Bachmann's Bundle's Unique Physiology: Reviewing How it Made an Atypical Flutter Even More Atypical.

A 69-year-old man with a history of previous ablation and cardiac surgery was found on cardiac electrophysiology study to have a macro-re-entrant left atrial flutter initially misdiagnosed as a micro-re-entrant right atrial tachycardia resulting from the unique conduction properties of Bachmann's bundle. (Level of Difficulty: Advanced.).

Limited Left Thoracoscopic Sympathectomy Effectively Silences Refractory Electrical Storm.

BACKGROUND: An electrical storm (ES) is a life-threatening condition that affects up to 20% of patients with implantable cardioverter defibrillators. In this small retrospective study, we report our results with left video-assisted thoracoscopic sympathectomy/ganglionectomy (VATSG) to treat refractory ES in low-ejection fraction patients who were not candidates for catheter ablation. METHODS: We identified 12 patients who presented with ES and underwent a total of 14 video-assisted thoracoscopic sympathectomy/ganglionectomy, including 3 patients on venoarterial extracorporeal membrane oxygenation. We reviewed demographic data, survival to discharge, number of cardioversions (before and after VATSG), need for readmissions, and need for right-sided procedures. RESULTS: In the 30 days before a left VATSG, mean number of shocks was 22.67 for all patients. For the patients who survived to discharge, the mean was 3.55 since surgery and the median was zero shocks after a median follow-up of 358 days. Six patients did not experience further cardioversions since the last VATSG and 5 were not readmitted for ventricular tachycardia. Two patients had staged bilateral procedures owing to recurrences; of those, 1 did not require further cardioversions. CONCLUSIONS: Limited left VATSG is an appropriate and effective initial treatment for ES patients who are not candidates for catheter ablation, including those on venoarterial extracorporeal membrane oxygenation for hemodynamic support.

Validation of a novel CARTOSEG™ segmentation module software for contrast-enhanced computed tomography-guided radiofrequency ablation in patients with atrial fibrillation.

INTRODUCTION: Visualization of left atrial (LA) anatomy using image integration modules has been associated with decreased radiation exposure and improved procedural outcome when used for guidance of pulmonary vein isolation (PVI) in atrial fibrillation (AF) ablation. We evaluated the CARTOSEG™ CT Segmentation Module (Biosense Webster, Inc.) that offers a new CT-specific semiautomatic reconstruction of the atrial endocardium. METHODS: The CARTOSEG™ CT Segmentation Module software was assessed prospectively in 80 patients undergoing AF ablation. Using preprocedural contrast-enhanced computed tomography (CE-CT), cardiac chambers, coronary sinus (CS), and esophagus were semiautomatically segmented. Segmentation quality was assessed from 1 (poor) to 4 (excellent). The reconstructed structures were registered with the electroanatomic map (EAM). PVI was performed using the registered 3D images. RESULTS: Semiautomatic reconstruction of the heart chambers was successfully performed in all 80 patients with AF. CE-CT DICOM file import, semiautomatic segmentation of cardiac chambers, esophagus, and CS was performed in 185 ± 105, 18 ± 5, 119 ± 47, and 69 ± 19 seconds, respectively. Average segmentation quality was 3.9 ± 0.2, 3.8 ± 0.3, and 3.8 ± 0.2 for LA, esophagus, and CS, respectively. Registration accuracy between the EAM and CE-CT-derived segmentation was 4.2 ± 0.9 mm. Complications consisted of one perforation (1%) which required pericardiocentesis, one increased pericardial effusion treated conservatively (1%), and one early termination of ablation due to thrombus formation on the ablation sheath without TIA/stroke (1%). All targeted PVs (n  =  309) were successfully isolated. CONCLUSIONS: The novel CT- CARTOSEG™ CT Segmentation Module enables a rapid and reliable semiautomatic 3D reconstruction of cardiac chambers and adjacent anatomy, which facilitates successful and safe PVI.

Location, variations, and predictors of epicardial fat mapping using multidetector computed tomography to assist epicardial ventricular tachycardia ablation.

