Development and structure of the atrial septum

Patent Foramen Ovale Embryology, Anatomy, and Physiology

Patent foramen ovale (PFO) is a common finding in the general population but may lead to serious conditions such as stroke from paradoxical embolism and platypnea orthodeoxia. A thorough understanding of the interatrial septal anatomy along with its assessment by different imaging modalities is critical in performing safe transcatheter PFO closure. Investigating the anatomy and right heart to left heart flows using transesophageal echocardiography or intracardiac echocardiography imaging must be done before undertaking closure of a PFO.

Formation of the interatrial septum: Insights obtained from cardiac computed tomographic angiography

We previously described a septal variant termed left atrial septal pouch (LASP). Present in a third of hearts, it results from incomplete fusion of the septum primum (SP) and septum secundum (SS). We assessed the prevalence of LASP using 64-section multidetector computed tomography and further characterized the different variants. Among 864 scans, 770 were of sufficient quality for assessment (428 male, aged 59.2 ± 11.7 years). They were classified on the basis of the degrees of fusion of the SP and SS into a completely fused septum (CFS), patent foramen ovale (PFO), or LASP. The lengths of the SS, SP, and overlapping SP, the maximal length of the foramen ovale (FO) floor, and the atrial dimensions were compared. A PFO was seen in 181 patients (23.5%), a LASP in 242 (31.4%), and a CFS in 339 (44.0%). There were significant differences in the length of the SS (PFO-13.6 ± 4.3 mm, LASP-17.6 ± 4.8 mm, CFS-14.3 ± 7.7 mm, p < 0.001). Hearts with LASPs had a longer overlapping SP than those with PFOs (PFO-6.3 ± 4.5 mm, LASP-13.1 ± 5.2 mm, p < 0.001). The maximal lengths of the FO floor showed differences in short axis (SAX) view (PFO-21.7 ± 4.5 mm, LASP-15.3 ± 4.3 mm, CFS-16.3 ± 4.3 mm, p < 0.001). Hearts with PFO and LASP showed similar SP lengths (27.3 ± 6.6 mm vs. 26.4 ± 6.6 mm, p = 0.10). There was a positive linear correlation between the length of the SS and the overlapping SP (R2 = 0.28, p < 0.001) with a weaker negative correlation between the SS length and maximal length of the FO floor (R2 = 0.02, p < 0.001). The groups showed similar atrial dimensions and volumes. Present in a third of patients, hearts with LASP have longer SS and overlapping SP.

Atrial septal pouches and ridges: Morphological features and potential implications in clinical practice

Incomplete or irregular fusion of the interatrial septum may result in several anatomic variants, including atrial septal pouches and ridges, whose knowledge and recognition are still poorly widespread in clinical practice. An educational review focused on the definition, clinical significance and diagnostic work-up of these anatomic findings was performed using PubMed, MEDLINE, Embase and Cochrane Central databases up to June 2023. Atrial septal pouches and ridges have been associated with an increased difficulty of catheter-based interventions requiring a transseptal approach, due to procedural challenges for transseptal puncture and the restricted motion of guidewires and catheters through the transseptal access. Additionally, left atrial septal pouch may serve as a thrombogenic nidus and a source of systemic embolism, mostly in the presence of factors leading to higher left atrial pressure and/or atrial blood stasis, which increase the risk of thrombus formation and embolic events, rather than for the only presence of left atrial septal pouch itself. Further investigations are needed in order to better elucidate the implications of such anatomic findings in daily clinical practice, and to provide the most appropriate decision-making strategies.

Anomalous pulmonary venous drainage due to malposition of septum primum: two case reports and literature review

Background

Anomalous pulmonary venous connection with malposition of septum primum (MSP) is a rare pediatric cardiovascular malformation. Although reports in the literature are scarce, accurate pre-operative imaging diagnosis is crucial for selecting the appropriate clinical intervention and determining the prognosis for affected children.

Case description

In both case reports, the cardiovascular malformations were incidental findings. In the second case, an enlarged cardiac silhouette was observed on chest x-ray due to pneumonia, which was subsequently confirmed by ultrasound. Combined with computed tomography angiography examination, the diagnosis of MSP-type anomalous pulmonary venous connection was established.

Conclusions

Comprehensive imaging examinations are essential in reducing misdiagnosis and achieving an accurate diagnosis of MSP-type anomalous pulmonary venous connection. The typical imaging findings for MSP-type anomalous pulmonary venous connection include absence or hypoplasia of the superior limbic band of the septum secundum, leftward displacement of the septum primum, and partial or total pulmonary vein drainage into the anatomical right atrium.

Patent Foramen Ovale and Atrial Septal Defect

Patent foramen ovale (PFO) and atrial septal defects (ASDs) are two types of interatrial communications with unique clinical presentations and management strategies. The PFO is a normal part of fetal development that typically closes shortly after birth but may persist in as many as 25% to 30% of adults. The communication between atria may result in paradoxic embolism and embolic stroke. On the other hand, ASDs (anatomically defined as secundum, primum, sinus venosus, and coronary sinus in order of prevalence) typically result in right heart volume overload and are often associated with other congenital defects. The diagnostic methods, treatment options including surgical and percutaneous approaches, and potential complications are described. Both conditions underline the significance of precise diagnosis and appropriate management to mitigate risks and ensure optimal patient outcomes.

