Clinical Outcomes following Left Atrial Appendage Occlusion: A Single-Center Experience.

INTRODUCTION: Percutaneous left atrial appendage closure is an established alternative to anticoagulation therapy for stroke prophylaxis among patients with nonvalvular atrial fibrillation. There are currently no guidelines on the choice of antithrombotic therapy following placement of the Watchman® device, the optimal time to discontinue anticoagulation or the duration of follow-up imaging after device deployment. Our main objective was to evaluate clinical outcomes among these patients. METHODS: We conducted a retrospective review of patients who received a Watchman® device at Mayo Clinic sites between January 2010 and December 2018. We constructed Cox-proportional hazard models to evaluate the effect of specific variables on clinical outcomes. RESULTS: 231 patients were identified (33% female), median age was 77 years, CHA2DS2-VASc score was 5 and HASBLED score was 4. We found no difference in clinically significant bleeding based on initial antithrombotic choice. However, patients with prior gastrointestinal bleeding were more likely to have a bleeding event in the first 6 weeks following Watchman® implantation (HR 9.40, 95% CI 2.15-41.09). Device sizes of 24-27 mm were significantly associated with a decreased risk of thromboembolic events (HR 0.15, 95% CI 0.04-0.55) compared to 21-mm devices. Peridevice leak (PDL) sizes appeared to either remain the same or increase on follow-up imaging. DISCUSSION/CONCLUSIONS: This observational study showed no statistically significant difference in bleeding risk related to initial antithrombotic choice. Smaller device sizes were associated with thromboembolic events, and longitudinal PDL assessment using transesophageal echocardiography showed these frequently do not decrease in size. Larger studies are needed.

Fundamentals of Cardiac Mapping.

To characterize cardiac activity and arrhythmias, electrophysiologists can record the electrical activity of the heart in relation to its anatomy through a process called cardiac mapping (electroanatomic mapping, EAM). A solid understanding of the basic cardiac biopotentials, called electrograms, is imperative to construct and interpret the cardiac EAM correctly. There are several mapping approaches available to the electrophysiologist, each optimized for specific arrhythmia mechanisms. This article provides an overview of the fundamentals of EAM.

Effect of Charge Delivery on Thromboembolism During Radiofrequency Ablation in Canines.

OBJECTIVES: This study investigated whether delivering negative charge to catheter tips reduces thromboembolism during catheter ablation. BACKGROUND: Radiofrequency (RF) ablation prevents atrial fibrillation that can cause stroke or death. However, ablation itself can cause stroke (2%) or silent ischemia (2% to 41%), possibly via particulate debris that embolizes after coagulum adherence to catheter surfaces. Coagulum formation on RF catheters can be prevented by applying negative charge, but it is unknown if charge reduces peripheral thromboembolism. METHODS: Paired (Charge ON vs. OFF) endocardial RF ablations were performed in 9 canines using nonirrigated RF catheters. Continuous negative charge was delivered via -100 µA of DC current applied to ablation catheter electrodes. Intracardiac echocardiography was used to navigate the catheter and to monitor coagulum formation. In a subset of 5 canines, microemboli flowing through polyester tubing between the femoral artery and vein (extracorporeal loop) were monitored with bubble counters and inline filter fabric. After each ablation, catheter-tip coagulum and blood particles deposited on the filters were quantified using photography and imaging software (ImageJ, U.S. National Institutes of Health, Bethesda, Maryland). RESULTS: Negative charge significantly decreased the extracorporeal loop median filter area covered by particles (n = 19 pairs) by 10.2 mm2 (p = 0.03), and decreased median filter particles by 349 (p = 0.03). Negative charge also decreased the percentage of the catheter tip surface area covered by coagulum (n = 39 pairs) by 7.2% (p = 0.03). CONCLUSIONS: Negative charge delivery to ablation catheter tips during RF ablation can reduce particulate embolization material in an extracorporeal loop, and potentially reduce thromboembolic risk associated with RF ablation.

Retained cardiac implantable electronic device fragments are not associated with magnetic resonance imaging safety issues, morbidity, or mortality after orthotopic heart transplant.

