Anatomy of the Atria Umberto Barbero & Siew Yen Ho

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Anatomy of the atria

Umberto Barbero & Siew Yen Ho

Herzschrittmachertherapie + Elektrophysiologie German Journal of Cardiac Pacing and Electrophysiology

ISSN 0938-7412

Herzschr Elektrophys DOI 10.1007/s00399-017-0535-x

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Herzschr Elektrophys Umberto Barbero1 ·SiewYenHo2 https://doi.org/10.1007/s00399-017-0535-x 1 Cardiology Unit, Città della Salute e della Scienza Hospital, University of Turin, Turin, Italy Received: 25 June 2017 2 Cardiac Morphology Unit, Royal Brompton and Hareﬁeld NHS Foundation Trust and Imperial College Accepted: 5 October 2017 London, London, UK © The Author(s) 2017. This article is an open access publication. Anatomy of the atria A road map to the left atrial appendage

Introduction ventional cardiologists performing LAA anatomical landmarks for the location of closure to facilitate understanding of the the atrioventricular node (. Fig. 1b, c). Theleftatrialappendage(LAA)isahighly images, choosing the device, and pre- The hinge line of the septal leaflet of the complex structure that has received in- venting complications. Equally impor- tricuspid valve marks the anterior border creasing attention in recent years, pri- tant is the anatomical understanding of ofthetriangle,whiletheinferiorborderis marily because over 90% of thrombi in the right atrium and the atrial septum, the orifice of the coronary sinus, with the patients with atrial fibrillation (AF) occur which constitute the endocardial access atrioventricular node located superiorly here [1], whichincreasesthe riskofstroke route to the LAA. In addition, the op- within the triangle’s apex [11]. A small, threefold [2]. To manage this complica- erator should pay close attention to the usually fenestrated, crescentic flap, the tion, percutaneous LAA occlusion has spatial relationship of the atrial chambers thebesian valve, guards the orifice of the evolved [3] and European guidelines for to structures neighboring the epicardial coronary sinus. The latter might be di- management of AF now recommend it in surface. lated, suggesting the presence of a persis- patients at high risk for stroke who have tent left superior vena cava draining into contraindications for long-term oral an- The right atrium the coronary sinus [12]or,rarely,anoma- ticoagulation (Class IIb Indication, Level lous pulmonary venous connection. The of Evidence B) [4]. When delivering catheters into the heart, terminalcrest(crista terminalis)isa mus- Previously, the LAA was ligated, sta- the first chamber encountered is the right cle band that marks the lateral and poste- pled, or amputated during elective open- atrium. The atrium is best considered in rior border between the pectinated wall heart surgery. Surgical techniques con- terms of three components: the venous of the appendage and the smooth wall tinuetoevolvewiththetypeofsutures part, the appendage, and the vestibule of venous component. Pectinate muscles used and the delivery of clips through (. Fig. 1a). The remaining wall is the arisefromthecresttolinetheendocar- sternotomy or thoracotomy. In recent septum shared withthe leftatrium, which dial surface of the appendage. The atrial years, however, percutaneous procedures per se is crucial for the interventional walls in between the branching pectinate are increasingly used and there are now cardiologist to have a firm understanding muscles are exceptionally thin with only several devices available for implantation of its anatomy. afewstrandsofmyocytessandwiched within the LAA to occlude its orifice. In The eustachian valve, guarding the en- between epi- and endocardial surfaces. addition, there is an epicardial LAA ex- trance of the inferior caval vein, is a vari- The anterolateral course of the terminal clusion system that enables percutaneous ably developed flap. Usually it is a tri- crest at the entrance of the superior vena suture ligation of the LAA via combined angular flap of fibrous or fibromuscular cava is the landmark for the location of pericardial and transseptal access [5, 6]. tissue that inserts medially to the eu- the sinus node [13]. There are more closure devices under- stachian ridge (or sinus septum), which going trials or in development [7]. Each is the border between the oval fossa and The atrial septum of these implants, whether delivered en- the coronary sinus. Occasionally it is docardially or epicardially, have different a filigreed mesh, or a perforated flap, The atrial septum separates the atrial characteristics and exclusion criteria for which can be so extensive as to stretch chambers (. Figs. 1a and 2). Although fitting and occluding the LAA. High-res- across the superior caval vein orifice and the atrial chambers are designated right olution imaging techniques can now be is described as Chiari’s network [9]. The and left, the atrial septum does not run in used to study the anatomy of the LAA free border of the eustachian valve con- the anterior–posterior orthogonal plane. [8], but there are still limitations in pro- tinues into the musculature of the sinus Instead, it is obliquely orientated such viding information about wall thickness septum, as a fibrous strand called the that the left atrium is situated somewhat and neighboring structures. Therefore, tendon of Todaro [10]. It is of partic- posterior to the right atrium. Struc- knowledge of the left atrium and the ular importance, being one of the bor- turally, this component is more complex LAA anatomy is mandatory for inter- ders of Koch’s triangle that delineates the than it appears at first glance [14]. The