Acto3D: an open-source user-friendly volume rendering software for high-resolution 3D fluorescence imaging in biology

Advances in fluorescence microscopy and tissue-clearing have revolutionised 3D imaging of fluorescently labelled tissues, organs and embryos. However, the complexity and high cost of existing software and computing solutions limit their widespread adoption, especially by researchers with limited resources. Here, we present Acto3D, an open-source software, designed to streamline the generation and analysis of high-resolution 3D images of targets labelled with multiple fluorescent probes. Acto3D provides an intuitive interface for easy 3D data import and visualisation. Although Acto3D offers straightforward 3D viewing, it performs all computations explicitly, giving users detailed control over the displayed images. Leveraging an integrated graphics processing unit, Acto3D deploys all pixel data to system memory, reducing visualisation latency. This approach facilitates accurate image reconstruction and efficient data processing in 3D, eliminating the need for expensive high-performance computers and dedicated graphics processing units. We have also introduced a method for efficiently extracting lumen structures in 3D. We have validated Acto3D by imaging mouse embryonic structures and by performing 3D reconstruction of pharyngeal arch arteries while preserving fluorescence information. Acto3D is a cost-effective and efficient platform for biological research.

Cor Triatriatum Dexter With a Sinus Venosus Atrial Septal Defect in a 50-Year-Old Woman: A Case Report

The diagnosis of atrial septal defect (ASD) may be delayed until adulthood or even later in life as it is a well-tolerated congenital heart disease. If patients are not examined and investigated well in childhood, the diagnosis may be delayed until later in adulthood when patients present with palpitations and sometimes dyspnea due to the right chambers dilatation from right ventricular volume overload. In this report, we present a case of a 50-year-old female patient with symptoms of heart failure and atrial fibrillation who was found to have dilated right cardiac chambers, dilated pulmonary artery, severe tricuspid regurgitation, pulmonary hypertension, and a pulmonary-to-systemic flow ratio (Qp/Qs) of more than 1.5 by transthoracic echocardiography and Doppler, indicating left to right shunt at the atrial level. However, transthoracic echocardiography could not visualize the defect, and two-dimensional (2D) transesophageal echocardiography was done in this patient and documented the presence of a sinus venosus ASD with an incomplete cor triatriatum dexter membrane; all four pulmonary veins were identified going to the left atrium. Since the presence of an incomplete cor triatriatum dexter membrane (despite causing no symptoms) makes the percutaneous closure of the sinus venosus ASD and the percutaneous repair of tricuspid regurgitation very difficult, we decided to advise surgical ASD closure and tricuspid valve repair for the patient.

Molecular Pathways and Animal Models of Atrioventricular Septal Defect

The development of a fully functional four-chambered heart is critically dependent on the correct formation of the structures that separate the atrial and ventricular chambers. Perturbation of this process typically results in defects that allow mixing of oxygenated and deoxygenated blood. Atrioventricular septal defects (AVSD) form a class of congenital heart malformations that are characterized by the presence of a primary atrial septal defect (pASD), a common atrioventricular valve (cAVV), and frequently also a ventricular septal defect (VSD). While AVSD were historically considered to result from failure of the endocardial atrioventricular cushions to properly develop and fuse, more recent studies have determined that inhibition of the development of other components of the atrioventricular mesenchymal complex can lead to AVSDs as well. The role of the dorsal mesenchymal protrusion (DMP) in AVSD pathogenesis has been well-documented in studies using animal models for AVSDs, and in addition, preliminary data suggest that the mesenchymal cap situated on the leading edge of the primary atrial septum may be involved in certain situations as well. In this chapter, we review what is currently known about the molecular mechanisms and animal models that are associated with the pathogenesis of AVSD.

Human Cardiac Development

Many aspects of heart development are topographically complex and require three-dimensional (3D) reconstruction to understand the pertinent morphology. We have recently completed a comprehensive primer of human cardiac development that is based on firsthand segmentation of structures of interest in histological sections. We visualized the hearts of 12 human embryos between their first appearance at 3.5 weeks and the end of the embryonic period at 8 weeks. The models were presented as calibrated, interactive, 3D portable document format (PDF) files. We used them to describe the appearance and the subsequent remodeling of around 70 different structures incrementally for each of the reconstructed stages. In this chapter, we begin our account by describing the formation of the single heart tube, which occurs at the end of the fourth week subsequent to conception. We describe its looping in the fifth week, the formation of the cardiac compartments in the sixth week, and, finally, the septation of these compartments into the physically separated left- and right-sided circulations in the seventh and eighth weeks. The phases are successive, albeit partially overlapping. Thus, the basic cardiac layout is established between 26 and 32 days after fertilization and is described as Carnegie stages (CSs) 9 through 14, with development in the outlet component trailing that in the inlet parts. Septation at the venous pole is completed at CS17, equivalent to almost 6 weeks of development. During Carnegie stages 17 and 18, in the seventh week, the outflow tract and arterial pole undergo major remodeling, including incorporation of the proximal portion of the outflow tract into the ventricles and transfer of the spiraling course of the subaortic and subpulmonary channels to the intrapericardial arterial trunks. Remodeling of the interventricular foramen, with its eventual closure, is complete at CS20, which occurs at the end of the seventh week. We provide quantitative correlations between the age of human and mouse embryos as well as the Carnegie stages of development. We have also set our descriptions in the context of variations in the timing of developmental features.

The Role of Echocardiography in the Assessment of the Interatrial Septum and Patent Foramen Ovale as an Emboligenic Source

A comunicação do septo atrial (CIA) representa, aproximadamente, de 6%-10% dos defeitos cardíacos congênitos, com incidência de 1 em 1.500 nascidos vivos.1 Forame oval patente (FOP) é mais comum e está presente em mais de 20%-25% dos adultos.2 Síndromes clínicas associadas a CIA e FOP são variáveis, com implicações abrangendo a medicina pediátrica e adulta, neurologia e cirurgia.

