Effect of ablation pattern on mechanical function in the atrium.

BACKGROUND: Atrial fibrillation (AF) is often treated with catheter ablation, which induces scar formation to isolate misfiring electrical signals in the left atrium. Successful ablation restores sinus rhythm at the cost of replacing viable myocardium with scar. The impact of ablation scar on mechanical function of the left atrium is poorly understood. OBJECTIVE: We used a computational model to simulate various ablation patterns and determine their effect on atrial global and regional mechanical function. METHODS: A coupled finite-element and hemodynamic circuit model of the left atrium that represents the regional and global mechanics in paroxysmal AF patients was modified to simulate different ablation patterns: step-wise pulmonary vein isolation (PVI), wide area circumferential ablation (WACA), and a posterior ablation developed by nContact, Inc (Morrisville, NC, USA). Atrial pressure-volume relationships and regional wall motion were compared among the models. RESULTS: Ablation increased passive stiffness and decreased active work performed by the atrium. Active emptying volume decreased with increasing scar by up to 44% (11 mL) at a scar volume of 31%. At matched scar volumes, WACA decreased active emptying more severely than PVI and nContact. Similarly, wall motion was depressed most in the WACA model because WACA involved portions of the lateral wall with higher baseline motion. CONCLUSION: Simulated ablation depressed atrial mechanical function to an extent that depended on both scar volume and location, primarily through reducing active emptying. Placing ablation scar in regions with high baseline motion resulted in greater depression of active function, while ablation of the posterior wall was less disruptive.

The differential diagnosis of wide QRS complex tachycardia.

Wide complex tachycardia is defined as a cardiac rhythm with a rate greater than 100 beats/min (bpm) and a QRS complex duration greater than 0.10 to 0.12seconds (s) in the adult patient; wide complex tachycardia (WCT) in children is defined according to age-related metrics. The differential diagnosis of the WCT includes ventricular tachycardia and supraventricular tachycardia with aberrant intraventricular conduction, including both relatively benign and life-threatening dysrhythmias. This review focuses on the differential diagnosis of WCT with a discussion of strategies useful in making the appropriate diagnosis, when possible.

Catheter Ablation of Arrhythmia During Pregnancy.

Cardiac arrhythmia as a complication of pregnancy can be problematic to maternal health and fetal life and development. Catheter ablation of tachyarrhythmias during pregnancy has been successfully performed in selected patients with limited experience. Techniques to limit maternal and fetal radiation exposure, including intracardiac echo and electroanatomic mapping systems, are particularly important in this setting. Specific accommodations are necessary in the care of the gravid patient during catheter ablation.

Major complications and mortality within 30 days of an electrophysiological procedure at an academic medical center: implications for developing national standards.

BACKGROUND: Despite growing attention to performance and quality measures, national standards for reporting of outcomes after all electrophysiology (EP) procedures have not yet been developed. We sought to characterize the incidence and timing of adverse events up to 30 days after EP procedures at a tertiary academic medical center. METHODS AND RESULTS: We prospectively followed all patients undergoing EP procedures between January 2010 and September 2012. All were followed for 30 days postprocedure either in clinic or by telephone. Major complications were defined as events related to the procedure that led to prolongation of hospital stay or readmission, required additional procedural intervention, or resulted in death or significant injury. These were further categorized as intraprocedure, postprocedure, or postdischarge events. Seven EP physicians collectively adjudicated whether complications were directly related to the procedure. A total of 3,213 procedures were performed. Major complications occurred in 2.2% of patients; 49% of these events occurred after discharge. Death occurred in 0.6% of patients; 73% of these deaths were found to be secondary to worsening of the patient's underlying comorbid conditions and unrelated to the procedure. CONCLUSIONS: When considering national standards for reporting outcomes of all EP procedures, continued follow-up after discharge is important. In our cohort, half of major complications occurring within 30 days occurred after discharge. In addition, three-quarters of deaths within 30 days were not directly related to the procedure and caution should be used in using all-cause mortality as an outcome measure for EP procedures.

Ablation of incessant left atrial tachycardia without fluoroscopy in a pregnant woman.