BACKGROUND: A significant number of ventricular tachycardia circuits are located close to the epicardial surface and are amendable to epicardial ablation. Epicardial fat often interferes with substrate mapping and ablation, though little is known regarding the distribution of fat and its fluctuation with the cardiac cycle. METHODS: We studied 40 patients who underwent a 64-slice multidetector computed tomography in order to describe patterns of epicardial fat distribution, variation during cardiac cycle, and clinical predictors of epicardial fat. Multiplanar reconstructions were analyzed during systole and diastole in six cross-sections. Epicardial fat thickness was measured across multiple wall segments in each view. RESULTS: Epicardial fat was found to be thicker in areas overlying coronary vasculature (7.8 ± 2.6 mm vs 3.5 ± 0.9 mm, P = 0.001), along with the right ventricular wall (3.9 ± 0.8 mm vs 2.6 ± 0.6 mm, P = 0.001) and the ventricular base (6.1 ± 1.7 mm vs 4.6 ± 1.6 mm, P < 0.01). Epicardial fat thickness increased 27% during systole as compared to diastole (4.9 ± 2.7 mm vs 6.2 ± 3.0 mm, P = 0.04). Variation with cardiac cycle was most evident along the right ventricular wall (3.9 ± 0.8 mm vs 5.0 ± 1.3 mm, P = 0.001) and nonvascular areas (P = 0.001), especially at the ventricular base (3.7 ± 1.1 mm vs 5.3 ± 1.5 mm, P = 0.001). In multivariate logistic regression, we found that age >50 years (P = 0.031) and coronary artery disease (P = 0.023) were statistically correlated with epicardial fat >5-mm thickness and body mass index > 33 (P = 0.052) nearly so. CONCLUSIONS: Baseline epicardial fat thickness >5 mm is common in areas typically targeted during epicardial ablation and further increases during the cardiac cycle. Simple clinical characteristics can identify patients with >5 mm epicardial fat in which preprocedural computed tomography imaging and three-dimensional fat map reconstruction may facilitate epicardial ablation.

Identifying Potentially Avoidable Readmissions: A Medication-Based 15-Day Readmission Risk Stratification Algorithm.

BACKGROUND: Stratifying patients according to 15-day readmission risk would be useful in identifying those who may benefit from targeted interventions during and/or following hospital discharge that are designed to reduce the likelihood of readmission. METHODS: A prediction model was derived via a case-control analysis of patients discharged from a tertiary hospital in Singapore using multivariate logistic regression. The model was validated in two independent external cohorts separated temporally and geographically. Model discrimination was assessed using the C-statistic, while calibration was assessed using the Hosmer-Lemeshow χ2 and the Brier score statistics. RESULTS: A total of 1291 patients were included with 670, 101, and 520 patients in the derivation, temporal, and geographical validation cohorts, respectively. Age (odds ratio [OR] 1.02, 95% confidence interval [CI] 1.01-1.03, p=0.008), anemia (OR 2.08, 95% CI 1.15-8.05, p=0.015), malignancy (OR 3.37, 95% CI 1.16-9.80, p=0.026), peptic ulcer disease (OR 3.05, 95% CI 1.12-8.26, p=0.029), chronic obstructive pulmonary disease (OR 3.16, 95% CI 1.24-8.05, p=0.016), number of discharge medications (OR 1.06, 95% CI 1.01-1.12, p=0.026), discharge to nursing homes (OR 3.57, 95% CI 1.57-8.34, p=0.003), and premature discharge against medical advice (OR 5.05, 95% CI 1.20-21.23, p=0.027) were independent predictors of 15-day readmission risk. The model demonstrated reasonable discrimination on the temporal and geographical validation cohorts with a C-statistic of 0.65 and 0.64, respectively. Model miscalibration was observed in both validation cohorts. CONCLUSION: A 15-day readmission risk prediction model is proposed and externally validated. The model facilitates the targeting of interventions for patients who are at high risk of an early readmission.

A review of the LARIAT device: insights from the cumulative clinical experience.