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called septal hypertrophy, transgression through the rim can hinder needle pen- etration and, being a thicker structure, can restrict maneuverability after crossing, besides increasing the risk of exiting the heart, dissecting into the fatty tissues, and causing hemopericardium [16]. At particular risk is the anterior rim of the fossa, which is adjacent to the aortic mound. The latter is seen as a protuber- ance of the atrial wall into the right atrial cavity. Because the aorta is just in front of the anterior walls of both atria, direct- ing the puncture needle too anteriorly is likely to result in the needle entering the transverse pericardial sinus with a risk of aortic perforation (. Fig. 2c, d). Owing to the more apical attachment of the tricuspid compared with the mitral valve at the septum level, the vestibule of the right atrium overlies the crest of the muscular ventricular septum (. Fig. 2b). Consequently, the compact atrioventricular node situated on the slope of the crest is within 1 mm or so of the endo- Fig. 1 8 a Dissection of the atria following removal of their anterior walls viewed from a left anterior cardial surface of the right atrium at the perspective to show their components.b Right lateral view of the opened right atrium shows the oval apex of the triangle of Koch [17]. fossa (OF) and its surrounding rim as well as the landmarks for the triangle of Koch.The orifice of the The ideal site for crossing the septum coronary sinus (arrow) is guarded by a fenestrated thebesian valve.The short, broken line continuing to safely reach the left atrium is through fromthefreeedgeoftheeustachianvalve(ev) marks the tendon of Todaro, while the hinge line of the tricuspid valve marks the anterior border (longbroken line). At the apex lies the membranous septum the thin valve of the fossa. Although (pale area). The irregular shape marks the anticipated site of the compact atrioventricular node with generally expected to be in the middle itsinferiorextensions. Theshort, dotted linemarksthe “septal”isthmus, andthe long, dotted line marks of the septal wall, the location and size thecavo-tricuspidisthmus. cThisspecimenisdisplayedinsimilarorientationandithasbeendissected of the oval fossa varies from patient to to show the subendocardial myocardial architecture.The landmarks for the triangle of Koch and isth- patient[18]. Furthermore, abnormalities muses are superimposed.cs coronary sinus, ICV and IVC inferior caval vein, L and RIPV left and right inferior pulmonary vein, L and RSPV right and left superior pulmonary vein.(Fig. 1a reproduced from of the thorax such as kyphoscoliosis or of [14], with permission by AHA; Fig. 1b and 1c reproduced from [26], with permission by Wiley) the cardiovascular system like a marked left ventricular hypertrophy may result in displacement of the plane of the atrial right atrial view of the septal aspect can This is because the adhesion of the valve septum and hence the oval fossa [19]. be misleading because it gives the im- to the rim is incomplete, and this patency Patients with patches, PFO-occluder de- pression of an extensive septum. is the patent foramen ovale (PFO), which vices, thicklyfibrosed septum thatmaybe In reality, the site of the true sep- appearslikeacrescent-likeedgeonthe due to previous transseptal procedures, tum is the area of the thin flap valve of left atrial aspect. ( Fig. 2a, d). and aneurysmal valves [20]oftheoval the oval fossa and its apposition to the The superior rim of the fossa is then fossa are particularly challenging to per- muscular rim (limbus) that surrounds it the infolded wall between the superior forate. The last of these is defined as (. Fig. 1b, c). During fetal life, the fossa caval vein and the right pulmonary veins a saccular excursion of >1 cm away from valve allows blood to flow from the right (. Fig. 2b). Sandwiched between the fold the plane of the atrial septum. In these atrium to the left atrium through the are epicardial tissues, frequently contain- hearts, the fossa membrane often is thin- oval foramen (ostium secundum). After ing the arterial supply to the sinus node. ner, devoid of muscle cells, and mainly birth, the fossa valve completely adheres In some patients, the epicardial fat may composed of connective tissue, making to the left atrial margin of the rim in increase the thickness of the infolding it more resistant to being perforated and most hearts, sealing the fossa opening. up to 1–2 cm. A thickness of >2 cm on yet more likely to be “tented” deep into In about one quarter to one third of the noninvasive imaging is increasingly re- the left atrial cavity with a greater risk of normal population, there is probe pa- ported as indicative of lipomatous hy- reaching the lateral wall. tency of the oval fossa, even though the pertrophy, with an incidence of up to Even with a transseptal puncture valve is large enough to overlap the rim. 8% [15]. Even in hearts without so- through the fossa valve, the relationship