BACKGROUND: Management of symptomatic atrial arrhythmia in pregnancy remains a challenge. In this case report, a pregnant woman with incessant tachycardia underwent successful left atrial ablation. The entire procedure was performed without fluoroscopy. METHODS AND RESULTS: A 20-year-old woman, 27 weeks pregnant, was admitted with congestive cardiac failure and incessant atrial tachycardia. She had an elevated brain natriuretic peptide (BNP) and chest X-ray demonstrating heart failure. The 12-lead electrocardiogram (ECG) showed atrial tachycardia with a cycle length of 310 ms, inverted P waves in lead I and the inferior leads, and a ventricular rate of 84 bpm during 2:1 block. Echocardiogram showed a global reduction in left ventricular function with a left ventricular ejection fraction (LVEF) of 0.40. Electrical cardioversion failed. Rate control could not be achieved with beta-blockers and calcium antagonists. Amiodarone with repeat cardioversion was also unsuccessful. The patient then underwent catheter ablation. The entire procedure was performed using intracardiac echocardiography (ICE) and electroanatomical mapping with no fluoroscopy. Electrophysiology (EP) study and an activation map of the left atrium confirmed a focal left atrial tachycardia which was successfully ablated. Six weeks postablation, the left ventricular function had normalized and the patient delivered a healthy child at term, without complication. CONCLUSION: Ablation of left atrial tachycardia using ICE and electroanatomical guidance is feasible in pregnant women.

Sonication of explanted cardiac rhythm management devices for the diagnosis of pocket infections and asymptomatic bacterial colonization.

BACKGROUND: Correct diagnosis of the causative organism is critical for the treatment of pacemaker and defibrillator pocket infections. No gold standard for this exists, although swab and tissue cultures are frequently used. The purpose of this study was to determine the value of ultrasonication of explanted generators in the diagnosis of pocket infections and asymptomatic bacterial colonization. METHODS: Samples were prospectively collected during pacemaker and defibrillator generator extractions for elective replacements, upgrades, or pocket infections. The devices were placed in an ultrasonicator for 5 minutes and the fluid sent for culture, along with swab and tissue cultures. RESULTS: Eighty-two patients with pacemakers (n = 46) or defibrillators (n = 36) underwent generator explantation, 66 of these for elective reasons and 16 for pocket infection. In patients with pocket infection, 15 (94%) received a definitive bacterial diagnosis using a combination of all three-culture modalities. Cultures were positive in 15 sonicated fluid, 13 tissue, and 11 swab samples, with Staphylococcus aureus and other skin flora commonly seen. In asymptomatic patients, 14 (21%) had positive cultures. Cultures were positive in 11 sonicated fluid, eight tissue, and two swab samples. Skin flora was commonly seen, but three of the sonicated fluid cultures grew gram-negative rods. No patients with asymptomatic colonization developed clinical infection during the follow-up period. CONCLUSIONS: Ultrasonication is an inexpensive and simple technique that improves the bacteriologic diagnosis of device pocket infections. It also identifies a significant proportion of patients with asymptomatic colonization, although this is not a marker of future pocket infection.

Dynamic registration of preablation imaging with a catheter geometry to guide ablation in a Swine model: validation of image integration and assessment of catheter navigation accuracy.

BACKGROUND: Catheter ablation of atrial and ventricular tachyarrhythmia involves anatomically based cardiac ablation strategies. CT and MRI images provide the most detailed cardiac anatomy available. Integration of these images into a mapping system should produce detailed and accurate models suitable to guide ablation. OBJECTIVE: The purpose of this study was to validate and assess the accuracy of a novel CT and MRI image integration algorithm designed to facilitate catheter navigation and ablation. METHODS: Using a lateral thoracotomy, markers were sutured to the epicardial surface of each cardiac chamber in 12 swine. Detailed CT/MRI anatomy was imported into the mapping system. The CT/MRI image was then integrated with a detailed catheter geometry of the relevant chamber using a new image integration algorithm. The epicardial markers, identified from the CT/MRI images, were then displayed on the surface of the integrated image. Guided only by the integrated CT/MRI, a single RF lesion was directed at the corresponding endocardial site for each epicardial marker. At autopsy, the distance from the endocardial RF lesion to the target site was assessed. RESULTS: The mean position error (CT/MRI) for the left atrium was 2.5 +/- 2.4 mm/5.1 +/- 3.9 mm, for the right atrium 6.2 +/- 6.5 mm/4.3 +/- 2.2 mm, for the right ventricle 6.2 +/- 4.3 mm/6.6 +/- 5.3 mm, and for the left ventricle 4.7 +/- 3.4 mm/3.1 +/- 2.7 mm. There was no cardiac perforation or tamponade. CONCLUSION: CT and MRI images can be effectively utilized for catheter navigation when integrated into a mapping system. This novel registration module with dynamic registration provides effective guidance for ablation.