Atrial fibrillation (AF) is the most common arrhythmic disorder world-wide, accounting for 15 % of all strokes. Management of stroke risk in AF is complicated by intolerance of anti-coagulation (AC) therapy and difficulty maintaining therapeutic range in patients treated with warfarin. The left atrial appendage (LAA) is a source of thrombus in AFrelated thrombo-embolic events and surgical LAA exclusion (LAAO) is commonly performed during cardiac surgery in AF patients. Surgical approaches are limited by a high incidence of incomplete closure with a potential for consequent thrombo-embolic events as well as the morbidity of an open-heart procedure. More recently, percutaneous approaches to LAAO have been developed. The LARIAT device is an epicardial LAA exclusion system that enables percutaneous suture ligation of the LAA via combined, pericardial and trans-septal access. The device has 510k Federal Drug Administration (FDA) clearance for soft-tissue ligation and has been studied in canine models in pre-clinical studies as well as published series of clinical experience with LARIAT LAAO. The history, patient selection, procedural technique and complications of LARIAT LAAO are reviewed here. Additionally, insights and procedural improvements that have been elucidated from clinical series and outcomes from the collective experience are discussed. The LARIAT's epicardial approach to LAA ligation is unique compared with other percutaneous LAA exclusion devices, however more data regarding device safety and efficacy is needed for the LARIAT to emerge as an established therapy for stroke prevention in AF.

Safety of computed tomography in patients with cardiac rhythm management devices: assessment of the U.S. Food and Drug Administration advisory in clinical practice.

OBJECTIVES: To assess the safety of computed tomography (CT) imaging in patients with cardiac rhythm management (CRM) devices, which was subject to an advisory from the U.S. Food and Drug Administration (FDA) in 2008. BACKGROUND: The FDA warned about potential interference of CT imaging with CRM devices and made recommendations for clinical practice despite only limited evidence. METHODS: All 516 CT scans that involved direct radiation exposure of CRM devices (332 defibrillators, 184 pacemakers) at 2 large-volume centers between July 2000 and May 2010 were included. The primary outcome was a composite endpoint of death, bradycardia or tachycardia requiring termination of the scan or an immediate intervention, unplanned hospital admission, reprogramming of the device, inappropriate defibrillator shocks, or device replacement/revision thought to be due to CT imaging. Significant changes in device parameters were sought as a secondary outcome (control group 4:1 ratio). RESULTS: The main finding was that none of the CTs were associated with the primary outcome. With serial device interrogations, there were no differences in changes in battery voltage or lead parameters between devices exposed to radiation and their controls. Potentially significant changes in device parameters were observed in a small group of devices (both the CT group and control group), but no definitive link to CT was confirmed, and there were no associated clinical consequences. CONCLUSIONS: The findings suggest that the presence of CRM devices should not delay or result in cancellation of clinically indicated CT imaging procedures, and provide evidence that would be helpful when the FDA advisory is re-evaluated.

Assessment of ventricular tachycardia scar substrate by intracardiac echocardiography.

BACKGROUND: Intracardiac echocardiography (ICE) is increasingly used to guide complex ablation procedures. This study aimed to assess the scar substrate of ventricular tachycardia (VT) by ICE in patients undergoing VT ablation. METHODS: In 22 patients undergoing VT ablation (10 ischemic, 12 nonischemic), the Biosense CARTOSOUND module (Biosense Webster, Diamond Bar, CA, USA) was used for three-dimensional reconstruction of the ventricles. The characteristics and appearance with ICE imaging of voltage-defined scar zones (bipolar voltage <0.5 mV), border zones (0.5-1.5 mV), and normal myocardium (>1.5 mV) on electroanatomic maps were evaluated. The standard image analysis software Image J (National Institutes of Health, Bethesda, MD, USA) was used to analyze signal intensity (mean pixel signal intensity unit [SIU]) and heterogeneity (standard deviation of signal intensity in analyzed area) on ICE images. RESULTS: A total of 83 myocardial areas were analyzed from two-dimensional ICE images (15 scars, 31 border zones, and 37 normal). Voltage-defined scar zones had increased signal intensities compared to border zones (149 SIU vs 104 SIU, P < 0.0001) and normal myocardium (88 SIU, P < 0.0001). Border zones were more likely to have heterogeneous densities compared to normal myocardium (standard deviation of signal intensity 20 SIU vs 12 SIU, P < 0.0001). In receiver-operator characteristic analyses, signal intensity ≥ 137 SIU differentiated scar from nonscar zones (area under curve 0.91, P < 0.0001). Software-based color enhancement of areas with signal intensity ≥ 137 SIU allowed identification of the VT substrate in all 15 patients with voltage-defined scar zones. CONCLUSIONS: ICE provides important information about the VT anatomical substrate and may have potential to identify areas of scarred myocardium.

