Patient-specific mitral leaflet segmentation from 4D ultrasound

Segmenting the mitral valve during closure and throughout a cardiac cycle from four dimensional ultrasound (4DUS) is important for creation and validation of mechanical models and for improved visualization and understanding of mitral valve behavior. Current methods of segmenting the valve from 4DUS either require extensive user interaction and initialization, do not maintain the valve geometry across a cardiac cycle, or are incapable of producing a detailed coaptation line and surface. We present a method of segmenting the mitral valve annulus and leaflets from 4DUS such that a detailed, patient-specific annulus and leaflets are tracked throughout mitral valve closure, resulting in a detailed coaptation region. The method requires only the selection of two frames from a sequence indicating the start and end of valve closure and a single point near a closed valve. The annulus and leaflets are first found through direct segmentation in the appropriate frames and then by tracking the known geometry to the remaining frames. We compared the automatically segmented meshes to expert manual tracings for both a normal and diseased mitral valve, and found an average difference of 0.59 +/- 0.49 mm, which is on the order of the spatial resolution of the ultrasound volumes (0.5-1.0 mm/voxel).

Validation of 3D echocardiographic assessment of left ventricular volumes, mass, and ejection fraction in neonates and infants with congenital heart disease: a comparison study with cardiac MRI

BACKGROUND

quantitative assessment and validation of left ventricular (LV) volumes and mass in neonates and infants with complex congenital heart disease (CHD) is important for clinical management but has not been undertaken. We compared matrix-array 3D echocardiography (3D echo) measurements of volumes, mass, and ejection fraction (EF) with those measured by cardiac MRI in young patients with CHD and small LVs because of either young age or LV hypoplasia.

METHODS AND RESULTS

thirty-five patients aged <4 years (median, 0.8 years) undergoing MRI were prospectively enrolled. Three-dimensional echo was acquired immediately after MRI, and volume, mass, and EF measurements, using summation of discs methodology, were compared with MRI. Three-dimensional echo end-diastolic volume (24.4±15.7 versus 24.8±46.4 mL; P=0.01; intraclass correlation coefficient [ICC], 0.96) and end-systolic volume (12.3±8.6 versus 9.6±6.8 mL; P<0.001; ICC, 0.90) correlated with MRI with small mean differences (-0.49 mL [P=0.6] and 2.7 mL [P=0.001], respectively). Three-dimensional echo EF was smaller than MRI by 9.3% (P<0.001), and 3D echo LV mass measurements were comparable to MRI (17.3±10.3 versus 17.6±12 g; P<0.77; ICC, 0.93), with a small mean difference (1.1 g; P=0.28). There was good intra- and interobserver reliability for all measurements.

CONCLUSIONS

in neonates and infants with CHD and small LVs (age appropriate or hypoplastic), matrix-array 3D echo measurements of mass and volumes compare well with MRI, providing an important modality for ventricular size and performance analysis in these patients, particularly in those with left-side heart obstructive lesions.

Mitral annulus segmentation from 3D ultrasound using graph cuts

The shape of the mitral valve annulus is used in diagnostic and modeling applications, yet methods to accurately and reproducibly delineate the annulus are limited. This paper presents a mitral annulus segmentation algorithm designed for closed mitral valves which locates the annulus in three-dimensional ultrasound using only a single user-specified point near the center of the valve. The algorithm first constructs a surface at the location of the thin leaflets, and then locates the annulus by finding where the thin leaflet tissue meets the thicker heart wall. The algorithm iterates until convergence metrics are satisfied, resulting in an operator-independent mitral annulus segmentation. The accuracy of the algorithm was assessed from both a diagnostic and surgical standpoint by comparing the algorithm's results to delineations made by a group of experts on clinical ultrasound images of the mitral valve, and to delineations made by an expert with a surgical view of the mitral annulus on excised porcine hearts using an electromagnetically tracked pointer. In the former study, the algorithm was statistically indistinguishable from the best performing expert (p=0.85) and had an average RMS difference of 1.81+/-0.78 mm to the expert average. In the latter, the average RMS difference between the algorithm's annulus and the electromagnetically tracked points across six hearts was 1.19+/-0.17 mm .

Real-Time Three-Dimensional Ultrasound for Guiding Surgical Tasks

OBJECTIVE

As a stand-alone imaging modality, two-dimensional (2D) ultrasound (US) can only guide basic interventional tasks due to the limited spatial orientation information contained in these images. High-resolution real-time three-dimensional (3D) US can potentially overcome this limitation, thereby expanding the applications for US-guided procedures to include intracardiac surgery and fetal surgery, while potentially improving results of solid organ interventions such as image-guided breast, liver or prostate procedures. The following study examines the benefits of real-time 3D US for performing both basic and complex image-guided surgical tasks.

MATERIALS AND METHODS

Seven surgical trainees performed three tasks in an acoustic testing tank simulating an image-guided surgical environment using 2D US, biplanar 2D US, and 3D US for guidance. Surgeon-controlled US imaging was also tested. The evaluation tasks were (1) bead-in-hole navigation; (2) bead-to-bead navigation; and (3) clip fixation. Performance measures included completion time, tool tip trajectory, and error rates, with endoscope-guided performance serving as a gold-standard reference measure for each subject.

RESULTS

Compared to 2D US guidance, completion times decreased significantly with 3D US for both bead-in-hole navigation (50%, p = 0.046) and bead-to-bead navigation (77%, p = 0.009). Furthermore, tool-tip tracking for bead-to-bead navigation demonstrated improved navigational accuracy using 3D US versus 2D US (46%, p = 0.040). Biplanar 2D imaging and surgeon-controlled 2D US did not significantly improve performance as compared to conventional 2D US. In real-time 3D mode, surgeon-controlled imaging and changes in 3D image presentation made by adjusting the perspective of the 3D image did not diminish performance. For clip fixation, completion times proved excessive with 2D US guidance (> 240 s). However, with real-time 3D US imaging, completion times and error rates were comparable to endoscope-guided performance.

CONCLUSIONS

Real-time 3D US can guide basic surgical tasks more efficiently and accurately than 2D US imaging. Real-time 3D US can also guide more complex surgical tasks which may prove useful for procedures where optical imaging is suboptimal, as in fetal surgery or intracardiac interventions.

Predictors of technical success and postnatal biventricular outcome after in utero aortic valvuloplasty for aortic stenosis with evolving hypoplastic left heart syndrome

BACKGROUND

Aortic stenosis in the midgestation fetus with a normal-sized or dilated left ventricle predictably progresses to hypoplastic left heart syndrome when associated with certain physiological findings. Prenatal balloon aortic valvuloplasty may improve left heart growth and function, possibly preventing evolution to hypoplastic left heart syndrome.

METHODS AND RESULTS

Between March 2000 and October 2008, 70 fetuses underwent attempted aortic valvuloplasty for critical aortic stenosis with evolving hypoplastic left heart syndrome. We analyzed this experience to determine factors associated with procedural and postnatal outcome. The median gestational age at intervention was 23 weeks. The procedure was technically successful in 52 fetuses (74%). Relative to 21 untreated comparison fetuses, subsequent prenatal growth of the aortic and mitral valves, but not the left ventricle, was improved after intervention. Nine pregnancies (13%) did not reach a viable term or preterm birth. Seventeen patients had a biventricular circulation postnatally, 15 from birth. Larger left heart structures and higher left ventricular pressure at the time of intervention were associated with biventricular outcome. A multivariable threshold scoring system was able to discriminate fetuses with a biventricular outcome with 100% sensitivity and modest positive predictive value.