BACKGROUND: Cardiac implantable electronic device therapy (CIED) has revolutionized treatment for advanced heart failure. Most patients considered for orthotopic heart transplantation (OHT) are treated with implantable cardioverter defibrillators, cardiac resynchronization therapy, or both. These CIEDs are surgically extracted at the time of transplant. Occasionally, CIEDs are incompletely removed. Little is known about the outcomes of post-OHT patients with retained CIED fragments. METHODS: We identified 200 consecutive patients that underwent OHT at our institution between April 2006 and December 2014 and performed a retrospective analysis of available radiographic images and clinical records. Chest radiographs prior to and following OHT were reviewed for the presence of CIED or retained CIED fragments. The outcomes of patients with retained CIED fragments that had subsequent magnetic resonance imaging (MRI) studies performed were further investigated. RESULTS: One hundred eighty of 200 patients were identified as having CIED prior to OHT, of which 29 had retained CIED fragments after OHT. Most retained CIED fragments originated from superior vena cava defibrillator coils. There were no adverse events in the retained CIED fragment cohort, and survival was unaffected. Ten patients with retained CIED fragments safely underwent a total of 28 MRIs after OHT, all of diagnostic quality. CONCLUSION: Retained CIED fragments are not associated with adverse events or increased mortality after OHT. Diagnostic MRI has been safely performed in patients with retained CIED fragments after incomplete device extraction. Retrieval of these fragments prior to MRI does not appear warranted given the demonstrated safety and preserved image quality in this population.

Initial Experience with the BioSig PURE EP™ Signal Recording System: An Animal Laboratory Experience.

Current signal recording and processing systems have come a long way since their initial inception and use. There is, however, still ample scope for improvement, not only in the troubleshooting of their limitations, but also in the expansion of the boundaries in the recording of intracardiac signals. Here, we recount our experience with the use of the PURE EP™ signal recording system (BioSig Technologies, Inc., Minneapolis, MN, USA) in the animal laboratory.

Novel Percutaneous Epicardial Autonomic Modulation in the Canine for Atrial Fibrillation: Results of an Efficacy and Safety Study.

BACKGROUND: Endocardial ablation of atrial ganglionated plexi (GP) has been described for treatment of atrial fibrillation (AF). Our objective in this study was to develop percutaneous epicardial GP ablation in a canine model using novel energy sources and catheters. METHODS: Phase 1: The efficacy of several modalities to ablate the GP was tested in an open chest canine model (n = 10). Phase 2: Percutaneous epicardial ablation of GP was done in six dogs using the most efficacious modality identified in phase 1 using two novel catheters. RESULTS: Phase 1: Direct current (DC) in varying doses (blocking [7-12 µA], electroporation [300-500 µA], ablation [3,000-7,500 µA]), radiofrequency ablation (25-50 W), ultrasound (1.5 MHz), and alcohol (2-5 mL) injection were successful at 0/8, 4/12, 5/7, 3/8, 1/5, and 5/7 GP sites. DC (500-5,000 µA) along with alcohol irrigation was tested in phase 2. Phase 2: Percutaneous epicardial ablation of the right atrium, oblique sinus, vein of Marshall, and transverse sinus GP was successful in 5/6 dogs. One dog died of ventricular fibrillation during DC ablation at 5,000 µA. Programmed stimulation induced AF in six dogs, preablation and no atrial arrhythmia in three, flutter in one, and AF in one postablation. Heart rate, blood pressure, effective atrial refractory period, and local atrial electrogram amplitude did not change significantly postablation. Microscopic examination showed elimination of GP, and minimal injury to atrial myocardium. CONCLUSION: Percutaneous epicardial ablation of GP using DC and novel catheters is safe and feasible and may be used as an adjunct to pulmonary vein isolation in the treatment of AF in order to minimize additional atrial myocardial ablation.

Prevention of Coagulum Formation With Simultaneous Charge Delivery in Radiofrequency Ablation: A Canine Model.