Inflammation and sudden cardiac death in a community-based population of older adults: the Cardiovascular Health Study.

BACKGROUND: Inflammation is linked to adverse cardiovascular events, but its association with sudden cardiac death (SCD) has been controversial. Older subjects, who are at particular risk for SCD, were underrepresented in previous studies addressing this issue. OBJECTIVE: The purpose of this study was to study the association between inflammation and SCD in a community-based population of older adults. METHODS: In the Cardiovascular Health Study, 5806 and 5382 participants had measurements of C-reactive protein (CRP) and interleukin-6 (IL6), respectively, and were followed for up to 17 years. SCD risk as a function of baseline IL-6 and CRP was assessed in the overall population and in a group of participants without known prevalent cardiac disease. RESULTS: In univariate analyses, both IL-6 (hazard ratio [HR] 1.79 for 1+ log IL-6, 95% confidence interval [CI] 1.50-2.13; 5th vs 1st quintile HR 3.36, 95% CI 2.24-5.05) and CRP (HR 1.31 for 1+ log CRP, 95% CI 1.18-1.45; 5th vs 1st quintile HR 2.00, 95% CI 1.40-2.87) were associated with SCD risk. In covariate-adjusted analyses, accounting for baseline risk factors, incident myocardial infarction, and heart failure, the association with SCD risk persisted for IL-6 (HR 1.26 for 1+ log IL-6, 95% CI 1.02-1.56; 5th vs 1st quintile HR 1.63, 95% CI 1.03-2.56) but was significantly attenuated for CRP (HR 1.13 for 1+ log CRP, 95% CI 1.00-1.28; 5th vs 1st quintile HR 1.34, 95% CI 0.88-2.05). Similar findings were observed in participants without prevalent cardiac disease. CONCLUSION: Greater burden of inflammation, assessed by IL-6 levels, is associated with SCD risk beyond traditional risk factors, incident myocardial infarction, and heart failure.

Atrial arrhythmias after lung transplantation: epidemiology, mechanisms at electrophysiology study, and outcomes.

BACKGROUND: Atrial arrhythmias (AAs) including atrial fibrillation (AF) and atrial tachycardia (AT) are often observed after cardiothoracic surgery. Our aim was to evaluate the prevalence and mechanism of AAs after lung transplantation. METHODS AND RESULTS: All patients (n=127) after bilateral sequential lung transplantation followed at our institution over 20 years were included. All patients received postoperative rhythm monitoring and clinic visits with ECG at 1, 3, 6, and 12 months, or as needed. AAs occurred in 40 of 127 (31.5%) patients over 4.2+/-4.1 years. AA prevalence at postoperation and 1, 3, 6, 12, and >12 months was 24%, 11%, 3%, 2%, 4%, and 11%, respectively. Early AAs were predominantly AF, whereas all AAs >12 months were AT. Time to first AF versus AT was 11+/-9 versus 1485+/-2462 days (P=0.09). Male sex, age, and preoperative AA predicted any early (<3 months) AA but did not predict late AA. Early AA did not predict late AT. In 4 patients with drug-resistant AT, electrophysiology studies found AT involving the pulmonary vein/left atrium anastomoses in 3 patients, including donor-to-recipient conduction in 1, border zone macroreentry in 2, and cavotricuspid isthmus dependent flutter in 1; all patients were successfully treated with ablation. CONCLUSIONS: AAs after lung transplantation are common. Although AF is common early, AF is rare after healing of left atrial incisions, which probably result in surgical pulmonary vein isolation with rare exception. This raises the question of whether additional surgical or ablation lines at the time of lung transplantation would prevent late AA.