Deep learning in vivo catheter tip locations for photoacoustic-guided cardiac interventions.

Significance: Interventional cardiac procedures often require ionizing radiation to guide cardiac catheters to the heart. To reduce the associated risks of ionizing radiation, photoacoustic imaging can potentially be combined with robotic visual servoing, with initial demonstrations requiring segmentation of catheter tips. However, typical segmentation algorithms applied to conventional image formation methods are susceptible to problematic reflection artifacts, which compromise the required detectability and localization of the catheter tip. Aim: We describe a convolutional neural network and the associated customizations required to successfully detect and localize in vivo photoacoustic signals from a catheter tip received by a phased array transducer, which is a common transducer for transthoracic cardiac imaging applications. Approach: We trained a network with simulated photoacoustic channel data to identify point sources, which appropriately model photoacoustic signals from the tip of an optical fiber inserted in a cardiac catheter. The network was validated with an independent simulated dataset, then tested on data from the tips of cardiac catheters housing optical fibers and inserted into ex vivo and in vivo swine hearts. Results: When validated with simulated data, the network achieved an F1 score of 98.3% and Euclidean errors (mean ± one standard deviation) of 1.02±0.84 mm for target depths of 20 to 100 mm. When tested on ex vivo and in vivo data, the network achieved F1 scores as large as 100.0%. In addition, for target depths of 40 to 90 mm in the ex vivo and in vivo data, up to 86.7% of axial and 100.0% of lateral position errors were lower than the axial and lateral resolution, respectively, of the phased array transducer. Conclusions: These results demonstrate the promise of the proposed method to identify photoacoustic sources in future interventional cardiology and cardiac electrophysiology applications.

Determinants of acute irreversible electroporation lesion characteristics after pulsed field ablation: the role of voltage, contact, and adipose interference.

AIMS: Pulsed field ablation (PFA) is a non-thermal ablative approach in which cardiomyocyte death is obtained through irreversible electroporation (IRE). Data correlating the biophysical characteristics of IRE and lesion characteristics are limited. The aim of this study was to assess the effect of different procedural parameters [voltage, number of cycles (NoCs), and contact] on lesion characteristics in a vegetal and animal model for IRE. METHODS AND RESULTS: Two hundred and four Russet potatoes were used. Pulsed field ablation lesions were delivered on 3 cm cored potato specimens using a multi-electrode circular catheter with its dedicated IRE generator. Different voltage (from 300 to 1200 V) and NoC (from 1 to 5×) protocols were used. The impact of 0.5 and 1 mm catheter-to-specimen distances was tested. A swine animal model was then used to validate the results observed in the vegetable model. The association between voltage, the NoCs, distance, and lesion depth was assessed through linear regression. An almost perfect linear association between lesion depth and voltage was observed (R2 = 0.95; P < 0.001). A similarly linear relationship was observed between the NoCs and the lesion depth (R2 = 0.73; P < 0.001). Compared with controls at full contact, a significant dampening on lesion depth was observed at 0.5 mm distance (1000 V 2×: 2.11 ± 0.12 vs. 0.36 ± 0.04, P < 0.001; 2.63 ± 0.10 vs. 0.43 ± 0.08, P < 0.001). No lesions were observed at 1.0 mm distance. CONCLUSION: In a vegetal and animal model for IRE assessment, PFA lesion characteristics were found to be strongly dependent on voltage settings and the NoCs, with a quasi-linear relationship. The lack of catheter contact was associated with a dampening in lesion depth.

Quality assessment of cardiac magnetic resonance myocardial scar imaging prior to ventricular arrhythmia ablation.

