The Hyperattenuating Crescent Sign Is Not Necessarily a Sign of Impending Aortic Aneurysm Rupture.

BACKGROUND: The "crescent sign" is a hyperattenuating crescent-shaped region on CT within the mural thrombus or wall of an aortic aneurysm. Although it has previously been associated with aneurysm instability or impending rupture, the literature is largely based on retrospective analyses of urgently repaired aneurysms. We strove to more rigorously assess the association between an isolated "crescent sign" and risk of impending aortic rupture. METHODS: Patients were identified by querying a single health system PACS database for radiology reports noting a crescent sign. Adult patients with a CT demonstrating a descending thoracic, thoracoabdominal, or abdominal aortic aneurysm and "crescent sign" between 2004 and 2019 were included, with exclusion of those showing definitive signs of aortic rupture on imaging. RESULTS: A total of 82 patients were identified. Aneurysm size was 7.1 ± 2.0 cm. Thirty patients had emergent or urgent repairs during their index admission (37%), 19 had elective repairs at a later date (23%), and 33 patients had no intervention due to either patient choice or prohibitive medical comorbidities (40%). Patients without intervention had a median follow up of 275 days before death or loss to follow up. In patients undergoing elective intervention, 6,968 patient-days elapsed between presentation and repair, with zero episodes of acute rupture (median 105 days). Patients undergoing elective repair had smaller aneurysms compared to those who underwent emergent/urgent repair (6.2 ± 1.3 vs. 7.7 ± 2.1 cm, P = 0.008). No surgical candidate with an aneurysm smaller than 8 cm ruptured. There were 31 patients with previous axial imaging within 2 years prior to presentation with a "crescent sign," with mean aneurysm growth rate of 0.85 ± 0.62 cm per 6 months [median 0.65, range 0-2.6]. Those with aneurysms sized below 5.5 cm displayed decreased aneurysm growth compared to patients with aneurysm's sized 5.5-6.5 cm or patients with aneurysms greater than 6.5 cm (0.12 vs. 0.64 vs. 1.16 cm per 6 months, P= 0.002). CONCLUSIONS: The finding of an isolated radiographic "crescent sign" without other signs of definitive aortic rupture (i.e., hemothorax, aortic wall disruption, retroperitoneal bleeding) is not necessarily an indicator of impending aortic rupture, but may be found in the setting of rapid aneurysm growth. Many factors, including other associated radiographic findings, aneurysm size and growth rate, and patient symptomatology, should guide aneurysm management in these patients. We found that patients with minimal symptoms, aneurysm sizes below 6.5 cm, and no further imaging findings of aneurysm instability, such as periaortic fat stranding, can be successfully managed with elective intervention after optimization of comorbid factors with no evidence of adverse outcomes.

Dynamic Annular Modeling of the Unrepaired Complete Atrioventricular Canal Annulus.

BACKGROUND: Repair of complete atrioventricular canal (CAVC) is often complicated by atrioventricular valve regurgitation, particularly of the left-sided valve. Understanding the 3-dimensional (3D) structure of the atrioventricular canal annulus before repair may help to inform optimized repair. However, the 3D shape and movement of the CAVC annulus has been neither quantified nor rigorously compared with a normal mitral valve annulus. METHODS: The complete annuli of 43 patients with CAVC were modeled in 4 cardiac phases using transthoracic 3D echocardiograms and custom code. The annular structure was compared with the annuli of 20 normal pediatric mitral valves using 3D metrics and statistical shape analysis (Procrustes analysis). RESULTS: The unrepaired CAVC annulus varied in shape significantly throughout the cardiac cycle. Procrustes analysis visually demonstrated that the average normalized CAVC annular shape is more planar than the normal mitral annulus. Quantitatively, the annular height-to-valve width ratio of the native left CAVC atrioventricular valve was significantly lower than that of a normal mitral valve in all systolic phases (P < .001). CONCLUSIONS: The left half of the CAVC annulus is more planar than that of a normal mitral valve with an annular height-to-valve width ratio similar to dysfunctional mitral valves. Given the known importance of annular shape to mitral valve function, further exploration of the association of 3D structure to valve function in CAVC is warranted.