OBJECTIVES: This study reports on a novel method to prevent coagulum formation by continuously delivering a negative charge to the catheter tip to repel negatively charged fibrinogen molecules during RF ablation. BACKGROUND: Radiofrequency (RF) ablation for cardiac arrhythmias is associated with a 70% incidence of coagulum formation on the catheter tip during ablation and a 10% incidence of thromboembolic events. Catheter tip thrombus can impede RF energy to the tissue, reducing efficacy and increasing procedure times. METHODS: A novel circuit was built to deliver a negative, fixed-offset, direct current-based charge using a 9-V battery, placed in parallel with an RF delivery unit during RF ablation. In in vivo canine experiments, standard ablation catheters were advanced into atria and ventricles under fluoroscopic guidance. The presence of thrombus with and without RF delivery was identified with intracardiac echocardiography. RESULTS: Scanning electron microscopy of the catheter tips showed clot coverage of the catheter tip to be 90% for noncharged catheters compared to 0% (p < 0.01) in negatively charged catheters. Volume of clot formed on the catheter tip decreased with increased amount of charge (140 ± 5.3 arbitrary units with no charge vs. 0 arbitrary units with a 100-µA current delivering negative charge, p < 0.01). Application of a negative charge did not affect the quality of the intracardiac electrogram or induce malignant ventricular arrhythmias. CONCLUSIONS: Negative-charge delivery to ablation catheter tips and tissue during RF ablation is feasible and safe and can eliminate coagulum formation, potentially reducing thromboembolic complications.

Distinguishing ventricular arrhythmia originating from the right coronary cusp, peripulmonic valve area, and the right ventricular outflow tract: utility of lead I.

INTRODUCTION: Outflow tract ventricular arrhythmia (OTVA) can be complicated to target for ablation when originating from either the periaortic or pulmonary valve (PV) region. Both sites may present with a small R wave in lead V1. However, the utility of lead I in distinguishing these arrhythmia locations is unknown. METHODS AND RESULTS: Thirty-six consecutive patients (mean age 41 ± 14 years, 13 male) underwent catheter ablation for OTVA. OTVA origin was determined from intracardiac electrogram tracings and electroanatomic maps. Observers blinded to results measured QRS waveform amplitude and duration from standard 12-lead ECG tracings. Measurements with highest diagnostic performance were modeled into an algorithm. Sites of successful ablation were anterior right ventricular outflow tract (RVOT; n = 6), posterior RVOT (n = 4), PV (n = 18), and right coronary cusp (RCC; n = 8). Highest performing surface ECG discriminators were from lead I to V1 vectors: RCC, lead I R wave ≥ 1.5 mV, and V1 R wave ≥2.0 mV (sensitivity 87%, specificity 93%); PV, V1 R wave > 0 mV, and lead I R/(R+S) ≤ 0.75 (sensitivity 78%, specificity 72%); anterior RVOT, V1 R wave = 0 mV, and lead I R/(R+S) <0.4 (sensitivity 67%, specificity 97%); posterior RVOT, V1 R wave > 0 mV, and lead I R/(R+S) > 0.75 (sensitivity 75%, specificity 84%). Sequential algorithmic application of these criteria resulted in an overall accuracy of 72% in predicting site of OTVA origin. CONCLUSIONS: A relatively large R wave in lead I is seen with RCC origin but not PV origin. A sequential algorithm has limited but potentially significant value beyond assessment of lead I in approaching OTVA.

Common pitfalls in interpreting pacemaker electrocardiograms in the emergency department.

