Automated white-matter tractography using a probabilistic diffusion tensor atlas: Application to temporal lobe epilepsy

Diffusion-weighted magnetic resonance imaging allows researchers and clinicians to identify individual white matter fiber tracts and map their trajectories. The reliability and interpretability of fiber-tracking procedures is improved when a priori anatomical information is used as a guide. We have developed an automated method for labeling white matter fiber tracts in individual subjects based on a probabilistic atlas of fiber tract locations and orientations. The probabilistic fiber atlas contains 23 fiber tracts and was constructed by manually identifying fiber tracts in 21 healthy controls and 21 patients with temporal lobe epilepsy (TLE). The manual tract identification method required approximately 40 h of manual editing by a trained image analyst using multiple regions of interest to select or exclude streamline fibers. Identification of fiber tracts with the atlas does not require human intervention, but nonetheless benefits from the a priori anatomical information that was used to manually identify the tracts included in the atlas. We applied this method to compare fractional anisotropy--thought to be a measure of white matter integrity--in individual fiber tracts between control subjects and patients with TLE. We found that the atlas-based and manual fiber selection methods produced a similar pattern of results. However, the between-group effect sizes using the atlas-derived fibers were generally as large or larger than those obtained with manually selected fiber tracks.

Pathways to approval of pediatric cardiac devices in the United States: challenges and solutions

Patients treated by pediatric interventional cardiologists and cardiac surgeons often have unmet medical device needs that pose a challenge to the current regulatory evaluation and approval process in the United States. In this report we review current US Food and Drug Administration regulatory processes, review some unique aspects of pediatric cardiology and cardiac surgery that pose challenges to these processes, and discuss possible alternate pathways to cardiac device evaluation and approval for children. Children deserve to benefit from new and refined cardiac devices and technology designed explicitly for their conditions.

Distributed source modeling of language with magnetoencephalography: application to patients with intractable epilepsy

PURPOSE

To examine distributed patterns of language processing in healthy controls and patients with epilepsy using magnetoencephalography (MEG), and to evaluate the concordance between laterality of distributed MEG sources and language laterality as determined by the intracarotid amobarbital procedure (IAP).

METHODS

MEG was performed in 10 healthy controls using an anatomically constrained, noise-normalized distributed source solution (dynamic statistical parametric map, dSPM). Distributed source modeling of language was then applied to eight patients with intractable epilepsy. Average source strengths within temporoparietal and frontal lobe regions of interest (ROIs) were calculated, and the laterality of activity within ROIs during discrete time windows was compared to results from the IAP.

RESULTS

In healthy controls, dSPM revealed activity in visual cortex bilaterally from approximately 80 to 120 ms in response to novel words and sensory control stimuli (i.e., false fonts). Activity then spread to fusiform cortex approximately 160-200 ms, and was dominated by left hemisphere activity in response to novel words. From approximately 240 to 450 ms, novel words produced activity that was left-lateralized in frontal and temporal lobe regions, including anterior and inferior temporal, temporal pole, and pars opercularis, as well as bilaterally in posterior superior temporal cortex. Analysis of patient data with dSPM demonstrated that from 350 to 450 ms, laterality of temporoparietal sources agreed with the IAP 75% of the time, whereas laterality of frontal MEG sources agreed with the IAP in all eight patients.

DISCUSSION

Our results reveal that dSPM can unveil the timing and spatial extent of language processes in patients with epilepsy and may enhance knowledge of language lateralization and localization for use in preoperative planning.

Source estimates for MEG/EEG visual evoked responses constrained by multiple, retinotopically-mapped stimulus locations

Studying the human visual system with high temporal resolution is a significant challenge due to the limitations of the available, noninvasive measurement tools. MEG and EEG provide the millisecond temporal resolution necessary for answering questions about intracortical communication involved in visual processing, but source estimation is ill-posed and unreliable when multiple; simultaneously active areas are located close together. To address this problem, we have developed a retinotopy-constrained source estimation method to calculate the time courses of activation in multiple visual areas. Source estimation was disambiguated by: (1) fixing MEG/EEG generator locations and orientations based on fMRI retinotopy and surface tessellations constructed from high-resolution MRI images; and (2) solving for many visual field locations simultaneously in MEG/EEG responses, assuming source current amplitudes to be constant or varying smoothly across the visual field. Because of these constraints on the solutions, estimated source waveforms become less sensitive to sensor noise or random errors in the specification of the retinotopic dipole models. We demonstrate the feasibility of this method and discuss future applications such as studying the timing of attentional modulation in individual visual areas.

Abdominal aortic pulsed wave Doppler patterns reliably reflect clinical severity in patients with coarctation of the aorta

OBJECTIVE

There are situations in which standard echocardiography does not adequately define the aortic arch. We sought to determine what additional information could be gained by analyzing abdominal aortic Doppler flows in coarctation.

DESIGN

Previously recorded echocardiographic data were reviewed in 70 controls and 248 patients with coarctation, including abdominal aortic values for pulsatility indices, pulse delay, and presence of early diastolic reversal. Ability of these variables to distinguish controls from coarctation patients and to assess coarctation severity was assessed.

RESULTS

Corrected maximum instantaneous gradient and all abdominal aortic flow variables were associated with severity of obstruction. Early diastolic reversal was universally absent in significant coarctation. Threshold values for other parameters associated with significant obstruction were: corrected pulse delay >or=3.4 msec(1/2), pulsatility index <2.0, and systolic to diastolic velocity ratio <3.6. A combined abdominal aortic "variable" (absence of early diastolic reversal and corrected pulse delay >or=2.8 msec(1/2)) was found to be the best predictor of clinical coarctation status (positive predictive value = 93%, negative predictive value = 88%).

