1. ANOMALOUS CARDIAC CIRCULATION CAUSING INSIDIOUS ONSET HEART FAILURE
THE GERBODE DEFECT :
ANOMALOUS CARDIAC CIRCULATION
CAUSING INSIDIOUS ONSET HEART FAILURE
Mohamad Syafeeq Faeez MNa, Anna Misyail ARb, Norafida Ba , Mohd Hazeman Za , Idris Ia, Subapriya Sa
aDepartment of Imaging and bDepartment of Medicine, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia
Introduction
Ventricular septal defect (VSD) is the commonest congenital heart defect occurring in 1.56 to 53.2 per 1000 live births [1]. However, the Gerbode defect is an even rarer condition with occurrence of <1% of all congenital heart defects [2] and can also be an acquired condition [3]. It permits shunting from the left ventricle to the right atrium, first reported in 1958 by Gerbode et al [4]. There are 2 forms of this defect; either direct, or indirect via a VSD. Pre-operative diagnosis of this condition is difficult, mostly by echocardiography.
Case Report
A previously well 37-year-old lady was admitted to our medical ward with a short history of fever and cough. Upon further questioning, patient admitted to having bouts of shortness of breath and reduced effort tolerance consistent with heart failure symptoms for the past few years. On examination, she had signs and symptoms of heart failure. Cardiac auscultation revealed a pansystolic murmur, loudest at the left lower sternal edge. Echocardiography showed dilated RA/LA/RV, dilated pulmonary artery, and mild tricuspid regurgitation. A small AV defect was detected, and prompted a computed tomography pulmonary angiography (CTPA) imaging for further investigation.
Computed tomography pulmonary angiography (CTPA) 3A 1 2 RA LV
Fig 1: Axial CT scan image (soft tissue window, W:250, L:50) showing contrast flowing through an abnormal communication between the right atrium and left ventricle (black arrow). This image depicts the Gerbode defect.
Fig 2 : Axial CT scan image, soft tissue window (W:250, L:50). This image demonstrates normal contrast filling in the pulmonary arteries, therefore confirming there is no massive pulmonary embolism. Enlarged pulmonary artery (black arrow), signifies long-standing pulmonary arterial hypertension, likely due to congestive heart failure.
Fig 3 : Coronal CT scan image (lung window, W: 1500, L:-500), showing several segments of patchy opacities (black arrows) scattered throughout both lung fields, which may be due to foci of pulmonary hemorrhage, commonly seen in long-standing pulmonary hypertension.
Discussion
Of the various forms of congenital heart defects, the Gerbode defect constitutes a rare entity. It has an occurrence of less than 1% of all congenital heart defects. Previously, most diagnoses were made intra-operatively. There are 2 forms of this defect, either direct or indirect. A direct defect is said to occur when there is a communication between blood in the left ventricle through a small area in the membranous septum, directly into the right atrium. This permits left ventricular to right atrial shunting. The communication is above the tricuspid valve, also known as supra-valvular. In an indirect defect, a defect is present in the tricuspid valve, permitting shunting of blood from the left ventricle to the right ventricle, then through the tricuspid valve into the right atrium. This communication thus occurs below the tricuspid valve, hence also known as infra-valvular. Apart from the congenital form, there are also acquired causes of LV to RA shunts; these may be due to a weakened membranous septum due to a previous operation, or due to previous infective endocarditis. In our case, it remains a question as to whether she has the congenital or acquired form, though an acquired cause seemed more likely as her symptoms presented quite late and not at childhood. Imaging may be of help in terms of reaching to a diagnosis, and in making better pre-operative preparation. CTPA scan features for this patient were of the direct type, which included an abnormal communication between the left ventricle and right atrium. Contrast backflow was noted in the dilated right atrium. There was a ventriculo-atrial defect located superior to the tricuspid valve. Presence of pulmonary hypertension was also detected.
Conclusion
An accurate and prompt diagnosis is of utmost importance when cardiac shunting is suspected to occur, especially in young patients presenting with heart failure symptoms. The Gerbode defect is a possible differential diagnosis to be considered. The use of CTPA imaging serves as a complementary investigation to help anatomical localization of the Gerbode defect and in evaluation of potential complications of this condition.
References
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