Pre-surgical Prediction of Ischemic Mitral Regurgitation Recurrence Using In Vivo Mitral Valve Leaflet Strains.

Ischemic mitral regurgitation (IMR) is a prevalent cardiac disease associated with substantial morbidity and mortality. Contemporary surgical treatments continue to have limited long-term success, in part due to the complex and multi-factorial nature of IMR. There is thus a need to better understand IMR etiology to guide optimal patient specific treatments. Herein, we applied our finite element-based shape-matching technique to non-invasively estimate peak systolic leaflet strains in human mitral valves (MVs) from in-vivo 3D echocardiographic images taken immediately prior to and post-annuloplasty repair. From a total of 21 MVs, we found statistically significant differences in pre-surgical MV size, shape, and deformation patterns between the with and without IMR recurrence patient groups at 6 months post-surgery. Recurrent MVs had significantly less compressive circumferential strains in the anterior commissure region compared to the recurrent MVs (p = 0.0223) and were significantly larger. A logistic regression analysis revealed that average pre-surgical circumferential leaflet strain in the Carpentier A1 region independently predicted 6-month recurrence of IMR (optimal cutoff value - 18%, p = 0.0362). Collectively, these results suggest greater disease progression in the recurrent group and underscore the highly patient-specific nature of IMR. Importantly, the ability to identify such factors pre-surgically could be used to guide optimal treatment methods to reduce post-surgical IMR recurrence.

Dynamic Volumetric Assessment of the Aortic Root: The Influence of Bicuspid Aortic Valve Competence.

BACKGROUND: Aortic root evaluation is conventionally based on 2-dimensional measurements at a single phase of the cardiac cycle. This work presents an image analysis method for assessing dynamic 3-dimensional changes in the aortic root of minimally calcified bicuspid aortic valves (BAVs) with and without moderate to severe aortic regurgitation. METHODS: The aortic root was segmented over the full cardiac cycle in 3-dimensional transesophageal echocardiographic images acquired from 19 patients with minimally calcified BAVs and from 16 patients with physiologically normal tricuspid aortic valves (TAVs). The size and dynamics of the aortic root were assessed using the following image-derived measurements: absolute mean root volume and mean area at the level of the ventriculoaortic junction, sinuses of Valsalva, and sinotubular junction, as well as normalized root volume change and normalized area change of the ventriculoaortic junction, sinuses of Valsalva, and sinotubular junction over the cardiac cycle. RESULTS: Normalized volume change over the cardiac cycle was significantly greater in BAV roots with moderate to severe regurgitation than in normal TAV roots and in BAV roots with no or mild regurgitation. Aortic root dynamics were most significantly different at the mid-level of the sinuses of Valsalva in BAVs with moderate to severe regurgitation than in competent TAVs and BAVs. CONCLUSIONS: Echocardiographic reconstruction of the aortic root demonstrates significant differences in dynamics of BAV roots with moderate to severe regurgitation relative to physiologically normal TAVs and competent BAVs. This finding may have implications for risk of future dilatation, dissection, or rupture, which warrant further investigation.

Intraoperative post-annuloplasty three-dimensional valve analysis does not predict recurrent ischemic mitral regurgitation.

