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Background: Atrial stretch causes remodeling that predisposes to atrial fibrillation. We tested the hypothesis that peaks in left atrial (LA) wall stress are associated with focal remodeling., Methods and Results: Nineteen patients underwent LA mapping before catheter ablation for persistent atrial fibrillation. Finite Element Analysis was used to predict wall stress distribution based on LA geometry from CT. The relationship was assessed between wall stress and (1) electrogram voltage and (2) complex fractionated atrial electrograms (CFAE), using CFAE mean (the mean interval between deflections). Wall stress varied widely within atria and between subjects (median, 36 kPa; interquartile range, 26-51 kP). Peaks in wall stress (≥90th percentile) were common at the pulmonary vein (PV) ostia (93%), the appendage ridge (100%), the high posterior wall (84%), and the anterior wall and septal regions (42-84%). Electrogram voltage showed an inverse relationship across quartiles for wall stress (19% difference across quartiles, P=0.016). There was no effect on CFAE mean across quartiles of wall stress. Receiver operating characteristic analysis showed high wall stress was associated with low voltage (ie, <0.5 mV) and electrical scar (ie, <0.05 mV; both P<0.0001) and with absence of CFAE (ie, CFAE mean <120 ms; P<0.0001). However, peaks in wall stress and CFAE were found at 88% of PV ostia., Conclusions: Peaks in wall stress were associated with areas of low voltage, suggestive of focal remodeling. Although peaks in wall stress were not associated with LA CFAE, the PV ostia may respond differently.

Objectives: We attempted to classify causes of ischemic stroke in young adults using a progressive diagnostic algorithm and the ASCO (atherosclerosis, small-vessel disease, cardiac source, other cause) classification system., Methods: Patients aged 16-54 years consecutively treated for acute ischemic stroke in a tertiary stroke unit were included in this retrospective analysis. Causes of stroke were classified using the ASCO system, which assigns a graded level of likelihood to each potential cause in individual patients. The initial etiologic workup included brain imaging, magnetic resonance or CT angiography of cerebral and cervical vessels, EKG, and routine blood studies. Patients without a definite cause of ischemic stroke after initial evaluation underwent transesophageal echocardiography., Results: We included 318 patients (195 men and 123 women); 131 patients were aged 16-44 years, and 187 were aged 45-54 years. A definite cause of stroke (ASCO grade 1) could be identified in 145 patients (45.5%). An uncertain cause of stroke (ASCO grade 2) was found in 59 (18.5%) further patients. Most (130 of 145) definite causes were identified by initial evaluation. The 2 major definite or uncertain causes of stroke were patent foramen ovale associated with atrial septal aneurysm (PFO-ASA) (20 of 131 [15.3%]) and dissection of the cervical or cerebral artery (19 of 131 [14.5%]) in patients aged 16-44 years and large-vessel atherosclerosis (37 of 187 [19.8%]) and PFO-ASA (23 of 187 [12.3%]) in patients aged 45-54 years., Conclusions: Our findings suggest that PFO-ASA may be a major cause of ischemic stroke in young adults., (Copyright © 2011 by AAN Enterprises, Inc.)

Background: The primary objective of this study was to develop an image-guided, noninvasive procedure to create or enlarge an atrial septal defect for the treatment of neonates with hypoplastic left heart syndrome and an intact or restrictive atrial septum. Histotripsy is an innovative ultrasonic technique that produces nonthermal, mechanical tissue fractionation through the use of high-intensity ultrasound pulses. This article reports the pilot in vivo study to create an atrial septal defect through the use of extracardiac application of histotripsy in an open-chest canine model., Methods and Results: In 10 canines, the atrial septum was exposed to histotripsy by an ultrasound transducer positioned outside the heart. Ultrasound pulses of 6-microsecond duration at a peak negative pressure of 15 MPa and a pulse repetition frequency of 3.3 kHz were generated by a 1-MHz focused transducer. The procedure was guided and monitored by real-time ultrasound imaging. In 9 of 10 canines, an atrial septal defect was produced, and shunting across the atrial septum was visualized. Pathology of the hearts showed atrial septal defects with minimal damage to surrounding tissue. No damage was found on the epicardial surface of the heart or other structures., Conclusions: Under real-time ultrasound guidance, atrial septal defects were successfully created with extracardiac histotripsy in a live canine model. Although further studies in an intact animal model are needed, these results provide promise of histotripsy becoming a valuable clinical tool.

Background: Atrial septal defect (ASD) flow can be measured indirectly by velocity-encoded cardiovascular magnetic resonance (veCMR) of the pulmonary artery and aorta. Imaging the secundum ASD en face could potentially enable direct flow measurement and provide valuable information about ASD size, shape, location, and proximity to other structures., Methods and Results: Forty-four patients referred for possible transcatheter ASD closure underwent a comprehensive standard evaluation, including transesophageal and/or intracardiac echocardiography and invasive oximetry. CMR was performed in parallel and included direct en face veCMR after an optimal double-oblique imaging plane was determined that accounted for ASD flow direction and cardiac-cycle interatrial septal motion. ASD flow measured by direct en face veCMR correlated better with invasive oximetry than indirect (pulmonary artery and aorta) veCMR (r=0.80 versus r=0.66). Additionally, 95% limits of agreement were narrower (+/-3.9 versus +/-5.1 L/min). En face veCMR determined that defects usually were eccentrically shaped (major/minor axis length >1.5) rather than circular, with 16% having extreme eccentricity (major/minor >2.0). Overall, ASD size by both veCMR and intracardiac echocardiography correlated with final device size; however, in small to medium defects (<3 cm(2)) and extremely eccentric defects, veCMR correlated better with final device size than did intracardiac echocardiography. Importantly, CMR identified additional information in 9 patients (20%) that altered clinical management. Specifically, en face veCMR detected additional defects (n=3), large ASD with insufficient rim tissue (n=2), and sinus venosus defect with anomalous pulmonary vein (n=1). Cine and/or morphological imaging detected interrupted inferior vena cava (n=2) and sinus of Valsalva aneurysm (n=1)., Conclusions: En face veCMR with an optimized imaging plane can determine ASD flow, size, and morphology. CMR provided information incremental to comprehensive standard evaluation that altered clinical management in 20% of patients.