Image integration using intracardiac ultrasound and 3D reconstruction for scar mapping and ablation of ventricular tachycardia.

BACKGROUND: Ablation of ventricular tachycardia (VT) reduces implantable cardioverter defibrillator shocks. Intracardiac ultrasound (ICE) can visualize and quantify the function of all left ventricular wall segments. We thus hypothesized that ICE could identify scar tissue and provide a guide to facilitate substrate-guided VT ablation. METHODS: Eighteen patients underwent VT ablation with real time ICE mapping from the right atrium and ventricle with online 3D-image reconstruction of scar segments. The left ventricle was also scar mapped by traditional electroanatomic mapping (CARTO) for comparison. Images from these 2 scar mapping techniques were compared to each other as well as to a preprocedure transthoracic echocardiogram. RESULTS: The average age was 65 +/- 12 years and 12 (67%) were male (15 [83%] had ischemic cardiomyopathy). Two patients (12%) had recurrence of their clinical VT (1 remained on an antiarrhythmic medication, the other had a repeat ablation) over a follow-up of 127 +/- 33 days. No periprocedural or long-term adverse events occurred. A total of 248 wall segments were analyzed. All 3 modalities were concordant in scar identification in 193 (78%) segments. The ICE segments correlated with the electroanatomic map in 213 (86%) segments versus 198 (80%), which correlated with transthoracic echocardiography and electroanatomic mapping (P = 0.046). Specifically, the ICE wall motion scores were closer to the electroanatomic mapping in the basal segments and showed a higher accuracy in ischemic heart disease. CONCLUSION: These data demonstrate that real time ICE images provide accurate chamber geometries and scar boundaries of the left ventricle. These scar borders were more accurate than transthoracic echocardiography and illustrate the feasibility of ICE for substrate-based ablation for VT.

Managing superior vena cava syndrome as a complication of pacemaker implantation: a pooled analysis of clinical practice.

BACKGROUND: Superior vena cava syndrome (SVCS) is a rare complication of pacemaker implantation. Numerous methods have been employed to treat this condition, ranging from anticoagulation and thrombolysis to surgical interventions and stenting. However, thus far only small case series have been reported and there is no currently accepted standard of care. METHODS: Our group preformed a PubMed literature search to identify cases of symptomatic SVCS that developed following implantation of permanent pacemakers or implanatable cardioverter defibrillators and were treated with one of five different modalities: anticoagulation, thrombolysis, venoplasty, stenting, and surgical reconstuction. Duration of follow-up and incidence of recurrence of symptoms were the main end-points. RESULTS: One hundred and four eligible cases from 74 different publications were identified, in which SVCS presented at a median of 48 (range 0-396) months after device implantation. We found that over the last 40 years, conservative treatments have been replaced by surgical reconstruction, and most recently by stenting, as the most common therapeutic modality employed. Anticoagulation, thrombolysis, and venoplasty alone were all associated with high recurrence rates. Surgery and stenting were more successful: recurrence rates were 12% and 5% over a median follow-up of 16 (range: 2-179) and 9.5 (range: 2-60) months, respectively. CONCLUSIONS: Currently, transvenous stenting is the most common treatment used for pacemaker-related SVCS, usually with conservation of the implanted leads. Both surgery and stenting appear to be effective treatments, with low incidences of recurrent SVCS over the first 12 months, but there is unfortunately a paucity of data on long-term outcomes. (PACE 2010; 420-425).

Real-time rotational ICE imaging of the relationship of the ablation catheter tip and the esophagus during atrial fibrillation ablation.