CONCLUSIONS

Technically successful aortic valvuloplasty alters left heart valvar growth in fetuses with aortic stenosis and evolving hypoplastic left heart syndrome and, in a subset of cases, appeared to contribute to a biventricular outcome after birth. Fetal aortic valvuloplasty carries a risk of fetal demise. Fetuses undergoing in utero aortic valvuloplasty with an unfavorable multivariable threshold score at the time of intervention are very unlikely to achieve a biventricular circulation postnatally.

In utero valvuloplasty for pulmonary atresia with hypoplastic right ventricle: techniques and outcomes

BACKGROUND

Prenatal intervention for fetuses with pulmonary atresia with an intact ventricular septum (PA/IVS) has the potential to alter right heart physiologic features in utero, facilitating right heart growth and improving the prospect of a biventricular outcome after birth.

METHODS

Since 2002, we have considered prenatal intervention for fetal PA/IVS in patients with (1) membranous pulmonary atresia, with identifiable pulmonary valve (PV) leaflets or membrane; (2) an intact or highly restrictive ventricular septum; and (3) right heart hypoplasia, with a tricuspid valve annulus z score of -2 or below and an identifiable but small right ventricle. Intervention was performed through direct cardiac puncture under ultrasound guidance, with percutaneous access or access through a limited laparotomy.

RESULTS

Ten fetuses underwent attempted balloon dilation of the PV in utero. The first 4 procedures were technically unsuccessful, and the most-recent 6 were technically successful. Compared with control fetuses with PA/IVS who did not undergo prenatal intervention and had univentricular outcomes after birth, the tricuspid valve annulus, right ventricle length, and PV annulus grew significantly more from midgestation to late gestation in the 6 fetuses who underwent successful interventions.

CONCLUSIONS

In utero perforation and dilation of the PV in midgestation fetuses with PA/IVS is technically feasible and may be associated with improved right heart growth and postnatal outcomes for fetuses with moderate right heart hypoplasia in midgestation. There is an important learning curve for this procedure, and much remains to be learned about the selection of appropriate fetuses for prenatal intervention.

Effectiveness of balloon valvuloplasty for palliation of mitral stenosis after repair of atrioventricular canal defects

Closure of a mitral valve (MV) cleft, small left-sided cardiac structures, and ventricular imbalance all may contribute to mitral stenosis (MS) after repair of atrioventricular canal (AVC) defects. MV replacement is the traditional therapy but carries high risk in young children. The utility of balloon mitral valvuloplasty (BMV) in postoperative MS is not established and may offer alternative therapy or palliation. Since 1996, 10 patients with repaired AVC defects have undergone BMV at a median age of 2.5 years (range 8 months to 14 years), a median of 2 years after AVC repair. At catheterization, the median value of mean MS gradients was 16 mm Hg (range 12 to 22) and was reduced by 34% after BMV. Before BMV, there was mild mitral regurgitation in 9 of 10 patients, which increased to severe in 1 patient. All patients were alive at follow-up (median 5.4 years). Repeat BMV was performed in 4 patients, 10 weeks to 18 months after initial BMV. One patient underwent surgical valvuloplasty; 3 underwent MV replacement 2, 3, and 28 months after BMV. In the 6 patients (60%) with a native MV at most recent follow-up (median 3.2 years), the mean Doppler MS gradient was 9 mm Hg, the median weight had doubled, and weight percentile had increased significantly. In conclusion, BMV provides relief of MS in most patients with repaired AVC defects; marked increases in mitral regurgitation are uncommon. Because BMV can incompletely relieve obstruction and increase mitral regurgitation, it will not be definitive in most patients but will usually delay MV replacement to accommodate a larger prosthesis.

Usefulness of intra-operative epicardial three-dimensional echocardiography to guide aortic valve repair in children

The aim of this study was to determine the additional important information obtained on prebypass epicardial 3-dimensional imaging (E-3D) compared with transesophageal 2-dimensional echocardiography (TEE-2D) in young patients who undergoing aortic valve repair. From January 2004 to May 2007, all patients who underwent reconstructive surgery of the native aortic valve and intraoperative TEE-2D and E-3D were retrospectively reviewed. Thirteen structural anatomic variables of the aortic valve for TEE-2D and E-3D were evaluated, scored, and compared (by a blinded observer) with intraoperative surgical findings. Nineteen patients underwent valve repair. The median age at surgery was 10 years (range 1 day to 24 years). The primary aortic valve disease was regurgitation (n = 19), and 2 patients had additional valvar stenosis. TEE-2D and E-3D were able to detect 82% (n = 204) and 91% (n = 225), respectively, of the intraoperative findings (n = 247) (p = 0.006). Individual evaluation scores were higher for E-3D (median 12, interquartile range 11 to 13) than for TEE-2D (median 11, interquartile range 10 to 12) (p = 0.01) compared with surgical findings (score 13). Differences in detection sensitivity occurred for commissural fusion (n = 7), leaflet perforation or deficiency (n = 5), and leaflet prolapse (n = 2). TEE-2D was more likely to have false-negative findings than E-3D (36 vs 16 findings, p = 0.001). In conclusion, intraoperative E-3D provides additional important information over TEE-2D for aortic valve repair in young patients. Such 3-dimensional echocardiographic imaging has become an important intraoperative modality for valve repair at the investigators' institution.

Biventricular repair in patients with heterotaxy syndrome

OBJECTIVE

Complex intracardiac and extracardiac anatomy is often confronted during biventricular repair in patients with heterotaxy syndrome. We examined factors affecting surgical outcomes in these patients.

METHODS

Between January 1990 and July 2007, 371 patients received a diagnosis of heterotaxy syndrome; 91 (91/371, 24.5%) underwent biventricular repair. Left atrial isomerism was present in 73% (66/91) and right atrial isomerism in 10% (9/91), with indeterminate atrial anatomy in 17% (16/91). Median age at biventricular repair was 6.8 months (5 days to 22.3 years). Systemic venous anomalies were present in 75 patients, pulmonary venous anomalies in 26, and endocardial cushion defects in 36. Transposition complexes were present in 15 patients with atrioventricular discordance in 10; 8 underwent double switch, 2 received a physiologic repair, 2 underwent arterial switch, and 3 underwent the Rastelli operation. Other conotruncal anomalies included double-outlet right ventricle in 10 patients, tetralogy of Fallot in 3, and hemitruncus in 2. Separation of systemic from pulmonary venous return included intra-atrial baffling in 48 patients and extracardiac grafting in 2. Combined lesions were common, occurring in 99% (90/91). Statistical analysis with Kaplan-Meier and Cox proportional hazards models were performed.

RESULTS

Average follow-up was 44.9 +/- 57.5 months (3 days to 189.3 months). Kaplan-Meier estimated survival was 93.4% at 10 years; unbalanced complete atrioventricular canal was the only risk factor for mortality (P = .006). Subsequent procedures were common with a 10-year freedom from reoperation or reintervention of 38% +/- 7.5%. Arrhythmias occurred in 36 (39.6%) patients; bradyarrhythmia in 27 (29.7%) and tachyarrhythmia in 15 (16.5%). Freedom from any arrhythmia was 53.9% +/- 6.7% at 10 years.

CONCLUSIONS

Excellent survival for patients with heterotaxy undergoing biventricular repair can be expected, even for multiple, complex lesions. Reintervention is common, and arrhythmia is a long-term concern. This experience shows that patients with heterotaxy syndrome and complex cardiac anatomy can be considered for biventricular repair. Patients with unbalanced complete atrioventricular canal are a high-risk group for which selection criteria are particularly important.

