The most common intracardiac tumors found in fetuses, infants, and children are rhabdomyomas (Abushaban et al., 1993; Holley et al., 1995). Rhabdomyomas can involve the myocardium, endocardium, pericardium, papillary muscles, cardiac valves, and the pulmonary and aortic outflow tracts (Gava et al., 1990). Rhabdomyomas occur with equal frequency in the right and left ventricles. In 30% of cases, one or both atria are involved (Deeg et al., 1990).

Tuberous sclerosis is a neurocutaneous disorder resulting from hamartomatous growths that can occur in any organ. Interestingly, there is an age-related presentation of the lesions in different organs in tuberous sclerosis (Kwiatkowski and Short, 1994). Rhabdomyomas are primarily the fetal manifestation of tuberous sclerosis (Bader et al., 2003). The classic presentation of tuberous sclerosis, however, is later in life, when the hallmark findings are facial angiofibromas, seizures, and mental retardation.

Overall, intracardiac tumors are extremely rare in infants and children. In one series of children presenting to a pediatric cardiology referral unit, 0.08% had an intracardiac tumor as their referring symptom. Cardiac tumors are found in 0.0017% to 0.25% of pediatric autopsies (Groves et al., 1992). The most likely diagnosis for an intracardiac tumor is rhabdomyoma.

The incidence of intracardiac tumors has been estimated from antenatal sonographic studies. In a series of 794 congenital cardiac malformations derived from more than 10,000 fetal scans, 11 cardiac tumors were identified (0.11%) (Groves et al., 1992). Similar numbers were reported by Holley et al. (1995), who identified 19 fetuses with intracardiac tumors in ~ 14,000 fetal echocardiographic reports (=0.14%).

In 1982, DeVore et al. was the first to describe an intracardiac tumor. A fetus was identified at 26 weeks of gestation with a dense, echogenic mass within the heart. On presentation, however, these authors were not sure whether the mass was extrinsic to the heart or within it. M-mode echocardiography demonstrated that the mass was in the heart. This fetus later became hydropic and died in utero. Subsequently there have been multiple reports of fetuses with large echogenic masses demonstrated clearly by prenatal sonography (Figure 58-1). In many of these cases, the mother was known to be affected with tuberous sclerosis. In other cases, the in utero demonstration of a rhabdomyoma prompted further assessment of both parents, with retrospective diagnosis of one of the parents with tuberous sclerosis.

A consistent theme among many of these case reports is that early sonographic examinations were negative for the presence of intracardiac tumors (Brackley et al., 1999). The tumors were found during the late second trimester but no earlier than 22 weeks of gestation. For example, Green et al. (1991) described a mother who was known to have tuberous sclerosis, who had undergone left nephrectomy for multiple angiomyolipomas of both kidneys, and who was known to have subependymal periventricular lesions by her computed tomographic (CT) scan. Sonographic examinations performed on her fetus at 13 and 16 weeks of gestation were completely normal. At 33 weeks, however, multiple solid cardiac tumors were noted in the left ventricle and intraventricular septum. The fetal central nervous system and renal examinations were within normal limits. In another case reported by Gava et al. (1990), cardiomegaly developed in a fetus with normal sonographic examinations at 10 and 23 weeks of gestation and anechodense mass in the wall of the rightventricle and right atrium at 31 weeks. Over the remaining course of pregnancy, new intracardiac tumors developed in this fetus. The mother, who was previously thought to be healthy, was subsequently diagnosed with a renal angiolipoma, consistent with a diagnosis of tuberous sclerosis.

With increasing prenatal sonographic experience in the diagnosis of intracardiac tumors, it is now clear that they do not become apparent until around 20 weeks of gestation. They undergo their maximal growth between 22 and 32 weeks of gestation and rarely grow after 35 weeks of gestation (Nir et al., 2001).

In fetuses identified with an intracardiac tumor, the following sonographic findings should be noted: the presence or absence of hydrops, whether the tumor is single or multiple, the morphology and characteristics of the intracardiac tumor(s), and the presence of or potential for obstruction of cardiac flow (Groves et al., 1992). The fetal cardiac rhythm should also be observed, as these fetuses are at particular risk for the development of dysrhythmias. Because of the multiple case reports documenting a normal sonographic examination during the first and early second trimesters, all women at high risk for a fetus with tuberous sclerosis (due to a positive family history) should have sequential sonographic examinations, beginning at 20 to 22 weeks of gestation (Journel et al., 1986; Gava et al., 1990; Green et al., 1991; Groves et al., 1992). Another potential intracardiac sonographic finding is diffuse ventricular myocardial thickening (Coates and McGahan, 1994).

Once an intracardiac tumor has been identified, a careful search should be undertaken for associated malformations. The associated findings most likely to occur in the setting of tuberous sclerosis include renal cysts and intracranial abnormalities, such as subependymal nodules (Chen et al., 2005a). Two fetuses have been described with tuberous sclerosis and agenesis of the corpus callosum (Barth et al., 1978; van Oppen et al., 1991). It is unclear whether this finding is related to tuberous sclerosis.

The fetal kidneys should be closely examined. Renal lesions are extremely common in older patients with tuberous sclerosis. For example, angiomyolipoma is found in 47% to 73% of affected patients (Blethyn et al., 1991). Renal cysts are found in 18% to 53% of adult patients with tuberous sclerosis, and both angiomyolipoma and renal cysts are found in 12% to 27% of patients with tuberous sclerosis (Blethyn et al., 1991). Thus, it would seem likely that some patients with tuberous sclerosis will present antenatally with renal cysts. In one case report, a fetus at 28 weeks of gestation was described with a large echogenic unilateral cystic kidney (Blethyn et al., 1991). Initially, this was considered to be consistent with the adult form of polycystic kidney disease or a renal hamartoma. Postnatally, seizures developed in this infant, who had an abnormal electroencephalogram. The definitive diagnosis of tuberous sclerosis was not made until 2 months of age, when calcified cortical tubers were demonstrated on cranial CT examination.

If multiple tumors are present, the diagnosis is rhabdomyoma until proven otherwise (Green et al., 1991). If a single intracardiac tumor is demonstrated, the diagnosis is still most likely to be rhabdomyoma, but other causes in decreasing order of frequency of occurrence in the perinatal period are teratoma, fibroma (Figure 58-2), vascular tumors, and myxoma. If the tumor is a rhabdomyoma there is a greater than 50% chance that the fetus has tuberous sclerosis (Table 58-1). Intracardiac myxoma is the most common tumor in adults, but it is extremely rare during the perinatal period (Chitayat et al., 1988). Characteristic findings of myxoma include its location in the left atrium and/or the interatrial septum (Gava et al., 1990). Rhabdomyomas have a characteristic echodense appearance on sonography. If a cyst is present within the mass, it is less likely to be rhabdomyoma. Extracardiac masses that can potentially mimic rhabdomyoma include bronchopulmonary sequestration (see Chapter 34) and congenital cystic adenomatoid malformation of the lung (see Chapter 35) (Calhoun et al., 1991). Fetal echocardiography is recommended to differentiate between intracardiac and extracardiac masses.