Herzschrittmachertherapie + Elektrophysiologie Abstract · Zusammenfassung of the fossa to the superior wall or roof Herzschr Elektrophys https://doi.org/10.1007/s00399-017-0535-x of the left atrium, the orifices of the © The Author(s) 2017. This article is an open access publication. pulmonary veins, and the mitral valve are important considerations for inter- U. Barbero · S. Y. Ho ventional procedures, especially in LAA Anatomy of the atria. A road map to the left atrial appendage closure procedure where the entrance of the needle should be directed toward the Abstract plane of the LAA ostium. In cases where The left atrial appendage (LAA) has received The components of the atria, particularly increasing attention in recent years because the LAA as well as the atrial septum, are the fossa is situated more superiorly than of thrombi formation in patients with atrial described with emphasis on their spatial usual, the puncture site could lead to fibrillation, which increases the risk of stroke. relationships to neighboring cardiac and the atrial roof. The location is compa- In patients who have contraindications for extracardiac structures. Sound knowledge rabletocrossingatthesiteofaPFO, long-term oral anticoagulation therapy, of the atrial anatomy including endocardial although the latter may also direct the percutaneous procedures are used to occlude and epicardial aspects is necessary. This will the LAA and there are now several devices help interventionists take full advantage catheter toward the anterosuperior wall available for implantation, both endocardially of imaging techniques when assessing the of the left atrium (. Fig. 2d), affecting and epicardially. Despite the high-resolution suitability of the LAA anatomy for closure, ease of catheter handling and access to imaging techniques on hand today, selecting the optimal device types and sizes, reach target areas. As will be described limitations remain in providing information and guiding the LAA closure procedure, later, the LAA ostium could be more about wall thickness and neighboring thereby reducing potential complications and structures; therefore, in-depth knowledge increasing procedural success. or less cephalad, anterior, or posterior; of the normal atrial anatomy is mandatory its assessment is essential to select the when considering such interventions. Here, Keywords best position for transseptal puncture in the anatomy of the right and left atria is Heart atria · Atrial appendage · Atrial order to align the device to the target reviewed with relevance to interventional fibrillation · Puncture · Occlusion area. procedures required for LAA occlusion.

