Shumpei Mori

Revisiting the Anatomy of the Living Heart.

An understanding of the complexity of cardiac anatomy is required by all who seek, in the setting of cardiac disease, to interpret the images confronting them. Although the mysteries of cardiac structure have been extensively addressed, significant gaps continue to exist between the descriptions provided by morphologists and by those working in the clinical setting. In part, this reflects the limitations in providing 3D visualization of such a complicated organ. Current 3D imaging technology now permits visualization of the cardiac components using datasets obtained in the living individual. These advances, furthermore, demonstrate the anatomy in the setting of the heart as imaged within the thorax. It has been failure to describe the heart as it lies within the thorax that remains a major deficiency of many morphologists relying on the dissecting room to provide the gold standard. Describing the heart in attitudinally appropriate fashion, a basic rule of clinical anatomy, creates the necessary bridges between anatomists and clinicians. The rapid progression of cardiac interventional techniques, furthermore, emphasizes the need to revisit cardiac anatomy using a multidisciplinary approach. In this review, therefore, we illustrate the advantages of an attitudinally correct approach to cardiac anatomy. We then focus on the morphology of the arterial roots, revealing the accuracy that can now be achieved by clinicians using datasets obtained during life.

Development and Morphology of the Ventricular Outflow Tracts

It is customary, at the current time, to consider many, if not most, of the lesions involving the ventricular outflow tract in terms of conotruncal malformations. This reflects the introduction, in the early 1940s, of the terms conus and truncus to describe the components of the developing outflow tract. The definitive outflow tracts in the postnatal heart, however, possess three, rather than two, components. These are the intrapericardial arterial trunks, the arterial roots, and the subvalvar ventricular outflow tracts. Congenital lesions afflicting the arterial roots, however, are not currently considered to be conotruncal malformations. This suggests a lack of logic in the description of cardiac development and its use as a means of categorizing congenital malformations. It is our belief that the developing outflow tract, like the postnatal outflow tracts, can readily be described in tripartite fashion, with its distal, intermediate, and proximal components forming the primordiums of the postnatal parts. In this review, we present evidence obtained from developing mice and human hearts to substantiate this notion. We show that the outflow tract, initially with a common lumen, is divided into its aortic and pulmonary components by a combination of an aortopulmonary septum derived from the dorsal wall of the aortic sac and outflow tract cushions that spiral through its intermediate and proximal components. These embryonic septal structures, however, subsequently lose their septal functions as the outflow tracts develop their own discrete walls. We then compare the developmental findings with the anatomic arrangements seen postnatally in the normal human heart. We show how correlations with the embryologic findings permit logical analysis of the congenital lesions involving the outflow tracts.

The Significance of the Interleaflet Triangles in Determining the Morphology of Congenitally Abnormal Aortic Valves: Implications for Noninvasive Imaging and Surgical Management

A comprehensive understanding of the normal and abnormal aortic root is paramount if we are to improve not only our assessment of the aortic root and its components but also the surgical approach to reconstructing this complex structure when congenitally malformed. Most anatomic and imaging-based classifications of the normal root recognize and describe the basic components, which include the shape and size of the three aortic sinuses and their three valvar leaflets, as well as the sinutubular junction and proximal ascending aorta. However, the three interposing fibrous interleaflet triangles, which share an intimate relationship with all elements of the root, are often ignored. In consequence, the important role the interleaflet triangles play in determining the function of the normal and congenitally malformed aortic root is underappreciated. Additionally, the subtle asymmetries found in the normal aortic root, such as differences between the sizes of the described components, underlie its hemodynamic efficiency. In this review the authors describe the complex structure of the normal aortic root, contrasting these normal characteristics with those found in the unicuspid and bicuspid variants of congenitally malformed aortic valves. Many of these features are readily recognizable using current imaging modalities and so should become a standard part of the description of aortic valvar disease. The authors believe that this thorough morphologic approach will provide a framework for the re-creation of a more normal aortic root at the time of repair or replacement, thereby improving current outcomes.