Mitral Annulus Segmentation from Three-Dimensional Ultrasound

An accurate and reproducible segmentation of the mitral valve annulus from 3D ultrasound is useful to clinicians and researchers in applications such as pathology diagnosis and mitral valve modeling. Current segmentation methods, however, are based on 2D information, resulting in inaccuracies and a lack of spatial coherence. We present a segmentation algorithm which, given a single user-specified point near the center of the valve, uses max-flow and active contour methods to delineate the annulus geometry in 3D. Preliminary comparisons to manual segmentations and a sensitivity study show the algorithm is both accurate and robust.

Matrix-Array 3-Dimensional Echocardiographic Assessment of Volumes, Mass, and Ejection Fraction in Young Pediatric Patients With a Functional Single Ventricle

Background— Quantitative assessment of ventricular volumes and mass in pediatric patients with single-ventricle physiology would aid clinical management, but it is difficult to obtain with 2-dimensional echocardiography. The purpose of the present study was to compare matrix-array 3-dimensional echocardiography (3DE) measurements of single-ventricle volumes, mass, and ejection fraction with those measured by cardiac magnetic resonance (CMR) in young patients.

Methods and Results— Twenty-nine patients (median age, 7 months) with a functional single ventricle undergoing CMR under general anesthesia were prospectively enrolled. The 3DE images were acquired at the conclusion of the CMR. Twenty-seven of 29 3DE data sets (93%) were optimal for 3DE assessment. Two blinded and independent observers performed 3DE measurements of volume, mass, and ejection fraction. The 3DE end-diastolic volume correlated well ( r =0.96) but was smaller than CMR by 9% ( P <0.01), and 3DE ejection fraction was smaller than CMR by 11% ( P <0.01). There was no significant difference in measurements of end-systolic volume and mass. The 3DE interobserver differences for mass and volumes were not significant except for ejection fraction (8% difference; P <0.05). Intraobserver differences were not significant.

Conclusions— In young pediatric patients with a functional single ventricle, matrix-array 3DE measurements of mass and volumes compare well with those obtained by CMR. 3DE will provide an important modality for the serial analysis of ventricular size and performance in young patients with functional single ventricles.

Fast block flow tracking of atrial septal defects in 4D echocardiography

We are working to develop beating-heart atrial septal defect (ASD) closure techniques using real-time 3D ultrasound guidance. The major image processing challenges are the low-image quality and the processing of information at high-frame rate. This paper presents comparative results for ASD tracking in time sequences of 3D volumes of cardiac ultrasound. We introduce a block flow technique, which combines the velocity computation from optical flow for an entire block with template matching. Enforcing adapted similarity constraints to both the previous and first frames ensures optimal and unique solutions. We compare the performance of the proposed algorithm with that of block matching and region-based optical flow on eight in vivo 4D datasets acquired from porcine beating-heart procedures. Results show that our technique is more stable and has higher sensitivity than both optical flow and block matching in tracking ASDs. Computing velocity at the block level, our technique tracks ASD motion at 2 frames/s, much faster than optical flow and comparable in computation cost to block matching, and shows promise for real-time (30 frames/s). We report consistent results on clinical intra-operative images and retrieve the cardiac cycle (in ungated images) from error analysis. Quantitative results are evaluated on synthetic data with maximum tracking errors of 1 voxel.

Etiology, management, and outcome of pediatric pericardial effusions

The objective of this study was to determine the contemporary etiologies, treatment, and outcomes of moderate and large pericardial effusions in pediatric patients. We reviewed pediatric patients with moderate or large effusions diagnosed at Children's Hospital Boston. Effusion size was determined in offline review of echocardiograms. One hundred sixteen patients with moderate or large pericardial effusions were identified. The age range was 1 day to 17.8 years (median 8.6). The size of the pericardial effusions ranged from 0.5 to 4.7 cm (median 2.1). Neoplastic disease was present in 39% of patients, collagen vascular disease in 9%, renal disease in 8%, bacterial infection in 3%, and human immunodeficiency virus (HIV) in 2%; 37% were idiopathic. Pericardial drainage procedures were performed in 47 patients (41%). Of these, 29 (63%) had recurrent effusions leading to repeat drainage in 12 (41%). Pericardial effusions resolved within 3 months in 83% of patients who underwent drainage and in 91% of patients who did not. In summary, pediatric pericardial effusions were rarely caused by bacterial infections in this study population and were more frequently idiopathic or associated with neoplastic disease. Pericardial effusions often reaccumulated after drainage. The majority of both drained and undrained effusions resolved within 3 months.

Effect of pulmonary artery angioplasty on exercise function after repair of tetralogy of Fallot

BACKGROUND

The slope of the minute ventilation versus CO2 production relationship (VE/VCO2 slope) is an index of gas exchange efficiency during exercise. In patients with repaired tetralogy of Fallot (rTOF), it correlates negatively with exercise capacity and is one of the best predictors of peak oxygen consumption (VO2). In these patients, the magnitude of the VE/VCO2 slope is related to the severity of pulmonary blood flow maldistribution (PBFM). The purpose of this study was to determine whether, in patients with rTOF, improvements in PBFM after a successful balloon angioplasty procedure (BAP) result in improvements in peak VO2 and gas exchange during exercise.

METHODS

Seventeen patients with rTOF and residual pulmonary artery stenoses referred for BAP were recruited. Exercise tests were performed and PBFM determined before and after BAP.

RESULTS

Nine patients (group 1) had a successful BAP (ie, improvement of >5 percentage points in PBFM); 8 did not (group 2). Patients in group 1 had significantly greater improvements in VE/VCO2 slope, peak VO2, and peak oxygen pulse (an index of forward stroke volume at peak exercise) than did patients in group 2. A significant correlation existed between the improvement in PBFM and the decline in the VE/VCO2 slope (r = -0.70, P = .002). Changes in peak oxygen pulse accounted for 89% of the improvement in peak VO2.

CONCLUSIONS

In these patients, a successful BAP resulted in improved peak VO2 and more efficient gas exchange during exercise. The improvement in peak VO2 appeared to be mediated by an increase in forward stroke volume.

Real-time tracking and shape analysis of atrial septal defects in 3D echocardiography

RATIONALE AND OBJECTIVES

Real-time cardiac ultrasound (US) allows monitoring the heart motion during intracardiac beating heart procedures. Our application assists pediatric atrial septal defect (ASD) closure techniques using real-time 3D US guidance and rigid instruments. ASD tracking is also an important tool for facilitating systematic clinical studies of the dynamic behavior of the intra-atrial communication. One major image processing challenge is associated with the required processing of information at high frame rate, especially given the low image quality.

MATERIALS AND METHODS

We present an optimization scheme for a block flow technique, which combines the probability-based velocity computation for an entire block (a 3D volume centered on the ASD) with cyclic template matching. The adapted similarity imposes constraints both locally (from frame to frame) to conserve energy, and globally (from a reference template) to minimize cumulative errors. The algorithm is optimized for fast and reliable results. For tests, we use three intra-operational 4D ultrasound sequences of clinical infant beating hearts with ASD.

RESULTS

Computing velocity at the block level with an optimized scheme, our technique tracks ASD motion at a frequency of 60 frames/s on clinical 4D datasets. Results are stable and accurate for changes in resolution and block size. In particular, we show robust real-time tracking and preliminary segmentation results of the ASD shape, size and orientation as a function of time.