The left atrium Anatomie der Vorhöfe. Ein Übersichtsplan für das linke Herzohr

Following the direction of blood flow Zusammenfassung inside the left atrium, the atrial cham- Das linke Herzohr („left atrial appendage“, Verschluss erforderlich sind, erörtert. Die ber begins at the pulmonary veno-atrial LAA) erhielt in den letzten Jahren verstärkte Bestandteile der Vorhöfe, insbesondere des junctionsand terminatesatthe fibro-fatty Aufmerksamkeit wegen Thrombenbildung LAA und des Vorhofseptums, werden mit tissue plane that marks the atrioventric- bei Patienten mit Vorhofflimmern, was Betonung auf ihre räumlichen Beziehungen das Risiko eines Schlaganfalls erhöht. Bei zu benachbarten kardialen und extrakardialen ular junction at the mitral orifice. A dis- Patienten mit Kontraindikationen für eine Strukturen beschrieben. Eine gründliche tinctive appendage, considerably smaller Langzeitantikoagulationstherapie werden Kenntnis der Vorhofanatomie einschließlich than its counterpart on the right side, perkutane Interventionen zum Verschluss des ihrer endokardialen und epikardialen Aspekte extends from the aforementioned main LAA genutzt. Mittlerweile sind verschiedene ist notwendig. Dies trägt dazu bei, dass body of the atrium (. Fig. 3). Apart from Systeme zur Implantation verfügbar, die Operateure das Potenzial bildgebender sowohl endokardial als auch epikardial. Verfahren voll ausschöpfen können, wenn sie the appendage, whichhasa fairlywell-de- Trotz heute vorhandener hochauflösender die Eignung des LAA für eine Verschlussin- fined opening (the os to the appendage), Bildgebungsverfahren bestehen weiterhin tervention beurteilen, optimale Gerätetypen the other component parts of the atrium Einschränkungen hinsichtlich Informationen und -größen auswählen und die LAA- including the septal aspect do not have über die Wanddicke und benachbarte Verschlussintervention leiten; somit werden clear anatomic demarcations. The flap Strukturen, daher ist bei Erwägung potenzielle Komplikationen vermindert und derartiger Interventionen ein detailliertes der Operationserfolg gesteigert. valveoftheovalfossaoccupiesthesep- Wissen über die normale Vorhofanatomie tal aspect and it overlaps the fossa rim Voraussetzung. In der vorliegenden Arbeit Schlüsselwörter that is on the right atrial side. A cres- wird die Anatomie des rechten und linken Herzvorhöfe · Herzohr · Vorhofflimmern · centic mark at the anticipated site of the Vorhofs dargestellt sowie ihre Bedeutung Punktion · Verschluss PFO is the anterocephalad margin of the für interventionelle Verfahren, die zum LAA- valve membrane (. Fig. 2a). If transseptal access is gained by passing through this tunnel-like opening from the right is smooth on the endocardial surface, changes in orientation of the myocar- atrium, it is worth noting that the di- without a clear distinction between ve- dial strands; usually the areas of abrupt rection of the catheter on entering the nous and atrial walls, especially where change are accompanied by a change in left atrium is toward the anterocephalad the terminal parts of the veins are fun- wall thickness [21]. wall, which often is particularly thin. nel-shaped. One of the most important Viewed from within the atrial cavity, The posterior part of the left atrium aspects is that the posterior left atrial wall the endocardial surface has the appear- receiving the pulmonary veins is its is not uniform in thickness. The trans- ance of ridges in between the superior venous component. Mainly, the wall muralmusculatureofthewallshows and inferior venous orifices. In addition,

