Impact of a Multidisciplinary Treatment Pathway for Atrial Fibrillation in the Emergency Department on Hospital Admissions and Length of Stay: Results of a Multi-Center Study.

Background Variability in the management of atrial fibrillation (AF) in the emergency department (ED) leads to avoidable hospital admissions and prolonged length of stay (LOS). In a retrospective single-center study, a multidisciplinary AF treatment pathway was associated with a reduced hospital admission rate and reduced LOS. To assess the applicability of the AF pathway across institutions, we conducted a 2-center study. Methods and Results We performed a prospective, 2-stage study at 2 tertiary care hospitals. During the first stage, AF patients in the ED received routine care. During the second stage, AF patients received care according to the AF pathway. The primary study outcome was hospital admission rate. Secondary outcomes included ED LOS and inpatient LOS. We enrolled 104 consecutive patients in each stage. Patients treated using the AF pathway were admitted to the hospital less frequently than patients who received routine care (15% versus 55%; P<0.001). For admitted patients, average hospital LOS was shorter in the AF pathway cohort than in the routine care cohort (64 versus 105 hours, respectively; P=0.01). There was no significant difference in the average ED LOS between AF pathway and routine care cohorts (14 versus 12 hours, respectively; P=0.32). Conclusions In this prospective 2-stage, 2-center study, utilization of a multidisciplinary AF treatment pathway resulted in a 3.7-fold reduction in admission rate and a 1.6-fold reduction in average hospital LOS for admitted patients. Utilization of the AF pathway was not associated with a significant change in ED LOS.

Pulmonary vein isolation for atrial fibrillation in the postpneumonectomy population: a feasibility, safety, and outcomes study.

BACKGROUND: Pulmonary vein isolation (PVI) of the remnant pulmonary vein (PV) stumps in pneumonectomy patients has not been well characterized. METHODS: This is a multicenter observational study of patients with a remnant PV stump after pneumonectomy. Consecutive patients with a history of pneumonectomy and who had undergone RF ablation for drug refractory AF were identified from the AF database at the participating institutions. RESULTS: There were 15 patients in whom pneumonectomy was performed, for resection of tumors in 10, infection in 4, and bullae in 1 patient and who underwent RF ablation for AF. The mean age was 63 ± 7 years. The stumps were from the right lower PV in 5, left upper PV in 5, left lower PV in 3, and right upper PV in 2 patients. All the PV stumps were electrically active with PV potentials and 9 (60%) of them had triggered activity. PVI was performed in 14 and focal isolation in 1 patient. At 1-year follow-up, 80% were free of AF, off of antiarrhythmic medications. CONCLUSION: PV stumps in AF patients with previous pneumonectomy are electrically active and are frequently the sites of active firing. Isolation of these PV stumps can be accomplished safely and effectively using catheter ablation with no practical concern for PV stenosis or compromising PV stump integrity.

A combined anatomic and electrophysiologic substrate based approach for sudden cardiac death risk stratification.

BACKGROUND: Although left ventricular ejection fraction (LVEF) is the primary determinant for sudden cardiac death (SCD) risk stratification, in isolation, LVEF is a sub-optimal risk stratifier. We assessed whether a multi-marker strategy would provide more robust SCD risk stratification than LVEF alone. METHODS: We collected patient-level data (n = 3355) from 6 studies assessing the prognostic utility of microvolt T-wave alternans (MTWA) testing. Two thirds of the group was used for derivation (n = 2242) and one-third for validation (n = 1113). The discriminative capacity of the multivariable model was assessed using the area under the receiver-operating characteristic curve (c-index). The primary endpoint was SCD at 24 months. RESULTS: In the derivation cohort, 59 patients experienced SCD by 24 months. Stepwise selection suggested that a model based on 3 parameters (LVEF, coronary artery disease and MTWA status) provided optimal SCD risk prediction. In the derivation cohort, the c-index of the model was 0.817, which was significantly better than LVEF used as a single variable (0.637, P < .001). In the validation cohort, 36 patients experienced SCD by 24 months. The c-index of the model for predicting the primary endpoint was again significantly better than LVEF alone (0.774 vs 0.671, P = .020). CONCLUSIONS: A multivariable model based on presence of coronary artery disease, LVEF and MTWA status provides significantly more robust SCD risk prediction than LVEF as a single risk marker. These findings suggest that multi-marker strategies based on different aspects of the electro-anatomic substrate may be capable of improving primary prevention implantable cardioverter-defibrillator treatment algorithms.