CONCLUSIONS

In the absence of a ductus arteriosus, abdominal aortic Doppler parameters can reliably predict the presence of significant coarctation. When early diastolic reversal was present, obstruction was always absent. Lack of early diastolic reversal with a prolonged pulse delay was the best predictor of significant obstruction. Abdominal aortic Doppler evaluation should become a routine part of the evaluation of patients with known or suspected coarctation.

Alzheimer disease: quantitative structural neuroimaging for detection and prediction of clinical and structural changes in mild cognitive impairment

PURPOSE

To use structural magnetic resonance (MR) images to identify a pattern of regional atrophy characteristic of mild Alzheimer disease (AD) and to investigate whether presence of this pattern prospectively can aid prediction of 1-year clinical decline and increased structural loss in mild cognitive impairment (MCI).

MATERIALS AND METHODS

The study was conducted with institutional review board approval and compliance with HIPAA regulations. Written informed consent was obtained from each participant. High-throughput volumetric segmentation and cortical surface reconstruction methods were applied to MR images from 84 subjects with mild AD, 175 with MCI, and 139 healthy control (HC) subjects. Stepwise linear discriminant analysis was used to identify regions that best can aid discrimination of HC subjects from subjects with AD. A classifier trained on data from HC subjects and those with AD was applied to data from subjects with MCI to determine whether presence of phenotypic AD atrophy at baseline was predictive of clinical decline and structural loss.

RESULTS

Atrophy in mesial and lateral temporal, isthmus cingulate, and orbitofrontal areas aided discrimination of HC subjects from subjects with AD, with fully cross-validated sensitivity of 83% and specificity of 93%. Subjects with MCI who had phenotypic AD atrophy showed significantly greater 1-year clinical decline and structural loss than those who did not and were more likely to have progression to probable AD (annual progression rate of 29% for subjects with MCI who had AD atrophy vs 8% for those who did not).

CONCLUSION

Semiautomated, individually specific quantitative MR imaging methods can be used to identify a pattern of regional atrophy in MCI that is predictive of clinical decline. Such information may aid in prediction of patient prognosis and increase the efficiency of clinical trials.

Hybrid intraoperative pulmonary artery stent placement for congenital heart disease

Percutaneous branch pulmonary artery (PA) stenting can be challenging, especially in patients with stenosis of the right ventricular (RV) outflow tract or tortuous PA branches. In these cases, a hybrid procedure deploying PA stent(s) during cardiac surgery provides an alternative to relieve branch PA stenosis. The Mayo Clinic Congenital Cardiac surgical database was used to identify all patients having hybrid PA stent procedures. Retrospective analysis of clinical data, procedural details, and outcomes was performed. Between January 1997 and November 2006, 24 patients (15 females), median age 15 years (range 3 to 67 years), had hybrid PA stent procedures. A total of 27 stents were deployed. A left PA stent was placed in 13, right PA stent in 8; 3 patients had bilateral PA stents. Primary cardiac diagnoses were pulmonary atresia (9), tetralogy of Fallot (7), tricuspid atresia (2), and others (6). Maximum balloon diameters ranged from 8 to 16 mm (median = 12 mm). Concomitant surgical procedures performed were RV to PA conduit replacement or RV outflow tract reconstruction (14), pulmonary valve replacement (7), and others (3). Two procedures were performed following complications of percutaneous procedure. There were no deaths or PA damage. There were 2 cases of distal stent migration. Repeat stent dilations within 6 months were performed in 3 patients. In conclusion, hybrid PA stenting can play an important role in the management of congenital heart disease with complex branch PA anatomy. It also can be used as an emergency rescue procedure following complications of percutaneous transcatheter procedures, such as stent embolization. Hybrid procedures were safe and effective in most patients, although stent positioning remains critical. Intraoperative fluoroscopy and active suture fixation of the proximal stent may reduce the need for late reintervention.

Diffusion tensor imaging correlates of memory and language impairments in temporal lobe epilepsy

OBJECTIVE

To investigate the relationship between white matter tract integrity and language and memory performances in patients with temporal lobe epilepsy (TLE).

METHODS

Diffusion tensor imaging (DTI) was performed in 17 patients with TLE and 17 healthy controls. Fractional anisotropy (FA) and mean diffusivity (MD) were calculated for six fiber tracts (uncinate fasciculus [UF], arcuate fasciculus [AF], fornix [FORX], parahippocampal cingulum [PHC], inferior fronto-occipital fasciculus [IFOF], and corticospinal tract [CST]). Neuropsychological measures of memory and language were obtained and correlations were performed to evaluate the relationship between DTI and neuropsychological measures. Hierarchical regression was performed to determine unique contributions of each fiber tract to cognitive performances after controlling for age and hippocampal volume (HV).

RESULTS

Increases in MD of the left UF, PHC, and IFOF were associated with poorer verbal memory in TLE, as were bilateral increases in MD of the AF, and decreases in FA of the right AF. Increased MD of the AF and UF, and decreased FA of the AF, UF, and left IFOF were related to naming performances. No correlations were found between DTI measures and nonverbal memory or fluency in TLE. Regression analyses revealed that several fibers, including the AF, UF, and IFOF, independently predicted cognitive performances after controlling for HV.

