Ultrasound and magnetic resonance imaging in the assessment of a fetal intracardiac mass

Abstract

We report on a 29-year-old Caucasian woman who had a routine anomaly scan performed at 20 weeks' gestation. Fetal echocardiography demonstrated an enlarged, echogenic and homogeneous interventricular septum measuring 10 × 10 mm in diameter (Figure 1). There was a reduction in the size of each ventricular cavity, the left ventricle was slit-like and the right ventricle was apically truncated. The arterial relationship was normal and there was no evidence of outflow tract obstruction. There was good ventricular function in systole and diastole. The fetus was not hydropic and Doppler ultrasound examination showed no abnormalities in the ductus venosus. Ultrasound examination showing transverse section of the fetal thorax with an enlarged ventricular septum at 20 weeks' gestation. The diagnosis was that of a cardiac tumor. Other much less likely diagnoses included hypertrophic cardiomyopathy and hypertrophy secondary to a distal obstructive lesion. History and clinical examination were negative for tuberous sclerosis. Invasive testing for metabolic disorders such as Pompe's disease was declined by the patient. At 28 weeks' gestation, magnetic resonance imaging (MRI) was performed. MRI demonstrated a hyperintense well circumscribed mass measuring 30 × 24 × 20 mm (Figure 2). Its signal was much higher than that of the surrounding myocardium, supporting the diagnosis of a tumor rather than hypertrophy. Magnetic resonance images of (a) transverse and (b) sagittal sections of the fetal thorax, showing the interventricular tumor at 28 weeks' gestation. Ultrasound examination at 30 weeks' gestation demonstrated a severe reduction in biventricular cavity size with a narrow and distorted left ventricular outflow tract. There was reduced left ventricular free wall motion. There was no evidence of hydrops. It was felt that elective delivery should be delayed until after 34 weeks' gestation. Thereafter, surgical resection of the fetal tumor could be considered. However, at 32 weeks' gestation intrauterine fetal death was confirmed. Labor was induced and a stillborn 2165-g female fetus was delivered vaginally. At postmortem examination, fetal biometry was consistent with gestational age and the fetus was non-dysmorphic. The body weight to heart weight ratio indicated that the heart was three times the normal weight. The interventricular septum contained a 3 × 2-cm non-encapsulated tumor (Figure 3). Histologically, the tumor had a heterogeneous structure: a vascularized mesodermal tumor with central calcification and necrosis. These findings were consistent with a fibroma. The site of the tumor made it probable that the cause of fetal death was cardiac arrhythmia rather than obstruction of the outflow tract. Gross pathological specimen at postmortem examination showing the ventricular tumor. Fetal cardiac tumors are rare. The most common type is rhabdomyoma1. Its typical appearance on ultrasound examination is of multiple hyperechogenic, well circumscribed, homogeneous masses in the ventricular wall or interventricular septum2. Fibromas are the second most common tumor. These are usually found as solitary masses and are seen on ultrasound examination as hyperechoic lesions often associated with calcification and cystic degeneration3. Fibromas often involve the interventricular septum and cause death by ventricular arrhythmia owing to local compression of the conduction system4. In general, the management of fetal cardiac tumors is conservative. The approach is to optimize neonatal outcome while avoiding iatrogenic premature delivery. Certain lesions may be amenable to surgical resection following delivery. In cases where the tumor is intracardiac, therapeutic options are limited and the prognosis is poor5. Fetal MRI has been used increasingly to confirm equivocal ultrasound findings. It is seldom employed to assess the heart6-8 and some authors believe that MRI is not useful9. In the case described here, fetal MRI was of value as it demonstrated a single, well circumscribed lesion in the interventricular septum. This appearance was consistent with the diagnosis of a tumor and helped exclude cardiomyopathy or hypertrophy secondary to a distal obstructing lesion. Although making the correct antenatal diagnosis did not alter the outcome, this case does demonstrate the evolving role of MRI. However, real-time ultrasound examination will remain invaluable in assessing cardiac function. It is likely that in future both MRI and ultrasound modalities will be used in combination to make a diagnosis and delineate prognosis. S. Ong*, M. Usher-Somers*, S. Philip , P. Miller?, K. Foster?, T. Marton , W. Martin*, M. Kilby*, * Fetal Medicine Department, Birmingham Women's Hospital, B15 2TG, UK, Department of Pathology, Birmingham Women's Hospital, B15 2TG, UK, Department of Obstetrics, City Hospital, Birmingham, UK, ? Department of Cardiology, Birmingham Children's Hospital, Birmingham, UK, ? Department of Radiology, Birmingham Children's Hospital, Birmingham, UK