BACKGROUND: High ischemic mitral regurgitation (IMR) recurrence rates continue to plague IMR repair with undersized ring annuloplasty. We have previously shown that pre-repair three-dimensional echocardiography (3DE) analysis is highly predictive of IMR recurrence. The objective of this study was to determine the quantitative change in 3DE annular and leaflet tethering parameters immediately after repair and to determine if intraoperative post-repair 3DE parameters would be able to predict IMR recurrence 6 months after repair. METHODS: Intraoperative pre- and post-repair transesophageal real-time 3DE was performed in 35 patients undergoing undersized ring annuloplasty for IMR. An advanced modeling algorhythm was used to assess 3D annular geometry and regional leaflet tethering. IMR recurrence (≥ grade 2) was assessed with transthoracic echocardiography 6 months after repair. RESULTS: Annuloplasty significantly reduced septolateral diameter, commissural width, annular area, and tethering volume and significantly increased all segmental tethering angles (except A2). Intraoperative post-repair annular geometry and leaflet tethering did not differ significantly between patients with recurrent IMR (n = 9) and patients with non-recurrent IMR (n = 26). No intraoperative post-repair predictors of IMR recurrence could be identified. CONCLUSIONS: Undersized ring annuloplasty changes mitral geometry acutely, exacerbates leaflet tethering, and generally fixes IMR acutely, but it does not always fix the delicate underlying chronic problem of continued left ventricular dilatation and remodeling. This may explain why pre-repair 3D valve geometry (which reflects chronic left ventricular remodeling) is highly predictive of recurrent IMR, whereas immediate post-repair 3D valve geometry (which does not completely reflect chronic left ventricular remodeling anymore) is not.

Quantitative three-dimensional echocardiographic analysis of the bicuspid aortic valve and aortic root: A single modality approach.

BACKGROUND: Patients with bicuspid aortic valves (BAV) are heterogeneous with regard to patterns of root remodeling and valvular dysfunction. Two-dimensional echocardiography is the standard surveillance modality for patients with aortic valve dysfunction. However, ancillary computed tomography or magnetic resonance imaging is often necessary to characterize associated patterns of aortic root pathology. Conversely, the pairing of three-dimensional (3D) echocardiography with novel quantitative modeling techniques allows for a single modality description of the entire root complex. We sought to determine 3D aortic valve and root geometry with this quantitative approach. METHODS: Transesophageal real-time 3D echocardiography was performed in five patients with tricuspid aortic valves (TAV) and in five patients with BAV. No patient had evidence of valvular dysfunction or aortic root pathology. A customized image analysis protocol was used to assess 3D aortic annular, valvular, and root geometry. RESULTS: Annular, sinus and sinotubular junction diameters and areas were similar in both groups. Coaptation length and area were higher in the TAV group (7.25 ± 0.98 mm and 298 ± 118 mm2 , respectively) compared to the BAV group (5.67 ± 1.33 mm and 177 ± 43 mm2 ; P = .07 and P = .01). Cusp surface area to annular area, coaptation height, and the sub- and supravalvular tenting indices did not differ significantly between groups. CONCLUSIONS: Single modality 3D echocardiography-based modeling allows for a quantitative description of the aortic valve and root geometry. This technique together with novel indices will improve our understanding of normal and pathologic geometry in the BAV population and may help to identify geometric predictors of adverse remodeling and guide tailored surgical therapy.

The value of preoperative 3-dimensional over 2-dimensional valve analysis in predicting recurrent ischemic mitral regurgitation after mitral annuloplasty.