CONCLUSIONS

The results suggest that structural compromise to multiple fiber tracts is associated with memory and language impairments in patients with temporal lobe epilepsy. Furthermore, we provide initial evidence that diffusion tensor imaging tractography may provide clinically unique information for predicting neuropsychological status in patients with epilepsy.

Subcortical and cerebellar atrophy in mesial temporal lobe epilepsy revealed by automatic segmentation

PURPOSE

To determine the validity and utility of using automated subcortical segmentation to identify atrophy of the hippocampus and other subcortical and cerebellar structures in patients with mesial temporal lobe epilepsy (MTLE).

METHODS

Volumetric MRIs were obtained on 21 patients with MTLE (11 right, 10 left) and 21 age- and gender-matched healthy controls. Labeling of subcortical and cerebellar structures was accomplished using automated reconstruction software (FreeSurfer). Multivariate analysis of covariance (MANCOVA) was used to explore group differences in intracranial-normalized, age-adjusted volumes and structural asymmetries. Step-wise discriminant function analysis was used to identify the linear combination of volumes that optimized classification of individual subjects.

RESULTS

Results revealed the expected reduction in hippocampal volume on the side ipsilateral to the seizure focus, as well as bilateral reductions in thalamic and cerebellar gray matter volume. Analysis of structural asymmetries revealed significant asymmetry in the hippocampus and putamen in patients compared to controls. The discriminant function analysis revealed that patients with right and left MTLE were best distinguished from one another using a combination of subcortical volumes that included the right and left hippocampus and left thalamus (91-100% correct classification using cross-validation).

DISCUSSION

Volumetric data obtained with automated segmentation of subcortical and cerebellar structures approximate data from previous studies based on manual tracings. Our data suggest that automated segmentation can provide a clinically useful means of evaluating the nature and extent of structural damage in patients with MTLE and may increase diagnostic classification of patients, especially when hippocampal atrophy is mild.

Double inlet left ventricle

Double inlet left ventricle is a common form of univentricular atrioventricular connection. The clinical presentation is varied depending on associated lesions and the arrangement of great arteries. Management generally involves staging toward the ultimate goal of Fontan palliation. With advances in noninvasive diagnosis, surgical and postoperative care outcomes have significantly improved in the past decade. Most patients with double inlet left ventricle can go to school, play recreationally, and are gainfully employed. Some patients continue to pose difficult and frustrating medical problems, including arrhythmias, ventricular failure, atrioventricular valve insufficiency, subaortic obstruction, protein-losing enteropathy, and plastic bronchitis.

Regional neocortical thinning in mesial temporal lobe epilepsy

PURPOSE

To determine the nature and extent of regional cortical thinning in patients with mesial temporal lobe epilepsy (MTLE).

METHODS

High-resolution volumetric MRIs were obtained on 21 patients with MTLE and 21 controls. Mean cortical thickness was measured within regions of interest and point-by-point across the neocortex using cortical reconstruction and parcellation software.

RESULTS

Bilateral thinning was observed within frontal and lateral temporal regions in MTLE patients relative to controls. The most striking finding was bilateral cortical thinning in the precentral gyrus and immediately adjacent paracentral region and pars opercularis of the inferior frontal gyrus, extending to the orbital region. Within the temporal lobe, bilateral thinning was observed in Heschl's gyrus only. Ipsilateral only thinning was observed in the superior and middle temporal gyri, as well as in the medial orbital cortex. Greater asymmetries in cortical thickness were observed in medial temporal cortex in patients relative to controls. Individual subject analyses revealed that this asymmetry reflected significant ipsilateral thinning of medial temporal cortex in 33% of patients, whereas it reflected ipsilateral thickening in 20% of MTLEs.

DISCUSSION

Patients with MTLE show widespread, bilateral pathology in neocortical regions that is not appreciated on standard imaging. Future studies are needed that elucidate the clinical implications of neocortical thinning in MTLE.

Intermediate follow-up following intravascular stenting for treatment of coarctation of the aorta

BACKGROUND

We report a multiinstitutional study on intermediate-term outcome of intravascular stenting for treatment of coarctation of the aorta using integrated arch imaging (IAI) techniques.

METHODS AND RESULTS

Medical records of 578 patients from 17 institutions were reviewed. A total of 588 procedures were performed between May 1989 and Aug 2005. About 27% (160/588) procedures were followed up by further IAI of their aorta (MRI/CT/repeat cardiac catheterization) after initial stent procedures. Abnormal imaging studies included: the presence of dissection or aneurysm formation, stent fracture, or the presence of reobstruction within the stent (instent restenosis or significant intimal build-up within the stent). Forty-one abnormal imaging studies were reported in the intermediate follow-up at median 12 months (0.5-92 months). Smaller postintervention of the aorta (CoA) diameter and an increased persistent systolic pressure gradient were associated with encountering abnormal follow-up imaging studies. Aortic wall abnormalities included dissections (n = 5) and aneurysm (n = 13). The risk of encountering aortic wall abnormalities increased with larger percent increase in CoA diameter poststent implant, increasing balloon/coarc ratio, and performing prestent angioplasty. Stent restenosis was observed in 5/6 parts encountering stent fracture and neointimal buildup (n = 16). Small CoA diameter poststent implant and increased poststent residual pressure gradient increased the likelihood of encountering instent restenosis at intermediate follow-up.