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walls of the left atrium and its tip is directed anterosuperiorly, overlapping the left border of the right ventricular out- flow tract or the pulmonary trunk and the main stem of the left coronary or the circumflex artery (. Fig. 3). It is not uncommon to find the tip of the appendage directed laterally and back- ward, while in a few hearts the tip portion passes behind the arterial pedicle to sit in the transverse pericardial sinus. There is broad variability in LAA morphology, a fact that complicates adequate evaluation. Several studies have described the LAA as a long tubular and hooked structure with different lobes. In one study based on computed tomography (CT) and magnetic resonance imaging (MRI), the LAA was classified into four morphological groups: the cactus, with a dominant central lobe with secondary lobes extending from the central lobe in both superior and inferior directions; the chickenwing, withabendintheproximal or middle part of the dominant lobe and sometimes secondary lobes; the wind- sock, with one dominant lobe of suffi- cient length as the primary structure; the cauliflower, with limited overall length Fig. 2 8 a Longitudinal cut through the left atrium and left ventricle showing the endocardial surface and more complex internal characteris- oftheseptalwalloftheatrialcomponentindistinguishablefromtheanteriorandposteriorwallsother tics with a variable number of lobes with- than for the crescent-like margin (open arrow) that marks the site of the patent foramen ovale if it is out a dominant one. The more lobes and persistent. Note the location of the coronary sinus (CS) relative to the inferior wall.b Longitudinal cut pouches the LAA has, the higher the risk throughthefourcardiacchambersshowingtheatrialseptuminprofile. Theflooroftheovalfossa(open arrow) is the true septum. Asterisks mark the levels of attachments of the tricuspid and mitral valves at of thrombus formations inside for AF pa- the septum. The inferior pyramidal space (smallarrow) is covered by the vestibule of the right atrium. tients [27]. However, this classification c Histological section taken through the short axis of the heart showing the thin flap valve (open ar- of the morphology should be made with row) and the muscular rim of the fossa (smallarrows). Note the uneven thickness of the left atrial wall. caution because imaging the same ap- d View of the septal component showing a patent foramen ovale (openarrow). Its opening is behind pendage from different perspectives can the anterior wall of the left atrium and the transverse pericardial sinus.ICV inferior caval vein, SCV su- periorcaval vein, LI left inferior,LS left superior, RI right inferior, and RS right superior pulmonary veins. change its appearance [28]. (Reproduced from [14], with permission by AHA) As shown in . Fig. 4,itisalsouseful to describe the LAA according to three there is a ridge-like structure between the band, which is the most prominent mus- regions: the ostium, the neck (or landing entrance of the left superior pulmonary cular interatrial bridge [25]. Myocardial zone for devices), and the lobar regions. vein and the os of the LAA, first described strands from its superior rightward arm Within the appendage are pectinate mus- by Keith in 1907 [22] and today better can be traced toward the location of the cles. Unlike the pectinate muscles in the known as the Coumadin ridge [23]orleft sinus node and the terminal crest. Left- rightatrium, however, the pectinate mus- lateral ridge. This “ridge” is a fold that ward, the bundle runs toward the LAA cles in the left atrium do not arise from has thicker muscle in the anterosuperior where it branches, passing to either side adistinctmusclebundlethatislikeacrista portion and within it runs the remnant of the appendage and then reuniting to terminalis. Instead, they present with co- of the vein of Marshall, abundant auto- continue into the musculature of the lat- conut-palm leaf arrangement especially nomic nerve bundles, and a small atrial eral and postero-inferior atrial walls [26]. at the borders between superior and in- artery that, in some cases, is the sinus ferior surfaces, or are strap-like, or re- nodal artery [24]. The left atrial appendage semble a palmyra-palm leaf arrangement Passing across the subepicardium of near the border with the atrial vestibule the anterior left atrial wall is Bachmann’s In most hearts the appendage extends [29]. On imaging, the thicker bundles bundle, also known as the interauricular from between the anterior and lateral may be mistaken for thrombi or intra-

