Introduction

Secundum atrial septal defect (ASD) is a common congenital heart disease and accounts for approximately 6% to 10% of all congenital cardiac defects[₁]. The most frequent ASD was the OO type (FS) with 64.78%, followed by common atrium, true FS, FP, superior and inferior sinus venosus, types each one with 2.81% and one coronary sinus venosus type (1.40%)[₃]. Understanding the cardiac anatomy in the malformation of atrioventricular septal defect is an absolute prerequisite for successful surgery, and should be facilitated by recognizing the fundamental nature of the morphology[₄]. Abnormal apoptosis and retarded developmental growth are proposed as pathogenic mechanisms[₃].

Case Presentation

Our case was a 8-years-old woman. She was admitted to our Pediatric Cardiology Outpatient Clinic with complaints of exertional dyspnea and increasing fatigue. The transthoracic echocardiography (TTE) which was performed in admittance, showed a dropout image in interatrial septum compatible with large ASD and dilatation of right-sided structures of the heart (diameter of right ventricle: 31.6 millimeters). Cardiac catheterization showed atrial septal defect. Cardiac catheterization pointed out no additional pathology. Qp/Qs was calculated 1.57. Pulmonary/systemic vascular resistance was 0.4 (Figure 1).

Figure 1

Figure 1

She was operated under endotracheal general anesthesia and in supine position.Following a median sternotomy,pericardium was opened longitudinally. After heparinization, extra-corporeal circulation is established between the venae cavae and the ascending aorta. A cross clamp was placed on aorta and by antegrade intermittant isothermic blood cardioplegia from aortic root,cardiac arrest was established.Hypothermia was moderate (32ºc).A vent was placed via the right superior pulmonary vein. Standart right atriotomy was made. ASD was evaluated regarding its localization, size, other related cardiac structures and possible associated abnormalities.We explorated a muscular limbic band localized at middle of this large atrial septal defect (Figures 2&3).

Figure 2

Figure 2

Figure 3

Figure 3

We resected this band primarily. After this step ASD was made an uniform defect with exicision of this band. We performed an e-PTFE patch closure of atrial septal defect. Right atriotomy was closed in a standard fashion. Postoperative rhythm was sinusal. She didn’t required inotropic support during weaning from cardiopulmonary bypass and early postoperative period. The post-operative course was uneventful with successful anatomical correction.Postoperatively an echocardiographic investigation was revealed no residual shunt for the repaired ASD. She was followed at our outpatient clinic without additional problem.

Discussion

Heart morphogenesis comprises 2 major consecutive steps, chamber formation followed by septation. Septation is the remodeling of the heart from a single-channel peristaltic pump to a dual-channel, synchronously contracting device with 1-way valves. In the human heart, septation occurs between 4 and 7 weeks of development. Cardiac looping and chamber formation bring the contributing structures into position to engage in septation[₅].

The recent identification of a second mesodermal region as a source of cardiomyocytes has challenged the views on the formation of the heart[₆]. This second source of cardiomyocytes is localized centrally on the embryonic disc relative to the remainder of the classic cardiac crescent, a region also called the pharyngeal mesoderm. During evolution, the heart developed initially only with the components required for a systemic circulation, namely a sinus venosus, a common atrium, a 'left' ventricle and an arterial cone, the latter being the myocardial outflow tract as seen in the heart of primitive fishes. These components developed in their entirety from the classic cardiac crescent[₆].

In the study of Wessels et al., the development of the atrial chambers in the human heart was investigated immunohistochemically using a set of previously described antibodies. This study demonstrates a poorly appreciated role of the dorsal mesocardium in cardiac development. From the earliest stage investigated onward, the mesenchyme of the dorsal mesocardium protrudes into the dorsal wall of the primary atrial segment. This dorsal mesenchymal protrusion is continuous with a mesenchymal cap on the leading edge of the primary atrial septum. Closure of the primary atrial foramen by the primary atrial septum occurs as a consequence of the fusion of these mesenchymal structures[₇].

The morphologically and topographically knowledge of atrial septal defect is useful to interpret the imaging studies of this cardiopathy and is basic for the surgeon and the interventionist cardiologist[₃]. Echocardiography was the most frequently used investigative modality in all defect sizes and types[₈]. The transthoracic approach was successful in capturing sufficient data to create 3-D images, which can provide an accurate assessment of secundum ASD[₉].Before repair,we suggest that use cardiac catheterization to fully evaluate a secundum ASD if it is large.

The timing of repair was mainly dependent on patient age and symptomatology in different defects, with the presence of associated anomalies contributing to that in primum and sinus venosus ASD[₈]. Atrial septal defects may close spontaneously during the first few years of life[₂₁₀]. Most centers advocate elective closure of moderate-to-large ASDs between 4 and 6 years of age[₂₁₁]. Surgical closure of ASD has a low perioperative mortality and morbidity[₂].