CONCLUSIONS

Abnormalities were observed at intermediate follow-up following IS placement for treatment of native and recurrent coarctation of the aorta. Not exceeding a balloon:coarctation ratio of 3.5 and avoidance of prestent angioplasty decreased the likelihood of encountering an abnormal follow-up imaging study in patients undergoing intravascular stent placement for the treatment of coarctation of the aorta. We recommend IAI for all patients undergoing IS placement for treatment of CoA.

Embolization of a pulmonary arterial pseudoaneurysm with endovascular coils

Unrecognized pseudoaneurysm or rupture of a pulmonary artery is a rare but potentially catastrophic complication of pulmonary arterial catheterization. Herein, we describe a teenage patient with a pulmonary arterial pseudoaneurysm, probably iatrogenic, who presented with haemoptysis following catheterization of the right heart. The pseudoaneurysm was successfully embolized using coils inserted by catheter. Increased awareness of this lesion, its rapid recognition, and prompt therapy are the keys to a successful outcome.

Human cortical representations for reaching: mirror neurons for execution, observation, and imagery

We used functional magnetic resonance imaging (fMRI) to map the cortical representations of executed reaching, observed reaching, and imagined reaching in humans. Whereas previous studies have mostly examined hand actions related to grasping, hand-object interactions, or local finger movements, here we were interested in reaching only (i.e. the transport phase of the hand to a particular location in space), without grasping. We hypothesized that mirror neuron areas specific to reaching-related representations would be active in all three conditions. An overlap between executed, observed, and imagined reaching activations was found in dorsal premotor cortex as well as in the superior parietal lobe and the intraparietal sulcus, in accord with our hypothesis. Activations for observed reaching were more dorsal than activations typically reported in the literature for observation of hand-object interactions (grasping). Our results suggest that the mirror neuron system is specific to the type of hand action performed, and that these fronto-parietal activations are a putative human homologue of the neural circuits underlying reaching in macaques. The parietal activations reported here for executed, imagined, and observed reaching are also consistent with previous functional imaging studies on planned reaching and delayed pointing movements, and extend the proposed localization of human reach-related brain areas to observation as well as imagery of reaching.

Procedural results and acute complications in stenting native and recurrent coarctation of the aorta in patients over 4 years of age: a multi-institutional study

BACKGROUND

We report a multi-institutional experience with intravascular stenting (IS) for treatment of coarctation of the aorta.

METHODS AND RESULTS

Data was collected retrospectively by review of medical records from 17 institutions. The data was broken down to prior to 2002 and after 2002 for further analysis. A total of 565 procedures were performed with a median age of 15 years (mean=18.1 years). Successful reduction in the post stent gradient (<20 mm Hg) or increase in post stent coarctation to descending aorta (DAo) ratio of >0.8 was achieved in 97.9% of procedures. There was significant improvement (P<0.01) in pre versus post stent coarctation dimensions (7.4 mm+/-3.0 mm vs. 14.3+/-3.2 mm), systolic gradient (31.6 mm Hg+/-16.0 mm Hg vs. 2.7 mm Hg+/-4.2 mm Hg) and ratio of the coarctation segment to the DAo (0.43+/-0.17 vs. 0.85+/-0.15). Acute complications were encountered in 81/565 (14.3%) procedures. There were two procedure related deaths. Aortic wall complications included: aneurysm formation (n=6), intimal tears (n=8), and dissections (n=9). The risk of aortic dissection increased significantly in patients over the age of 40 years. Technical complications included stent migration (n=28), and balloon rupture (n=13). Peripheral vascular complications included cerebral vascular accidents (CVA) (n=4), peripheral emboli (n=1), and significant access arterial injury (n=13). Older age was significantly associated with occurrence of CVAs. A significant decrease in the technical complication rate from 16.3% to 6.1% (P<0.001) was observed in procedures performed after January 2002.

CONCLUSIONS

Stent placement for coarctation of aorta is an effective treatment option, though it remains a technically challenging procedure. Technical and aortic complications have decreased over the past 3 years due to, in part, improvement in balloon and stent design. Improvement in our ability to assess aortic wall compliance is essential prior to placement of ISs in older patients with coarctation of the aorta.

A novel integrated MEG and EEG analysis method for dipolar sources

The ability of magnetoencephalography (MEG) to accurately localize neuronal currents and obtain tangential components of the source is largely due to MEG's insensitivity to the conductivity profile of the head tissues. However, MEG cannot reliably detect the radial component of the neuronal current. In contrast, the localization accuracy of electroencephalography (EEG) is not as good as MEG, but EEG can detect both the tangential and radial components of the source. In the present study, we investigated the conductivity dependence in a new approach that combines MEG and EEG to accurately obtain, not only the location and tangential components, but also the radial component of the source. In this approach, the source location and tangential components are obtained from MEG alone, and optimal conductivity values of the EEG model are estimated by best-fitting EEG signal, while precisely matching the tangential components of the source in EEG and MEG. Then, the radial components are obtained from EEG using the previously estimated optimal conductivity values. Computer simulations testing this integrated approach demonstrated two main findings. First, there are well-organized optimal combinations of the conductivity values that provide an accurate fit to the combined MEG and EEG data. Second, the radial component, in addition to the location and tangential components, can be obtained with high accuracy without needing to know the precise conductivity profile of the head. We then demonstrated that this new approach performed reliably in an analysis of the 20-ms component from human somatosensory responses elicited by electric median-nerve stimulation.