INTRODUCTION: Atrioesophageal fistula is a rare complication of atrial fibrillation (AF) ablation that should be avoided. We investigated whether rotational intracardiac echocardiography (ICE) can help to minimize ablation close to the esophagus. METHODS AND RESULTS: We studied 41 patients referred for catheter ablation of refractory AF. A rotational ICE catheter was inserted into the (LA) to determine the location of the esophagus. The esophagus was identified to be either adjacent to the pulmonary vein (PV) ostium or to a cuff 2 cm outside the ostium. Circumferential ablation was performed at the PV ostium, with the exact ablation location determined by ICE. The relationship of the catheter tip to the esophagus was imaged during energy delivery, allowing interruption when respiration moved the tip closer to the esophagus. Out of 41 patients, the esophagus was seen near left-sided PVs in 32 and near right-sided PVs in three patients. The median distance from LA endocardium to esophagus was 2.2 mm (range, 1.4-6 mm). In 21 of 35 patients with a closely related esophagus, ablation over the esophagus was avoided by ablating either lateral or medial to the esophagus. In 14 patients, the esophagus could not be avoided, and risk was minimized by limiting lesion size. Significant movement (>10 mm) of the esophagus during the procedure occurred in 3/41 cases. CONCLUSION: Rotational ICE can accurately determine the distance of ablation sites from the esophagus. Real-time imaging of the relationship of the ablation catheter tip to the esophagus may reduce the incidence of esophageal injury.

The prevalence of extracardiac findings by multidetector computed tomography before atrial fibrillation ablation.

BACKGROUND AND OBJECTIVES: The study was designed to determine the prevalence of extracardiac findings discovered during multidetector computed tomography (CT) (MDCT) examinations before atrial fibrillation ablation. Multidetector CT has become a valuable tool in detailing left atrial anatomy before catheter ablation. The incidence of extracardiac findings has been reported for electron beam CT calcium scoring and coronary MDCT, but no data exist for the prevalence of extracardiac findings discovered before atrial fibrillation ablation with MDCT. METHODS AND RESULTS: Clinical reports from MDCT examinations before atrial fibrillation ablation and interpretations by 2 radiologists blinded to the clinical reports were reviewed for significant additional extracardiac findings and recommendations for follow-up. In 149 patients who underwent MDCT, the mean age was 55.9 +/- 11.0 years, 75% were men, and 47% had a history of smoking. Extracardiac findings were identified in 69% of patients with clinical, 90% of reader 1, and 97% of reader 2 interpretations (kappa = 0.086). Follow-up was recommended in 30% of clinical, 50% of reader 1, and 38% of reader 2 interpretations (kappa = 0.408). Pulmonary nodules were the most common additional finding and reason for suggested follow-up for all interpreters. CONCLUSIONS: The prevalence of extracardiac abnormalities detected by MDCT is considerable. Significant variability in their identification exists between interpreters, but there is good agreement about the need for further follow-up. It is important that those who interpret these examinations are adequately trained in the identification and interpretation of both cardiac and extracardiac findings.

Characterization of the mitral isthmus for atrial fibrillation ablation using intracardiac ultrasound from within the coronary sinus.

BACKGROUND: Atrial fibrillation (AF) ablation involving the mitral isthmus and/or the coronary sinus (CS) may result in circumflex artery (Cx) or other collateral structure damage. OBJECTIVE: The purpose of this study was to investigate the feasibility of intracardiac echocardiographic (ICE) imaging from within the CS to characterize mitral isthmus anatomy and guide ablation. METHODS: A 9-Fr sheath was introduced into the CS of 30 patients before AF ablation. A 9-Fr rotational ICE catheter was then advanced within the sheath to the distal CS adjacent to the lateral left atrial (LA) wall. Serial cross-sectional images to document the relations of the LA, Cx, CS, esophagus, and pericardium were obtained at multiple points within the CS during a pullback to the CS ostium. RESULTS: The Cx was identified in 62/150 positions in 25/30 patients. The median (range) of the LA-Cx distance was 3.3 mm (0.7-19.6 mm), and the median CS-Cx distance was 2.0 mm (0.4-9.7 mm). The esophagus was seen in 36/150 positions in 17/30 patients. The median CS-esophagus distance was 4.0 mm (1.4-16.2 mm). The proximity of the Cx and esophagus to the LA and CS varied considerably. The median CS-mitral annulus distance was 11.9 mm (4.1-21.6 mm). After CS cannulation, the ICE imaging took 5 +/- 2 minutes and required 120 +/- 60 seconds of fluoroscopy. CONCLUSIONS: Mitral isthmus anatomy can be accurately characterized by rotational ICE imaging from within the CS. There is great variability in the location and proximity of the Cx, CS, esophagus, and pericardium to the LA. Real-time identification of these structures could help to plan ablation strategies and potentially reduce complications.

