Thomas J. Bunch

Three-dimensional ultrasound for image-guided mapping and intervention: methods, quantitative validation, and clinical feasibility of a novel multimodality image mapping system.

Background— Multiple factors create discrepancies between electroanatomic maps and merged, preacquired computed tomographic images used in guiding atrial fibrillation ablation. Therefore, a Carto-based 3D ultrasound image system (Biosense Webster Inc) was validated in an animal model and tested in 15 atrial fibrillation patients.nnMethods and Results— Twelve dogs underwent evaluation using a newly developed Carto-based 3D ultrasound system. After fiducial clip markers were percutaneously implanted at critical locations in each cardiac chamber, 3D ultrasound geometries, derived from a family of 2D intracardiac echocardiographic images, were constructed. Point-source error of 3D ultrasound-derived geometries, assessed by actual real-time 2D intracardiac echocardiographic clip sites, was 2.1±1.1 mm for atrial and 2.4±1.2 mm for ventricular sites. These errors were significantly less than the variance on CartoMerge computed tomographic images (atria: 3.3±1.6 mm; ventricles: 4.8±2.0 mm; P< 0.001 for both). Target ablation at each clip, guided only by 3D ultrasound-derived geometry, resulted in lesions within 1.1±1.1 mm of the actual clips. Pulmonary vein ablation guided by 3D ultrasound-derived geometry resulted in circumferential ablative lesions. Mapping in 15 patients produced modestly smaller 3D ultrasound versus electroanatomic map left atrial volumes (98±24 cm3 versus 109±25 cm3, P< 0.05). Three-dimensional ultrasound-guided pulmonary vein isolation and linear ablation in these patients were successfully performed with confirmation of pulmonary vein entrance/exit block.nnConclusions— These data demonstrate that 3D ultrasound images seamlessly yield anatomically accurate chamber geometries. Image volumes from the ultrasound system are more accurate than possible with CartoMerge computed tomographic imaging. This clinical study also demonstrates the initial feasibility of this guidance system for ablation in patients with atrial fibrillation.nnReceived September 18, 2007; accepted April 7, 2008. nn# CLINICAL PERSPECTIVE {#article-title-2}Background—Multiple factors create discrepancies between electroanatomic maps and merged, preacquired computed tomographic images used in guiding atrial fibrillation ablation. Therefore, a Carto-based 3D ultrasound image system (Biosense Webster Inc) was validated in an animal model and tested in 15 atrial fibrillation patients. Methods and Results—Twelve dogs underwent evaluation using a newly developed Carto-based 3D ultrasound system. After fiducial clip markers were percutaneously implanted at critical locations in each cardiac chamber, 3D ultrasound geometries, derived from a family of 2D intracardiac echocardiographic images, were constructed. Point-source error of 3D ultrasound-derived geometries, assessed by actual real-time 2D intracardiac echocardiographic clip sites, was 2.1±1.1 mm for atrial and 2.4±1.2 mm for ventricular sites. These errors were significantly less than the variance on CartoMerge computed tomographic images (atria: 3.3±1.6 mm; ventricles: 4.8±2.0 mm; P<0.001 for both). Target ablation at each clip, guided only by 3D ultrasound-derived geometry, resulted in lesions within 1.1±1.1 mm of the actual clips. Pulmonary vein ablation guided by 3D ultrasound-derived geometry resulted in circumferential ablative lesions. Mapping in 15 patients produced modestly smaller 3D ultrasound versus electroanatomic map left atrial volumes (98±24 cm3 versus 109±25 cm3, P<0.05). Three-dimensional ultrasound-guided pulmonary vein isolation and linear ablation in these patients were successfully performed with confirmation of pulmonary vein entrance/exit block. Conclusions—These data demonstrate that 3D ultrasound images seamlessly yield anatomically accurate chamber geometries. Image volumes from the ultrasound system are more accurate than possible with CartoMerge computed tomographic imaging. This clinical study also demonstrates the initial feasibility of this guidance system for ablation in patients with atrial fibrillation.

New generation of electro-anatomic mapping: full intracardiac ultrasound image integration

Surrogate electro-anatomic-derived geometries are used as the three-dimensional (3D) basis for mapping of cardiac arrhythmias. While merged computed tomography (CT) imaging may provide stellar pulmonary vein (PV) and left atrial (LA) anatomy, the applied scans must be obtained prior to ablation, and may not reflect physiologic conditions at the time of intervention. Patient-specific, ultrasound-derived 3D imaging has been developed as an alternative basis for new generation electro-anatomic mapping. An electro-anatomic sensor positioned at the tip of the phased-array intracardiac ultrasound catheter, provides the means to specify both location and orientation of each image as the context for creating the 3D volumes for co-registration with electro-anatomic mapping. Specific anatomic details such as the pulmonary veins, membranous fossa, papillary muscles, or valve structures derived from real-time imaging can also be integrated into each segmented volume. This presentation reviews the basis and methods for this novel multi-modality image fusion for the creation of robust, nearly real-time anatomic images for guiding electro-anatomic mapping and ablation without requiring pre-acquired CT image sets, with accompanying limitations.