CONCLUSIONS

We present an optimized block flow technique for real-time tracking of ASD to assist in minimally invasive beating heart surgery. Our method proposes the standard use of references for processing repetitive data. This paper represents, to our knowledge, the first study on the dynamic morphology of ASD that takes into account the angular effect introduced by the slanted position of the intra-atrial communication with respect to the US probe.

Changes in left heart hemodynamics after technically successful in-utero aortic valvuloplasty

OBJECTIVE

Severe aortic stenosis in the mid-gestation fetus can progress to hypoplastic left heart syndrome (HLHS). @ In-utero aortic valvuloplasty is an innovative therapy to promote left ventricular growth and function and potentially to prevent HLHS. This study evaluated the effects of mid-gestation fetal balloon aortic valvuloplasty on subsequent fetal left ventricular function and left heart Doppler characteristics.

METHODS

We reviewed fetuses with aortic stenosis that underwent attempted in-utero aortic valvuloplasty between 2000 and 2006. Pre-intervention and the latest post-intervention fetal echocardiograms were analyzed to characterize changes in left heart function and Doppler characteristics in utero.

RESULTS

Forty-two fetuses underwent attempted aortic valvuloplasty during the study period, 12 of which were excluded from analysis secondary to inadequate follow-up data, termination or fetal demise. Study fetuses (n = 30) underwent pre-intervention echocardiography at a median gestational age of 23 weeks, and were followed for a median of 66 +/- 23 days post-intervention. In 26 fetuses, aortic valvuloplasty was technically successful. Among these 26, left heart physiology was abnormal pre-intervention and improved or normalized after intervention in most cases: biphasic mitral inflow was present in 5/25 (20%) cases pre-intervention and in 21/23 (91%) post-intervention (P < 0.001); moderate or severe mitral regurgitation was present in 14/26 (54%) cases pre-intervention and in 5/23 (22%) post-intervention (P = 0.02); bidirectional flow across the patent foramen ovale was present in 0/26 cases pre-intervention and in 6/25 (24%) post-intervention (P = 0.01); antegrade flow in the transverse arch was present in 0/25 cases pre-intervention and in 17/26 (65%) post-intervention (P < 0.001). The left ventricular ejection fraction increased from 19 +/- 10% pre-intervention to 39 +/- 14% post-intervention (P < 0.001). These changes were not observed in control fetuses (n = 18).

CONCLUSION

Fetal aortic valvuloplasty, when technically successful, improves left ventricular systolic function and left heart Doppler characteristics.

Three-Dimensional Echocardiography in Congenital Heart Disease

Matrix array technology has brought three-dimensional echocardiography into the clinical practice of cardiology. Arguably, this advancement is most notable in the field of pediatric cardiology. Full-volume acquisitions now can be undertaken in the youngest of infants with excellent image quality. This article illustrates the clinical application of three-dimensional echocardiography in congenital heart disease.

Variables Influencing the Accuracy of Right Ventricular Volume Assessment by Real-time 3-Dimensional Echocardiography: An In Vitro Validation Study

BACKGROUND

Preliminary experience with matrix-array real-time (RT) 3-dimensional echocardiography (3DE) in pediatric patients has demonstrated consistently lower right ventricular volume (RVV) compared with magnetic resonance imaging. Our hypothesis was that variables in RT 3DE acquisition and offline analysis, including gain settings, thickness, and orientation of disks, could alter RVV measurements.

METHODS

Displacements of water from latex models derived from excised lamb hearts were used for comparison. RT 3DE volume acquisitions were performed using a matrix-array probe (2-4 MHz); RVVs were calculated offline using summation of disks method.

RESULTS

No significant difference and excellent agreement was found for comparison of RT 3DE with displacement of water using 5-mm cut planes, optimal gain settings, and short-axis tracings. Different gain settings and long-axis tracings significantly affected RVV. A slice thickness of 13 mm or greater affected volume measurements.

CONCLUSIONS

RT 3DE can accurately measure RVV. Specific variables will alter volumes measurements and must be considered in clinical studies.

Coarctectomy reduces neoaortic arch obstruction in hypoplastic left heart syndrome

OBJECTIVE

Neoaortic arch obstruction after stage I palliation is an important risk factor affecting interstage mortality in patients with hypoplastic left heart syndrome, with no accepted standard surgical approach. We sought to determine the efficacy of different techniques for aortic arch reconstruction to reduce the incidence of postoperative neoaortic arch obstruction.

METHODS

From January 2000 through June 2005, 210 patients underwent stage I palliation. To enlarge the aortic arch, 12 (6%) patients had a direct connection, 115 (55%) patients had an aortic homograft, 53 (25%) patients had a pulmonary homograft patch, and 30 (14%) patients had autologous pericardium. Independent of the technique for aortic enlargement, 55 (26%) children had coarctectomy.

RESULTS

Eighty patients had a significant arch gradient, as determined by means of echocardiography, and of these, 50 required balloon angioplasty, surgical arch augmentation, or both. Preoperative aortic coarctation was consistently linked to neoaortic arch obstruction (P = .032). Patients having aortic arch enlargement by means of direct connection or with autologous pericardium were less likely to have neoaortic arch obstruction (P = .049). Coarctectomy resulted in a lower incidence of neoaortic arch obstruction, as determined by means of echocardiography (P = .015), or need for reintervention (P = .01).

CONCLUSIONS

Patients with hypoplastic left heart syndrome undergoing aortic arch enlargement with autologous tissue are less likely to require intervention for neoaortic arch obstruction compared with those having homograft patch reconstruction. Excision of all ductal tissue by means of coarctectomy reduces the risk of recurrent aortic arch obstruction. An aggressive approach to reconstruction of the arch and the use of autologous tissue at the time of stage I palliation is advocated.

Aortic Root Translocation Plus Arterial Switch for Transposition of the Great Arteries With Left Ventricular Outflow Tract Obstruction

OBJECTIVES

The goal of our study was to report our intermediate-term results with aortic root translocation plus arterial switch for d-transposition of the great arteries with left ventricular outflow tract obstruction.

BACKGROUND

A d-transposition of the great arteries with left ventricular outflow tract obstruction represents a difficult surgical problem. The Rastelli procedure is the usual approach to this condition. However, recurrent left ventricular outflow tract obstruction and early conduit obstruction as well as arrhythmias and troublesome late mortality are significant limitations.

METHODS

From 1993 to 2005, 11 children (8 male, 3 female) ages 1 month to 11 years (median age 7 months) have undergone aortic root autograft translocation plus arterial switch to correct d-transposition of the great arteries with left ventricular outflow tract obstruction. The native aortic root was excised from the right ventricle infundibulum and inserted into the left ventricular outflow, enlarging the outflow tract by resecting the outlet septum and an appropriate-size ventricular septal defect patch. After coronary artery reimplantation, right ventricular outflow reconstruction was achieved with a homograft.

RESULTS

There were no early or late deaths. With a median follow-up of 59 months (range 2 to 137 months), 5 patients required 6 conduit replacement procedures at a median time of 53 months. Two patients required an implantable defibrillator for ventricular arrhythmias. None of the patients have developed left ventricular outflow tract obstruction.

CONCLUSIONS

Aortic root autograft plus arterial switch procedure is a good option for the surgical management of infants and children with d-transposition of the great arteries and left ventricular outflow tract obstruction and results in a more anatomic repair compared with Rastelli operation. Intermediate-term results indicate good relief of left ventricular outflow tract obstruction and need for conduit replacement compares favorably with the Rastelli procedure for this lesion.

