Novel mapping techniques for rotor core detection using simulated intracardiac electrograms.

BACKGROUND: Catheter ablation is associated with limited success rates in patients with persistent atrial fibrillation (AF). Currently, existing mapping systems fail to identify critical target sites for ablation. Recently, we proposed and validated several techniques (multiscale frequency [MSF], Shannon entropy [SE], kurtosis [Kt], and multiscale entropy [MSE]) to identify pivot point of rotors using ex-vivo optical mapping animal experiments. However, the performance of these techniques is unclear for the clinically recorded intracardiac electrograms (EGMs), due to the different nature of the signals. OBJECTIVE: This study aims to evaluate the performance of MSF, MSE, SE, and Kt techniques to identify the pivot point of the rotor using unipolar and bipolar EGMs obtained from numerical simulations. METHODS: Stationary and meandering rotors were simulated in a 2D human atria. The performances of new approaches were quantified by comparing the "true" core of the rotor with the core identified by the techniques. Also, the performances of all techniques were evaluated in the presence of noise, scar, and for the case of the multielectrode multispline and grid catheters. RESULTS: Our results demonstrate that all the approaches are able to accurately identify the pivot point of both stationary and meandering rotors from both unipolar and bipolar EGMs. The presence of noise and scar tissue did not significantly affect the performance of the techniques. Finally, the core of the rotors was correctly identified for the case of multielectrode multispline and grid catheter simulations. CONCLUSION: The core of rotors can be successfully identified from EGMs using novel techniques; thus, providing motivation for future clinical implementations.

VIEgram - Analysis and Visualization of Intracardiac Electrograms on Patient-Specific 3D Atria Model.

Over the last few years, the use of cardiac mapping for effective diagnosis and treatment of arrhythmias has increased significantly. In the clinical environment, electroanatomical mapping (EAM) is performed during the electrophysiological procedures using proprietary systems such as CARTO, EnSite Precision, RHYTHMIA, etc. These systems generate the 3D model of patient-specific atria with the electrical activity (i.e., intracardiac electrograms (iEGMs)) displayed on it, for further identification of the sources of arrhythmia and for guiding cardiac ablation therapy. Recently, several novel techniques were developed to perform iEGMs analysis to more accurately identify the arrhythmogenic sites. However, there is a difficulty in incorporating the results of iEGMs analysis back to EAM systems due to their proprietary constraints. This created a hurdle in the further development of novel techniques to help navigate patient-specific clinical ablation therapy. Thus, we developed an open source software, VIEgram1, that allows researchers to visualize the results of the various iEGMs analysis on a patient-specific 3D atria model. It eliminates the dependency of the academic environment on the proprietary EAM systems, thereby making the process of retrospective mapping extremely convenient and time efficient. Here, we demonstrate the features of VIEgram such as visual inspection of iEGMs, flexibility in implementing custom iEGMs analysis techniques and interpolation schemes, and spatial analysis.

Trends in reported industry payments to physicians practicing cardiac electrophysiology from 2013 to 2018 in the United States.

INTRODUCTION: The need for transparency in financial relationships in the healthcare system, has culminated in Open Payments database, managed by the Center for Medicare and Medicaid Services (CMS). Since its inception in 2013, the trend in such payments to physicians practicing cardiac electrophysiology was not examined. METHODS AND RESULTS: Payment information reported to CMS from January 2013 to December 2018 was obtained from the publicly available Open Payments data set using the online query tool. The data were analyzed by an individual provider and by state. An in-depth analysis of payments in the year 2018 payments was performed. From 2014 to 2018, there was an 18% increase in the total number of payments reported from 88 877 payments in 2014 to 105 000 in 2018. Despite the increase in the total number of payments reported, the average payment steadily decreased over time, resulting in an overall reduction in the total amount of payments from 2014 to 2018 ($34.9 million to $28.2 million). Payments to the top 5% of individual recipients have also decreased over this time. In 2018, 2888 unique providers received reportable payments, a total of 105 000 payments, with a median payment amount of $1378 (interquartile range: $165-$5781). The majority of these payments were for food and beverage (82%) and travel/lodging (10%). The top five payers include Boston Scientific, Medtronic Vascular, Abbott Laboratories, Janssen Pharmaceuticals, and Biotronik. CONCLUSION: Among cardiac electrophysiologists, there is increased reporting of payments in the Open Payments program over time, with a notable decrease in the payment amount.