The number of patients receiving pacemakers and defibrillators has grown substantially over the last 20 years. In addition, the complexity and sophistication of these devices have increased, making diagnosis of pacemaker problems using the electrocardiogram (ECG) more difficult for clinicians in the emergency department. This article will focus on a few of the pitfalls to be avoided when interpreting paced ECGs. Pacemaker algorithms designed to minimize right ventricular pacing may be confused with pathologic failure to output. Automatic capture threshold detection schemes may be misinterpreted as failure to capture as well as undersensing due to the extra "backup" pacemaker spikes noted on rhythm strips. Device testing done in the emergency department may produce waveforms on monitor resembling ventricular tachycardia if pacemaker-mediated tachycardia is produced accidentally. Ventricular safety pacing algorithms may also be misinterpreted as failure to sense appropriately, triggering questions about pacemaker malfunction. Certain types of true undersensing may resemble morphologies consistent with pacemaker lead dislodgment. In addition, sophisticated programming features designed to mimic normal physiology could be misconstrued as pacemaker malfunction. These include pacemaker hysteresis and sleep mode. The presence of frequent premature ventricular complexes would cause a pacemaker to inhibit ventricular pacing appropriately. However, this could produce a palpated heart rate that is substantially lower than the programmed lower rate of the device due to reduced perfusion by the premature ventricular complexes, again raising questions about the appropriate functioning of the pacemaker. All of these situations will be discussed in detail along with approaches to systematically examining the paced ECGs to minimize the risk of misinterpretation. Pacemaker timing cycles as they relate to troubleshooting of the paced ECG will also be introduced.

Characteristics of premature ventricular complexes as correlates of reduced left ventricular systolic function: study of the burden, duration, coupling interval, morphology and site of origin of PVCs.

BACKGROUND: Frequent premature ventricular complexes (PVCs) can cause a decline in left ventricular ejection fraction (LVEF). We investigated whether the site of origin and other PVC characteristics are associated with LVEF. METHODS: We retrospectively studied 70 consecutive patients (mean age 42 ± 17 years, 40 [57%] female) with no other cause of cardiomyopathy undergoing ablation of PVCs. We analyzed the association of a reduced LVEF, defined by LVEF <50% on echocardiography, with features of PVCs obtained from electrocardiography, 24- or 48-hour Holter monitor and electrophysiology study. RESULTS: Patients with reduced LVEF (n = 17) as compared to normal LVEF (n = 53) had an increased burden of PVCs (29.3 ± 14.6% vs 16.7 ± 13.7%, P = 0.004), higher prevalence of nonsustained ventricular tachycardia (VT) [13 (76%) vs 21 (40%), P = 0.01], longer PVC duration (154.3 ± 22.9 vs 145.6 ± 20.8 ms, P = 0.03) and higher prevalence of multiform PVCs [15 (88%) vs 31 (58%), P = 0.04]. There was no significant difference in prevalence of sustained VT, QRS duration of normally conducted complexes, PVC coupling interval, or delay in PVC intrinsicoid deflection. Patients with fascicular PVCs (n = 5) had higher mean LVEF compared to others (66.2 ± 4.0% vs 53.0 ± 10.0%, P = 0.002). There was no association of LVEF with other PVC foci or with left-bundle versus right-bundle branch block morphologies. The threshold burden of PVCs associated with reduced LVEF was lower for right as compared to left ventricular PVCs. CONCLUSION: In addition to the PVC burden, other characteristics like a longer PVC duration, presence of nonsustained VT, multiform PVCs and right ventricular PVCs might be associated with cardiomyopathy.

Correlative anatomy for the electrophysiologist, part II: cardiac ganglia, phrenic nerve, coronary venous system.

Cardiac Ganglia, Phrenic Nerve, Coronary Venous System. There is an increasing need for invasive electrophysiologists to appreciate the exact anatomy of the epicardial space and the coronary veins. The location of the epicardial fat, the complementary relationship with the main cardiac veins, and the location of sensitive structures (arteries, phrenic nerve, esophagus) have become required knowledge for electrophysiologists, and accessing the epicardial space with this thorough knowledge of the pericardial sinuses and recesses is essential to allow radiographic correlation during catheter manipulation. In this review, we briefly describe the anatomy of the pericardial space and then discuss the specific correlation for the invasive electrophysiologist, highlighting epicardial access, catheter navigation, and avoidance of collateral injury, with specific attention to the important recesses of the pericardial space, their regional anatomy, and radiographic correlation when navigating catheters to these locations. We also discuss the anatomy of the main cardiac veins in the context of catheter mapping and ablation of the epicardial substrate through the venous system and without subxiphoid pericardial access. In part II of this series we discuss the detailed regional anatomy of the cardiac ganglia, phrenic nerve, and coronary venous system.