OBJECTIVES: Repair for ischemic mitral regurgitation with undersized annuloplasty is characterized by high recurrence rates. We sought to determine the value of pre-repair 3-dimensional echocardiography over 2-dimensional echocardiography in predicting recurrence at 6 months. METHODS: Intraoperative transesophageal 2-dimensional echocardiography and 3-dimensional echocardiography were performed in 50 patients undergoing undersized annuloplasty for ischemic mitral regurgitation. Two-dimensional echocardiography annular diameter and tethering parameters were measured in the apical 2- and 4-chamber views. A customized protocol was used to assess 3-dimensional annular geometry and regional leaflet tethering. Recurrence (grade ≥2) was assessed with 2-dimensional transthoracic echocardiography at 6 months. RESULTS: Preoperative 2- and 3-dimensional annular geometry were similar in all patients with ischemic mitral regurgitation. Preoperative 2- and 3-dimensional leaflet tethering were significantly higher in patients with recurrence (n = 13) when compared with patients without recurrence (n = 37). Multivariate logistic regression revealed preoperative 2-dimensional echocardiography posterior tethering angle as an independent predictor of recurrence with an optimal cutoff value of 32.0° (area under the curve, 0.81; 95% confidence interval, 0.68-0.95; P = .002) and preoperative 3-dimensional echocardiography P3 tethering angle as an independent predictor of recurrence with an optimal cutoff value of 29.9° (area under the curve, 0.92; 95% confidence interval, 0.84-1.00; P < .001). The predictive value of the 3-dimensional geometric multivariate model can be augmented by adding basal aneurysm/dyskinesis (area under the curve, 0.94; 95% confidence interval, 0.87-1.00; P < .001). CONCLUSIONS: Preoperative 3-dimensional echocardiography P3 tethering angle is a stronger predictor of ischemic mitral regurgitation recurrence after annuloplasty than preoperative 2-dimensional echocardiography posterior tethering angle, which is highly influenced by viewing plane. In patients with a preoperative P3 tethering angle of 29.9° or larger (especially when combined with basal aneurysm/dyskinesis), chordal-sparing valve replacement should be strongly considered.

Modeling the Myxomatous Mitral Valve With Three-Dimensional Echocardiography.

BACKGROUND: Degenerative mitral valve disease is associated with variable and complex defects in valve morphology. Three-dimensional echocardiography (3DE) has shown promise in aiding preoperative planning for patients with this disease but to date has not been as transformative as initially predicted. The clinical usefulness of 3DE has been limited by the laborious methods currently required to extract quantitative data from the images. METHODS: To maximize the utility of 3DE for preoperative valve evaluation, this work describes an automated 3DE image analysis method for generating models of the mitral valve that are well suited for both qualitative and quantitative assessment. The method is unique in that it captures detailed alterations in mitral leaflet and annular morphology and produces image-derived models with locally varying leaflet thickness. The method is evaluated on midsystolic transesophageal 3DE images acquired from 22 subjects with myxomatous degeneration and from 22 subjects with normal mitral valve morphology. RESULTS: Relative to manual image analysis, the automated method accurately represents both normal and complex leaflet geometries with a mean boundary displacement error on the order of one image voxel. A detailed quantitative analysis of the valves is presented and reveals statistically significant differences between normal and myxomatous valves with respect to numerous aspects of annular and leaflet geometry. CONCLUSIONS: This work demonstrates a successful methodology for the relatively rapid quantitative description of the complex mitral valve distortions associated with myxomatous degeneration. The methodology has the potential to significantly improve surgical planning for patients with complex mitral valve disease.

Preoperative Three-Dimensional Valve Analysis Predicts Recurrent Ischemic Mitral Regurgitation After Mitral Annuloplasty.

BACKGROUND: Valve repair for ischemic mitral regurgitation (IMR) with undersized annuloplasty rings is characterized by high IMR recurrence rates. Patient-specific preoperative imaging-based risk stratification for recurrent IMR would optimize results. We sought to determine if prerepair three-dimensional (3D) echocardiography combined with a novel valve-modeling algorithm would be predictive of IMR recurrence 6 months after repair. METHODS: Intraoperative transesophageal real-time 3D echocardiography was performed in 50 patients undergoing undersized ring annuloplasty for IMR and in 21 patients with normal mitral valves. A customized image analysis protocol was used to assess 3D annular geometry and regional leaflet tethering. IMR recurrence (≥ grade 2) was assessed with two-dimensional transthoracic echocardiography 6 months after repair. RESULTS: Preoperative annular geometry was similar in all IMR patients, and preoperative leaflet tethering was significantly higher in patients with recurrent IMR (n=13) than in patients in whom IMR did not recur (n=37) (tethering index: 3.91 ± 1.01 vs 2.90 ± 1.17, p = 0.008; tethering angles of A3: 23.5° ± 8.9° vs 14.4° ± 11.4°, p = 0.012; P2: 44.4° ± 8.8° vs 28.2° ± 17.0°, p = 0.002; and P3: 35.2° ± 6.0° vs. 18.6° ± 12.7°, p < 0.001). Multivariate logistic regression analysis revealed the preoperative P3 tethering angle as an independent predictor of IMR recurrence with an optimal cutoff value of 29.9° (area under the curve, 0.92; 95% confidence interval, 0.84 to 1.00; p < 0.001). CONCLUSIONS: 3D echocardiography combined with valve modeling is predictive of recurrent IMR. Preoperative regional leaflet tethering of segment P3 is a strong independent predictor of IMR recurrence after undersized ring annuloplasty. In patients with a preoperative P3 tethering angle of 29.9° or larger, chordal-sparing valve replacement rather than valve repair should be strongly considered.