Optimal angulations for obtaining an en face view of each coronary aortic sinus and the interventricular septum: Correlative anatomy around the left ventricular outflow tract

An optimal image intensifier angulation used for obtaining an en face view of a target structure is important in electrophysiologic procedures performed around each coronary aortic sinus (CAS). However, few studies have revealed the fluoroscopic anatomy of the target area. This study investigated the optimal angulation for each CAS and the interventricular septum (IVS). The study included 102 consecutive patients who underwent computed tomography coronary angiography. The optimal angle for each CAS was determined by rotating the volume‐rendered image around the vertical axis. The angle formed between the anteroposterior axis and IVS was measured using the horizontal section. The frontal direction was defined as zero, positive, or negative if the en face view of the target CAS was obtained in the frontal view, left anterior oblique (LAO) direction, or right anterior oblique (RAO) direction, respectively. The optimal angles for the left, right, and non‐CASs were 120.3 ± 10.5°, 4.8 ± 16.3°, and −110.0 ± 13.8°, respectively. The IVS angle was 42.6 ± 8.5°. Accordingly, the optimal image intensifier angulations for the left, right, and non‐CASs and the IVS were estimated to be RAO 60°, LAO 5°, LAO 70°, and RAO 50°, respectively. The IVS angle was the most common independent predictor of the optimal angle for each CAS. Differences in the optimal angulations for each CAS and the IVS are demonstrated. The biplane angulation needs to be tailored according to the individual patients and target structures for electrophysiologic procedures. Clin. Anat. 28:494–505, 2015.

Association between the rotation and three-dimensional tortuosity of the proximal ascending aorta

Age‐related morphological changes of the aorta, including dilatation and elongation, have been reported. However, rotation has not been fully investigated. We focused on the rotation of the ascending aorta and investigated its relationship with tortuosity. One hundred and two consecutive patients who underwent computed tomography coronary angiography were studied. The angle at which the en face view of the volume‐rendered image of the right coronary aortic sinus (RCS) was obtained without foreshortening was defined as the rotation index. It was defined as zero if the RCS was squarely visible in the frontal view, positive if it rotated clockwise toward the left anterior oblique (LAO) direction, and negative if it rotated counter‐clockwise toward the right anterior oblique (RAO) direction. The tortuosity was evaluated by measuring the biplane tilt angles formed between the ascending aorta and the horizontal line. The mean rotation index, posterior tilt angle viewed from the RAO direction (αRAO), and anterior tilt angle viewed from the LAO direction (αLAO) were 4.8 ± 16.3, 60.7 ± 7.0°, and 63.6 ± 9.0°, respectively. Although no correlation was observed between the rotation index and the αLAO (β = −0.0761, P = 0.1651), there was a significant negative correlation between the rotation index and αRAO (β = −0.1810, P < 0.0001). In multivariate regression analysis, the rotation index was an independent predictor of the αRAO (β = −0.1274, P = 0.0008). Clockwise rotation of the proximal ascending aorta exacerbates the tortuosity by tilting the aorta toward the posterior direction. Clin. Anat. 27:1200–1211, 2014.

Clinical structural anatomy of the inferior pyramidal space reconstructed from the living heart: Three-dimensional visualization using multidetector-row computed tomography

The inferior pyramidal space (IPS) comprises the epicardial visceral adipose tissue wedged between the bottoms of the four cardiac chambers from the postero‐inferior epicardial surface of the heart. Understanding the complex anatomy around the IPS is important for clinical cardiologists. Although leading anatomists and radiologists have clarified the anatomy of the IPS in detail, few studies have demonstrated this anatomy in three dimensions. The aim of this study was to visualize the three‐dimensional anatomy of the IPS reconstructed from the living heart using multidetector‐row computed tomography. We also developed an original paper model of the IPS to enhance understanding of its intricate structure. Clin. Anat. 28:878–887, 2015.

Clinical cardiac structural anatomy reconstructed within the cardiac contour using multidetector‐row computed tomography: Atrial septum and ventricular septum

Cardiologists are increasingly becoming involved in procedures associated with the atrial septum and ventricular septum, such as transseptal puncture and selective site pacing. Moreover, detailed knowledge about the architecture of the atrial septum and ventricular septum is now available from studies by radiologists and anatomists. However, from the viewpoint of clinical cardiologists, many questions about the three‐dimensional cardiac structural anatomy that relate closely to routine invasive procedures remain unresolved. Although modern multidetector‐row computed tomography could provide answers, interventional cardiologists might have not considered the potential of this equipment, as only a few have performed studies with both radiological imaging and cadaveric hearts. Detailed knowledge of the three‐dimensional fluoroscopic cardiac structural anatomy could help to reduce the need for contrast medium injection and radiation exposure, and to perform safe interventions. In this article, we present a series of cardiac structural images, including images of the atrial septum and ventricular septum, reconstructed in combination with the cardiac contour using multidetector‐row computed tomography. We also discuss the clinical implications of the findings on the basis of accumulated insights of research pioneers. We hope that the present images will serve as a bridge between the fields of cardiology, radiology, and anatomy, and encourage cardiologists to integrate their accumulated insights into the three‐dimensional clinical images of the living heart. Clin. Anat. 29:342–352, 2016.