High-resolution scar characterization using late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR) is useful for guiding ventricular arrhythmia (VA) treatment. However, imaging study quality may be degraded by breath-holding difficulties, arrhythmias, and implantable cardioverter-defibrillators (ICDs). We evaluated the effect of image quality on left ventricle (LV) base to apex scar interpretation in pre-VA ablation LGE-CMR. 43 consecutive patients referred for VA ablation underwent gradient-recalled-echo LGE-CMR. In ICD patients (n = 24), wide-bandwidth inversion-recovery suppressed ICD artifacts. In non-ICD patients, single-shot steady-state free-precession LGE-CMR could also be performed to reduce respiratory motion/arrhythmia artifacts. Study quality was assessed for adequate/limited scar interpretation due to cardiac/respiratory motion artifacts, ICD-related artifacts, and image contrast. 28% of non-ICD patients had studies where image quality limited scar interpretation in at least one image compared to 71% of ICD patient studies (p = 0.012). A median of five image slices had limited quality per ICD patient study, compared to 0 images per non-ICD patient study. Poorer quality in ICD patients was largely due to motion-related artifacts (54% ICD vs 6% non-ICD studies, p = 0.001) as well as ICD-related image artifacts (25% of studies). In VA ablation patients with ICDs, conventional CMR protocols frequently have image slices with limited scar interpretation, which can limit whole-heart scar assessment. Motion artifacts contribute to suboptimal image quality, particularly in ICD patients. Improved methods for motion and ICD artifact suppression may better delineate high-resolution LGE scar features of interest for guiding VA ablation.

Clinical outcomes of catheter ablation of ventricular tachycardia in patients with arrhythmogenic right ventricular cardiomyopathy: Insights from the Johns Hopkins ARVC Program.

BACKGROUND: Previous studies of radiofrequency catheter ablation (RFA) of ventricular tachycardia (VT) in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), relying on limited numbers of procedures, have not reported VT-free survival in parallel for single and multiple procedures (ie, after the last procedure). Data regarding the impact of RFA on VT burden are scarce. OBJECTIVE: The purpose of this study was to provide new insights on clinical outcomes based on a large series of VT ablation procedures from the current era in ARVC patients. METHODS: We evaluated consecutive patients with definite ARVC who underwent RFA procedures between 2009 and 2019 at our center. We assessed VT-free survival, for single and multiple procedures, and changes in VT burden and antiarrhythmic drugs (AADs) after RFA. RESULTS: Among 116 patients, there were 166 RFA procedures, 106 (63.9%) of which involved epicardial ablation. Cumulative freedom from VT after a single procedure was 68.6% and 49.8% at 1 and 5 years, respectively. Cumulative VT-free survival after multiple procedures was 81.8% and 69.6% at 1 and 5 years, respectively. VT burden per RFA was reduced after vs before ablation (mean 0.7 vs 10.0 events/year; P <.001). Furthermore, VT burden per patient was reduced after last ablation vs before first ablation (mean 0.5 vs 10.9 events/year; P <.001). Use of AADs decreased after ablation (22.2% vs 51.9%; P <.001). CONCLUSION: In ARVC patients, RFA provided good VT-free survival after a single procedure, with multiple procedures required for more sustained freedom from VT recurrence. Marked reduction in VT burden permitted discontinuation of AADs.

Long-Term Outcomes of Bilateral Cardiac Sympathetic Denervation for Refractory Ventricular Tachycardia.

OBJECTIVES: This study sought to explore the long-term arrhythmic outcomes of bilateral cardiac sympathetic denervation (BCSD). BACKGROUND: BCSD has been associated with improved arrhythmic outcomes in patients with refractory ventricular arrhythmias. However, whether BCSD antiarrhythmic effects are sustained long after the procedure is still uncertain. METHODS: We included consecutive patients who underwent BCSD because of refractory ventricular tachycardia (VT) and had at least 18 months of follow-up. VT recurrence after BCSD was evaluated to assess arrhythmic outcomes. The occurrence of VT episodes within the first 12 weeks after the procedure was assessed to explore the impact of early VT recurrence on late arrhythmia-free survival. RESULTS: Twenty patients (42 ± 16 years; 55% male) were included in the analysis. Nineteen (95%) patients had structural heart disease (left ventricular ejection fraction: 0.46 ± 0.14). Class I or class III drugs failed for all patients, and the mean number of VT ablation procedures was 2.5 ± 1.6. Over a mean follow-up of 1,300 ± 321 days (median: 1,276 days [Interquartile range (IQR): 1,181 to 1,480 days), 11 (55%) patients remained VT free after sympathectomy. Freedom from sustained VT or implantable cardioverter-defibrillator shock was 60% (95% confidence interval: 0.35 to 0.77) and 54.5% (95% confidence interval: 0.31 to 0.73) after BCSD at 1 and 4 years. Early VT recurrence was not associated with worse late arrhythmia-free survival rates. CONCLUSIONS: BCSD was associated with longstanding antiarrhythmic effects in patients with refractory ventricular arrhythmias. The occurrence of VT episodes early after the procedure was not associated with worse late arrhythmic outcomes.