O interesse adicional na anatomia do septo interatrial (SIA) aumentou substancialmente nas últimas duas décadas, com evolução simultânea dos procedimentos percutâneos envolvendo cardiopatia estrutural do lado esquerdo e procedimentos eletrofisiológicos. Idealmente, essas intervenções baseadas em cateter requerem rota direta para o átrio esquerdo (AE) através do SIA, necessitando completo entendimento de sua anatomia. Atualmente, tecnologias de imagem sofisticadas e não invasivas como ecocardiografia transesofágica bidimensional (ETE 2D) e tridimensional (ETE 3D), ressonância cardíaca (RMC) e tomografia computadorizada (TC) passaram por um extraordinário desenvolvimento tecnológico, fornecendo detalhes anatômicos das estruturas cardíacas visualizadas em formato 2D e 3D e são essenciais para diagnóstico e tratamento de pacientes com doenças cardíacas.

A avaliação da anatomia e anormalidades do SIA, portanto, requer abordagem padronizada e sistemática, integrando modalidades diagnósticas e fornecendo avaliação adequada e uniforme para terapias cirúrgicas e transcateter.

Multimodality imaging approach of patent foramen ovale: Practical considerations for transient ischemic attack/stroke

A patent foramen ovale, which is present in up to 25% of the population, is a risk factor for cryptogenic stroke (which accounts for 15%-40% of strokes) and transient ischemic attack via paradoxical embolism. This narrative review focuses on the multimodality imaging approach of the diagnosis and periprocedural guidance of patent foramen ovale, with an emphasis on the use of agitated saline as contrast medium in echocardiography, starting from embryologic aspects. Therefore, we aimed to make a concise and complete presentation of the protocol used for this type of evaluation, along with multimodality imaging approach of the patent foramen ovale and practical considerations for transient ischemic attack/stroke.

A pictorial account of the human embryonic heart between 3.5 and 8 weeks of development

Heart development is topographically complex and requires visualization to understand its progression. No comprehensive 3-dimensional primer of human cardiac development is currently available. We prepared detailed reconstructions of 12 hearts between 3.5 and 8 weeks post fertilization, using Amira® 3D-reconstruction and Cinema4D®-remodeling software. The models were visualized as calibrated interactive 3D-PDFs. We describe the developmental appearance and subsequent remodeling of 70 different structures incrementally, using sequential segmental analysis. Pictorial timelines of structures highlight age-dependent events, while graphs visualize growth and spiraling of the wall of the heart tube. The basic cardiac layout is established between 3.5 and 4.5 weeks. Septation at the venous pole is completed at 6 weeks. Between 5.5 and 6.5 weeks, as the outflow tract becomes incorporated in the ventricles, the spiraling course of its subaortic and subpulmonary channels is transferred to the intrapericardial arterial trunks. The remodeling of the interventricular foramen is complete at 7 weeks.

Morphological Study of Fossa Ovalis in Formalin-Fixed Human Hearts and Its Clinical Importance

Background and Objectives: Our study aimed to investigate the gross anatomy aspects of the fossa ovalis (FO) and the presence of some anatomical variation resulting from the incomplete fusion of septum primum and septum secundum, such as an atrial septal pouch (SP) and left atrial septal ridge. Materials and Methods: Thirty-one adult human hearts removed from formalin-fixed specimens were examined to provide information about the morphology of the FO. The organs were free of any gross anatomically visible pathological conditions. Results: The most common variants were the FO located in the inferior part of the interatrial septum (64.51%), circular (61.3%), with a net-like structure (51.62%), prominent limbus (93.55%), and patent foramen ovale (PFO) (25.8%). The right SP was observed in 9.67% of specimens, the left SP was observed in 29.03% of cases, and in 51.61% of cases, a double SP was observed. One sample presented a right SP and a double left SP, and one case showed a triple left SP, which was not reported previously to our knowledge. Conclusions: Knowledge of the interatrial septal anatomy becomes important for interventional cardiologists and should be documented before transeptal puncture.

The Tale-Tell Heart: Evolutionary tetrapod shift from aquatic to terrestrial life-style reflected in heart changes in axolotl (Ambystoma mexicanum)

BACKGROUND

During amphibian metamorphosis, the crucial moment lies in the rearrangement of the heart, reflecting the changes in circulatory demands. However, little is known about the exact shifts linked with this rearrangement. Here, we demonstrate such myocardial changes in axolotl (Ambystoma mexicanum) from the morphological and physiological point of view.

RESULTS

Micro-CT and histological analysis showed changes in ventricular trabeculae organization, completion of the atrial septum and its connection to the atrioventricular valve. Based on Myosin Heavy Chain and Smooth Muscle Actin expression we distinguished metamorphosis-induced changes in myocardial differentiation at the ventricular trabeculae and atrioventricular canal. Using optical mapping, faster speed of conduction through the atrioventricular canal was demonstrated in metamorphic animals. No differences between the groups were observed in the heart rates, ventricular activation times, and activation patterns.

CONCLUSIONS

Transition from aquatic to terrestrial life-style is reflected in the heart morphology and function. Rebuilding of the axolotl heart during metamorphosis was connected with reorganization of ventricular trabeculae, completion of the atrial septum and its connection to the atrioventricular valve, and acceleration of AV conduction.

Role of the Epicardium in the Development of the Atrioventricular Valves and Its Relevance to the Pathogenesis of Myxomatous Valve Disease

This paper is dedicated to the memory of Dr. Adriana "Adri" Gittenberger-de Groot and in appreciation of her work in the field of developmental cardiovascular biology and the legacy that she has left behind. During her impressive career, Dr. Gittenberger-de Groot studied many aspects of heart development, including aspects of cardiac valve formation and disease and the role of the epicardium in the formation of the heart. In this contribution, we review some of the work on the role of epicardially-derived cells (EPDCs) in the development of the atrioventricular valves and their potential involvement in the pathogenesis of myxomatous valve disease (MVD). We provide an overview of critical events in the development of the atrioventricular junction, discuss the role of the epicardium in these events, and illustrate how interfering with molecular mechanisms that are involved in the epicardial-dependent formation of the atrioventricular junction leads to a number of abnormalities. These abnormalities include defects of the AV valves that resemble those observed in humans that suffer from MVD. The studies demonstrate the importance of the epicardium for the proper formation and maturation of the AV valves and show that the possibility of epicardial-associated developmental defects should be taken into consideration when determining the genetic origin and pathogenesis of MVD.