One-stage neonatal corrective repair for d-transposition of the great arteries and complete atrio-ventricular canal

Association of d-transposition of the great arteries and complete atrio-ventricular canal constitutes an uncommon and complex cardiac anomaly usually associated with poor prognosis. We report our experience on one-stage neonatal repair for d-transposition of the great arteries and complete atrio-ventricular canal. Between August 1997 and 2005, four patients (two males and two females) underwent anatomical correction for d-transposition of the great arteries and complete atrio-ventricular canal using an arterial switch procedure and two-patch repair. Mean age and weight at operation were 20 days (range from 3 to 28 days) and 3.2kg (range from 2.7 to 3.5kg), respectively. None of the patients received preoperative palliative procedure. Associated lesions were left outflow tract obstruction in three patients and multiple muscular ventricular septal defects in two patients. All four patients survived the operation. There was one in-hospitality death due to fungal sepsis. One patient required late re-operation for left ventricular outflow tract obstruction and left atrio-ventricular valve regurgitation. For a mean follow-up of 67 months (range from 51 to 90 months) all patients are asymptomatic and with no residual defects. Corrective repair of d-transposition of the great arteries and complete atrio-ventricular canal can be successfully achieved in this very challenging population during the neonatal period.

Determinants of Left Ventricular Dysfunction After Anatomic Repair of Congenitally Corrected Transposition of the Great Arteries

BACKGROUND

Early results for anatomic repair of congenitally corrected transposition of the great arteries are excellent with respect to right ventricular and tricuspid valve function. However, development of left ventricular (systemic ventricle) dysfunction late after repair remains a concern. In this study we sought to determine factors leading to late impairment in left ventricular performance.

METHODS

From August 1992 to July 2005, 44 patients (median age at surgery, 1.6 years; range, 0.6 to 39.6 years) with congenitally corrected transposition of the great arteries had anatomic repair. Left ventricular function and mitral regurgitation were evaluated by echocardiography at follow-up. Twenty-three patients had a Rastelli procedure, and 21 underwent an arterial switch. Twelve patients (27%) were pacemaker dependent at latest follow-up.

RESULTS

Early mortality was 4.5% (n = 2) with 1 late death as a result of leukemia. Median follow-up was 3.0 years (range, 7 days to 12.4 years). Left ventricular function remained unchanged (normal) in 35 patients, improved in 1 patient, and deteriorated in 8 patients (18%). Mitral regurgitation was unchanged in 30 patients, improved in 6 patients, and worsened in 8 patients (18%). Development of left ventricular dysfunction was significantly associated with pacemaker implantation (p = 0.005) and a widened QRS (>20% > 98% percentile of normal; p = 0.03).

CONCLUSIONS

Anatomic repair of congenitally corrected transposition can be performed with low operative mortality. However, late left ventricular dysfunction is not uncommon, with higher incidence in those requiring pacing and with a prolonged QRS. Resynchronization may be of value in patients requiring a pacemaker.

Three-dimensional echo and videocardioscopy-guided atrial septal defect closure

BACKGROUND

Current real-time three-dimensional echocardiography systems (RT3DE) can provide sufficient visualization to permit atrial septal defect (ASD) closure. However, detailed visualization of small objects inside the heart is still suboptimal because of limited resolution, which is a limitation for clinical application. We evaluate the complementary use of videocardioscopy in image-guided ASD closure.

METHODS

In a pig model (n = 5), a 4-mm to 8-mm ASD was created with RT3DE guidance. Defect closure was accomplished with a catheter-based patch-delivery system fixed around the defect with mini-anchors under combined RT3DE and videocardioscopy guidance. The endoscope was inserted into the heart through a custom built port designed to allow visualization in the presence of blood.

RESULTS

All ASDs were successfully closed. The combination of RT3DE and videocardioscopy allowed detailed visualization of intracardiac structures, instruments, patch, and mini-anchors.

CONCLUSIONS

Beating-heart ASD closure can be achieved with combined RT3DE and videocardioscopy imaging. Use of videocardioscopy provides high-resolution imaging and likely improves safety of the image-guided procedure.

Anatomy and echocardiography of discordant atrioventricular connections

The most appropriate way of describing the congenital cardiac malformations unified because the atrial chambers are joined across the atrioventricular junctions to morphologically inappropriate ventricles has long been contentious. In the past, the lesions have been described in such arcane terms as mixed levocardia,1 while “ventricular inversion” still retains it currency in some circles. As we will show in this review, the abnormal arrangements at the atrioventricular junctions can be found with various patterns, but most frequently the patients also have the arterial trunks arising from morphologically inappropriate ventricles. This combination is best described as congenitally corrected transposition, and will form the focus of our review. It is salutary to note that, when von Rokitansky gave the first description of this combination,2 one of his illustrations was ideally suited to aid the understanding of modern-day echocardiographers (Fig. 1). We hope to emulate von Rokitansky in our own review.

Fetal Aortic Valve Stenosis and the Evolution of Hypoplastic Left Heart Syndrome

Background— Fetal aortic valvuloplasty may prevent progression of aortic stenosis (AS) to hypoplastic left heart syndrome (HLHS). Predicting which fetuses with AS will develop HLHS is essential to optimize patient selection for fetal intervention. The aim of this study was to define echocardiographic features associated with progression of midgestation fetal AS to HLHS.

Methods and Results— Fetal echocardiograms were reviewed from 43 fetuses diagnosed with AS and normal left ventricular (LV) length at ≤30 weeks’ gestation. Of 23 live-born patients with available follow-up data, 17 had HLHS and 6 had a biventricular circulation. At the time of diagnosis, LV length, mitral valve, aortic valve, and ascending aortic diameter Z-scores did not differ between fetuses that ultimately developed HLHS and those that maintained a biventricular circulation postnatally. However, all of the fetuses that progressed to HLHS had retrograde flow in the transverse aortic arch (TAA), 88% had left-to-right flow across the foramen ovale, 91% had monophasic mitral inflow, and 94% had significant LV dysfunction. In contrast, all 6 fetuses with a biventricular circulation postnatally had antegrade flow in the TAA, biphasic mitral inflow, and normal LV function. With advancing gestation, growth arrest of left heart structures became evident in fetuses developing HLHS.

Conclusions— In midgestation fetuses with AS and normal LV length, reversed flow in the TAA and foramen ovale, monophasic mitral inflow, and LV dysfunction are predictive of progression to HLHS. These physiological features may help refine patient selection for fetal intervention to prevent the progression of AS to HLHS.

Echo-morphological correlates concerning the functionally univentricular heart in the setting of isomeric atrial appendages

It has long been known that the most complex combinations of cardiac malformations are those found in the setting of the so-called “splenic syndromes”.1 Many aspects of these syndromes have been controversial over recent years, not least the presence or absence of features of isomerism within the heart.2,3 Recent experience with genetic manipulation of mice, nonetheless, has now shown that it is possible to generate unequivocal evidence of cardiac isomerism, particularly in those animals which show features of right isomerism when the genes responsible for morphologically leftness are knocked out.4 Furthermore, when the crucial philosophical principle known as the “morphological method”5 is applied to the hearts of patients known to have visceral heterotaxy, it is equally clear that patients falling within these groups, when judged on the extent of the pectinate muscles relative to the atrioventricular junctions, exhibit isomerism of either the morphologically right or left atrial appendages.3

Three-dimensional echo-guided beating heart surgery without cardiopulmonary bypass: atrial septal defect closure in a swine model

OBJECTIVE

In this study, we tested 3 techniques of atrial septal defect closure under real-time 3-dimensional echocardiography guidance in a swine model.