Admission predictors of in-hospital mortality and subsequent long-term outcome in survivors of ventricular fibrillation out-of-hospital cardiac arrest: A population-based study

Background: Survival following out-of-hospital cardiac arrest (OHCA) from ventricular fibrillation (VF) is poor and dependent on a rapid emergency response system. Improvements in emergent early response have resulted in a higher percentage of patients surviving to admission. However, the admission variables that predict both short- and long-term survival in a region with high discharge survival following OHCA require further study in order to identify survivors at subsequent highest risk. Methods: All patients with OHCA arrest in Olmsted County Minnesota between 1990 and 2000 who received defibrillation of VF by emergency services were included in the population-based study. Baseline patient admission characteristics in survivor and nonsurvivor groups were compared. Survivors to hospital discharge were prospectively followed to determine long-term survival. Results: Two hundred patients suffered a VF arrest. Of these patients, 145 (73%) survived to hospital admission (7 died within the emergency department) and 79 (40%) were subsequently discharged. Sixty-six (83%) were male, with an average age of 61.9 ± 15.9 years. Univariate predictors of in-hospital mortality included call-to-shock time (6.6 vs. 5.5 min, p = 0.002), a nonwitnessed arrest (75.4 vs. 92.4%, p = 0.008), in-field use of epinephrine (27.8 vs. 93.4%, p < 0.001), age (68.1 vs. 61.9 years, p = 0.017), hypertension (36.1 vs. 14.1%, p = 0.005), ejection fraction (32.4 vs. 42.4, p = 0.012), and use of digoxin (34.9 vs. 12.7%, p = 0.002). Of all these variables, hypertension [hazard ratio (HR) 4.0, 95% CI 1.1–14.1, p = 0.03], digoxin use (HR 4.5, 95% CI 1.3–15.6, p = 0.02), and epinephrine requirement (HR 62.0, 95% CI 15.1–254.8, p < 0.001) were multivariate predictors of in-hospital mortality. Nineteen patients (24%) had died prior to the survey follow-up. Five patients experienced a cardiac death, resulting in a 5-year expected cardiac survival of 92%. Multivariate variables predictive of long-term mortality include digoxin use (HR 3.02, 95% CI 1.80–5.06, p < 0.001), hypertension (HR 2.06, 95% CI 2.12–3.45, p = 0.006), and call-to-shock time (HR 1.18, 95% CI 1.01–1.38, p = 0.038). Conclusion: A combined police/fire/EMS defibrillation program has resulted in an increase of patients surviving to hospital admission after OHCA. This study confirms the need to decrease call-to-shock times, which influence both in-hospital and long-term mortality. This study also identifies the novel demographic variables of digoxin and hypertension, which were also independent risk factors of increased in-hospital and long-term mortality. Identification of these variables may provide utility in identifying those at high-risk of subsequent mortality after resuscitation.

14. Ventricular Fibrillation & Out-of-Hospital Cardiac Arrest14.4 The Changing Landscape of Ventricular Fibrillation in Cardiac Arrest

Objective To define the apparent changes in ventricular fibrillation (VF) as cause of out-of-hospital cardiac arrest. (OHCA)nnMethods Retrospective analysis of prospectively acquired observational data of OHCA in a population-controlled setting with a single emergency medical service (EMS) system between 1991-2004.nnResults In the study period there were 338 all-cause arrests, with 203 (57%) in homes, 85 (24%) in public locations, and 69 (19%) in other locations (hotels, nursing homes). VF incidence during 1991-1997 was 24/100 000/person-yr and during 1998-2004 it was 11/100 000/person-yr (p<0.001). During 1991-1997, 61/110 (55%) of arrests in homes were in VF and from 1998-2004, 32/93 (34%) were in VF (p=0.003). During 1991-1997 48/51 (94%) of arrests in public places were in VF and from 1998-2004 22/34 (64%) were in VF (p<0.001).nnConclusion VF as the cause of OHCA declined dramatically in both home and public settings, both in absolute numbers and in percentage of initial rhythm. This decreased incidence has obvious implications for potential cost-effective and therapeutic benefit from placement of automated external defibrillators.