Herzschrittmachertherapie + Elektrophysiologie The percutaneous devices systems, however, have a round shape to fill or cover the ostium. A round implant over an oval orifice may leave crevices on either side of the implant, leading to incomplete sealing of the orifice. Nevertheless, the significance of residual leaks after device implantation is not clear. Ramondo et al. stated that the diam- eter of the ostium is in relation to the length of the LAA, which is a crucial measurement in order to permit com- plete deployment of the device into the LAA [33]. Another critical issue for the entry of the deployment catheter is the distance between the LAA orifice and the point at which the LAA first deviates from its original course. It has been re- ported that for deviations of between 7 and12mmfromtheostium[32], if the deployment catheter is advanced too far it may easily exit the appendage into the pericardial space, especiallysince parts of its wall in between the pectinate muscles are paper-thin. The risk of a hemopericardium, as already mentioned, should not be overlooked [34]. 8 Fig. 3 aEndocardialaspectoftheleftatriumshowingtheovalostiumoftheappendage,theleftlat- Aside from the paper-like thickness eral ridge separating it from the left inferior(LI)andsuperior(LS)pulmonary veins, and its proximityto of the LAA wall itself, the morphology themitralvalve(MV).b,cLeftlateralviewoftheoutsideofaheartshowingthenarrowappendageover- lyingthe course ofthe interventricularveinandartery (v, arrowheads)withitstiptowardtherightven- of the atrial wall in the proximity of the tricularoutflowtract. Theappendageisdeflectedbackwardinc. dThe ostium ofthe appendage (dou- LAA orifice is also an important consid- ble arrows)inrelationtotheleftcoronaryartery(LCA). PT pulmonary trunk, LAA left atrial appendage. eration when deploying catheters in the (Reproduced from [32], with permission from BMJ Publishing Group Ltd.) left atrium. In almost 50% of heart spec- imenstherearepitsortroughsthattend atrial masses [30]. The remainder of the ing proximal portion of the LAA is too to occur in isolation or in clusters located LAA wall in between the muscle bundles short to accommodate a device. A cone- on the anterolateral and lateral atrial wall is exceptionally thin. shaped LAA with a progressive reduc- [32]. Interventionists should be aware Patients with chronic AF frequently tion in dimensions from its orifice to its that, as during maneuvers, catheters and have LAA remodeling in which there distal tip might pose a particular prob- delivery sheaths may become lodged in is dilation, stretching, and reduction in lem for secure seating of the occlusion the pits/troughs. This could potentially pectinatemusclevolume, aswellasendo- device that is further aggravated by the increase the risk of perforation since the cardial fibroelastosis [31]. Because some lack of trabeculations in the LAA land- atrial wall is extremely thin inside the de- LAA morphologies are more challenging ing zone region and hence increasing the pressions, comparable to the paper-thin for device closure than others, careful risk of device migration or embolization. areas within the LAA. evaluation of its anatomy is required be- Furthermore, if a plug type of device is Finally, we should not forget that the fore any planned procedure. A chicken- used, the chosen disc may be too small entrances of the pulmonary veins, the wing LAA morphology, characterized by to adequately seal the ostium since it is atrial appendage, and part of the left an early (<20 mm from the ostium) and considerably wider than the landing zone atrial body are in close vicinity to im- severe bend, is one of the most diffi- [5]. portant structures surrounding the heart cult anatomic variations for LAA closure Previous studies [29, 32] showed that (. Figs. 3 and 4). The introduction of [5]. A secondary lobe originating close to the shape of the ostium is mostly ellipti- LAA closure devices has increased the the ostium can pose problems, because cal or oval (. Fig. 3a). Round, teardrop, need for knowledge of subtler anatomi- it may not be covered after device de- or triangular shapes are far less common. cal aspects that might be very useful for ployment. Two large lobes of a similar ThissuggeststhattosealtheLAAorifice understanding possible difficulties dur- size separated by a large rim in between adequately without oversizing, devices ing the device implantation, such as its them may cause problems if the remain- may need to be elliptical for a snug fit. relation with the left pulmonary veins