Stellate ganglion block and cardiac sympathetic denervation in patients with inappropriate sinus tachycardia.

BACKGROUND: Inappropriate sinus tachycardia (IST) remains a clinical challenge because patients often are highly symptomatic and not responsive to medical therapy. OBJECTIVE: To study the safety and efficacy of stellate ganglion (SG) block and cardiac sympathetic denervation (CSD) in patients with IST. METHODS: Twelve consecutive patients who had drug-refractory IST (10 women) were studied. According to a prospectively initiated protocol, five patients underwent an electrophysiologic study before and after SG block (electrophysiology study group). The subsequent seven patients had ambulatory Holter monitoring before and after SG block (ambulatory group). All patients underwent SG block on the right side first, and then on the left side. Selected patients who had heart rate reduction ≥15 beats per minute (bpm) were recommended to consider CSD. RESULTS: The mean (SD) baseline heart rate (HR) was 106 (21) bpm. The HR significantly decreased to 93 (20) bpm (P = .02) at 10 minutes after right SG block and remained significantly slower at 97(19) bpm at 60 minutes. Left SG block reduced HR from 99 (21) to 87(16) bpm (P = .02) at 60 minutes. SG block had no significant effect on blood pressure or HR response to isoproterenol or exercise (all P > .05). Five patients underwent right (n = 4) or bilateral (n = 1) CSD. The clinical outcomes were heterogeneous: one patient had complete and two had partial symptomatic relief, and two did not have improvement. CONCLUSION: SG blockade modestly reduces resting HR but has no significant effect on HR during exercise. Permanent CSD may have a modest role in alleviating symptoms in selected patients with IST.

Achieving durable mitral isthmus block: Challenges, pitfalls, and methods of assessment.

BACKGROUND AND OBJECTIVES: Macroreentrant atrial tachycardias often occur following atrial fibrillation ablation, most commonly due to nontransmural lesions in prior ablation lines. Perimitral atrial flutter is one such arrhythmia which requires ablation of the mitral isthmus. Our objectives were to review the literature regarding ablation of the mitral isthmus and to provide our approach for assessment of mitral isthmus block. METHODS: We review anatomical considerations, ablation strategies, and assessment of conduction block across the mitral isthmus, which is subject to several pitfalls. Activation sequence and spatial differential pacing techniques are discussed for assessment of both endocardial and epicardial bidirectional mitral isthmus block. RESULTS: Traditional methods for verifying mitral isthmus block include spatial differential pacing, activation mapping, and identification of double potentials. Up to 70% of cases require additional ablation in the coronary sinus (CS) to achieve transmural block. Interpretation of transmural block is subject to six pitfalls involving pacing output, differentiation of endocardial left atrial recordings from epicardial CS recordings, identification of a slowly conducting gap in the line, and catheter positioning during spatial differential pacing. Interpretation of unipolar electrograms can identify nontransmural lesions. We employ a combined epicardial and endocardial assessment of mitral isthmus block, which involves using a CS catheter for epicardial recording and a duodecapolar Halo catheter positioned around the mitral annulus for endocardial recording. CONCLUSIONS: The assessment of transmural mitral isthmus block can be challenging. Placement of an endocardial mapping catheter around the mitral annulus can provide a precise assessment of conduction across the mitral isthmus.

Evaluation of Multiscale Frequency Approach for Visualizing Rotors in Patients with Atrial Fibrillation.