Saddle-Shaped Annuloplasty Improves Leaflet Coaptation in Repair for Ischemic Mitral Regurgitation.

BACKGROUND: Current repair results for ischemic mitral regurgitation (IMR) with undersized annuloplasty rings are characterized by high IMR recurrence rates. Current annuloplasty rings treat annular dilatation, but they do little to improve (and may actually exacerbate) leaflet tethering. New saddle-shaped annuloplasty rings have been shown to maintain or restore a more physiologic annular and leaflet geometry and function. Using a porcine IMR model, we sought to demonstrate the influence of annuloplasty ring shape on leaflet coaptation. METHODS: Eight weeks after posterolateral infarct, eight pigs with grade 2+ or higher IMR were randomized to undergo either a 28-mm flat ring annuloplasty (n = 4) or a 28-mm saddle-shaped ring annuloplasty (n = 4). Real-time three-dimensional echocardiography and a customized image analysis protocol allowed three-dimensional assessment of leaflet coaptation before and after annuloplasty. RESULTS: Total leaflet coaptation area was significantly higher after saddle-shaped ring annuloplasty (109.6 ± 26.9 mm(2)) compared with flat ring annuloplasty (46.2 ± 7.7 mm(2), p <0.01). After annuloplasty, total coaptation area decreased by 87.5 mm(2) (or 65%) in the flat annuloplasty group (p = 0.01), whereas total coaptation area increased by 22.2 mm(2) (or 25%) in the saddle-shaped annuloplasty group (p = 0.28). CONCLUSIONS: This study shows that the use of undersized saddle-shaped annuloplasty rings in mitral valve repair for IMR improves leaflet coaptation, whereas the use of undersized flat annuloplasty rings worsens leaflet coaptation. Because one of Carpentier's fundamental principles of mitral valve repair (durability) is to create a large surface of coaptation, saddle-shaped annuloplasty may increase repair durability.

Validation of semiautomated and locally resolved aortic wall thickness measurements from computed tomography.

OBJECTIVE: Aortic wall thickness (AWT) is important for anatomic description and biomechanical modeling of aneurysmal disease. However, no validated, noninvasive method for measuring AWT exists. We hypothesized that semiautomated image segmentation algorithms applied to computed tomography angiography (CTA) can accurately measure AWT. METHODS: Aortic samples from 10 patients undergoing open thoracoabdominal aneurysm repair were taken from sites of the proximal or distal anastomosis, or both, yielding 13 samples. Aortic specimens were fixed in formalin, embedded in paraffin, and sectioned. After staining with hematoxylin and eosin and Masson's trichrome, sections were digitally scanned and measured. Patients' preoperative CTA Digital Imaging and Communications in Medicine (DICOM; National Electrical Manufacturers Association, Rosslyn, Va) images were segmented into luminal, inner arterial, and outer arterial surfaces with custom algorithms using active contours, isoline contour detection, and texture analysis. AWT values derived from image data were compared with measurements of corresponding pathologic specimens. RESULTS: AWT determined by CTA averaged 2.33 ± 0.66 mm (range, 1.52-3.55 mm), and the AWT of pathologic specimens averaged 2.36 ± 0.75 mm (range, 1.51-4.16 mm). The percentage difference between pathologic specimens and CTA-determined AWT was 9.5% ± 4.1% (range, 1.8%-16.7%). The correlation between image-based measurements and pathologic measurements was high (R = 0.935). The 95% limits of agreement computed by Bland-Altman analysis fell within the range of -0.42 and 0.42 mm. CONCLUSIONS: Semiautomated analysis of CTA images can be used to accurately measure regional and patient-specific AWT, as validated using pathologic ex vivo human aortic specimens. Descriptions and reconstructions of aortic aneurysms that incorporate locally resolved wall thickness are feasible and may improve future attempts at biomechanical analyses.