Efficacy of catheter ablation for premature ventricular contractions in arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Premature ventricular contractions (PVCs) may be found in any stage of arrhythmogenic right ventricular cardiomyopathy (ARVC) and have been associated with the risk of sustained ventricular tachycardia (VT). OBJECTIVE: To investigate the role of PVC ablation in ARVC patients. METHODS: We studied consecutive ARVC patients who underwent PVC ablation due to symptomatic high PVC burden. Mean daily PVC burden and antiarrhythmic drug (AAD) use were assessed before and after the procedure. Complete long-term success was defined as more than 80% reduction in PVC burden off of membrane-active AADs. RESULTS: Eight patients (37 ± 15 years; 4 males) underwent PVC ablation. The mean daily PVC burden before ablation ranged from 5.4% to 24.8%. A total of 7 (87.5%) patients underwent epicardial ablation. Complete acute elimination of PVCs was achieved in 4 (50%) patients (no complications). The mean daily PVC burden variation ranged from an 87% reduction to a 26% increase after the procedure. Over a median follow-up of 345 days (range: 182-3004 days), only one (12.5%) patient presented complete long-term success, and 6 (75%) patients either maintained or increased the need for Class I or Class III AADs. A total of 2 (25%) patients experienced sustained VT for the first time following the ablation procedure, requiring repeat ablation. No death or heart transplantation occurred. CONCLUSION: PVC ablation was not associated with a consistent reduction of the PVC burden in ARVC patients with symptomatic, frequent PVCs. PVC ablation may be reserved for highly symptomatic patients who failed AADs. Additional investigation is required to improve the efficacy of PVC ablation in ARVC patients.

Trans-nasal high-flow dehumidified air in acute migraine headaches: A randomized controlled trial.

BACKGROUND: Intranasal high flow of dehumidified (dry) air results in evaporative cooling of nasal passages. In this randomized clinical trial, we investigated the effect of dry gas induced nasal cooling on migraine headaches. METHODS: In this single-blind study, acute migraineurs were randomized to either nasal high-flow dry oxygen, dry air, humidified oxygen or humidified air (control) at 15 L/min for 15 min. All gases were delivered at 37°C. Severity of headache and other migraine associated symptoms (International Classification for Headache Disorders, 3rd edition criteria) were recorded before and after therapy. The primary endpoint was change in pain scores, while changes in nausea, photosensitivity and sound sensitivity scores served as secondary endpoints. A linear regression model was employed to estimate the impact of individual treatment components and their individual interactions. RESULTS: Fifty-one patients (48 ± 15 years of age, 82% women) were enrolled. When compared to the control arm (humidified air), all therapeutic arms showed a significantly greater reduction in pain scores (primary endpoint) at 2 h of therapy with dry oxygen (-1.6 [95% CI -2.3, -0.9]), dry air (-1.7 [95% CI -2.6, -0.7)]), and humidified oxygen (-2.3 [95% CI -3.5, -1.1]). A significantly greater reduction in 2-h photosensitivity scores was also noted in all therapeutic arms (-1.8 [95% CI -3.2, -0.4], dry oxygen; -1.7 [95% CI -2.9, -0.4], dry air; (-2.1 [95% CI -3.6, -0.6], humidified oxygen) as compared to controls. The presence of oxygen and dryness were independently associated with significant reductions in pain and photosensitivity scores. No adverse events were reported. CONCLUSION: Trans-nasal high-flow dry gas therapy may have a role in reducing migraine associated pain.Clinical Trial registration: NCT04129567.

Effects of High-Flow Transesophageal Dry Air on Core Temperature: A Novel Method of Therapeutic Hypothermia.

