Discussion
The cardiac chambers develop in utero.
The ventricles are divided by the interventricular septum and IVS development ends at birth(1).
Problems with IVS development can cause defects in the muscular or membranous septum seen after birth.
In the neonatal period,
most IVS defects are located in the muscular ventricular septum(1).
Kirklin et al.
classified VSDs as anterior,
midmuscular,
apical,
and posterior; 50% of neonatal heart defects are VSDs.
In 80% of VSD cases,
there are other congenital heart defects,
while 20% of the cases are isolated VSDs.
Most VSDs close spontaneously during the first year of life(1).
In adulthood,
IVS defects are rarely diagnosed in the membranous septum(3).
In an MDCT study of 402 cardiac patients,
Choi et al.
reported,
in 3402 cardiac MDCT studies,
only eight VSAs,
for an incidence of 2.4 0.24% (2,3).
In 1408 cardiac MDCT studies,
we have found only one case of VSA.
In adulthood,
IVS defects are seen in the membranous septum.
Given the lower pressure in the right ventricle (RV) compared to the left ventricle,
aneurysms grow from the IVS defect into the RV(2).
A VSA can cause clinical findings depending on its location and size(2).
The size of VSDs arising from an IVS defect in adulthood depends on the pressure gradient across the IVS(3).
VSAs tend to grow toward the RV and can cause RV outlet narrowing as they grow(2).
Other causes of RV outlet narrowing include pulmonary stenosis,
a double-chambered RV,
double-outlet RV complex,
and aortic regurgitation.
Pulmonary stenosis is the most common RV outlet pathology(2,4).
Such patients can be diagnosed easily with echography(4).
Not all patients with IVS defects develop a VSA.
In patients with open defects,
a shunt can develop between the right and left ventricles(2,4).
The clinical complaints depend on the size of the IVS defect.
Larger defects cause double-outlet RV complex(4).
In these patients,
hemodynamic problems arise from the large connection between the right and left ventricles.
Other cases might be asymptomatic for years.
Embolisms can develop in the venous system in many ways,
including coagulation problems,
trauma,
and air embolisms caused by intravenous interventions.
Venous embolisms usually travel to the lungs(1).
In some cases,
an embolism from the venous system can paradoxically pass into the arterial system via an IVS defect.
In adults,
membranous septal defects can cause paradoxical embolisms(4).
A VSA can appear as a “pseudo mass” in routine CT and MRI studies depending on the contrast material timing(2).
Closed atrial septal defects(ASD) and VSAs might cause atrial and intraventricular filling defects.
Primary cardiac tumors and metastatic lesions are usually seen within the atria(4).
In cancer patients who develop a VSA,
routine CT and MRI studies might suggest false metastasis(2).
VSA should be included in the differential diagnosis in patients with a cardiac mass.
CT and MRI can be used to diagnose VSA(1,3).
In cardiac MRI,
four-chamber images and sequenced contrast imaging are very helpful in diagnosing aneurysms.
The diagnostic superiority of cardiac MRI is because the lesion contents show different signal properties in different sequences and contrast patterns in contrast sequences(2).
The rapid filling and emptying of contrast material from the lesion on MRI and the absence of solid components are typical of aneurysms.
The movement of contrast material within the ventricles in cardiac MRI perfusion sequences is helpful for diagnosing aneurysms.
On MRI,
thrombi in a VSA appear as filling defects(2).
In cardiac MDCT studies,
images are obtained when the coronary arteries fill with contrast material or when the contrast material is within the left ventricle or aorta.
VSAs grow into the right ventricle because of the higher pressure in the left ventricle(1).
Therefore,
the ideal time for VSA imaging is when the left ventricle is full of contrast material,
but the right ventricle has none(2).
That is why cardiac MDCT is useful for VSA imaging.
ECG-synchronized techniques enable high-resolution cardiac MDCT images.
Cardiac MDCT can also be used to study the morphology of VSAs and the aneurysm lumen(2,3).
In our case,
the IVS defect grew into an aneurysm in the right ventricle.
VSAs growing into right ventricle can cause narrowing of the ventricular outlet and hemodynamic problems.
Our patient had no clinical RV outlet pathology despite the large size of the VSA(2).