Results of transcatheter Fontan fenestration to treat protein losing enteropathy

Transcatheter fenestration to create an interatrial communication has been used to treat patients with protein losing enteropathy (PLE) after Fontan operation. No systematic data have been reported assessing the results of this procedure. Our institutional database was queried to identify patients after Fontan operation who had transcatheter fenestration to treat PLE. Clinical notes, laboratory data, echocardiograms, and cardiac catheterization data were reviewed. From 1995 to 2005, 16 transcatheter fenestration procedures were performed in seven patients. Median age at fenestration was 18 years (range 13-41 years). Median duration of follow-up was 3.6 years (range 0.2-10.4 years). Techniques for fenestration included blade/balloon septostomy, stent placement, Amplatzer-fenestrated ASD device, and balloon dilation of previous stent. Size of the fenestration created was 5.2 +/- 1.1 mm. Systemic venous pressure remained unchanged after fenestration. Cardiac index increased significantly. Reduction of ascites and edema was noted after 9 of the 16 procedures. Ten of 16 (63%) of fenestrations spontaneously occluded. Three patients are free of ascites although recurrence of PLE occurred in all. One patient with a patent fenestration continues to have ascites. Two patients had Fontan takedown. One patient had conversion to a fenestrated extracardiac conduit Fontan and died postoperatively. The results of transcatheter Fontan fenestration are often disappointing. Maintaining fenestration patency is difficult. Even after "successful" fenestration, resolution of PLE may be incomplete and recurrences have occurred in all. Early consideration should be given to Fontan takedown or cardiac transplant in severely symptomatic patients with PLE who do not respond to fenestration. Transcatheter fenestration may be a bridge to a definitive procedure.

Parietal and superior frontal visuospatial maps activated by pointing and saccades

A recent study from our laboratory demonstrated that parietal cortex contains a map of visual space related to saccades and spatial attention and identified this area as the likely human homologue of the lateral intraparietal (LIP). A human homologue for the parietal reach region (PRR), thought to preferentially encode planned hand movements, has also been recently proposed. Both of these areas, originally identified in the macaque monkey, have been shown to encode space with eye-centered coordinates. Functional magnetic resonance imaging (fMRI) of humans was used to test the hypothesis that the putative human PRR contains a retinotopic map recruited by finger pointing but not saccades and to test more generally for differences in the visuospatial maps recruited by pointing and saccades. We identified multiple maps in both posterior parietal cortex and superior frontal cortex recruited for eye and hand movements, including maps not observed in previous mapping studies. Pointing and saccade maps were generally consistent within single subjects. We have developed new group analysis methods for phase-encoded data, which revealed subtle differences between pointing and saccades, including hemispheric asymmetries, but we did not find evidence of pointing-specific maps of visual space.

Transcatheter closure of ischemic and post-traumatic ventricular septal ruptures

Post-traumatic ventricular septal defects (VSD) can occur after acute MI or iatrogenically after invasive surgical procedures. Emergency surgery is associated with high perioperative mortality and postsurgical shunt in up to 20% of patients. Transcatheter closure (TCC) of post MI VSD may be an alternative that avoids the high risk of surgery. We report a lower mortality and morbidity than surgical closure in the post infarction VSD's even with a short interval between defect occurrence and percutaneous device placement. Furthermore, in patients with a failed or suboptimal surgical result adjunctive percutaneous closure may be beneficial and offers an alternative to redo VSD repair. Finally, in patients who suffer an unexpected traumatic VSD post surgical procedure, percutaneous closure offers an alternative with excellent results.

Smoothing and cluster thresholding for cortical surface-based group analysis of fMRI data

Cortical surface-based analysis of fMRI data has proven to be a useful method with several advantages over 3-dimensional volumetric analyses. Many of the statistical methods used in 3D analyses can be adapted for use with surface-based analyses. Operating within the framework of the FreeSurfer software package, we have implemented a surface-based version of the cluster size exclusion method used for multiple comparisons correction. Furthermore, we have a developed a new method for generating regions of interest on the cortical surface using a sliding threshold of cluster exclusion followed by cluster growth. Cluster size limits for multiple probability thresholds were estimated using random field theory and validated with Monte Carlo simulation. A prerequisite of RFT or cluster size simulation is an estimate of the smoothness of the data. In order to estimate the intrinsic smoothness of group analysis statistics, independent of true activations, we conducted a group analysis of simulated noise data sets. Because smoothing on a cortical surface mesh is typically implemented using an iterative method, rather than directly applying a Gaussian blurring kernel, it is also necessary to determine the width of the equivalent Gaussian blurring kernel as a function of smoothing steps. Iterative smoothing has previously been modeled as continuous heat diffusion, providing a theoretical basis for predicting the equivalent kernel width, but the predictions of the model were not empirically tested. We generated an empirical heat diffusion kernel width function by performing surface-based smoothing simulations and found a large disparity between the expected and actual kernel widths.