Left atrial decompression as a palliative minimally invasive treatment for congestive heart failure caused by myxomatous mitral valve disease in dogs: 17 cases (2018-2019)

OBJECTIVE

To determine whether left atrial decompression (LAD) would reduce left atrial pressure (LAP) in dogs with advanced myxomatous mitral valve disease (MMVD) and left-sided congestive heart failure (CHF) and to describe the LAD procedure and hemodynamic alterations and complications.

ANIMALS

17 dogs with advanced MMVD and left-sided CHF that underwent LAD.

PROCEDURES

The medical record database was retrospectively reviewed for all LAD procedures attempted in dogs with MMVD and left-sided CHF between October 2018 and June 2019. Data were collected regarding signalment (age, breed, weight, and sex), clinical signs, treatment, physical examination findings, and diagnostic testing before and after LAD. Procedural data were also collected including approach, technique, hemodynamic data, complications, and outcome.

RESULTS

18 LAD procedures performed in 17 patients were identified. Dogs ranged in age from 7.5 to 16 years old (median, 11 years) and ranged in body weight from 2.9 to 11.6 kg (6.4 to 25.5 lb) with a median body weight of 7.0 kg (15.4 lb). Minimally invasive creation of an atrial septal defect for the purpose of LAD was successful in all dogs without any intraoperative deaths. Before LAD, mean LAP was elevated and ranged from 8 to 32 mm Hg with a median value of 14 mm Hg (reference value, < 10 mm Hg). Following LAD, there was a significant decrease in mean LAP (median decrease of 6 mm Hg [range, 1 to 15 mm Hg]). Survival time following LAD ranged from 0 to 478 days (median, 195 days).

CONCLUSIONS AND CLINICAL RELEVANCE

For dogs with advanced MMVD and left-sided CHF, LAD resulted in an immediate and substantial reduction in LAP.

Morphometric study of fossa ovale in human cadaveric hearts: embryological and clinical relevance

Atrial septal defect (ASD) is the 5th common congenital abnormality at birth. Secundum atrial defect and patent foramen ovale (PFO) are the most common atrial septal defects. In this setting, the anatomical functional characterization of the interatrial septum seems to be of paramount importance not only for device selection but also for therapeutic intervention. This study was carried out to evaluate the morphometric parameters of fossa ovale (FOv) in the human adult cadaveric hearts. For this study, 50 normal cadaveric human hearts available in the department of Anatomy over the period of 3 years were used where size, position, shape, nature of the FOv was noted. The size of the fossa was measured and prominence, location, and extent of the limbus fossa ovalis were observed. The probe patency of foramen ovale (FO) was confirmed. In most specimens, the fossa was oval (80%), the average transverse diameter was 24.21 mm, and the vertical diameter 26.84 mm. In 84% rim was raised. In 56% of cases, the fossa was present at the middle of the interatrial septum. The patency of foramen was observed in 3%. The findings of the present study provide pertinent information on the morphology of the FOv, which may be useful for device selection in treating ASDs and PFO. This would definitely help the clinicians in a deeper understanding of the region as very few cadaveric studies are available in the literature at present.

Quantified growth of the human embryonic heart

The size and growth patterns of the components of the human embryonic heart have remained largely undefined. To provide these data, three-dimensional heart models were generated from immunohistochemically stained sections of ten human embryonic hearts ranging from Carnegie stage 10 to 23. Fifty-eight key structures were annotated and volumetrically assessed. Sizes of the septal foramina and atrioventricular canal opening were also measured. The heart grows exponentially throughout embryonic development. There was consistently less left than right atrial myocardium, and less right than left ventricular myocardium. We observed a later onset of trabeculation in the left atrium compared to the right. Morphometry showed that the rightward expansion of the atrioventricular canal starts in week 5. The septal foramina are less than 0.1 mm² and are, therefore, much smaller than postnatal septal defects. This chronological, graphical atlas of the growth patterns of cardiac components in the human embryo provides quantified references for normal heart development. Thereby, this atlas may support early detection of cardiac malformations in the foetus.This article has an associated First Person interview with the first author of the paper.

A rare case of hypoplastic coronary sinus partially draining into right superior vena cava: A case report

BACKGROUND

The hypoplastic coronary sinus (CS) is a rare anomaly of the cardiac venous system, wherein some of the tributaries fail to join the CS. These tributaries usually drain into atrial chambers through dilated thebesian channels. We report the first case where the tributaries are draining into the right superior vena cava (SVC).

CASE SUMMARY

A case of ischemic cardiomyopathy with severe LV systolic dysfunction with NYHA class III symptoms was taken for CRTD implantation. CS venogram after direct cannulation from left subclavian access revealed a hypoplastic CS. The part of CS beyond the attachment of the oblique vein of the left atrium to CS (distal to the posterolateral vein) formed a common channel and was draining into the right-sided SVC. The posterolateral vein was of sufficient caliber so that an left ventricle (LV) lead could be implanted, and the CRTD procedure could be completed.

