduction, frequency spectrum shift, and their impact on atrial lesion formation in the atrial fibrillation (AF) model. Furthermore, we hypothesize that the high fidelity recording from the MEs allows improved discrimination of ablated tissues from nonablated tissues. METHODS: Under fluoroscopic and NavX guidance, atrial ablation lesions were placed in 4 canines in chronic AF (>12 months in AF) to achieve intercaval, cavotricuspid isthmus, and left atrial contiguous lesions. Lesion times were titrated to the maximal loss of EGM amplitude as recorded from the MEs. Radiofrequency (RF) lesions were sequentially connected on the basis of the ME recordings of tissue viability. RESULTS: In lesions formed using a 4.5-mm irrigated catheter (172 lesions) and in those formed using an 8-mm catheter (155 lesions), the time to nadir of the EGM reduction was 22 ± 12 and 22 ± 9 seconds (NS:p>0.05). Contiguous transmural lesions were successfully placed and guided by the ME EGMs and confirmed by frequency spectra. CONCLUSION: In the chronic AF model, EGM reduction and frequency spectrum shift recorded from the MEs are twice the reduction recorded using the 4.5mm and 8mm tip to ring electrodes. RF titration based on the maximal EGM diminution is an effective approach to monitor lesion formation and may improve safety by preventing unnecessarily prolonged RF application. The ME EGM recording greatly facilitates placement of contiguous transmural linear lesions.

Cryotherapy of cardiac arrhythmia: From basic science to the bedside.

This review focuses on the basic science of cellular destruction by tissue freezing and application of transvenous cryocatheter technology to treat cardiac arrhythmia. Ideally, foci for arrhythmias are selectively ablated, arrhythmogenic tissues are destroyed, and reentry circuits are bisected in order to silence adverse electrical activity, with the goal of restoring normal sinus rhythm. The mechanism of ablation using cryotherapy results in distinct lesion qualities advantageous to radiofrequency (Khairy P, Chauvet M, Lehman J, et al. Lower incidence of thrombus formation with cryoenergy versus radiofrequency catheter ablation. Circulation 2003;107:2045-2050). This review is devoted to the mechanism of cryoablation, postablation histopathological changes, and how this information should be used by the clinicians to improve safety and maximize ablation success.

Pre-Clinical Investigation of a Low-Intensity Collimated Ultrasound System for Pulmonary Vein Isolation in a Porcine Model.

OBJECTIVES: The purpose of this study was to assess the feasibility of pulmonary vein (PV) isolation using low-intensity collimated ultrasound. BACKGROUND: Contemporary approaches to PV isolation are limited by the technical complexity of mapping and ablation. We describe a novel approach to left atrial anatomic rendering and PV isolation that aims to overcome some of these limitations by using low-intensity collimated ultrasound (LICU) system, which allows for near real-time geometry creation and automated ablation in a porcine model. METHODS: Twenty swine were anesthetized, and the LICU ablation catheter was placed in the left atrium via percutaneous transseptal access. Ultrasound M-mode-based anatomies of the inferior PVs were successfully created, and ablation was performed under automatic robotic control along a user-defined lesion path. One animal was excluded because of device failure. RESULTS: All target PVs in the 19 remaining animals were isolated acutely, requiring a mean of 1.6 applications. Ten animals were sacrificed acutely, and the remaining 9 survived for 35 ± 11 days. Of these 9, 1 animal was excluded from analysis because the index lasso position could not be reliably recreated. PVs in 5 of 8 animals remained isolated at sacrifice. Of the 77 total histological sections, 62 lesions (80.5%) were noted to be transmural. Lesions were homogeneous and characterized by coagulative necrosis and fibrous tissue. The mean myocardial thickness was 2.66 ± 1.80 mm, and the mean lesion depth was 4.28 ± 1.97 mm. No extra cardiac or collateral lesions were noted. CONCLUSIONS: This study demonstrates the safety and efficacy of a novel noncontact ultrasound mapping and ablation system to produce continuous transmural lesions that can isolate PVs in a porcine model.

Maximal electrogram attenuation recorded from mini electrodes embedded on 4.5-mm irrigated and 8-mm nonirrigated catheters signifies lesion maturation.

BACKGROUND: The electrograms (EGMs) recorded from mini electrodes (ME) placed on the tip of the ablation electrode allow more precise EGM monitoring during lesion formation. Our objective was to define the lesion boundaries and extracardiac injuries resulting from 60-second RF application versus RF application time titrated to maximal attenuation of the ME EGM in the atria and ventricles using 4.5-mm irrigated and 8-mm catheters. METHODS: RF lesions were placed in both atria and ventricles in 13 (30-35 kg) canines; 6 (4.5-mm OI) and 7 (8 mm). The RF application time was fixed at 60 seconds or terminated at maximal ME EGM amplitude attenuation. RESULTS: Pre/postablation pacing thresholds, EGM amplitudes, and lesion dimensions were not significantly different between maximal EGM attenuation and 60-second RF application using either catheter. Atrial lesion transmurality was also similar for both catheters and groups 91.2% (4.5 mm) and 96% (8 mm) when the RF was titrated to the maximal EGM attenuation and 94.2% (4.5 mm) and 95% (8 mm) with 60-second RF. The 60-second RF ablation, however, presented with significant extracardiac injuries to the lungs and esophagus, along with char formation. Deep ventricular lesions were noted with maximal EGM attenuation that were not different from the 60-second RF ablation. CONCLUSION: Titration of the RF application time to the maximal EGM attenuation based on the ME recordings represents atrial lesion maturation and deep ventricular lesions. Prolonging the RF application results in greater extracardiac injury and char formation without increasing lesion size.