Thrombosis after septal closure device placement: a review of the current literature

Thrombus formation has been described for all types of commercially available transcatheter septal occlusion devices. Most reports have been single-institution case studies. Screening for hypercoagulable conditions prior to device placement and anticoagulation after device deployment has been variable. The objective of this study was to synthesize the current experience with device thrombosis; the Medline database from 1980 until 2004 was searched. Seventeen articles identified 54 unique patients with device thrombosis. Thrombus developed on eight different types of transcatheter devices. All commercially available devices had at least one reported case of thrombosis. Patient mean age was 44.2 +/- 9.8 years. Thrombosis was diagnosed at a mean of 5 months after device deployment. Prior to device placement, 12 patients had normal coagulation evaluations and 5 had coagulopathies. For 37 patients, no mention was made in the report of coagulation studies. Prior to device thrombosis, 26 patients received aspirin and clopidogrel, 15 patients received aspirin alone, 8 received warfarin, 2 heparin alone, 1 aspirin and warfarin. One patient with hemophilia A received no anticoagulation and in one case treatment prior to thrombosis was not reported. After device thrombosis, 35 patients were treated with warfarin with thrombus resolution, 2 had successful lytic therapy, 1 was treated with heparin alone. Sixteen patients had surgical explantation of the device. Septal occlusion device thrombosis is rare. All types of commercially available devices have been associated with thrombosis. All patients should have early (< or = 3 months) echocardiographic surveillance for device thrombosis. Thorough coagulation evaluation is imperative prior to transcatheter device placement.

Right Ventricular Function in Asymptomatic Individuals with a Systemic Right Ventricle

BACKGROUND

In congenital heart defects where the morphologic right ventricle (RV) supports the systemic circulation, RV failure is common yet develops gradually. We hypothesized that patients who are asymptomatic may have unrecognized RV dysfunction.

METHODS

Conventional and Doppler tissue/strain echocardiography were performed on consecutive patients with asymptomatic systemic RV caused by congenitally corrected transposition of the great arteries (ccTGA) and on age-matched control subjects. RV index of myocardial performance was measured using conventional echocardiography. Longitudinal tissue velocities, strain rate, and strain of the basal RV free wall were measured using Doppler tissue/strain echocardiography and compared with nonsystemic RV of the control subjects.

RESULTS

Mean age was 39.5 +/- 14.6 (n = 13) and 36 +/- 24 (n = 10) years for ccTGA and control groups, respectively. Mean RV index of myocardial performance was higher in patients with ccTGA than in control subjects (0.66 +/- 0.25 vs 0.28 +/- 0.12, P < .001). Mean RV tissue displacement (10.8 +/- 4.5 vs 20.3 +/- 3.9 mm, P < .0001), peak systolic strain rate (-1.16 +/- 0.3 vs -2.23 +/- 0.9 s(-1), P = .005), and peak systolic strain (-17.3 +/- 8.0 vs -30.6 +/- 11.0%, P = .008) were significantly lower in patients with ccTGA compared with control subjects, respectively.

CONCLUSION

Patients with asymptomatic ccTGA have quantifiable RV dysfunction by echocardiography.

Paradoxical emboli in children and young adults: role of atrial septal defect and patent foramen ovale device closure

OBJECTIVE

To describe a multicenter experience with patent foramen ovale (PFO) and atrial septal defect (ASD) device closure for presumed paradoxical emboli in children and young adults (<35 years old).

PATIENTS AND METHODS

Medical records were reviewed of patients who had device closure of an ASD or PFO, who were younger than 35 years, and who had a history of presumed paradoxical embolus between January 1999 and August 2005 at Mayo Clinic, Rochester, Minn, University of Parma, Parma, Italy, and Loyola University Medical Center, Maywood, Ill.

RESULTS

Forty-five patients fulfilled the inclusion criteria. Median patient age was 29.0 years (range, 5.0-34.9 years), and 23 patients (51%) were male. Clinical diagnoses included the following: stroke, 30 (67%); transient ischemic attack, 13 (29%); myocardial infarction, 1 (2%); and renal infarct, 1 (2%). Overall, 42 patients (93%) had a PFO, and 3 (7%) had an ASD. Seventeen patients had known cardiovascular disease risk factors: tobacco use (10 patients), hypercoagulable states (7 patients), systemic hypertension (3 patients), and hyperilpidemia (2 patients). No major procedural complications occurred. Median follow-up evaluation was performed at 5.3 months (range, 2.5-40.0 months). Forty-four patients (98%) had no recurrent neurologic events and no residual atrial shunt by contrast transthoracic echocardiography.

CONCLUSIONS

Cryptogenic ischemic events occur in young patients and have serious sequelae. The potential for paradoxical embolization through a PFO or an ASD should be assessed in all such patients. In our short-term follow-up, device closure was a safe alternative therapeutic option for children and young adults with presumed paradoxical emboli.

Outpatient echocardiographic assessment of complex pulmonary outflow stenosis: Doppler mean gradient is superior to the maximum instantaneous gradient

Evaluation of pulmonary outflow obstruction has focused on maximum instantaneous gradient (MIG). However, experience suggests that outpatient Doppler MIG often overstates the degree of stenosis. In this study of 132 patients with complex pulmonary stenosis, the mean Doppler gradient showed superior correlation and agreement with invasive peak-to-peak gradient (PPG) (r = 0.91, bias = -6 mm Hg). Agreement between mean gradient and PPG remained excellent for patients with prosthetic conduits (bias = -4 mm Hg). When PPG was 50 mm Hg more, both mean Doppler gradient and MIG corrected for prevalve velocity provided reasonable estimates of PPG (bias = -13 and +17 mm Hg, respectively). Uncorrected MIG remained significantly greater than PPG (bias = +27 mm Hg). Outpatient MIG consistently overstated subsequent PPG. In unselected patients with conduits or with PPG of 50 mm Hg or less, mean Doppler gradient provided the best prediction of PPG. These data provide a strong argument for the routine use of mean gradients in complex pulmonary stenosis.