DISCUSSION

Hypoplastic CS though has no pathological significance in the normal population but for CRT it can become a significant limitation. Tributaries of CS draining into right SVC are the rarest of the finding, the channel draining most likely is a remnant of the splanchnic plexus around the embryonic foregut that usually has a temporary communication with cardinal veins during intrauterine growth. This communication somehow has persisted and resulted in a channel between coronary vein and the SVC, which may be referred to as coronary veno-cardinal vein.

The Mesenchymal Cap of the Atrial Septum and Atrial and Atrioventricular Septation

In this publication, dedicated to Professor Robert H. Anderson and his contributions to the field of cardiac development, anatomy, and congenital heart disease, we will review some of our earlier collaborative studies. The focus of this paper is on our work on the development of the atrioventricular mesenchymal complex, studies in which Professor Anderson has played a significant role. We will revisit a number of events relevant to atrial and atrioventricular septation and present new data on the development of the mesenchymal cap of the atrial septum, a component of the atrioventricular mesenchymal complex which, thus far, has received only moderate attention.

Double outlet right atrium-A "bridge" across the bridging leaflets

INTRODUCTION

Mal-alignment between the inter-atrial septum (IAS) and the inter-ventricular septum (IVS) during cardiac embryogenesis results in abnormal atrioventricular (AV) connections ranging from doubleoulet left atrium (DOLA) to double outlet right atrium (DORA)1.

CASE REPORT

We report DORA resulting from partial override of the interatrial septum (IAS) across the cleft between the bridging leaflets of the left atrioventricular (AV) valve.

RESULTS

Successful surgical management with preservation of the orifice is described, leading to an unusual type of double orifice left AV valve.

DISCUSSION

The mal-alignment of the interatrial septum, resulting in it bridging the bridging leaflets, leads to an additional orifice between the RA and the LV and a unique form of right to left shunt. DORA can cause cyanosis depending on the size of the shunt and the compliance of the ventricles. Our patient was acyanotic, possibly due to the small size of the orifice and low LV compliance secondary to hypertrophy of the LV.

CONCLUSION

our case adds to the spectrum of atrial septal mal-alignment variant of DORA in the setting of AVSD without atrial and ventricular components, with RA to LV communication occurring via the smaller orifice of a left atrioventricular valve divided by the abnormal insertion of a partially overriding, mal-aligned atrial septum; a mechanism not described previously - the 'bridge' across the bridging leaflets!

The Efficacy of Contrast Transthoracic Echocardiography and Contrast Transcranial Doppler for the Detection of Patent Foramen Ovale Related to Cryptogenic Stroke

Background

Patent foramen ovale (PFO) has been linked to the pathophysiology of cryptogenic stroke. Contrast transesophageal echocardiography (cTEE) is the current gold standard for PFO diagnosis, but it has the disadvantage of being semi-invasive and does not exempt from risks. As a diagnostic test, the efficacy of contrast transthoracic echocardiography (cTTE) and contrast transcranial Doppler (cTCD) is controversial. This study is aimed at investigating the efficacy of cTTE and cTCD versus cTEE in PFO detection, exploring a more cost-effective and reliable method for the diagnosis of PFO related to cryptogenic stroke.

Methods

From August 2019 to January 2020, a total of 213 patients with suspected PFO were included in our study. All patients underwent cTEE, cTCD, and cTTE examinations. cTTE3 was named for using a cutoff of 3 beats to detect PFO during cTTE, and cTTE5 represented a cutoff of 5 beats. A cutoff of cTCD grade III was named cTCD III. A cutoff of grade IV was named cTCD IV. cTTE3+cTCD IV was used for the combination of a cutoff of 3 beats during cTTE with grade IV of cTCD. cTTE5+cTCD III combined a cutoff of 5 beats during cTTE with cTCD grade III. Taking cTEE as the gold standard, we compared the sensitivity, specificity, negative likelihood ratio (-LR), and misdiagnosis rate for PFO detection among the above methods.

Results

A total of 161 of 213 (76%) patients had PFO confirmed by cTEE. With the spontaneous Valsalva maneuver, the sensitivity, specificity, negative likelihood ratio (-LR), and misdiagnosis rate of cTTE3 in PFO diagnosis were 60%, 90%, 44%, and 10%, respectively, and those for cTTE5 were 76%, 78%, 31% and 22%, respectively. The sensitivity, specificity, negative likelihood ratio (-LR), and misdiagnosis rate of cTCD III were 80%, 71%, 29%, and 29%, respectively, while those for cTCD IV were 55%, 90%, 49%, and 10%, respectively. When cTTE and cTCD were combined to diagnose PFO, the specificity and misdiagnosis rate were significantly improved, especially cTTE3+cTCD IV, with 100% specificity and a misdiagnosis rate of 0.

Conclusion

cTTE or cTCD can be used for preliminary PFO related to cryptogenic stroke findings. The combination of the two methods can improve the specificity of PFO diagnosis, especially using the cutoff of cTTE3+cTCD IV.

Interatrial septum dissection and atrial wall hematoma following transseptal puncture: A systematic review of the literature

BACKGROUND

Interatrial septum (IAS) dissection due to transseptal puncture (TSP) is a rare, underreported complication of the procedure. Data on the mechanism, diagnosis, and management of this complication are lacking.

METHODS

We conducted a systematic review of all reported cases of IAS dissection with or without associated LA hematoma due to TSP, by thoroughly searching MEDLINE and EMBASE through May 2019.

RESULTS

After screening of n = 882 studies, eight studies with a total of 19 patients addressed the complication of IAS dissection and/or LA hematoma secondary to TSP. Median age was 63 years with a 1:1 male to female ratio. Ablation of atrial fibrillation was the most frequently reported procedure (84%). Diagnosis was established using fluoroscopy with contrast injection (58%), TEE (32%) or intracardiac echocardiography (5%). The mechanism identified involved puncture of the septum secundum portion of the IAS, leading to transient needle passage into the extracardiac space. In the majority of patients, the hematoma remained localized in the IAS and management was conservative with progressive resolution of the hematoma during follow-up (95%). Two patients (11%) required further intervention by either pericardiocentesis or surgical drainage due to hemodynamic instability.