Three-dimensional ultrasound-derived physical mitral valve modeling.

PURPOSE: Advances in mitral valve repair and adoption have been partly attributed to improvements in echocardiographic imaging technology. To educate and guide repair surgery further, we have developed a methodology for fast production of physical models of the valve using novel three-dimensional (3D) echocardiographic imaging software in combination with stereolithographic printing. DESCRIPTION: Quantitative virtual mitral valve shape models were developed from 3D transesophageal echocardiographic images using software based on semiautomated image segmentation and continuous medial representation algorithms. These quantitative virtual shape models were then used as input to a commercially available stereolithographic printer to generate a physical model of the each valve at end systole and end diastole. EVALUATION: Physical models of normal and diseased valves (ischemic mitral regurgitation and myxomatous degeneration) were constructed. There was good correspondence between the virtual shape models and physical models. CONCLUSIONS: It was feasible to create a physical model of mitral valve geometry under normal, ischemic, and myxomatous valve conditions using 3D printing of 3D echocardiographic data. Printed valves have the potential to guide surgical therapy for mitral valve disease.

Feasibility of in vivo human aortic valve modeling using real-time three-dimensional echocardiography.

BACKGROUND: Surgical techniques for aortic valve (AV) repair are directed toward restoring normal structural relationships in the aortic root and rely on detailed assessment of root and valve anatomy. Noninvasive three-dimensional (3D) imaging and modeling may assist in patient selection and operative planning. METHODS: Transesophageal real-time 3D echocardiographic images of 5 patients with normal AVs were acquired. The aortic root and the annulus were manually segmented at end diastole using a 36-point rotational template. The AV leaflets and the coaptation zone were manually segmented in parallel 1-mm cross sections. Quantitative 3D models of the AV and root were generated and used to measure standard anatomic parameters and were compared to conventional two-dimensional echocardiographic measurements. All measurements are given as mean±SD. RESULTS: Annular, sinus, and sinotubular junction areas were 4.1±0.6 cm2, 7.5±1.2 cm2, and 3.9±1.0 cm2, respectively. Root diameters (measured in three locations) by 3D model inspection and two-dimensional echocardiography measurement correlated (R2=0.75). Noncoapted areas of the left, right, and noncoronary leaflets were 1.9±0.2 cm2, 1.6±0.3 cm2, and 1.6±0.3 cm2, respectively. Mean coaptation areas for the left-right, left-noncoronary, and right-noncoronary coaptation zones were 87.7±36.9 mm2, 69.9±20.7 mm2, and 114.2±23.0 mm2, respectively. The mean ratio of noncoapted leaflet area to annular area was 1.3±0.2. CONCLUSIONS: High-resolution 3D models of the in vivo normal human aortic root and valve were generated using 3D echocardiography. Quantitative 3D models and analysis may assist in characterization of pathology and decision making for AV repair.

Statistical assessment of normal mitral annular geometry using automated three-dimensional echocardiographic analysis.