Isolated supravalvular pulmonary artery ridge in a 70-year-old man

Transthoracic echocardiography allows noninvasive assessment of the structure and function of the great vessels of the heart. We report a case of a 70-year-old man who had an isolated, mildly obstructive, supravalvular pulmonary artery ridge that was detected incidentally with transthoracic echocardiography. This report confirms the utility of transthoracic echocardiography in the detection of this condition and discusses quantification of this rare anomaly.

Double outlet right ventricle: opinions regarding management

In the current era of superb surgical results for congenital heart disease, several management options are available for patients born with double outlet right ventricle (DORV). The surgical repair of DORV is tailored to address the variety of abnormalities associated with this lesion. The treatment strategies are dependent upon the anatomy and relationship of the ventricular septal defect (VSD) and the great arteries. For patients with subaortic or doubly committed VSDs, without right ventricular outflow tract obstruction, the usual repair is an intraventricular tunnel from the VSD to the aorta. If right ventricular outflow tract obstruction exists, then augmentation of the right ventricular outflow tract or conduit placement from the right ventricle to the pulmonary artery is necessary. For the "Taussig-Bing anomaly" (subpulmonary VSD) an arterial switch operation is indicated with tunneling of the VSD to the neoaorta. For patients with a remote VSD, complex atrioventricular valve abnormalities, or unbalanced ventricles, a staged palliative approach is warranted. This approach will result in the patient having "single ventricle" physiology, and "Fontan anatomy" after the staging surgeries. Outcomes are determined by the surgery performed. Patients who require conduit placement from right ventricle to pulmonary artery will need subsequent surgery for replacement of the conduit. Complex intraventricular tunnels are at risk for developing subaortic obstruction. Patients who had arterial switch operations have thus far had excellent results. However, these patients may be at risk for development of neoaortic valve regurgitation requiring subsequent reoperation. Complex biventricular intracardiac repairs have been associated with a higher risk of reoperation. In the past 10 to 15 years, patients undergoing Fontan operations have had improved early and late survival. However, long-term problems after the Fontan operation include arrhythmia and development of protein-losing enteropathy.

Spatial maps in frontal and prefrontal cortex

Though the function of prefrontal cortex has been extensively investigated, little is known about the internal organization of individual prefrontal areas. Functional magnetic resonance imaging was used to show that some frontal and prefrontal cortical areas represent visual space in orderly, reproducible, topographic maps. The map-containing areas partly overlap dorsolateral prefrontal areas engaged by working memory tasks. These maps may be useful for attending to task-relevant objects at various spatial locations, an aspect of the executive control of attention.

Echocardiographic Assessment of Isolated Pulmonary Valve Stenosis: Which Outpatient Doppler Gradient Has the Most Clinical Validity?

Maximum instantaneous Doppler gradient has been the primary variable used to assess severity of pulmonary valve stenosis. However, recent observations suggest that outpatient maximum Doppler gradient often overstates clinical severity, as measured by catheter peak-to-peak gradient (PPG). This study sought to determine which outpatient Doppler gradient was most predictive of subsequently measured PPG. Ninety patients were included. Outpatient mean Doppler gradient showed the best correlation and agreement with the catheter PPG (r = 0.82, bias = -5 mm Hg). Maximum Doppler gradients, even when corrected for proximal velocity, consistently overestimated the PPG (bias = +21-26 mm Hg). Outpatient mean gradient was most predictive of subsequent PPG and should be used to determine whether to intervene for patients with isolated pulmonary valve stenosis. Use of only the maximum Doppler gradient to assess pulmonary valve stenosis will lead to a systematic overstatement of the severity of the stenosis.

Percutaneous closure of left ventricular-to-right atrial fistula after prosthetic mitral valve rereplacement using the Amplatzer duct occluder

A 70-year-old female with a history of rheumatic heart disease underwent rereplacement of mitral valve mechanical prosthesis in May 2003. Seven months later, she presented with progressive exertional dyspnea, exercise intolerance, and a new holosystolic/diastolic murmur. Echocardiography confirmed a large shunt through a fistula in the inferior limbus of the atrial septum with left ventricular-to-right atrial communication. We report the novel use of the Amplatzer duct occluder for closure of the fistulous tract.

Point-light biological motion perception activates human premotor cortex

Motion cues can be surprisingly powerful in defining objects and events. Specifically, a handful of point-lights attached to the joints of a human actor will evoke a vivid percept of action when the body is in motion. The perception of point-light biological motion activates posterior cortical areas of the brain. On the other hand, observation of others' actions is known to also evoke activity in motor and premotor areas in frontal cortex. In the present study, we investigated whether point-light biological motion animations would lead to activity in frontal cortex as well. We performed a human functional magnetic resonance imaging study on a high-field-strength magnet and used a number of methods to increase signal, as well as cortical surface-based analysis methods. Areas that responded selectively to point-light biological motion were found in lateral and inferior temporal cortex and in inferior frontal cortex. The robust responses we observed in frontal areas indicate that these stimuli can also recruit action observation networks, although they are very simplified and characterize actions by motion cues alone. The finding that even point-light animations evoke activity in frontal regions suggests that the motor system of the observer may be recruited to "fill in" these simplified displays.