METHODS

The operations were conducted under the sole guidance of a modified real-time 3-dimensional echocardiography guidance system with a x4 matrix transducer (Sonos 7500, Philips Medical Systems, Andover, Mass). Eighteen swine were anesthetized, and after median sternotomy, the echo probe was applied directly to the surface of the right atrium. To create an atrial septal defect, balloon atrial septostomy and atrial septal defect enlargement were performed. Subsequently, 3 different techniques of atrial septal defect closure were attempted: group I, direct suture closure; group II, closure of the atrial septal defect using the Amplatzer device (AGA Medical Corp, Golden Valley, Minn); and group III, patch closure of the atrial septal defect (n = 6 each).

RESULTS

Real-time 3-dimensional echocardiography guidance provided sufficient spatial resolution and a satisfactory frame rate to provide a "virtual surgeon's view" of the relevant anatomy during the entire procedure. All atrial septal defects were enlarged, and the mean final size was 8.5 +/- 1.8 mm. Atrial septal defect closure was successfully accomplished with all the 3 surgical techniques examined. In groups I and III, the needles (1-3 sutures) and staples (6-12 staples) penetrated the tissue and patch material consistently, whereas in group III, the Amplatzer atrial septal defect device was easily deployed. There was no incident device/staple embolization or air introduction. Neither intraoperative 2-dimensional color Doppler echocardiography nor postmortem macro-evaluation revealed any residual shunts.

CONCLUSIONS

Beating heart atrial septal defect closure under real-time 3-dimensional echocardiographic guidance is feasible and, unlike catheter-based devices, applicable for any type of secundum atrial septal defect.

Aortic valvuloplasty in the fetus: technical characteristics of successful balloon dilation

OBJECTIVES

To describe technical aspects of successful fetal aortic valvuloplasty, with particular attention to balloon size.

STUDY DESIGN

We retrospectively reviewed all procedural records and echocardiograms pertaining to 26 attempts at fetal aortic valve dilation performed at a single center over a period of 4 years. We assessed the effect of valvuloplasty as determined by echocardiographic appearance at the time of intervention and in follow-up.

RESULTS

In 20 of 26 fetuses who had technically successful aortic valve dilation (median balloon:annulus ratio=1.1), all had improved antegrade flow and 12 had at least mild regurgitation after dilation. Use of an oversized balloon was associated with the onset of moderate or severe aortic regurgitation, seen in 5 fetuses. This aortic regurgitation was well tolerated and improved through the remainder of gestation.

CONCLUSIONS

These data imply that fetal aortic valves can be dilated safely with larger balloons than are commonly used for postnatal dilation. The observation of spontaneous improvement in postdilation aortic regurgitation further suggests that fetal valve tissue behaves uniquely.

Balloon Dilation of Severe Aortic Stenosis in the Fetus

Background— Preventing the progression of fetal aortic stenosis (AS) to hypoplastic left heart syndrome (HLHS) requires identification of fetuses with salvageable left hearts who would progress to HLHS if left untreated, a successful in utero valvotomy, and demonstration that a successful valvotomy promotes left heart growth in utero. Fetuses meeting the first criterion are undefined, and previous reports of fetal AS dilation have not evaluated the impact of intervention on in utero growth of left heart structures.

Methods and Results— We offered fetal AS dilation to 24 mothers whose fetuses had AS. At least 3 echocardiographers assigned a high probability that all 24 fetuses would progress to HLHS if left untreated. Twenty (21 to 29 weeks’ gestation) underwent attempted AS dilation, with technical success in 14. Ideal fetal positioning for cannula puncture site and course of the needle (with or without laparotomy) proved to be necessary for procedural success. Serial fetal echocardiograms after intervention demonstrated growth arrest of the left heart structures in unsuccessful cases and in those who declined the procedure, while ongoing left heart growth was seen in successful cases. Resumed left heart growth led to a 2-ventricle circulation at birth in 3 babies.

Conclusions— Fetal echocardiography can identify midgestation fetuses with AS who are at high risk for developing HLHS. Timely and successful aortic valve dilation requires ideal fetal and cannula positioning, prevents left heart growth arrest, and may result in normal ventricular anatomy and function at birth.

Three-dimensional echocardiography–guided beating-heart surgery without cardiopulmonary bypass: A feasibility study

BACKGROUND

There is no current acceptable approach for intracardiac beating-heart interventions. We have adapted real-time 3-dimensional echocardiography with specialized instrumentation to facilitate beating-heart repair of atrial septal defects and mitral valve plasty to investigate the feasibility of real-time 3-dimensional echocardiography-guided cardiac surgery.

METHODS

In experiment I a modified real-time 3-dimensional echocardiography system with x4 matrix transducer was compared with 2-dimensional echocardiography in the performance of common surgical tasks. Completion times, deviation from an ideal trajectory, and an echogenic target were measured. In experiment II porcine atrial septal defects were closed with an original semiautomatic suturing device (n = 4) and with a 5-mm endoscopic stapler and a pericardial or polytetrafluoroethylene patch (n = 4). In experiment III a pulsatile porcine mitral valve model was developed, and suture placement through the anterior and posterior mitral leaflets was performed (n = 8). During all experiments, the operator was blinded to the target and operated on only with ultrasonic guidance.

RESULTS

In experiment I, compared with 2-dimensional echocardiographic guidance, completion times improved by 21% ( P <.01) with high-trajectory accuracy, and suture deviation was significantly smaller (2-dimensional echocardiography, 5.4 +/- 2.7 mm; 3-dimensional echocardiography, 1.7 +/- 0.7 mm; P <.05) in real-time 3-dimensional echocardiography-guided tasks. In experiments II and III in both atrial septal defect closure and mitral valve plasty, real-time 3-dimensional echocardiography provided satisfactory images and sufficient anatomic detail for suturing and patch deployment. All surgical tasks were successfully performed with accuracy.

CONCLUSIONS

Real-time 3-dimensional echocardiography provides adequate imaging and anatomic detail to act as a sole guide for surgical task performance. These initial experiments demonstrate the feasibility of beating-heart direct or patch closure of atrial septal defects and mitral valve plasty without cardiopulmonary bypass.

Three-dimensional echocardiography–guided atrial septectomy: An experimental study

OBJECTIVES

The surgical feasibility of beating-heart atrial septectomy under the guidance of two different types of real-time 3-dimensional echocardiography systems was examined.

METHODS

A modified real-time 3-dimensional echocardiography system with a x4 matrix transducer (Sonos 7500; Philips Medical Systems, Andover, Mass) or a mechanical 1-dimensional array transducer (SSD-5500; Aloka Co, Ltd, Tokyo, Japan) was used. Small porcine atrial septal defects (n = 8) were enlarged with a Kerrison bone punch in the tank model. In the animal studies, small atrial septal defects (n = 8) were enlarged with the same device through a transatrial port. In both experiments, the area of the atrial septal defect measured by real-time 3-dimensional echocardiography was compared with the area measured directly.

RESULTS

Real-time 3-dimensional echocardiography provided satisfactory images and sufficient anatomic detail for the atrial septectomy in both experimental settings. All the atrial septal defects were successfully enlarged; an increase of as much as 293% of the preoperative atrial septal defect area was achieved in the tank experiment, and an increase of as great as 449% of the preoperative area was achieved in the animal experiment. The size of the atrial shunt was increased significantly after the atrial septectomy relative to that before the surgery (P <.0001). The percentage enlargement of the atrial septal defect measured by real-time 3-dimensional echocardiography was strongly correlated with that measured directly (both r(2) = 0.997, P <.0001) Bland-Altman analysis showed close agreement between the results obtained by the two measurement methods in both models.

