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 techÂniques 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.