Acute myocardial infarction in a child: possible pathogenic role of patent foramen ovale associated with heritable thrombophilia

We report an 8-year-old girl who presented with clinical features of an acute myocardial infarction. The angiographic appearance of the coronary arteries was normal. A thrombophilic state caused by a homozygote genotype for the prothrombin G20210A mutation was detected, and a patent foramen ovale (PFO) with right-to-left shunting after Valsalva maneuver was demonstrated by transesophageal contrast echocardiography. No other embolic source was identified. We suggest that paradoxical embolization through a PFO resulted in a myocardial infarction in this young patient with hereditary thrombophilia. We closed the patient's PFO with a 25-mm PFO occluder. She was anticoagulated with warfarin for 6 months. After 6 months, a contrast echocardiogram showed no evidence of residual atrial shunt. There has been no evident recurrent paradoxical embolization.

Patent foramen ovale in cryptogenic stroke: current understanding and management options

There is increasing interest in the association between patent foramen ovale (PFO) and documented stroke of unknown cause, commonly referred to as cryptogenic stroke. We reviewed the literature and, on the basis of the available data, designed a diagnostic and treatment algorithm for patients with PFO and cryptogenic stroke. Patent foramen ovale is relatively common in the general population, but its prevalence is higher in patients with cryptogenic stroke. Importantly, paradoxical embolism through a PFO should be strongly considered in young patients with cryptogenic stroke. There is no consensus on the optimal management strategy, but treatment options include antiplatelet agents, warfarin sodium, percutaneous device closure, and surgical closure. High-risk features in the patient's history (ie, temporal association between Valsalva-inducing maneuvers and stroke, coexisting hypercoagulable state, recurrent strokes, and PFO with large opening, large right-to-left shunt, or right-to-left shunting at rest, and a coexisting atrial septal aneurysm) should prompt PFO closure.

Intracardiac echocardiographic guidance during transcatheter device closure of atrial septal defect and patent foramen ovale

OBJECTIVES

To describe our experience with intracardiac echocardiographic (ICE) guidance during transcatheter device closure of atrial septal defect (ASD) and patent foramen ovale (PFO) and to describe a detailed stepwise approach for performing ICE examinations.

PATIENTS AND METHODS

We reviewed the ICE results of all patients who underwent transcatheter device closure of ASD/PFO at the Mayo Clinic in Rochester, Minn, between October 2000 and November 2002. Conscious sedation was used, and all ICE studies were performed using a diagnostic ultrasound catheter.

RESULTS

Ninety-four patients (47 male; median age, 51 years [range, 17-81 years]) underwent ICE during transcatheter device closure of ASD/PFO. Total procedure time was 128 minutes (range, 27-320 minutes). ICE identified a previously unrecognized anatomical diagnosis in 32 of 94 patients. An additional ASD or PFO was found in 16 patients; a redundant atrial septum or an atrial septal aneurysm was found in 12 patients. There were few ICE complications (4%): 3 patients developed atrial fibrillation, and 1 developed supraventricular tachycardia; of these 4, 2 resolved spontaneously, and 2 required cardioversion with no recurrence.

CONCLUSION

ICE provides anatomical detail of ASD/PFO and cardiac structures facilitating congenital cardiac interventional procedures. ICE eliminates major drawbacks related to the use of transesophageal echocardiographic guidance for transcatheter device closure of ASD/PFO, specifically problems related to airway management. Finally, ICE gives the interventional cardiologist the ability to control all aspects of imaging without relying on additional echocardiographic support. We believe that ICE should be considered the preferred imaging technique for guidance of transcatheter device closure of ASD/PFO in adults and larger pediatric patients.

Transcatheter Amplatzer device closure of atrial septal defect and patent foramen ovale in patients with presumed paradoxical embolism

OBJECTIVE

To review our experience with, and profile the safety and efficacy of, the Amplatzer PFO (patent foramen ovale) occluder (APO) and Amplatzer septal occluder (ASO) used to close PFO and/or atrial septal defect (ASD) in patients with paradoxical embolism (PE).

PATIENTS AND METHODS

Between April 1998 and November 2002, 103 patients at the Mayo Clinic in Rochester, Minn, and Scottsdale, Ariz, mean age 52.4 years, with presumed PE (transient ischemic attack [n=22], stroke [n=77], or peripheral emboli [n=4]) underwent transcatheter device closure of PFO (n=81), ASD (n=12), and ASD/PFO (n=10) with 106 devices (APO [n=22] or ASO [n=84]).

RESULTS

All devices deployed successfully, and no patients died. Procedural complications included atrial fibrillation (n=2), vessel injury (n=3), profound sinus node dysfunction (n=1), and device embolization with successful retrieval (n=1). At 3 months, 7 of 95 monitored patients had trivial residual shunt; at 12 months, 2 of 28 monitored patients had trivial residual shunt. Three patients had recurrent events--2 transient ischemic attacks and 1 retinal artery occlusion--at a mean +/- SD follow-up of 8.3 +/- 8.1 months (range, 1-34 months). None of these 3 patients had residual shunt or evidence of intracardiac thrombus. The average annual recurrence of all events was 3.6% at 23 months. The overall mean +/- SD freedom from recurrence of all events was 98.9% +/- 1.2% and 83.8% +/- 10.2% at 12 and 29 months of follow-up, respectively.

CONCLUSIONS

Transcatheter device closure of PFO and/or ASD with use of APO/ASO in patients with presumed PE is effective and safe. Recurrent events may occur in the absence of a residual shunt.