An Update on the Energy Sources and Catheter Technology for the Ablation of Atrial Fibrillation.

The ablation of atrial fibrillation (AF) is an area of intense research in cardiac electrophysiology. In this review, we discuss the development of catheter-based interventions for AF ablation. We outline the pathophysiologic and anatomic bases for ablative lesion sets and the evolution of various catheter designs for the delivery of radiofrequency (RF), cryothermal, and other ablative energy sources. The strengths and weaknesses of various specialized RF catheters and alternative energy systems are delineated, with respect to efficacy and patient safety.

High-density biatrial pacing protects against atrial fibrillation by synchronizing left atrial tissue.

PURPOSE: The induction and sustainability of atrial fibrillation (AF) are most commonly due to pulmonary vein (PV) triggers and left atrial (LA) substrate. We hypothesized that simultaneous pacing of the PV ostia, LA, and right atrium (RA) reduces AF susceptibility by synchronizing atrial activity. METHODS: Mongrel dogs were rapidly paced and maintained in AF for 3 months before cardioversion. Pacing leads were then placed at PV ostia, LA, and RA sites. For single-site pacing (SSP), a drive train (S1) and premature stimulus (S2) were delivered from the same electrode. Multisite pacing (MSP) consisted of S1 at all leads simultaneously and S2 at one site. Pacing trials were performed with decremental S2 coupling intervals (CI) to endpoints of AF induction or refractoriness. RESULTS: AF induction was reduced by 40.0% with MSP vs. SSP (7.2% vs. 12.0%, p < 0.001). LA S2 sites were more likely to induce AF than RA sites (11.5% vs. 2.6%, p < 0.0001), with benefit of MSP over SSP at LA sites (8.6% vs. 14.6%, p < 0.0001). The CI for AF induction was longer with SSP vs. MSP (119.4 +/- 13.3 vs. 104.4 +/- 11.2 ms, p < 0.05). Atrial activation times were shortened with MSP vs. SSP (87.4 +/- 4.9 vs. 97.1 +/- 10 ms, p < 0.005). CONCLUSIONS: Atrial synchronization was shown by the decreased activation times with MSP. AF induction was reduced by 40.0% with MSP, supporting the hypothesis of decreased AF susceptibility with synchronization. This is the first study demonstrating AF protection with high-density pacing at LA sites associated with triggers and substrate for the induction and maintenance of AF.

Atrial and ventricular fibrosis induced by atrial fibrillation: evidence to support early rhythm control.

BACKGROUND: Atrial fibrillation (AF) with poorly controlled ventricular response is known to be detrimental to ventricular function, conversely, heart failure (HF) increases susceptibility to AF. OBJECTIVE: This study sought to examine the electropathological effects of 3 months of atrial fibrillation (AF) in dogs with and without concomitant ventricular dysfunction. METHODS: Three groups of dogs were studied: dogs with chronic AF induced by rapid pacing and concomitant ventricular dysfunction induced by rapid ventricular response with intact atrioventricular node (AVN), dogs with ablated AVN and AF while the ventricle was paced at 80 beats/min, and normal sham dogs. After 3 months of AF, the first 2 groups underwent direct current cardioversion (DCCV) to normal sinus rhythm and were monitored for 3 months, followed by retesting of AF susceptibility. Tissue fibrosis was assessed at various sites by trichrome staining and quantitative immunohistochemistry. RESULTS: AF was induced within 12 +/- 4 days and 30 +/- 13 days, respectively, in the intact and ablated AVN groups (P <.01). After 3 months of AF, left ventricular ejection fraction was 30.4% +/- 10.1% and 55% +/- 5% in the intact and ablated AVN groups (P <.01), respectively. After 3 months of normal sinus rhythm, AF was reinduced after 4 +/- 2 and 7.2 +/- 2 days, respectively (P = NS). There were no regional differences and an abundance of fibrosis within atria. Atrial fibrosis was significantly increased in intact AVN versus ablated AVN and sham groups, and also was greater in AVN-ablated versus sham dogs. Ventricular fibrosis was increased in intact AVN versus ablated AVN and sham groups and was not significantly different in ablated AVN and sham groups. CONCLUSION: AF without ventricular dysfunction results in atrial fibrosis and increased susceptibility to AF, suggesting that AF alone causes atrial fibrosis. AF with rapid ventricular response further increases atrial and ventricular fibrosis. Conversion to normal sinus rhythm should be done as early as possible to avoid atrial and ventricular fibrosis and increased susceptibility to AF.

Integrating telehealth as a strategy for patient management after discharge for cardiac surgery: results of a pilot study.

Advances in telecommunication technologies have improved access and availability of telehealth for use in healthcare. In cardiac care, telehealth has predominantly been used to manage patients with heart failure. The use of telehealth as a strategy for patient management after discharge for cardiac surgery can be beneficial in monitoring postoperative status and in the early detection of complications. This article provides an overview of the use of telehealth and telemanagement in cardiac patients and discusses the results of a pilot study as an example of an application of the use of telehealth for elderly cardiac surgery patients at high risk of postoperative complications.