Atrial Fibrillation (AF) is most common cardiac arrhythmia. It is associated with increased risk of stroke, heart failure and sudden cardiac death. Catheter ablation is a treatment used to control AF and has had suboptimal success for patients with persistent AF, which is primarily maintained by rotors outside of the pulmonary veins (PV) region. The pivot point (core) of the rotor is considered an efficient target for ablation. Currently available electro-anatomical mapping systems cannot accurately predict the exact location of the pivot point of rotors outside of the PV region, so there is a need for novel approaches to accurately identify and distinguish sites for ablation. Recently, a multiscale frequency (MSF) technique was developed for accurate identification of the pivot point of rotors and validated using optical mapping experiments in exvivo rabbit hearts, where electrical activity can be directly visualized. However, the nature of optical signals and its spatial resolution are very different from clinical intracardiac electrograms (iEGM). Here we extend the MSF approach to 3D iEGM and compare its prediction with the traditional dominant frequency (DF) approach, using Pearson's correlation and earth mover's distance methods. Our results demonstrate that the similarity between MSF and DF are high in some regions, but very low in other spatial regions of the human atria. This indicates the inconsistency in the traditional DF approach in identifying pivot points and identifying such low similarity regions can be used to find sites for successful ablation.

Mortality and Cerebrovascular Events After Heart Rhythm Disorder Management Procedures.

BACKGROUND: Recognition of rates and causes of hard, patient-centered outcomes of death and cerebrovascular events (CVEs) after heart rhythm disorder management (HRDM) procedures is an essential step for the development of quality improvement programs in electrophysiology laboratories. Our primary aim was to assess and characterize death and CVEs (stroke or transient ischemic attack) after HRDM procedures over a 17-year period. METHODS: We performed a retrospective cohort study of all patients undergoing HRDM procedures between January 2000 and November 2016 at the Mayo Clinic. Patients from all 3 tertiary academic centers (Rochester, Phoenix, and Jacksonville) were included in the study. All in-hospital deaths and CVEs after HRDM procedures were identified and were further characterized as directly or indirectly related to the HRDM procedure. Subgroup analysis of death and CVE rates was performed for ablation, device implantation, electrophysiology study, lead extraction, and defibrillation threshold testing procedures. RESULTS: A total of 48 913 patients (age, 65.7±6.6 years; 64% male) who underwent a total of 62 065 HRDM procedures were included in the study. The overall mortality and CVE rates in the cohort were 0.36% (95% confidence interval [CI], 0.31-0.42) and 0.12% (95% CI, 0.09-0.16), respectively. Patients undergoing lead extraction had the highest overall mortality rate at 1.9% (95% CI, 1.34-2.61) and CVE rate at 0.62% (95% CI, 0.32-1.07). Among patients undergoing HRDM procedures, 48% of deaths directly related to the HDRM procedure were among patients undergoing device implantation procedures. Overall, cardiac tamponade was the most frequent direct cause of death (40%), and infection was the most common indirect cause of death (29%). The overall 30-day mortality rate was 0.76%, with the highest being in lead extraction procedures (3.08%), followed by device implantation procedures (0.94%). CONCLUSIONS: Half of the deaths directly related to an HRDM procedure were among the patients undergoing device implantation procedures, with cardiac tamponade being the most common cause of death. This highlights the importance of the development of protocols for the quick identification and management of cardiac tamponade even in procedures typically believed to be lower risk such as device implantation.

Effect of Ventricular Arrhythmia Ablation in Patients With Heart Mate II Left Ventricular Assist Devices: An Evaluation of Ablation Therapy.

BACKGROUND: Patients with advanced heart failure (HF) are predisposed to ventricular arrhythmias (VAs), particularly following implantation of a left ventricular assist device (LVAD). There is minimal evidence for appropriate management strategies. OBJECTIVES: This study aimed to compare the burden of VA and response to ablation performed either before or following LVAD implantation. METHODS: We created a retrospective cohort of patients who underwent both VA ablation and Heart Mate II (Thoratec, Pleasanton, CA, USA) LVAD implantation at Mayo Clinic (Rochester, MN, USA). Patients were stratified based on whether they underwent VA ablation before (pre-LVAD) or after LVAD (post-LVAD) implantation. Descriptive analyses assessed 6-month arrhythmia burden in relation to LVAD implantation and VA ablation. RESULTS: A total of 9 patients underwent both LVAD implantation and VA ablation. There were 3 and 6 patients, respectively, in the pre-LVAD and post-LVAD cohorts. Among patients in the pre-LVAD cohort, the median number of VAs tended to increase after ablation (9 vs. 72) and decreased after LVAD implantation (72 vs. 63). Similarly among patients in the post-LVAD cohort, the median burden of VAs increased after LVAD implantation (1 vs. 22) and the median burden decreased after ablation (22 vs. 13). Two of 6 patients had substrate related to the LVAD inflow cannula site, while other substrate was not related directly to the cannula. CONCLUSIONS: In patients with progressive HF and LVAD implantation, ablation is associated with reduced VA rates. In LVAD patients, most VAs arise from substrate unrelated to the inflow cannula site.