The autonomic nervous system in cardiac electrophysiology: an elegant interaction and emerging concepts.

The autonomic nervous system plays an integral role in the modulation of normal cardiac electrophysiology. This is achieved via a complex network of pre- and postganglionic sympathetic and parasympathetic fibers that synapse on extrinsic and intrinsic cardiac ganglia and ultimately directly innervate cardiac myocytes. Alterations in autonomic tone may induce changes in local cellular electrophysiology that may manifest clinically in a number of ways, ranging from changes in heart rate to changes in heart rhythm. These relationships between autonomic tone and the evolution of cardiac dysrhythmias are areas of evolving research, with increasing evidence for a key role for autonomic ganglia in the pathogenesis of atrial fibrillation and sympathetic nerves in the predilection toward ventricular tachycardia in areas of myocardial scar. In this review, we highlight what is known about the anatomy and physiology of the cardiac autonomic nervous system, the evidence supporting the relationship of autonomic tone to clinically significant arrhythmias, and a variety of mechanisms (eg, direct ion channel effects) and diagnostic tools that exist to help define this relationship. Further emphasized are potential future avenues of research needed to elucidate the relationship between changes in normal autonomic tone and the pathogenesis of cardiac arrhythmias.

Correlative anatomy for the electrophysiologist, Part I: the pericardial space, oblique sinus, transverse sinus.

There is an increasing need for invasive electrophysiologists to appreciate the exact anatomy of the epicardial space and the coronary veins. The location of the epicardial fat, the complementary relationship with the main cardiac veins, and the location of sensitive structures (arteries, phrenic nerve, esophagus) have become required knowledge for electrophysiologists, and accessing the epicardial space with this thorough knowledge of the pericardial sinuses and recesses is essential to allow radiographic correlation during catheter manipulation. In this review, we briefly describe the anatomy of the pericardial space and then discuss the specific correlation for the invasive electrophysiologist, highlighting epicardial access, catheter navigation, and avoidance of collateral injury with specific attention to the important recesses of the pericardial space, their regional anatomy, and radiographic correlation when navigating catheters to these locations. We also discuss the anatomy of the main cardiac veins in the context of catheter mapping and ablation of the epicardial substrate through the venous system and without subxiphoid pericardial access. In Part I of this two-part series, we discuss the regional anatomy of the pericardial space, oblique sinus, and transverse sinus.

Use of an autologous blood recovery system during emergency pericardiocentesis in the electrophysiology laboratory.

INTRODUCTION: Emergency pericardiocentesis during electrophysiology procedures is often associated with significant aspiration of pericardial blood, requiring transfusion. We sought to assess the feasibility of urgent use of an autologous blood recovery system in the electrophysiology laboratory to autotransfuse blood aspirated from the pericardium. METHODS AND RESULTS: We retrospectively analyzed Mayo Clinic electrophysiology records for patients who had ablation procedure-related pericardial effusions requiring emergency pericardial drainage during an 8-month period. An autologous blood recovery system was used during pericardiocentesis to separate and clean packed red blood cells from the pericardial aspirate. These cells were returned acutely to the patient intravenously. The procedural safety, aspirated and autotransfused volumes, and efficacy of this approach were evaluated. During the study period, nine patients underwent pericardial drainage with autotransfusion using a cell-salvage instrument during electrophysiology procedures. The mean aspirated volume was 1,078 mL, with a mean autotransfused volume of 390 mL. For four patients, all with aspirated volumes of 1,100 mL or less, autotransfusion alone was sufficient to maintain hemodynamic stability and avoid allogeneic transfusion. One patient required surgical intervention because of ongoing pericardial bleeding. The ablation procedure was completed after aspiration in two patients. No procedural complications related to the use of the cell-salvage system occurred. CONCLUSION: Autologous blood recovery during pericardiocentesis is safe, convenient, and feasible. With early use it may decrease or eliminate the need for allogeneic blood transfusion and, in selected cases, may permit completion of the ablation procedure.