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Moreover, it is also important to consider neighboring outer structures whether attempting to close the LAA ostium from within the atrium or from the pericardial space. Owing to its slightly flattened shape, the lower surface of the LAA usually overlies the summit of the left ventricle while the upper surface is beneath the fibrous pericardium. A previous study [32] showed that the left anterior descending coronary artery and the circumflex artery are in close proximity to the LAA or its ostium and can be vulnerable to trauma during implantation of percutaneous devices, especially when devices are 20–40% larger than the os. It is well established that the sinus node artery arises from the right coronary system in about 60% of cases. However, there is still a significant pro- portion of cases in which the sinus node artery originates from the left coronary system. In the landmark study by Bus- quet et al., the sinus node artery was seen Fig. 4 8 a Left atrial appendage (LAA) regions are illustrated in a two-dimensional transesophageal to arise from the circumflex artery and echocardiography (TEE) view (45°). The black arrowhead indicates the circumflex artery (Lcx).b Corre- from the left lateral atrial artery in 30% sponding anatomic image.c Three-dimensional TEE reconstruction of the relationship between the and 8% of the cases, respectively [36]. LAA, the left upperpulmonary vein (LUPV), and the mitral valve (MV). d Corresponding anatomic view. When these run around the ostium of Ao aorta. (Reproduced from [5], with permission by Elsevier) the LAA, they can be at risk of trauma from devices. and the length and depth of the lateral 4 Type III in which the ostium is at the A previous anatomical study on the ridge as well as the distance to the mi- level of the left inferior pulmonary course of the phrenic nerves has demon- tral valve. These anatomical structures vein (. Fig. 5). strated that the left phrenic nerve runs are important for a better spatial under- along the pericardium overlying the LAA standing of the LAA ostium and neck CMR or CT studies before intervention [37]. This nerve may also be at risk if and could guide the approach for device may help to classify the different types of epicardial approaches are used. More- delivery in each individual [35]. A clas- ostium (or neck) and therefore may be over, on the epicardial aspect, the ante- sification suggested by López-Mínguez useful for selecting the devices and for the rior interventricular trunk and the ob- and colleagues [35]ofthe“LAAostium” site in which to perform the transseptal tuse marginal trunk join to form the left (which corresponds to the neck region in puncture. Type I is probably the most coronary lymphatic channel that passes other publications) according to its rela- suitable for device occlusion since the beneath the LAA and close to the os- tionship with the pulmonary veins is as broad LLR could favor a stable implant tium [38]. The great cardiac vein on follows: as well as having more distance from the its ascent to the atrioventricular groove 4 Type I, with the LAA ostium (neck) pulmonary vein. By contrast, types II also passes underneath the appendage cephalad and anterior to the left and III could present with an extremely but its course tends to veer away from superior pulmonary vein and usually narrow and pointed LLR, in which case the ostium. Therefore, the observations separated by a wide lateral ridge it could be more challenging to achieve concerning the spatial relationships of (LLR) abalancebetweendevicestabilitywithout structures and the atrial wall are still 4 Type II, when the most posterior risking pulmonary venous obstruction if highlyrelevant and important whencon- part of the ostium is very close to alargerdeviceisdeployed[35]. templating occlusion or exclusion of the the lateral ridge, which is thinner Apartfromtheleftpulmonaryveinsin LAA. and more marked than in type I and proximity to the ostium of the appendage, demarcates a well-defined limbus the mitral valve is also in its vicinity in Practical conclusion hearts where there is a narrow vestibule. An oversized device may impinge on the Percutaneous LAA closure is a relatively mitral orifice. new, but evolving treatment strategy

