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The detailed anatomy of the interatrial septum (IAS) and mitral annulus (MA) as observed on cardiac magnetic resonance, computed tomography and two-dimensional/three-dimensional transthoracic and transesophageal echocardiography is reviewed. The IAS comprises of two components: the septum primum that is membrane-like forming the floor of the fossa ovalis (FO) and the septum secundum that is a muscular rim that surrounds the FO. The latter is an enfolding of atrial wall forming an interatrial groove. Named Waterston’s groove, it is filled with adipose tissue on the epicardial side. Thus, the safest area for transseptal puncture (TSP) is within the limits of the FO floor, which provides direct interatrial access. While crossing an intact septum is a well-established procedure, TSP is a more complex and time-consuming procedure in the presence of patent foramen ovalis, aneurysmal FO or atrial septal defect closure devices. MA comprises two distinctive segments: an anterior-straight and a posterior-curved segment. The posterior MA is a thin, discontinuous fibrous ‘string’, interspersed with adipose tissue, where four components converge: the atrial and ventricular musculature, epicardial adipose tissue and the leaflet’s hinge line. In parts of where this fibrous string is deficient or absent, the posterior leaflet is inserted directly on ventricular and atrial myocardium rendering the MA less robust and producing an ‘asymmetric’ dilation. The marked vulnerability of posterior MA to calcifications might be due to its insertion on the crest of ventricular myocardium being subject to friction injury due to the contraction and relaxation of LV.

Interest in the anatomy of the interatrial septum (IAS) and its adjoining atrioventricular (AV) junction has risen enormously in the past two decades with the simultaneous evolution of left-sided percutaneous structural heart disease and complex electrophysiologic procedures. These procedures require, in fact, a direct route to the left atrium through the IAS. Thus, a thorough understanding of the complex anatomy of the IAS and AV junction is essential for performing a safe and effective transseptal puncture. There is a large amount of literature carefully describing the anatomy of the IAS and AV junction. These studies are based almost exclusively on anatomic specimens. Conversely, in this review the authors emphasize the role of noninvasive imaging techniques, in particular cardiac magnetic resonance, two- and three-dimensional transesophageal echocardiography, and computed tomography in visualizing specific aspects of the normal IAS and AV junction. Where appropriate, the authors present images side by side, with corresponding anatomic specimens.

Two-dimensional (2D) transthoracic echocardiography is one of the most used diagnostic tools in clinical cardiology. Similarly, 2D transesophageal echocardiography is considered an indispensable tool for cardiologists and cardiac anesthesiologists worldwide. However, because of their tomographic nature, both techniques display only thin cut planes of a given area of the heart, which are far from representing the “anatomic reality.” It is widely accepted that experienced echocardiographers are able to reconstruct mentally a three-dimensional image of any cardiac structure on the basis of their interpretation of multiple tomographic slices. However, this may not be the case with less experienced echocardiographers. In particular, the authors noticed that less experienced echocardiographers are almost totally unaware of which structures lie “nearby” a given 2D tomographic plane, that is, what is adjacent in the elevation plane. In this article, the authors report the use of three-dimensional transesophageal echocardiographic images to discover which structures are located nearby (i.e., “behind” and “in front”) the corresponding 2D cross-sections. The authors believe that this novel use of three-dimensional echocardiography is a unique aid to disclose what cannot be seen in a given 2D cross-section, thereby expanding our understanding of 2D echocardiographic anatomy. This may be an effective method to encourage all to “think” in three dimensions, even when they use 2D echocardiography.

In an era of catheter-based structural heart disease and left-side electrophysiologic interventions, transseptal puncture (TSP) is probably the most common transcatheter procedure. Experienced interventional cardiologists and electrophysiologists may safely perform TSP using fluoroscopic guidance alone. However, at present TSP is usually the first step in complex percutaneous catheter-based structural heart disease procedures and necessitate a precise site-specific TSP. Thus, in these procedures most interventional cardiologists perform TSP under fluoroscopic and two- or three-dimensional transesophageal echocardiographic guidance. The EchoNavigator system may provide a solution by fusing fluoroscopic and transesophageal echocardiographic images. In this review, the authors describe advantages and limitations of this new imaging system in guiding TSP and suggest specific echocardiographic-fluoroscopic fusion imaging perspectives that may facilitate TSP, making it potentially easier and safer.

Identification of the extent of scar transmurality in chronic ischemic heart disease is important because it correlates with viability. The aim of this retrospective study was to evaluate whether layer-specific two-dimensional speckle-tracking echocardiography allows distinction of scar presence and transmurality.

The identification of patients with mitral valve prolapse (MVP) presenting high arrhythmic risk remains challenging. Cardiovascular Magnetic Resonance (CMR) feature tracking (FT) may improve risk stratification. We analyzed the role of CMR-FT parameters in relation to the incidence of complex ventricular arrhythmias (cVA) in patients with MVP and mitral annular disjunction (MAD).

Three-dimensional (3D) transesophageal echocardiography (TEE) is subject to the same types of artifacts encountered on two-dimensional TEE. However, when displayed in a 3D format, some of the artifacts appear more “realistic,” whereas others are unique to image acquisition and postprocessing. Three-dimensional TEE is increasingly used in the setting of percutaneous catheter-based interventions and ablation procedures, and 3D artifacts caused by the metallic components of catheters and devices are particularly frequent. Knowledge of these artifacts is of paramount relevance to avoid misinterpretation of 3D images. Although artifacts and pitfalls on two-dimensional echocardiography are well described and classified, a systematic description of artifacts in 3D transesophageal echocardiographic images and how they affect 3D imaging is still absent. The aim of this review is to describe the most relevant artifacts on 3D TEE, with particular emphasis on those occurring during percutaneous interventions for structural heart disease and ablation procedures.

Mitral annular disjunction (MAD) is an abnormal insertion of the hinge line of the posterior mitral leaflet on the atrial wall: the mitral annulus shows a separation or “disjunction” between the leaflet–atrial wall junction and the crest of the left ventricle myocardium. This anomaly is often observed in patients with myxomatous mitral valve prolapse. The anatomical substrate of MAD remains unclear for the following reasons: (1) most studies are focused on the association between MAD and arrhythmias, rather than on pathomorphological aspects of MAD; and (2) the complex anatomic architecture of the posterior mitral annulus is often simply described as the posterior segment of a fibrous ring. The aims of this paper are to review the pertinent normal anatomy of the mitral valve and to propose new hypotheses on the morphological nature of MAD.