Assessment of catheter tip contact force resulting in cardiac perforation in swine atria using force sensing technology.

BACKGROUND: Force sensing is a recently developed technology that allows the determination of the contact force (CF) at the tip of the catheter during electrophysiology procedures. Previous studies suggested that the optimal CF for adequate catheter contact ranges between 10 and 40 g. The aim of this study was to determine the CF needed to cause perforation in the swine atria. METHODS AND RESULTS: Pericardial access was obtained at the beginning of the study in a swine model to drain pericardial effusions. Electroanatomic maps of the right atrium (RA) and left atrium (LA) were constructed. Ablation was performed using an irrigated-tip radiofrequency catheter equipped with force-sensing technology (30 W, 30 mL/min, for 30 seconds). Perforations of the LA and RA wall were intentionally performed in different locations with and without radiofrequency ablation. CF values preceding each perforation were recorded. A total of 111 cardiac perforations were achieved in 7 pigs. The overall average CF resulting in perforation was 175.8±60.4 g (range, 77 to 376 g). This was significantly lower after 30 seconds of radiofrequency delivery: 151.8±49.9 g versus 197±61.3 g (P=0.00005). The average value of CF resulting in perforation was not statistically different between the RA and the LA (169.6±61.6 g versus 181.7±59.3 g) (P=0.29). CONCLUSIONS: Perforation of the atrial wall in a swine model can occur over a wide range of CF values. Perforation can occur with a CF as low as 77 g. Ablation reduces the perforating force by 23%.

Electroanatomic mapping of the left ventricle in a porcine model of chronic myocardial infarction with magnetic resonance-based catheter tracking.

BACKGROUND: X-ray fluoroscopy constitutes the fundamental imaging modality for catheter visualization during interventional electrophysiology procedures. The minimal tissue discriminative capability of fluoroscopy is mitigated in part by the use of electroanatomic mapping systems and enhanced by the integration of preacquired 3-dimensional imaging of the heart with computed tomographic or magnetic resonance (MR) imaging. A more ideal paradigm might be to use intraprocedural MR imaging to directly image and guide catheter mapping procedures. METHODS AND RESULTS: An MR imaging-based electroanatomic mapping system was designed to assess the feasibility of navigating catheters to the left ventricle in vivo using MR tracking of microcoils incorporated into the catheters, measuring intracardiac ventricular electrograms, and integrating this information with 3-dimensional MR angiography and myocardial delayed enhancement images to allow ventricular substrate mapping. In all animals (4 normal, and 10 chronically infarcted swine), after transseptal puncture under fluoroscopic guidance, catheters were successfully navigated to the left ventricle with MR tracking (13 to 15 frames per second) by both transseptal and retrograde aortic approaches. Electrogram artifacts related to the MR imaging gradient pulses were successfully removed with analog and digital signal processing. In all animals, it was possible to map the entire left ventricle and to project electrogram voltage amplitude maps to identify the scarred myocardium. CONCLUSIONS: It is possible to use MR tracking to navigate catheters to the left ventricle, to measure electrogram activity, and to render accurate 3-dimensional voltage maps in a porcine model of chronic myocardial infarction, completely in the MR imaging environment. Myocardial delayed enhancement guidance provided dense sampling of the proximity of the infarct and accurate localization of complex infarcts.

Balloon catheter ablation to treat paroxysmal atrial fibrillation: what is the level of pulmonary venous isolation?

BACKGROUND: Unlike the initial balloon ablation catheters that were designed to deliver ablation lesions within the pulmonary veins (PVs), the current balloon prototypes are fashioned to deliver lesions at the PV ostia. OBJECTIVE: Using electroanatomical mapping, this study evaluates the actual location of ablation lesions generated by cryo-based, laser-based, or ultrasound-based balloon catheters. METHODS: In a total of 14 patients with paroxysmal atrial fibrillation, PV isolation was performed using either a cryoballoon catheter (8 patients), laser catheter (4 patients) or ultrasound balloon catheter (2 patients). Patients underwent preprocedural computed tomographic/magnetic resonance imaging. An intracardiac ultrasound catheter was used to aid in positioning the balloon catheter at the PV ostium/antrum. In all patients, sinus rhythm bipolar voltage amplitude maps (using either CARTO with computed tomographic/magnetic resonance image integration or NavX mapping) were generated at baseline and after electrical PV isolation as confirmed by use of a circular mapping catheter. RESULTS: Electrical isolation was achieved in 100% of the PVs. Electroanatomical mapping revealed that after ablation with any of the 3 balloon catheters, the extent of isolation included the tubular portions of each PV to the level of the PV ostia. However, the PV antral portions were left largely unablated with all 3 balloon technologies. CONCLUSION: Using the current generation of balloon ablation catheters, electrical isolation occurs at the level of the PV ostia, but the antral regions are largely unablated.