CONCLUSIONS

Real-time 3-dimensional echocardiography provides satisfactory images and sufficient anatomic detail for atrial septectomy. This experiment demonstrates the surgical feasibility of a beating-heart intracardiac procedure such as atrial septectomy under real-time 3-dimensional echocardiographic guidance.

Respiratory symptoms secondary to aortopulmonary collateral vessels in tetralogy of Fallot absent pulmonary valve syndrome

Hemodynamically significant systemic-to-pulmonary artery collaterals may represent an underappreciated cause of cardiorespiratory compromise in tetralogy of Fallot with absent pulmonary valve (TOF/APV). We retrospectively reviewed the angiographic, magnetic resonance imaging, operative, and autopsy reports of the 50 patients with TOF/APV managed at our institution in the past 10 years and demonstrated that at least 7 of 50 patients (14%) had significant aortopulmonary collaterals.

Tissue velocity Doppler assessment of atrial and ventricular electromechanical coupling and atrioventricular time intervals in normal subjects

Mechanical events and electromechanical coupling are analyzed simultaneously in the atria and ventricles using tissue velocity imaging. Normal values for these parameters are provided.

Application of robotics in congenital cardiac surgery

Over the past 5 years, robotic systems that combine advanced endoscopic imaging with computer-enhanced instrument control have been used for both coronary revascularization and intracardiac procedures in adults. In addition, endoscope positioning systems and articulated instruments with a robotic wrist mechanism have further expanded the potential applications for robotics in cardiac surgery. In pediatric cardiac surgery, potential applications can be divided into simple scope manipulation versus the use of 3-dimensional imaging and a robotic wrist for dissection and reconstruction. A voice-controlled robotic arm for scope manipulation can facilitate current pediatric thoracoscopic procedures such as ligation of patent ductus arteriosus and division of vascular rings. By using an advanced imaging system along with a robotic wrist, more complex extracardiac and even intracardiac procedures can be performed in children. Examples include coarctation repair, septal defect repair, and mitral or tricuspid valvuloplasty. Furthermore, with adequate intracardiac imaging, a robot-assisted off-pump approach to intracardiac pathology is conceivable. New real-time 3-dimensional echocardiography now offers sufficient resolution to enable such procedures, while the addition of instrument tracking, haptic feedback, and novel tissue fixation devices can facilitate safe and reliable intracardiac repair without extracorporeal circulation.

Three-dimensional echocardiography in congenital heart disease: a continuum of unfulfilled promises? No. A presently clinically applicable technology with an important future? Yes

Three-dimensional echocardiography has important clinical applications to congenital heart disease. Such applications include assessment of ventricular volumes, and unique imaging planes and projections of septae and atrio-ventricular and semi-lunar valves. Advances in ultrasound and computer technology will improve the process of three-dimensional echocardiography to continue to bring it to everyday clinical utility application.

Three-dimensional echocardiography of the atrial septum

This article details the important contribution of three-dimensional echocardiography for catheterization device closure of secundum atrial septal defects. Aspects presented include three-dimensional echocardiographic application in preselection of patients and in selection of the type and size of the atrial septal occluder devices. Unique three-dimensional echocardiographic imaging planes are shown that depict the size and shape of the defect, the important rim tissue surrounding the defect, and the images that demonstrate successful device placement. Details of the acquisition phase, digital reformatting, and the eventual rendering of standard three-dimensional echocardiographic imaging planes of the atrial septum are shown. Three-dimensional echocardiography not only provides important additional information, but also enhances understanding of standard two-dimensional studies.

Valve-sparing operation for balloon-induced aortic regurgitation in congenital aortic stenosis

OBJECTIVE

Aortic regurgitation after balloon dilation of congenital aortic stenosis may be treated with valve repair as an alternative to replacement.

METHODS

Charts and echocardiograms of all patients undergoing aortic valve operations after balloon dilation of congenital aortic stenosis at our institution between January 1988 and December 1999 were reviewed.

RESULTS

Twenty-one patients underwent valvuloplasty for predominant aortic regurgitation 9 months to 15 years (mean, 6.1 years) after balloon dilation. The mean +/- SD age at the time of the operation was 11 +/- 7 years. Aortic regurgitation was caused by a combination of commissural avulsion (10), cusp dehiscence with retraction (9), cusp tear (5), central incompetence (2), perforated cusp (1), or cusp adhesion to the aortic wall (1). Repair techniques included commissural reconstruction with a pericardial patch (8), pericardial patch cusp augmentation (6), primary suture repair (6), raphae release and debridement (4), commissurotomy (4), commissural resuspension with sutures (3), and cusp release (1). There were no deaths. At a mean follow-up of 30.1 months (range, 9 months-8 years), all patients were asymptomatic, and the grade of aortic regurgitation had been significantly reduced (P <.001). Left ventricular end-diastolic dimension z scores and proximal regurgitant jet/aortic anulus diameter ratios were significantly reduced (P <.001) and remained so over time. Freedom from reoperation for late failure was 100%, and overall freedom from reintervention was 80% at 3 years.

CONCLUSION

Aortic valve repair for balloon-induced aortic regurgitation is reproducible and durable at medium-term follow-up.

Three-dimensional echocardiographic measurement of left ventricular stroke volume in children: comparison with Doppler method

Three-dimensional echocardiography (3DE) allows calculation of ventricular volumes without geometric assumption on the ventricular shape. Our aim was to apply 3DE in a normal pediatric population and to compare the left ventricular stroke volume measurements to the Doppler method. Twenty-four normal patients (median age 7 years) underwent Doppler echocardiography and 3DE for left ventricular stroke volume calculation. The left ventricular stroke volume by Doppler method was calculated as the product of the aortic Doppler flow mean velocity and the area of the aortic annulus. The 3DE method was performed using a transthoracic rotational probe (TomTec) and left ventricular volumes were calculated using the Simpson's rule. The mean time for 3DE acquisition was 90 seconds without any sedation. 3DE correlated well with the Doppler method for left ventricular stroke volume measurements (y = 0.8x - 0.2, r = 0.94). The mean difference between the average values of left ventricular stroke volume obtained by Doppler method and 3DE was 5 +/- 4 ml. Intraobserver and interobserver variabilities in the left ventricular stroke volume measurement by 3DE were 2.6% and 4.4%. In conclusion, 3DE compared to the Doppler method is an accurate, noninvasive, and reproducible method to measure the left ventricular stroke volume in normal children.

Echocardiographic characteristics of successful deployment of the Das AngelWings atrial septal defect closure device: initial multicenter experience in the United States

The AngelWings device is a newer transcatheter device used for closure of secundum atrial septal defects (ASD) and patent foramen ovale (PFO), which consists of a self-centering, 2-disk system. Transesophageal echocardiography (TEE) plays a pivotal role in the deployment of the 2 disks of this device, on the appropriate sides of the atrial septum. The objective of this study is to describe the echocardiographic findings associated with successful deployment of the AngelWings device for closure of ASD and PFO. We evaluated the TEE studies of 70 patients enrolled in 4 United States centers, for closure of ASD and PFO with the AngelWings device. The TEE characteristics of successful and unsuccessful deployments were analyzed. Residual shunts across the atrial septum were assessed by TEE at the end of the procedure, 24 hours later by transthoracic echocardiography, and at 6 months by TEE. The deployment of the device was successful in 65 patients (93%). In the unsuccessful group, ASD size by TEE was larger (13.4 +/- 3.1 vs 8.9 +/- 4.7 mm, p <0.05). TEE was successful in identifying snagging of the device by intracardiac structures and prolapse of corners of the left or right atrial disk through the ASD, features that were difficult to identify by fluoroscopy. The echocardiographic characteristics outlined here are important guidelines for successful deployment of the AngelWings device.