Endomyocardial biopsy-integrating electrode at the bioptome tip.

BACKGROUND: The addition of electroanatomic mapping to a standard echo-guided endomyocardial biopsy could identify areas of abnormal pathology and increase the diagnostic yield of the procedure. METHODS AND RESULTS: In this demonstration of a novel technique, a 45-year-old woman with clinical suspicion for cardiac sarcoidosis underwent right ventricular bipolar electroanatomical mapping with identification of areas of signal fractionation and low voltage. A bioptome, configured to record an electrogram from the tip, was then visualized on the three-dimensional electroanatomic mapping (3DEAM) system, and directed to these areas. The biopsy was assisted by the use of a steerable introducer sheath, and by recording unipolar and extended bipolar signals from the bioptome tip. A prominent change in the signal was detected by the electrode at the bioptome tip when the jaws closed on the endomyocardial tissue. Patient tolerated the procedure without complications, and the biopsied samples were appropriate for pathological analysis. CONCLUSIONS: Using existing technology, the 3DEAM, which integrates unipolar and bipolar signal from the bioptome tip, is feasible, and can be safely added to a standard echocardiographically guided endomyocardial biopsy. Future studies should investigate whether such a technique could increase the safety and diagnostic yield of endomyocardial biopsies in patients with suspected cardiomyopathies.

Pericardial effusion following drain removal after percutaneous epicardial access for an electrophysiology procedure.

OBJECTIVES: To determine the frequency and predictors of pericardial effusion following epicardial sheath removal. BACKGROUND: Pericardial effusion can occur following cardiac surgical or interventional procedures including percutaneous epicardial access (EpiAcc), which is increasingly used as part of electrophysiology ablation procedures. METHODS: A retrospective analysis of the Mayo Clinic comprehensive electronic medical record was performed from all patients who underwent planned EpiAcc as part of an electrophysiology ablation procedure between January 1, 2004 and June 30, 2013. RESULTS: Of 144 patients (mean age 51.3 ± 15.5 years, 68% male) who underwent planned EpiAcc as part of an electrophysiology ablation (95.8% pericardial access success rate), seven (4.9%) developed a postoperative pericardial effusion requiring repeat EpiAcc. Inferior access was utilized in 74 (51.4%) patients. Patients with pericardial effusion tended to be younger (41.1 years vs 51.8 years, P = 0.08) and were more likely to have undergone inferior approach access (85.7% vs 49.6%, P = 0.06) than those who did not develop postoperative pericardial effusion. Seventy-one percent of patients with postoperative pericardial effusion versus 32.1% of patients without postoperative pericardial effusion had a preprocedure ejection fraction ≥55% (P = 0.03). There were no procedural-related deaths, and no difference in mortality between groups. CONCLUSIONS: Postoperative pericardial effusion requiring repeat access/drainage was relatively infrequent, occurring in 4.9% of patients shortly after epicardial procedures. While the majority occur early and therefore require close observation, some patients may present in a delayed manner.

Electrophysiologic characteristics of ventricular arrhythmias arising from the aortic mitral continuity-potential role of the conduction system.