Atrial tachycardia after ablation of persistent atrial fibrillation: identification of the critical isthmus with a combination of multielectrode activation mapping and targeted entrainment mapping.

BACKGROUND: Atrial tachycardia (AT) that develops after ablation of atrial fibrillation often poses a more difficult clinical situation than the index arrhythmia. This study details the use of an impedance-based electroanatomic mapping system (Ensite NavX) in concert with a specialized multielectrode mapping catheter for rapid, high-density atrial mapping. In this study, this activation mapping was combined with entrainment mapping to eliminate ATs developing late after atrial fibrillation ablation. METHODS AND RESULTS: All study patients developed AT after ablation for atrial fibrillation. The approach to AT ablation consisted of 4 steps: use of a 20-pole penta-array catheter to map the chamber rapidly during the rhythm of interest, analysis of the patterns of atrial activation to identify wave fronts of electric propagation, targeted entrainment at putative channels, and catheter ablation at these "isthmuses." All ablations were performed with irrigated radiofrequency ablation catheters. Forty-one ATs were identified in 17 patients (2.4+/-1.6 ATs per patient). Using the multielectrode catheter in conjunction with the Ensite NavX system, we created activation maps of 33 of 41 ATs (81%) (mean cycle length, 284+/-71 seconds) with a mean of 365+/-108 points per map and an average mapping time of 8+/-3 minutes. Of the 33 mapped ATs, 7 terminated either spontaneously or during entrainment maneuvers. Radiofrequency energy was used to attempt ablation of 26 ATs; 25 of 26 of the ATs (96%) were terminated successfully by ablation or catheter pressure. CONCLUSIONS: This study demonstrates a strategy for rapidly defining and eliminating the scar-related ATs typically encountered after ablation of atrial fibrillation.

Integration of cardiac magnetic resonance imaging with three-dimensional electroanatomic mapping to guide left ventricular catheter manipulation: feasibility in a porcine model of healed myocardial infarction.

OBJECTIVES: In a series of in vitro and in vivo experiments, we evaluated the feasibility of integrating three-dimensional (3D) magnetic resonance imaging (MRI) and electroanatomic mapping (EAM) data to guide real-time left ventricular (LV) catheter manipulation. BACKGROUND: Substrate-based catheter ablation of post-myocardial infarction ventricular tachycardia requires delineation of the scarred myocardium, typically using an EAM system. Cardiac MRI might facilitate this procedure by localizing this myocardial scar. METHODS: A custom program was employed to integrate 3D MRI datasets with real-time EAM. Initially, a plastic model of the LV was used to determine the optimal alignment/registration strategy. To determine the in vivo accuracy of the registration process, ablation lesions were directed at iatrogenic MRI-visible "targets" (iron oxide injections) within normal porcine LVs (n = 5). Finally, this image integration strategy was assessed in a porcine infarction model (n = 6) by targeting ablation lesions to the scar border. RESULTS: The in vitro experiments revealed that registration of the LV alone results in inaccurate alignment due primarily to rotation along the chamber's long axis. Inclusion of the aorta in the registration process rectified this error. In the iron oxide injection experiments, the ablation lesions were 1.8 +/- 0.5 mm from the targets. In the porcine infarct model, the catheter could be reliably navigated to the mitral valve annulus, and the ablation lesions were uniformly situated at the scar borders. CONCLUSIONS: These data suggest that registration of pre-acquired magnetic resonance images with real-time mapping is sufficiently accurate to guide LV catheter manipulation in a reliable and clinically relevant manner.

Intrapericardial echocardiography: a novel catheter-based approach to cardiac imaging.

