Cardiac Rhabdomyoma in an Adult With a Previous Presumptive Diagnosis of Septal Hypertrophy

An 18-year-old woman had been complaining of palpitations and had suffered several episodes of syncope. When the patient was 6 years of age, echocardiography had revealed a localized area of septal hypertrophy without left ventricular outflow tract obstruction, and she was diagnosed with hypertrophic cardiomyopathy. Because of her recent symptoms, she was referred for a number of neurological and cardiac investigations, including cardiovascular magnetic resonance imaging (CMR).

On CMR, there was a localized mass in the interventricular septum that extended from the level of the aortic valve toward the midcavity for a distance of approximately 50 mm, measuring 30 mm at its maximum width. On steady-state free precession cine, it appeared to be homogeneous without any definite demarcation from surrounding myocardium (Figure, A and B, and Movies I through V), and there was limited systolic motion of that part of the septum. There was no evidence of left ventricular outflow tract obstruction. No calcification was noted. T1-weighted imaging showed a homogeneous isointense signal compared with surrounding myocardium (Figure, C). T2 short tau inversion recovery images showed a hyperintense signal within the mass (Figure, D) that differentiated it from the surrounding myocardium. Perfusion imaging demonstrated complete opacification of the full thickness of the mass with almost immediate opacification of the central portion (Movie VI). There was early gadolinium uptake in the mass with enhancement that was more marked than in the surrounding myocardium (Figure, E). Abnormal late enhancement was visible across the entire thickness of the mass (Figure, F).

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Figure. A, Short-axis still image from an steady-state free precession cine obtained through the proximal septum. The markedly thickened septum (arrow) appears to be homogeneous with the rest of the left ventricle (LV) and right ventricle (RV) myocardium. B, Still image from an steady-state free precession cine showing the LV outflow tract (arrow). Despite the marked enlargement of the septum, there was no measured gradient in the LV outflow tract. C, Short-axis turbo spin echo image with T1 weighting demonstrates that the signal from the markedly thickened septum is isointense compared with the rest of the LV myocardium. D, Short-axis T2 short tau inversion recovery image demonstrates a hyperintense signal within the thickened septum, suggesting a different structure from the surrounding myocardium. E, Short-axis image obtained early after gadolinium injection with enhancement of the LV and RV cavities, as well as the myocardium, including the thickened septum. F, Short-axis image obtained late after gadolinium injection. Normal myocardium appears black. There is marked abnormal late enhancement throughout the entire segment of thickened septum.

We concluded that the markedly thickened appearance of the septum was due not to localized left ventricular hypertrophy but to the presence of a hamartoma. Subsequently, the patient’s episodes of syncope were classified as seizures, and further neurological investigation led to a diagnosis of tuberous sclerosis. This combination of her CMR imaging features and the presence of tuberous sclerosis resulted in a final diagnosis of cardiac rhabdomyoma.

CMR is well established in the evaluation of patients with hypertrophic cardiomyopathy and is ideally suited to the assessment of possible cardiac tumors. Factors in determining tumor type by CMR scanning include location and imaging features, such as intensity with T1 and T2 weighting, and whether there is contrast uptake.^1,2 Location and imaging features in the present case were certainly in keeping with rhabdomyoma except for the fact that there was only a single tumor, as rhabdomyomas are frequently multiple. The pattern documented in the present case suggested replacement of myocardium by abnormal tissue and supported the diagnosis of a tumor.

Cardiac rhabdomyoma is found in more than 50% of children with tuberous sclerosis complex.^3,4 There can be partial or complete resolution of the cardiac tumors, even as tumors elsewhere fail to regress; yet, cardiac rhabdomyoma has been documented to increase in size or appear de novo in some patients.³ Because cardiac rhabdomyoma tends to resolve, the patient is usually followed clinically unless the tumor gives rise to important left ventricular outflow tract obstruction, left ventricular failure, or arrhythmias. In this patient who has a tumor and episodes of loss of consciousness ascribed to seizures, it will be important to ensure that a future diagnosis of symptomatic arrhythmia is not missed.