CONCLUSIONS

IAS dissection with or without hematoma after TSP remains an underdiagnosed entity. The main mechanism involves lesion to the septum secundum portion of the IAS, resulting in needle passage into the extracardiac space and local bleeding. Although conservative management may be sufficient in the majority of cases, interventional cardiologists should be familiar with this complication and its diagnosis.

Echocardiographic Findings in Patients with Atrial Septal Aneurysm: A Prospective Case-Control Study

Background

Atrial septal aneurysm (ASA) is a congenital deformity of the interatrial septum with a prevalence of 1-2% in the adult population. Although ASA has been supposed to be an incidental finding in echocardiographic examination, its structural and clinical associations have gained an increasing interest.

Aim

To investigate and compare the clinical features and echocardiographic parameters between ASA patients and age- and gender-matched control group patients.

Methods

410 patients with ASA were enrolled in the study, prospectively. After the exclusion of 33 patients, the remaining 377 patients comprised the study group. The control group consisted of 377 age- and gender-matched patients without ASA.

Results

Aortic valve regurgitation and mitral valve regurgitation were more often observed in patients with ASA, and percentages of patients with ascending aortic aneurysm (AAA), patent foramen ovale (PFO), and atrial septal defect (ASD) were higher in ASA patients compared to control group patients. Aortic root diameter was larger in ASA patients compared to control group patients (29.2 ± 3.9, 28.6 ± 3.1, p=0.05, respectively). Ascending aorta diameter was higher in ASA patients compared to patients without ASA (44 ± 0.3, 41.5 ± 0.2, p=0.02). Logistic regression analysis revealed that mitral valve regurgitation (OR: 2.05, 95% CI : 1.44–2.92, p < 0.001) and PFO (OR: 11.62, 95% CI : 2.64–51.02, p=0.001) were positively and independently associated with the presence of ASA. AAA tended to be statistically and independently associated with ASA (OR: 2.69, 95% CI : 0.97–7.47, p=0.05).

Conclusions

We have demonstrated a higher incidence of mitral/aortic valvular regurgitations, AAA, PFO, and ASD in ASA patients compared to age- and gender-matched control group patients. In addition, we have shown that ASA is significantly and positively associated with mild mitral regurgitation and PFO.

Morphological variations of the interatrial septum in ovine heart

Smooth septum interatrial septum, patent foramen ovale (PFO) channel and atrial septal pouches (SPs) are commonly described variants in humans. Recent discoveries on the clinical significance of left-sided SP may encourage the creation of new strategies and devices for the management of SPs. However, these strategies may first be tested in the ovine model before implementation in humans. Unfortunately, little is known about the presence of SPs in ovine. In this study a total of 60 ovine (Ovis aries) hearts were examined. The interatrial septum morphology was assessed and the PFO channel and SPs were measured. The most commonly occurring variant were PFO channels (25.0%) with channel lengths of 5.4±2.3 mm. Smooth septums were observed in 18.3% of hearts. In the remaining cases, septums had a left septal ridge (15.0%), left SP (11.7%), left septal bridge (10.0%), right SP (10.0%), or had both a right SP and left septal ridge (10.0%). No double SPs were observed. The mean right SP depth was 3.4 ± 1.2 mm, and its mean ostium width and height were 7.9±1.8 mm and 2.8±1.0, respectively. For the left SP, the mean depth was 6.0±1.7mm, the ostium width was 7.9±2.4mm, and the ostium height was 4.1±1.6mm (range: 2.3-6.4mm). In conclusion the interatrial septum of ovine hearts exhibit morphologies that are more similar to humans than they are to swine, which should be taken into account during experimental studies. The presence of a left SP in sheep hearts make ovine models a promising alternative to the human heart for developing left-sided SP management devices and techniques.

Mechanism Sharing Between Genetic and Gestational Hypoxia-Induced Cardiac Anomalies

Background: Cardiac development is a dynamic process both temporally and spatially. These complex processes are often disturbed and lead to congenital cardiac anomalies that affect approximately 1% of live births. Disease-causing variants in several genetic loci lead to cardiac anomalies, with variants in transcription factor NKX2-5 gene being one of the largest variants known. Gestational hypoxia, such as seen in high-altitude pregnancy, has been known to affect cardiac development, yet the incidence and underlying mechanisms are largely unknown.

Methods and Results: Normal wild-type female mice mated with heterozygous Nkx2-5 mutant males were housed under moderate hypoxia (14% O₂) or normoxia (20.9% O₂) conditions from 10.5 days of gestation. Wild-type mice exposed to hypoxia demonstrate excessive trabeculation, ventricular septal defects, irregular morphology of interventricular septum as well as atrial septal abnormalities, which overlap with those seen in heterozygous Nkx2-5 mutant mice. Genome-wide transcriptome done by RNA-seq of a 2-day hypoxic exposure on wild-type embryos revealed abnormal transcriptomes, in which approximately 60% share those from Nkx2-5 mutants without hypoxia. Gestational hypoxia reduced the expression of Nkx2-5 proteins in more than one-half along with a reduction in phosphorylation, suggesting that abnormal Nkx2-5 function is a common mechanism shared between genetic and gestational hypoxia-induced cardiac anomalies, at least at a specific developing stage.

Conclusion: The results of our study provide insights into a common molecular mechanism underlying non-genetic and genetic cardiac anomalies.