Analysis of in vivo left atrial appendage morphology in patients with atrial fibrillation: a direct comparison of transesophageal echocardiography, planar cardiac CT, and segmented three-dimensional cardiac CT.

PURPOSE: Recent development of percutaneous left atrial appendage (LAA) occlusion devices has underscored the need for an accurate understanding of LAA morphology and the interchangeability of results from differing imaging modalities. The purpose of this study is to assess LAA morphology and location in AF patients, directly comparing transesophageal echocardiography (TEE), planar cardiac computed tomography (CT), and three-dimensional segmented CT reconstructions. METHODS: Fifty-three patients underwent adequate TEE and cardiac CT. Quantitative measurements of maximal LAA orifice diameters, widths, and depths were obtained from each imaging modality. Left atrial and LAA volumes were measured using segmented CT. RESULTS: The mean LAA orifice diameter for segmented CT, planar CT, and TEE was 28.5 +/- 4.5, 26.3 +/- 4.1, and 26.1 +/- 6.4 mm, respectively. CONCLUSIONS: LAA orifice measurements among these imaging modalities are not interchangeable. This difference may be clinically significant because of the need for accurate sizing of LAA occlusion devices. Use of preprocedural segmented CT may improve initial device sizing.

Ventricular Arrhythmias.

Ventricular tachycardia (VT) is the most common form of wide complex tachycardia and is associated with a high mortality rate. Electrocardiographic analysis remains paramount in diagnosis and helps to direct therapy. Antiarrhythmic agents, although effective in reducing arrhythmia burden, have never demonstrated a mortality benefit. The implantable cardioverter-defibrillator aids not only in the acute termination of ventricular arrhythmia, but provides a wealth of information for the long-term management of patients with VT. Contemporary treatment options such as catheter ablation are increasingly used and effective, but often remain imperfect, with recurrent VT being not uncommon.

Sleep, sleep apnea and atrial fibrillation: Questions and answers.

Sleep apnea (SA) is a common sleep disorder increasingly recognized as a risk for cardiovascular disease. Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with significant morbidity and mortality. An increasing number of investigations in recent years have linked SA to AF. In this review, we aim to provide a critical overview of the existing evidence in a question and answer format by addressing the following: What is the prevalent association between the two conditions (separating nocturnally detected AF episodes from AF as a prevalent condition)? Is SA a risk factor for incident AF? Is SA a risk factor for recurrence of AF following cardioversion/catheter-based ablation? What is the association between SA and AF in patients with heart failure? Are there signature electrocardiographic markers of AF found in patients with SA? Are there electrophysiology-based studies supporting the link between SA and AF? What other sleep characteristics (beyond SA) are found in patients with AF? What is the impact of SA treatment on AF? What is the effect of AF treatment on sleep? Finally, we address unsolved questions and suggest future directions to enhance our understanding of the AF-SA relationship.

Atrial Fibrillation and Objective Sleep Quality by Slow Wave Sleep.

BACKGROUND: Self-reported poor sleep quality has been suggested in patients with AF. Slow wave sleep (SWS) is considered the most restorative sleep stage and represents an important objective measure of sleep quality. The aim of this study was to compare quantity of SWS between patients with and without AF. METHODS AND RESULTS: We included patients with and without a documented history of AF by reviewing clinically indicated polysomnography data from a single sleep center. Patients on medications with potential influence on sleep architecture were excluded. Logistic regression was performed to determine the association between AF and SWS time (low vs. high) adjusting for age, gender, body mass index, and sleep apnea. In a 2:1 case-control set-up, a total of 205 subjects (139 with AF, 66 without AF) were included. Mean age was 62 (SD: 14.3) years and 59% were men. Patients with AF had lower SWS time (11.1 vs. 16.6 min, p=0.02). In multivariable analysis, prevalent AF was associated with low SWS independent of sleep apnea and other potential confounders (OR 2.5 [1.3, 5.0], p=0.006). Limiting the analysis to patients whose total sleep time was greater than 4 hours (by excluding N=31) resulted in more robust results (OR 3.9 [1.7, 9.7]. p=0.002). CONCLUSION: AF is associated with more impaired sleep quality as indicated by lower quantity of SWS. More studies are needed to explore the mechanistic interactions between AF and sleep.