BACKGROUND: The basis of mitral annuloplasty ring design has progressed from qualitative surgical intuition to experimental and theoretical analysis of annular geometry with quantitative imaging techniques. In this work, we present an automated three-dimensional (3D) echocardiographic image analysis method that can be used to statistically assess variability in normal mitral annular geometry to support advancement in annuloplasty ring design. METHODS: Three-dimensional patient-specific models of the mitral annulus were automatically generated from 3D echocardiographic images acquired from subjects with normal mitral valve structure and function. Geometric annular measurements including annular circumference, annular height, septolateral diameter, intercommissural width, and the annular height to intercommissural width ratio were automatically calculated. A mean 3D annular contour was computed, and principal component analysis was used to evaluate variability in normal annular shape. RESULTS: The following mean ± standard deviations were obtained from 3D echocardiographic image analysis: annular circumference, 107.0 ± 14.6 mm; annular height, 7.6 ± 2.8 mm; septolateral diameter, 28.5 ± 3.7 mm; intercommissural width, 33.0 ± 5.3 mm; and annular height to intercommissural width ratio, 22.7% ± 6.9%. Principal component analysis indicated that shape variability was primarily related to overall annular size, with more subtle variation in the skewness and height of the anterior annular peak, independent of annular diameter. CONCLUSIONS: Patient-specific 3D echocardiographic-based modeling of the human mitral valve enables statistical analysis of physiologically normal mitral annular geometry. The tool can potentially lead to the development of a new generation of annuloplasty rings that restore the diseased mitral valve annulus back to a truly normal geometry.

Increased wall stress of saccular versus fusiform aneurysms of the descending thoracic aorta.

BACKGROUND: Repair of fusiform descending thoracic aortic aneurysms (DTAs) is indicated when aneurysmal diameter exceeds a certain threshold; however, diameter-related indications for repair of saccular DTA are less well established. METHODS: Human subjects with fusiform (n = 17) and saccular (n = 17) DTAs who underwent computed tomographic angiography were identified. Patients with aneurysms related to connective tissue disease were excluded. The thoracic aorta was segmented, reconstructed, and triangulated to create a mesh. Finite element analysis was performed using a pressure load of 120 mm Hg and a uniform aortic wall thickness of 3.2 mm to compare the pressure-induced wall stress of fusiform and saccular DTAs. RESULTS: The mean maximum diameter of the fusiform DTAs (6.0 ± 1.5 cm) was significantly greater (p = 0.006) than that of the saccular DTAs (4.4 ± 1.8 cm). However, mean peak wall stress of the fusiform DTAs (0.33 ± 0.15 MPa) was equivalent to that of the saccular DTAs (0.30 ± 0.14 MPa), as found by using an equivalence threshold of 0.15 MPa. The mean normalized wall stress (peak wall stress divided by maximum aneurysm radius) of the saccular DTAs was greater than that of the fusiform DTAs (0.16 ± 0.09 MPa/cm vs. 0.11 ± 0.03 MPa/cm, p = 0.035). CONCLUSIONS: The normalized wall stress for saccular DTA is greater than that for fusiform DTA, indicating that geometric factors such as aneurysm shape influence wall stress. These results suggest that saccular aneurysms may be more prone to rupture than fusiform aneurysms of similar diameter, provide a theoretical rationale for the repair of saccular DTAs at a smaller diameter, and suggest investigation of the role of biomechanical modeling in surgical decision making is warranted.

Ischemic mitral regurgitation: a quantitative three-dimensional echocardiographic analysis.

BACKGROUND: A comprehensive three-dimensional echocardiography based approach is applied to preoperative mitral valve (MV) analysis in patients with ischemic mitral regurgitation (IMR). This method is used to characterize the heterogeneous nature of the pathologic anatomy associated with IMR. METHODS: Intraoperative real-time three-dimensional transesophageal echocardiograms of 18 patients with IMR (10 with anterior, 8 with inferior infarcts) and 17 patients with normal MV were analyzed. A customized image analysis protocol was used to assess global and regional determinants of annular size and shape, leaflet tethering and curvature, relative papillary muscle anatomy, and anatomic regurgitant orifice area. RESULTS: Both mitral annular area and MV tenting volume were increased in the IMR group as compared with patients with normal MV (mitral annular area=1,065±59 mm2 versus 779±44 mm2, p=0.001; and MV tenting volume=3,413±403 mm3 versus 1,696±200 mm3, p=0.001, respectively). Within the IMR group, patients with anterior infarct had larger annuli (1,168±99 mm2) and greater tenting volumes (4,260±779 mm3 versus 2,735±245 mm3, p=0.06) than the inferior infarct subgroup. Papillary-annular distance was increased in the IMR group relative to normal; these distances were largest in patients with anterior infarcts. Whereas patients with normal MV had very consistent anatomic determinants, annular shape and leaflet tenting distribution in the IMR group were exceedingly variable. Mean anatomic regurgitant orifice area was 25.8±3.0 mm2, and the number of discrete regurgitant orifices varied from 1 to 4. CONCLUSIONS: Application of custom analysis techniques to three-dimensional echocardiography images allows a quantitative and systematic analysis of the MV, and demonstrates the extreme variability in pathologic anatomy that occurs in patients with severe IMR.