Inspiratory and expiratory resistance cause right-to-left bubble passage through the foramen ovale

A patent foramen ovale (PFO) is linked to increased risk of decompression illness in divers. One theory is that venous gas emboli crossing the PFO can be minimized by avoiding lifting, straining and Valsalva maneuvers. Alternatively, we hypothesized that mild increases in external inspiratory and expiratory resistance, similar to that provided by a SCUBA regulator, recruit the PFO. Nine healthy adults with a Valsalva-proven PFO completed three randomized trials (inspiratory, expiratory, and combined external loading) with six levels of increasing external resistance (2-20 cmH2 O/L/sec). An agitated saline contrast echocardiogram was performed at each level to determine foramen ovale patency. Contrary to our hypothesis, there was no relationship between the number of subjects recruiting their PFO and the level of external resistance. In fact, at least 50% of participants recruited their PFO during 14 of 18 trials and there was no difference between the combined inspiratory, expiratory, or combined external resistance trials (P > 0.05). We further examined the relationship between PFO recruitment and intrathoracic pressure, estimated from esophageal pressure. Esophageal pressure was not different between participants with and without a recruited PFO. Intrasubject variability was the most important predictor of PFO patency, suggesting that some individuals are more likely to recruit their PFO in the face of even mild external resistance. Right-to-left bubble passage through the PFO occurs in conditions that are physiologically relevant to divers. Transthoracic echocardiography with mild external breathing resistance may be a tool to identify divers that are at risk of PFO-related decompression illness.

Some Isolated Cardiac Malformations Can Be Related to Laterality Defects

Human beings are characterized by a left–right asymmetric arrangement of their internal organs, and the heart is the first organ to break symmetry in the developing embryo. Aberrations in normal left–right axis determination during embryogenesis lead to a wide spectrum of abnormal internal laterality phenotypes, including situs inversus and heterotaxy. In more than 90% of instances, the latter condition is accompanied by complex and severe cardiovascular malformations. Atrioventricular canal defect and transposition of the great arteries—which are particularly frequent in the setting of heterotaxy—are commonly found in situs solitus with or without genetic syndromes. Here, we review current data on morphogenesis of the heart in human beings and animal models, familial recurrence, and upstream genetic pathways of left–right determination in order to highlight how some isolated congenital heart diseases, very common in heterotaxy, even in the setting of situs solitus, may actually be considered in the pathogenetic field of laterality defects.

Porcine heart interatrial septum anatomy

BACKGROUND

The left-sided atrial septal pouch (SP), a recently re-discovered anatomical structure within the human interatrial septum, has emerged as a possible source of thrombi formation and a trigger for atrial fibrillation, thereby potentially increasing the risk for ischemic stroke. In many studies, the swine interatrial septum has been used as model of the human heart. Also, possible new strategies and devices for management of the SPs may first be tested in this pig model. Therefore, in this study, we aimed to evaluate swine interatrial septum morphology and to compare it with the human analog, especially in the light of SP occurrence.

METHODS

A total of 75 swine (Sus scrofa f. domestica) hearts were examined. The interatrial septum morphology was assessed, and SPs were measured.

RESULTS

The most common variant of the interatrial septum was smooth septum (26.6%) followed by the patent foramen ovale channel and right SP (both 22.7%). No left or double SPs were observed. In 28.0% of all cases the fold of tissue (left septal ridge) was observed on the left side of the interatrial septum in the location where the left-sided SP should be expected. The mean length of the patent foramen ovale channel was 7.1±1.5mm. The mean right SP depth was 6.3±2.2mm, and its ostium width and height were 5.8±1.2 and 5.3±1.6mm, respectively.

CONCLUSIONS

There are significant differences between human and porcine interatrial septum morphology that should be taken into account during experimental studies. The absence of the left SP in swine results in the inability to use porcine heart as an experimental model for left-sided SP management.

The Dorsal Mesenchymal Protrusion and the Pathogenesis of Atrioventricular Septal Defects

Congenital heart malformations are the most common type of defects found at birth. About 1% of infants are born with one or more heart defect on a yearly basis. Congenital Heart Disease (CHD) causes more deaths in the first year of life than any other congenital abnormality, and each year, nearly twice as many children die in the United States from CHD as from all forms of childhood cancers combined. Atrioventricular septal defects (AVSD) are congenital heart malformations affecting approximately 1 in 2000 live births. Babies born with an AVSD often require surgical intervention shortly after birth. However, even after successful surgery, these individuals typically have to deal with lifelong complications with the most common being a leaky mitral valve. In recent years the understanding of the molecular etiology and morphological mechanisms associated with the pathogenesis of AVSDs has significantly changed. Specifically, these studies have linked abnormal development of the Dorsal Mesenchymal Protrusion (DMP), a Second Heart Field-derived structure, to the development of this congenital defect. In this review we will be discuss some of the latest insights into the role of the DMP in the normal formation of the atrioventricular septal complex and in the pathogenesis of AVSDs.

Lipomatous Atrial Septal Hypertrophy: A Review of Its Anatomy, Pathophysiology, Multimodality Imaging, and Relevance to Percutaneous Interventions

Lipomatous atrial septal hypertrophy (LASH) is a histologically benign cardiac lesion characterized by excessive fat deposition in the region of the interatrial septum that spares the fossa ovalis. The etiology of LASH remains unclear, though it may be associated with advanced age and obesity. Because of the sparing of the fossa ovalis, LASH has a pathognomonic dumbbell shape. LASH may be mistaken for various tumors of the interatrial septum. Histologically, LASH is composed of both mature and brown (fetal) adipose tissue, but the role of brown adipose tissue remains unclear. In interventional procedures requiring access to the left atrium, LASH may interfere with transseptal puncture, as traversing the thickened area can reduce the maneuverability of catheters and devices. This may cause the needle to enter the epicardial space, causing dangerous pericardial effusions. LASH was once considered a contraindication to percutaneous device closure of atrial septal defects because of an associated increased risk for incorrect device deployment. However, careful attention to preprocedural imaging and procedural intracardiac echocardiography enable interventional cardiologists to perform procedures in patients with LASH without serious complications. In this review article, the authors describe anatomic and functional aspects of LASH, with emphasis on their roles in percutaneous interventions.