Herzschrittmachertherapie + Elektrophysiologie Fig. 5 8 Classificationoftheleftatrialappendage(LAA):Type I,withtheLAAostiumcephaladandanteriortothe left superior pulmonary vein (LS) and usually separated by a wide lateral ridge (LLR); Type II, when the most posterior part of the ostium is very close to the lateral ridge, which is thinner and more marked than in type I and demarcates a well-defined limbus; Type III in which the ostium is atthelevel of theleftinferiorpulmonary vein (LI). CS coronary sinus, MV mitral valve.(Reproduced from [35], with permission by Wiley) to prevent embolic events in patients 11. Anderson RH, Ho SY,Becker AE (1983) The surgical References anatomy of the conduction tissues. Thorax suffering with nonvalvular AF. Sound 38(6):408–420 knowledge of atrial anatomy from both 1. Blackshear JL, Odell JA (1996) Obliteration of the 12. Anselmino M, Ferraris F, Cerrato N, Barbero U, left atrial appendage to reduce stroke in cardiac endocardial and epicardial aspects is ScaglioneM,GaitaF(2014)Leftpersistentsuperior surgicalpatientswithatrialfibrillation. AnnThorac vena cava and paroxysmal atrial fibrillation: the necessary. This knowledge will help Surg61:755–759 role of selective radio frequency transcatheter interventionists take advantage of 2. The Stroke Prevention in Atrial Fibrillation Inves- ablation. J Cardiovasc Med (Hagerstown) tigators (SPAF), Committee on Echocardiography imaging techniques when assessing the 15(8):647–652 (1998) Transesophageal echocardiographic corre- 13. Ho SY, Anderson RH, Sanchez-Quintana D (2002) suitability of the LAA anatomy for the lates of thromboembolism in high-risk patients Atrial structure and fibres: morphologic bases of closure, for selecting the optimal device with nonvalvular atrial fibrillation. Ann Intern Med atrialconduction. CardiovascRes54:325–336 128:639–647 types and sizes, and for guiding the LAA 14. Ho SY, Cabrera JA, Sanchez-Quintana D (2012) 3. Sievert H, Lesh MD, Trepels T et al (2002) Left atrial anatomy revisited. Circ Arrhythm closure procedure in order to reduce Percutaneous left atrial appendage transcatheter Electrophysiol5:220–228 complications and increase procedural occlusion to prevent stroke in high-risk patients 15. FykeFE3rd,TajikAJ,EdwardsWD,SewardJB(1983) with atrial fibrillation: early clinical experience. success. Diagnosis of lipomatous hypertrophy of the atrial Circulation105:1887–1889 septum by two-dimensional echocardiography. 4. Kirchhof P, Benussi S, Kotecha D, Ahlsson A, Atar JAmCollCardiol1:1352–1357 Corresponding address D, Casadei B et al (2016) 2016 ESC Guidelines 16. HoSY(2010)Embryologyandanatomyoftheatrial for the management of atrial fibrillation devel- septum. In: Thakur R, Natale A (eds) Transseptal S. Y. Ho, PhD oped in collaboration with EACTS. 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Am Compliance with ethical LARIAT(+) suture delivery device: early clinical HeartJ119:1401–1405 experience. IntJCardiol215:244–247 19. Tzeis S, Andrikopoulos G, Deisenhofer I, Ho SY, guidelines 7. Romero J, Natale A, Engstrom K, Di Biase L (2016) Theodorakis G (2010) Transseptal catheteriza- Leftatrialappendageisolationusingpercutaneous tion: considerations and caveats. Pacing Clin (endocardial/epicardial) devices: pre-clinical and Electrophysiol33:231–242 Conflict of interest. U.BarberoandS.Y.Hodeclare clinical experience. Trends Cardiovasc Med that they have no competing interests. 20. HoSY,McCarthyKP,RigbyML(2003)Morphological 26:182–199 features pertinent to interventional closure of 8. HeistEK,RefaatM,DanikSB etal(2006)Analysisof patentovalforamen. JIntervCardiol16:33–38 This article does not contain any studies with human the left atrial appendage by magnetic resonance 21. Ho SY, Sanchez-Quintana D, Cabrera JA, Anderson participants or animals performed by any of the au- angiography in patients with atrial fibrillation. RH(1999)Anatomyoftheleftatrium: implications thors. For the studies discussed here the relevant HeartRhythm3:1313–1318 for radiofrequency ablation of atrial fibrillation. ethical guidelines are provided therein. 9. Ho SY, Anderson RH, Sanchez-Quintana D (2002) JCardiovascElectrophysiol10:1525–1533 Gross structure of the atriums. More than 22. Keith A (1907) An account of the structures OpenAccess. Thisarticleisdistributedundertheterms anatomical curiosity? Pacing Clin Electrophysiol concerned in the production of the jugular pulse. of the Creative Commons Attribution 4.0 International 25(3):342–350 JAnatPhysiol42:1–25 License (http://creativecommons.org/licenses/by/ 10. TodaroF(1865)Novellericherchesopralastruttura 23. McKay T, Thomas L (2008) ‘Coumadin ridge’ 4.0/), which permits unrestricted use, distribution, muscolare delle orechiette del coure umano e in the left atrium demonstrated on three and reproduction in any medium, provided you give sopralavalvolad’Eustachio. Sperimentale16:217 dimensional transthoracic echocardiography. Eur appropriate credit to the original author(s) and the JEchocardiogr9(2):298–300 source, providealinktotheCreativeCommonslicense, and indicate if changes were made.

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Herzschrittmachertherapie + Elektrophysiologie