Clinical cardiac structural anatomy reconstructed within the cardiac contour using multidetector-row computed tomography: Left ventricular outflow tract.

The left ventricular outflow tract (LVOT) is a common site of idiopathic ventricular arrhythmia. Many electrocardiographic characteristics for predicting the origin of arrhythmia have been reported, and their prediction rates are clinically acceptable. Because these approaches are inductive, based on QRS‐wave morphology during the arrhythmia and endocardial or epicardial pacing, three‐dimensional anatomical accuracy in identifying the exact site of the catheter position is essential. However, fluoroscopic recognition and definition of the anatomy around the LVOT can vary among operators, and three‐dimensional anatomical recognition within the cardiac contour is difficult because of the morphological complexity of the LVOT. Detailed knowledge about the three‐dimensional fluoroscopic cardiac structural anatomy could help to reduce the need for contrast medium injection and radiation exposure, and to perform safe interventions. In this article, we present a series of structural images of the LVOT reconstructed in combination with the cardiac contour using multidetector‐row computed tomography. We also discuss the clinical implications of these findings based on the accumulated insights of research pioneers. Clin. Anat. 29:353–363, 2016.

Three-dimensional quantification and visualization of aortic calcification by multidetector-row computed tomography: A simple approach using a volume-rendering method

OBJECTIVE Three-dimensional (3-D) visualization and quantification of vascular calcification (VC) are important to accelerate the multidisciplinary investigation of VC. Agatston scoring is the standard approach for evaluating coronary artery calcification. However, regarding aortic calcification (AC), quantification methods appear to vary among studies. The aim of this study was to introduce a simple technique of simultaneous quantification and 3-D visualization of AC and provide validation data. METHODS The main study comprised of 126 patients who underwent the thoracoabdominal plain computed tomography scan as preoperative general evaluation. AC was quantified using a volume-rendering (VR) method (VR AC volume) by extracting the volume with a density ≥130 HU within the total aorta. The concordance and reproducibility of the VR AC volume were validated in comparison with the conventional slice-by-slice voxel-based AC quantification (volumetric AC score) using the Agatston scoring software. RESULTS Excellent concordance between the VR AC volume and volumetric AC score was confirmed (Spearman correlation coefficient = 0.9997, mean difference = -0.05 ± 0.23 mL, p <0.0001). Excellent intraobserver and interobserver reliabilities were demonstrated using the Bland-Altman analysis as the mean intraobserver difference was 0.00 mL (p = 0.9863) and the mean interobserver difference was -0.01 mL (p = 0.6612). CONCLUSION The VR method was validated to be feasible. This simple approach could overcome the limitation of the current method based on slice-by-slice pixel or voxel summation, which lacks 3-D visual information. Accordingly, this approach would be promising for accelerating the investigation of VC.

The association between wedging of the aorta and cardiac structural anatomy as revealed using multidetector-row computed tomography

The aortic root is wedged within the cardiac base. The precise extent of aortic wedging, however, and its influence on the surrounding cardiac structures, has not been systematically investigated. We analysed 100 consecutive patients, who underwent coronary arterial computed tomographic angiography. We assessed the extent of aortic wedging by measuring the vertical distance between the non‐adjacent aortic sinus and the inferior epicardium. A shorter distance indicates deeper aortic wedging. We assessed the tilt angle and diameter of the ascending aorta, the relative heights of the left atrial roof and the oval fossa, the shape of the proximal right coronary artery, the angle of the aorta relative to the left ventricular axis, and the lung volume. The mean extent of wedging was 42.7 ± 9.8 mm. Multivariate analysis revealed that ageing, male gender, increased body mass index, patients without cardiomyopathy, the extent of tilting and dilation of the ascending aorta, and lung volume were all independent predictors for deeper aortic wedging (R2 = 0.7400, P < 0.0001). The extent of wedging was additionally correlated with a relatively high left atrial roof (R2 = 0.1394, P < 0.0001) and oval fossa (R2 = 0.1713, P < 0.0001), the shepherds crook shape of the proximal right coronary artery (R2 = 0.2376, P < 0.0001), and the narrowness of the angulation of the root relative to the left ventricular axis (R2 = 0.2544, P < 0.0001). In conclusion, ageing, male gender, obesity, background cardiac disease, aortic tilting and dilation, and lung volume are all correlated with the extent of wedging of the aortic root within the cardiac base.