Cardiac dysfunction in twin-twin transfusion syndrome: a prospective, longitudinal study

OBJECTIVE

To use serial echocardiography to evaluate prospectively the cardiac dysfunction in twin-twin transfusion syndrome and determine its clinical course and outcome.

METHODS

Twin pregnancies presenting in the second trimester with sonographic evidence of twin-twin transfusion syndrome were managed with therapeutic reduction amniocenteses. Gestational age at diagnosis and delivery, number of amniocenteses performed, volume of amniotic fluid withdrawn, placentation, birth weight, hemoglobin at delivery, and perinatal outcome were recorded. Serial fetal echocardiography was carried out in a single tertiary center. Echocardiographic assessments included cardiac anatomy, chamber size, cardiothoracic ratio, interventricular septal thickness, ventricular systolic function, and the presence and severity of atrioventricular valve regurgitation. Postnatal echocardiograms were obtained on the surviving twins.

RESULTS

Twelve cases of twin-twin transfusion syndrome were evaluated with serial echocardiography. Evidence of cardiac dysfunction was present prenatally in 10 recipient twins. All of the donor twins had normal fetal echocardiographic assessments. The most common abnormalities detected prenatally in recipient twins were decreased ventricular function, tricuspid regurgitation, and cardiac chamber enlargement. A deterioration of cardiac function was observed in seven recipient twins with increasing gestational age. Four of the eight surviving recipient twins had persistent postnatal echocardiographic abnormalities on follow-up examinations after the first 28 days of life.

CONCLUSION

Prenatal cardiac dysfunction is common in recipient twins and can be transient, progressive, or persistent beyond the neonatal period.

Transoesophageal echocardiography during scoliosis repair: comparison with CVP monitoring

PURPOSE

Accurate haemodynamic assessment during surgical repair of scoliosis is crucial to the care of the patient. The purpose of this study was to compare transoesophageal echocardiography (TEE) with central venous pressure monitoring in patients with spinal deformities requiring surgery in the prone position.

METHODS

Twelve paediatric patients undergoing corrective spinal surgery for scoliosis/kyphosis in the prone position were studied. Monitoring included TEE, intra-arterial and central venous pressure monitoring (CVP). Haemodynamic assessment was performed prior to and immediately after positioning the patient prone on the Relton-Hall table. Data consisted of mean arterial blood pressure (mBP), heart rate (HR), CVP, left ventricular end-systolic and end-diastolic diameters (LVESD and LVEDD respectively) and fractional shortening (FS). Right ventricular (RV) function and tricuspid regurgitation (TR) were assessed qualitatively. Analysis was performed using descriptive statistics, Student's t test, sign rank, and correlation analysis.

RESULTS

There was an increase in CVP (8.7 mmHg to 17.7 mmHg; P < .01), and decreases in LVEDD (37.1 mm to 33.2 mm; P < .05), and mean blood pressure (75.0 mmHg to 65.7 mmHg; P < .05) when patients were placed in the prone position. Fractional shortening, LVESD, and HR did not change from the supine to the prone position. Right ventricular systolic function and tricuspid regurgitation were unchanged.

CONCLUSION

These data indicate that the CVP is a misleading monitor of cardiac volume in patients with kyphosis/scoliosis in the prone position. This is consistent with previous studies. In this clinical situation, TEE may be a more useful monitoring tool to assess on-line ventricular size and function.

New insights and observations in three-dimensional echocardiographic visualization of ventricular septal defects: experimental and clinical studies

BACKGROUND

The positions, sizes, and shapes of ventricular septal defects (VSDs) can be difficult to assess by 2-dimensional echocardiography (2DE). Volume-rendered 3-dimensional echocardiography (3DE) can provide unique views of VSDs from the left ventricular (LV) side, allowing complete assessment of their circumference and spatial orientations to other anatomic structures.

METHODS AND RESULTS

Seventeen experimentally created defects of various locations, sizes, and shapes were imaged and reconstructed in 9 explanted porcine hearts. From an en face projection, major and minor axis diameters of the defects were measured, and these data were compared with direct anatomic measurements. Optimal reconstructions of the VSDs were obtained in all heart specimens, accurately depicting their positions and shapes. The correlations between 3DE and anatomy for the VSD major and minor axis diameters were y=1.0x+0.3 (r=0.88, P<0.001) and y=1.0x-1.4 (r =0.89, P<0.001), respectively. Good agreement between the 2 methods was demonstrated for all measurements. Our experience from the in vitro model was then applied to patient studies. Optimal LV en face reconstructions were obtained in 45 of 51 patients, permitting detailed assessment of the positions, sizes, and shapes of the VSDs. In the 25 patients with comparative surgical measurements, the correlations between 3DE and surgery for the VSD major and minor axis diameters were y =0. 81x+2.1 (r=0.92, P<0.001) and y=0.73x+2.0 (r=0.91, P<0.001), respectively. Good agreement was demonstrated between measurements made by 3DE and those obtained at surgery.

CONCLUSIONS

3DE provides excellent visualization of various types of VSDs. From an LV en face projection, the positions, sizes, and shapes of VSDs can be accurately determined. Such precise imaging will be beneficial for surgical and catheter-based closure of difficult perimembranous and singular or multiple muscular VSDs.

MRI and echocardiography in children: how do they compare?

Clearly, both echocardiography and MRI play vital roles in the diagnosis and management of children with congenital heart defects. 2-D Doppler echocardiography is very easy to use in a vast array of clinical situations. The accuracy of the anatomic and hemodynamic findings are well accepted. In comparative studies, 2-D Doppler echocardiography appears preferable for intracardiac anatomy, whereas MRI appears preferable for extracardiac anatomy. In certain patients, Doppler echocardiography may not be able to optimally obtain the anatomic or hemodynamic information, and MRI should be used in these particular cases.

Effect of pulmonary artery stenoses on the cardiopulmonary response to exercise following repair of tetralogy of Fallot

Data from exercise tests, echocardiograms, and lung perfusion scans were analyzed to determine whether the excessive minute ventilation (VE) often encountered among patients with tetralogy of Fallot is due to ventilation-perfusion mismatch secondary to branch pulmonary artery stenoses. Patients with branch PA stenoses had lower peak oxygen consumptions and higher VE during exercise than did patients without stenoses, and a strong correlation existed between the degree of pulmonary blood flow maldistribution on lung perfusion scan and the amount of excessive VE during exercise.

Transcoronary ethanol ablation of the atrioventricular node in a young patient with tricuspid atresia

Catheter ablation of AV conduction with radiofrequency energy can be challenging in the presence of structural abnormalities of the AV junction, either congenitally or after reconstructive surgery. We used transcoronary ethanol to ablate the AV node in a patient with classic tricuspid atresia and refractory intraatrial reentry tachycardia. This approach provides an alternative means of creating complete heart block with catheter-based techniques, when radiofrequency catheter ablation is technically impossible or ineffective.