INTRODUCTION: Catheter ablation of ventricular arrhythmia (VA) at the fibrous aortic mitral continuity (AMC) has been described, yet the nature of the arrhythmogenic substrate remains unknown. METHODS: Procedural records of 528 consecutive patients undergoing ablation of VA at Mayo Clinic, Rochester, MN, were reviewed. The electrocardiographic and electrophysiologic characteristics of patients with successful ablation at the AMC were analyzed to characterize the underlying arrhythmogenic substrate. RESULTS: Of the 21 patients (mean age 53.2 ± 13.4 years, 47.6% male) who underwent ablation of VA at the AMC with acute success, prepotentials (PPs) were found at the ablation sites preceding the ventricular electrogram (VEGM) during arrhythmias in 13 (61.9%) patients and during sinus rhythm in 7 (53.8%) patients. VAs with PPs were associated with a significantly higher burden of premature ventricular complexes (PVCs; 26.1 ± 10.9% vs. 14.9 ± 10.1%, P = 0.03), shorter VEGM to QRS intervals (9.0 ± 28.5 milliseconds vs. 33.1 ± 8.8 milliseconds, P = 0.03), lower pace map scores (8.7 ± 1.6 vs. 11.4 ± 0.8, P = 0.001), and a trend toward shorter V-H intervals during VA (32.1 ± 38.6 milliseconds vs. 76.3 ± 11.1 milliseconds, P = 0.06) as compared to those without PP. A strong and positive correlation was found between V-H interval and QRS duration during arrhythmia in those with PPs (B = 2.11, R(2) = 0.97, t = 13.7, P < 0.001) but not in those without PPs. CONCLUSION: Local EGM characteristics and relative activation time of the His bundle suggest the possibility of conduction tissue as the origin for VA arising from the fibrous AMC. Specific identification and targeting of PPs when ablating VAs at this location may improve procedural success.

Transvenous stimulation of the renal sympathetic nerves increases systemic blood pressure: a potential new treatment option for neurocardiogenic syncope.

BACKGROUND: Neurocardiogenic syncope (NCS) is a common and sometimes debilitating disorder, with no consistently effective treatment. NCS is due to a combination of bradycardia and vasodilation leading to syncope. Although pacemaker devices have been tried in treating the bradycardic aspect of NCS, no device-based therapy exists to treat the coexistent vasodilation that occurs. The renal sympathetic innervation has been the target of denervation to treat hypertension. We hypothesized that stimulation of the renal sympathetic nerves can increase blood pressure and counteract vasodilation in NCS. METHODS AND RESULTS: High-frequency stimulation (800-900 pps, 10 V, 30-200 seconds) was performed using a quadripolar catheter in the renal vein of 7 dogs and 1 baboon. A significant increase in blood pressure (BP; mean [SD] systolic BP 117 [±28] vs. 128 [±33], diastolic BP 75 [±19] vs. 87 [±29] mmHg) was noted during the stimulation, which returned to baseline after cessation of stimulation. The mean increase in systolic and diastolic BP was 13.0 (±3.3) (P = 0.006) and 10.2 (±4.6) (P = 0.08), respectively. CONCLUSION: We report the first ever study of feasibility and safety of high-frequency electrical stimulation of the renal sympathetic innervation to increase BP in animal models. This has potential applications in the treatment of hypotensive states such as NCS.

Renal nerve stimulation for the treatment of neurocardiogenic syncope.

Neurocardiogenic syncope is a common disorder resulting from a transient increase in vagal tone and central sympathetic withdrawal leading to varying degrees of vasodilation and bradycardia. Hence an effective treatment should address both the bradycardia and vasodilation. We hypothesized that, stimulation of the renal sympathetic nerves using high frequency stimulation in the renal vein will increase blood pressure through an increase in sympathetic output and therefore may be of use in treating neurocardiogenic syncope. Renal nerve stimulation was performed under Isoflurane anesthesia in 5 dogs and 1 baboon using a 4mm quadripolar catheter in unilateral renal vein using a Grass stimulator (square wave, 120V, 900pps, 30-200s). A consistent increase in arterial systolic BP [mean (SD) pre- vs peak-stimulation 103 (±27) vs. 122 (±41) mmHg] and diastolic BP [69 (±19) vs. 82 (±31) mmHg] was noted during stimulation. Median interquartile change in systolic BP was 11 (5-22) mmHg and 6 (-2-16) mmHg in diastolic BP. To conclude, renal nerve stimulation through the renal vein increased BP. Potential applications include treatment of vasodilatory component of neurocardiogenic syncope and confirmation of successful renal nerve ablation for the treatment of hypertension.