CT imaging features of atrioventricular shunts: what the radiologist must know

In the last decade, cardiac computed tomography (CT) has gained mainstream acceptance for the noninvasive exclusion of significant coronary disease in a selected population. Improvements in electrocardiogram (ECG)-triggered imaging techniques also allow, by extension, a proper evaluation of the complete heart anatomy. Given the increasing worldwide clinical implementation of cardiac CT for coronary artery evaluation, radiologists can, incidentally, be confronted with unfamiliar and previously unsuspected non-coronary cardiac pathologies, including congenital morphological defects. This presence of congenital heart disease (CHD) should not be overlooked, being the most common form of birth defect, with a total birth prevalence of 9.1 per 1000 live births worldwide [1]. The prevalence of adult patients with CHD is estimated to be 3000 per million adults [2]. Ventricular septal defects (VSDs) are the most frequent subtypes of CHD, accounting together with atrial septal defects (ASDs) for nearly half of all CHD cases [1]. While some small defects are rarely symptomatic and can go undetected for life, others are clinically significant and require adequate and timely medical intervention. In this article, we present the CT imaging features of atrioventricular (AV) shunts, highlighting both their embryological origins and associated relevant clinical features.

TEACHING POINTS

• Congenital heart disease (CHD) is the most common birth defect. • Ventricular and atrial septal defects account for nearly half of CHD cases. • Atrioventricular defects can frequently be detected on a cardiac CT. • Radiologists must be able to identify clinically significant atrioventricular defects.

Mapping strategies in focal atrial tachycardias demonstrating early septal activation: distinguishing left from right

Determining the chamber of origin of focal atrial tachycardias (FATs) arising at or close to the septum might require biatrial mapping. This review focuses on the available tools and methods used to distinguish right atrial from left atrial origin before left atrial access is obtained. These include analysis of P wave morphology, assessing the timing of right atrial septal activation, the sequence of right atrial and/or biatrial activation and analysis of earliest electrogram morphology. The electroanatomical properties of the interatrial septum and coronary sinus that provide the basis for the above mentioned tools have also been briefly described.

Effect of body position and oxygen tension on foramen ovale recruitment

While there is an increased prevalence of stroke at altitude in individuals who are considered to be low risk for thrombotic events, it is uncertain how venous thrombi reach the brain. The patent foramen ovale (PFO) is a recruitable intracardiac shunt between the right and left atrium. We aimed to determine whether body position and oxygen tension affect blood flow through the PFO in healthy adults. We hypothesized that hypoxia and body positions that promote right atrial filling would independently recruit the PFO. Subjects with a PFO (n = 11) performed 11 trials, combining four different fractions of inhaled oxygen (FiO₂) (1.0, 0.21, 0.15, and 0.10) and three positions (upright, supine, and 45° head down), with the exception of FiO₂ = 0.10, while 45° head down. After 5 min in each position, breathing the prescribed oxygen tension, saline bubbles were injected into an antecubital vein and a four-chamber echocardiogram was obtained to evaluate PFO recruitment. We observed a high incidence of PFO recruitment in all conditions, with increased recruitment in response to severe hypoxia and some contribution of body position at moderate levels of hypoxia. We suspect that increased pulmonary vascular pressure, secondary to hypoxia-induced pulmonary vasoconstriction, increased right atrial pressure enough to recruit the PFO. Additionally, we hypothesize that the minor increase in breathing resistance that was added by the mouthpiece, used during experimental trials, affected intrathoracic pressure and venous return sufficiently to recruit the PFO.

Left septal atrial tachycardia after open-heart surgery: relevance to surgical approach, anatomical and electrophysiological characteristics associated with catheter ablation, and procedural outcomes

BACKGROUND

Septal atrial tachycardia (AT) can occur in patients without structural heart disease and in patients with previous catheter ablation of atrial fibrillation. We aimed to assess septal AT that occurs after open-heart surgery.

METHODS AND RESULTS

This study comprised 20 consecutive patients undergoing catheter ablation of macroreentrant AT after open-heart surgery. Relevance to surgical approach, mechanisms, anatomic and electrophysiological characteristics, and outcomes were assessed. Septal AT was identified in 7 patients who had all undergone mitral valve surgery. All septal ATs were localized in the left atrial septum, whereas 10 of 13 nonseptal ATs originated from the right atrium. Patients with left septal AT had a thicker fossa ovalis (median, 4.0; 25th-75th percentile, 3.6-4.2 versus 2.3; 1.6-2.6 mm; P=0.006) and broader area of low voltage (<0.3 mV) in the septum than patients with nonseptal AT (82; 76-89 versus 31; 28%-36%; P=0.02). Repeated gradual prolongations of the tachycardia cycle length without change of the septal circuit were observed in all patients with septal AT (70; 63-100 versus 15; 10-40 ms; P=0.0008). Although ablation terminated all ATs, recurrence of targeted ATs was more frequent in patients with left septal AT during 30-month follow-up (71 versus 0%; P=0.001).

CONCLUSIONS

Left septal AT after open-heart surgery was characterized by a thicker septum, more scar burden in the septum, and repeated prolongations of the tachycardia cycle length during ablation. Such an arrhythmogenic substrate may interfere with transmural lesion formation by ablation and may account for higher likelihood of recurrence of left septal AT.