BACKGROUND: Transvascular catheter-based intracardiac echocardiography has been successfully used to help guide catheter ablation and electrophysiologic procedures. It has recently been demonstrated that catheters can be safely placed into the pericardial space to allow for epicardial cardiac mapping and ablation. We evaluated the feasibility of catheter-based intrapericardial echocardiography (IPE) during such procedures to identify cardiac structures and visualize intracardiac catheters. METHODS: IPE was performed in 7 goats by placing a phased-array ultrasound transducer contained within a 10F steerable catheter into the pericardial space using the same transthoracic subxyphoid approach as used to map and ablate epicardial ventricular tachycardia. Images were obtained of cardiac structures and of intracardiac ablation catheters. After the procedure, the hearts were harvested to assess for possible IPE-related lesions. RESULTS: The IPE catheter could be easily placed inside the pericardial space in all animals. In 7 of 7 cases, longitudinal and short-axis views of right- and left-sided chambers and valves were obtained, similar in orientation to transesophageal echocardiography. Visualization of atrial appendages (6/7), pulmonary veins (6/7), coronary arteries (6/7), and coronary sinus (3/6) was also feasible. Assessment of intracardiac transvalvar and venous blood flow was achieved by spectral and color Doppler. The ablation catheter could be clearly visualized inside cardiac chambers. No arrhythmias were induced with IPE catheter manipulation. After harvesting the hearts, no lesions resulting from the procedure were observed. CONCLUSION: In this experimental setting, IPE was able to provide detailed images of cardiac structures and establish the relative position of the ablation catheter.

Para-Hisian entrainment: a novel pacing maneuver to differentiate orthodromic atrioventricular reentrant tachycardia from atrioventricular nodal reentrant tachycardia.

INTRODUCTION: Para-Hisian pacing during sinus rhythm can help to identify the presence of an accessory pathway (AP). In this maneuver, the retrograde activation time and pattern are compared during capture and loss-of-capture of the His bundle while pacing from a para-Hisian position. However, identification of a retrograde AP does not necessitate that it is operative during the tachycardia of interest; conversely, slowly conducting or "distant" bypass tracts may not be identified. We evaluated the utility of entrainment or resetting of tachycardias from the para-Hisian position to help distinguish atrioventricular nodal reentrant tachycardia (AVNRT) from orthodromic atrioventricular tachycardia (AVRT). METHODS AND RESULTS: Para-Hisian entrainment/resetting was evaluated in 50 patients: 33 with AVNRT and 17 with AVRT. The maneuvers were performed using a standard quadripolar catheter placed at the His position: low output for right ventricular (RV) capture and high output for both RV and His capture. The retrograde atrial activation sequence, SA interval (interval from stimulus to earliest retrograde atrial activation), and "local" VA interval (interval between the ventricular and atrial electrograms at the site of earliest retrograde atrial activation) were compared between His and His/RV capture. The DeltaSA was > 40 ms in patients with AVNRT and was < 40 ms in all but one patient with AVRT. In concert with the DeltaSA interval, the DeltaVA interval was able to fully define the mechanism of the tachycardia in all patients studied. CONCLUSION: Para-Hisian entrainment/resetting can determine the course of retrograde conduction operative during narrow complex tachycardias. It is a useful diagnostic maneuver in differentiating AVNRT and orthodromic AVRT.

Combined epicardial and endocardial electroanatomic mapping in a porcine model of healed myocardial infarction.

BACKGROUND: Substrate mapping of post-myocardial infarction ventricular tachycardia involves electroanatomic delineation of scarred tissue on the basis of electrogram characteristics during sinus rhythm. A percutaneous transthoracic technique was recently described that allows catheter mapping of the epicardial surface of the heart. This study sought to determine whether the epicardial extent of a myocardial infarct could be defined during sinus rhythm. METHODS AND RESULTS: In a porcine model of healed anterior wall myocardial infarction (n=13 animals), detailed in vivo left ventricular endocardial and ventricular epicardial electroanatomic mapping was performed. Catheter access to the pericardial space was achieved by subxyphoid puncture under fluoroscopic guidance. Bipolar electrogram amplitude and duration characteristics of normal tissue were established on the basis of in vivo epicardial mapping data in 8 additional normal animals. With the use of these criteria, radiofrequency lesions (4 to 11 per animal) were placed along the endocardial and epicardial scar borders as defined by the electroanatomic map. The area of epicardial scar defined by abnormal bipolar voltage correlated well with the dimensions measured on pathological examination. The size and location also correlated well with the scar dimensions defined by electrogram duration criteria. Late potentials were noted in the border zones of both surfaces of the scar. During pathological examination, the radiofrequency lesions were situated at the borders of the epicardial scar. CONCLUSIONS: A 3-dimensional construct of the infarcted myocardium can be rendered by combined epicardial and endocardial electroanatomic mapping. This experimental protocol is propaedeutic to future clinical studies incorporating endocardial and epicardial substrate mapping into catheter ablation strategies to treat post-myocardial infarction ventricular tachycardia.