Therapeutic hypothermia (TH) is one of the few proven neuroprotective modalities in clinical practice. However, current methods to achieve TH are suboptimal. We investigated a novel esophageal device that utilizes high-flow transesophageal dry air to achieve TH via evaporating cooling. Seven Yorkshire pigs (n = 7) underwent hypothermia therapy using a novel esophageal device that compartmentalizes a segment of esophagus through which high-flow dry air freely circulates in and out of the esophagus. Efficacy (primary objective) and safety (secondary objective) were evaluated in all animals. Safety assessment was divided into two sequential phases: (1) acute safety assessment (n = 5; terminal studies) to evaluate adverse events occurring during therapy, and (2) chronic safety assessment (n = 2; survival studies) to evaluate adverse events associated with therapy within 1 week of follow-up. After 1 hour of esophageal cooling (mean airflow rate = 64.2 ± 3.5 L/min), a significant reduction in rectal temperature was observed (37.3 ± 0.2°C → 36.3 ± 0.4°C, p = 0.002). The mean rectal temperature reduction was 1 ± 0.4°C. In none of the seven animals was oral or pharyngeal mucosa injury identified at postprocedural visual examination. In the two animals that survived, no reduction of food ingestion, signs of swallowing dysfunction or discomfort, or evidence of gastrointestinal bleeding was observed during the 1-week follow-up period. Open-chest visual inspection in those two animals did not show damage to the esophageal mucosa or surrounding structures. A novel esophageal device, utilizing high-flow transesophageal dry air, was able to efficiently induce hypothermia despite external heating. Therapy was well-tolerated, and no acute or chronic complications were found.

Epicardial Ablation of Ventricular Tachycardia in Arrhythmogenic Right Ventricular Cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease characterized by progressive fibrofatty replacement of the myocardium, right ventricular enlargement, and malignant ventricular arrhythmias. Ventricular tachycardia (VT) may be seen in all stages of the disease and is associated with sudden cardiac death. In patients who failed anti-arrhythmic medical therapy, catheter ablation has become an attractive therapeutic option to reduce VT burden and implantable cardioverter-defibrillator interventions. In this article, the authors aim to address the overall concepts of epicardial catheter ablation in ARVC, focusing on substrate characterization and ablation strategies.

Esophageal injury associated with catheter ablation for atrial fibrillation: Determinants of risk and protective strategies.

Catheter ablation has become an important element in the management of atrial fibrillation. Several technical advances allowed for better safety profiles and lower recurrence rates, leading to an increasing number of ablations worldwide. Despite that, major complications are still reported, and esophageal thermal injury remains a significant concern as atrioesophageal fistula (AEF) is often fatal. Recognition of the mechanisms involved in the process of esophageal lesion formation and the identification of the main determinants of risk have set the grounds for the development and improvement of different esophageal protective strategies. More sensitive esophageal temperature monitoring, safer ablation parameters and catheters, and different energy sources appear to collectively reduce the risk of esophageal thermal injury. Adjunctive measures such as the prophylactic use of proton-pump inhibitors, as well as esophageal cooling or deviation devices, have emerged as complementary methods with variable but promising results. Nevertheless, as a multifactorial problem, no single esophageal protective measure has proven to be sufficiently effective to eliminate the risk, and further investigation is still warranted. Early screening in the patients at risk and prompt intervention in the cases of AEF are important risk modifiers and yield better outcomes.

In Vivo Demonstration of Photoacoustic Image Guidance and Robotic Visual Servoing for Cardiac Catheter-Based Interventions.

