Keywords: sinus venosus atrial septal defect, posterior mitral valve leaflet hypoplasia, cardiac magnetic resonance
A 65-year-old female with a previous history of surgical ostium secundum atrial septal defect (ASD) repair in 1982 was admitted to our hospital for acute heart failure and atrial fibrillation with rapid ventricular response.
Transthoracic echocardiography revealed marked dilation of the right ventricle and right atrium, normal biventricular systolic function, severe functional tricuspid regurgitation, and estimated systolic pulmonary artery pressure of 34mmHg. Transesophageal echocardiography bubble study with agitated saline contrast revealed microbubbles in the left atrium and left ventricle one to two beats after administration, without any apparent intracardiac shunt (Figure 1). The study also demonstrated eccentric severe mitral regurgitation (MR) secondary to hypoplasia of the posterior mitral valve leaflet (PMVL) (Figure 2).
Cardiac magnetic resonance (CMR) imaging revealed two left-to-right shunts (Figure 3) - one located between the proximal portion of the inferior vena cava and the inferior wall of the left atrium (10.8mm), and another located between the inferior vena cava and the right inferior pulmonary vein (5mm). 3D CMR reconstruction confirmed these findings, which were compatible with sinus venosus atrial septal defect (SVASD).
Volumetric cine-CMR Qp:Qs ratio was 1.43, and invasive hemodynamic catheterization showed mild postcapillary pulmonary hypertension (mean PAP = 32mmHg) with pulmonary capillary pressure at 22mmHg and mildly increased pulmonary vascular resistance (1.89 Wood units).
After Heart Team discussion, surgical SVASD closure, mitral and tricuspid annuloplasty, and left atrial appendage closure were performed. Patient made a good recovery following surgical intervention and remained asymptomatic in the next months. Follow-up echocardiography showed marked reduction of right chamber volumes.
Ostium secundum is the most common type of ASD and is relatively easy to identify by first-line transthoracic echocardiography.1 However, SVASD are rare and located outside the true septum and near the entrance of the superior or inferior vena cava. Specifically, the inferior SVASD is the rarest type, presenting only in <1% of all ASD.2,3 SVASD, especially its superior subtype, are frequently associated with abnormal pulmonary venous drainage.
ASD can remain undiagnosed until adulthood. Furthermore, less frequent forms such as the inferior SVASD types are even more difficult to diagnose, as in the presented case. The occurrence of right atrium and right ventricular enlargement, combined with pulmonary hypertension, should raise the suspicion of an underlying ASD.
Hypoplasia or absence of the PMVL is a rare congenital heart disease that typically presents during childhood as severe mitral regurgitation. Although this condition has been associated with ASD4, its combination with an inferior venous sinus ASD form is extremely rare. Ostium secundum ASD and inferior SVASD probably coexisted in this patient, the first being surgically treated but the latter being overlooked. A careful assessment of the interatrial septum using advanced imaging tech­niques like transesophageal echocardiography, bubble study with agitated saline contrast, and CMR is warranted for accurate diagnosis in cases of unexplained right-side dilation.
To summarize, this case emphasizes the need for comprehensive evaluation of non-typical ASD, such as the sinus venosus type, in cases of concomitant hypoplasia of the PMVL and/or persistent unexplained right chamber dilatation.