Quantitative mitral valve modeling using real-time three-dimensional echocardiography: technique and repeatability.

BACKGROUND: Real-time three-dimensional (3D) echocardiography has the ability to construct quantitative models of the mitral valve (MV). Imaging and modeling algorithms rely on operator interpretation of raw images and may be subject to observer-dependent variability. We describe a comprehensive analysis technique to generate high-resolution 3D MV models and examine interoperator and intraoperator repeatability in humans. METHODS: Patients with normal MVs were imaged using intraoperative transesophageal real-time 3D echocardiography. The annulus and leaflets were manually segmented using a TomTec Echo-View workstation. The resultant annular and leaflet point cloud was used to generate fully quantitative 3D MV models using custom Matlab algorithms. Eight images were subjected to analysis by two independent observers. Two sequential images were acquired for 6 patients and analyzed by the same observer. Each pair of annular tracings was compared with respect to conventional variables and by calculating the mean absolute distance between paired renderings. To compare leaflets, MV models were aligned so as to minimize their sum of squares difference, and their mean absolute difference was measured. RESULTS: Mean absolute annular and leaflet distance was 2.4±0.8 and 0.6±0.2 mm for the interobserver and 1.5±0.6 and 0.5±0.2 mm for the intraobserver comparisons, respectively. There was less than 10% variation in annular variables between comparisons. CONCLUSIONS: These techniques generate high-resolution, quantitative 3D models of the MV and can be used consistently to image the human MV with very small interoperator and intraoperator variability. These data lay the framework for reliable and comprehensive noninvasive modeling of the normal and diseased MV.

In vivo noninvasive temperature measurement by B-mode ultrasound imaging.

OBJECTIVE: This study investigated the use of ultrasound image analysis in quantifying temperature changes in tissue, both ex vivo and in vivo, undergoing local hyperthermia. METHODS: Temperature estimation is based on the thermal dependence of the acoustic speed in a heated medium. Because standard beam-forming algorithms on clinical ultrasound scanners assume a constant acoustic speed, temperature-induced changes in acoustic speed produce apparent scatterer displacements in B-mode images. A cross-correlation algorithm computes axial speckle pattern displacement in B-mode images of heated tissue, and a theoretically derived temperature-displacement relationship is used to generate maps of temperature changes within the tissue. Validation experiments were performed on excised tissue and in murine subjects, wherein low-intensity ultrasound was used to thermally treat tissue for several minutes. Diagnostic temperature estimation was performed using a linear array ultrasound transducer, while a fine-wire thermocouple invasively measured the temperature change. RESULTS: Pearson correlations ± SDs between the image-derived and thermocouple-measured temperature changes were R² = 0.923 ± 0.066 for 4 thermal treatments of excised bovine muscle tissue and R² = 0.917 ± 0.036 for 4 treatments of in vivo murine tumor tissue. The average differences between the two temperature measurements were 0.87°C ± 0.72°C for ex vivo studies and 0.97°C ± 0.55°C for in vivo studies. Maps of the temperature change distribution in tissue were generated for each experiment. CONCLUSIONS: This study demonstrates that velocimetric measurement on B-mode images has potential to assess temperature changes noninvasively in clinical applications.