Cardiac interventional procedures are often performed under fluoroscopic guidance, exposing both the patient and operators to ionizing radiation. To reduce this risk of radiation exposure, we are exploring the use of photoacoustic imaging paired with robotic visual servoing for cardiac catheter visualization and surgical guidance. A cardiac catheterization procedure was performed on two in vivo swine after inserting an optical fiber into the cardiac catheter to produce photoacoustic signals from the tip of the fiber-catheter pair. A combination of photoacoustic imaging and robotic visual servoing was employed to visualize and maintain constant sight of the catheter tip in order to guide the catheter through the femoral or jugular vein, toward the heart. Fluoroscopy provided initial ground truth estimates for 1D validation of the catheter tip positions, and these estimates were refined using a 3D electromagnetic-based cardiac mapping system as the ground truth. The 1D and 3D root mean square errors ranged 0.25-2.28 mm and 1.24-1.54 mm, respectively. The catheter tip was additionally visualized at three locations within the heart: (1) inside the right atrium, (2) in contact with the right ventricular outflow tract, and (3) inside the right ventricle. Lasered regions of cardiac tissue were resected for histopathological analysis, which revealed no laser-related tissue damage, despite the use of 2.98 mJ per pulse at the fiber tip (379.2 mJ/cm2 fluence). In addition, there was a 19 dB difference in photoacoustic signal contrast when visualizing the catheter tip pre- and post-endocardial tissue contact, which is promising for contact confirmation during cardiac interventional procedures (e.g., cardiac radiofrequency ablation). These results are additionally promising for the use of photoacoustic imaging to guide cardiac interventions by providing depth information and enhanced visualization of catheter tip locations within blood vessels and within the beating heart.

Regional abnormalities on cardiac magnetic resonance imaging and arrhythmic events in patients with cardiac sarcoidosis.

BACKGROUND: Patients with cardiac sarcoidosis (CS) may present with arrhythmic events (AE): atrioventricular block (AVB) and/ or ventricular arrhythmias (VA). We sought to: (a) use regional analysis of cardiac magnetic resonance imaging (CMR) to describe anatomic and functional phenotypes of patients with CS and AE; (b) Assess the association of regional CMR abnormalities with the combined endpoint of death, heart transplantation (HT) and AE; and (c) use machine learning (ML) to predict the combined endpoint based on CMR features. METHODS: we included 76 patients with CS and CMR. We analyzed cine images to determine regional longitudinal (LS) and radial strain (RS); and late gadolinium enhancement imaging to determine regional scar burden (%scar). RESULTS: Patients with AVB (n = 7), compared with those without, had higher %scar in the anterior (21.8 ± 27.4 vs 5.1 ± 8.9; P = 0.0005) and anteroseptal (19.3 ± 24.5 vs 3.5 ± 5.5; P < .0001) walls. Patients with VA (n = 12), compared with those without, had higher %scar in the basal inferoseptum (20.4 ± 30.8 vs 8.3 ± 13.4; P = .03). During mean follow-up of 4.4 ± 3.3 years, four patients died or underwent HT; eight had VA; and zero developed AVB. Multiple regional abnormalities were associated with the combined endpoint, including scar in the anteroseptal wall (HR 1.06 [1.02-1.09] per 1%scar increase, P = .002). The ML algorithm predicted the combined endpoint with a C-statistic of 0.91. CONCLUSION: Regional CMR abnormalities are associated with AE in patients with CS.

Misdiagnosis of ARVC leading to inappropriate ICD implant and subsequent ICD removal - lessons learned.

INTRODUCTION: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited progressive cardiomyopathy characterized by frequent life-threatening arrhythmias. The diagnosis of ARVC is challenging and is on the basis of a set of major and minor criteria as described by the modified Task Force Criteria (TFC). We report our clinical experience in a series of patients who were misdiagnosed with ARVC and subsequently underwent removal of their implantable cardioverter defibrillator (ICD) after a re-evaluation at our center. METHODS AND RESULTS: We studied 12 patients who were misdiagnosed with ARVC and had ICD implantation before our assessment. All patients had a repeat evaluation and were scored according to TFC before ICD removal. Cardiac magnetic resonance imaging (CMR) studies performed at outside institutions during the initial evaluation were reported abnormal and classified as meeting major TFC in ninety percent of patients. The most common abnormality reported was fatty infiltration of the right ventricular (RV) free wall and/or presence of focal intra-myocardial fat in six patients (50%). On re-evaluation, none of these findings fulfilled the TFC for the diagnosis. CONCLUSION: This study demonstrated that high dependence on misinterpretation of CMR along with a misunderstanding of the TFC evaluation are the main reasons for the misdiagnosis of ARVC. Despite the updated criteria for almost a decade, this study reminds that the diagnosis of ARVC is complex and hence careful TFC evaluation and consideration of multiple cardiac test results should be the focused approach for clinicians when confronted with suspected ARVC patients.