A Mass-terful Image: A Case Highlighting the Diagnostic Power of Cardiac MR

Description of Clinical Presentation: A 44-year-old female with a history of recently diagnosed metastatic colorectal cancer s/p diverting colostomy, presented with left-sided weakness and was found to have a right M2 occlusion requiring mechanical thrombectomy. Pertinent laboratory investigations included a leukocytosis of 17 thou/L, high sensitivity troponin 59 ng/L, and proBNP 6099 pg/mL. Blood cultures were obtained and remained negative throughout the hospital course. She was found to have an intra-cardiac mass along with evidence of extra-cardiac metastatic disease. She was discharged home with plan to follow-up outpatient to determine timing for chemotherapy initiation.

Diagnostic Techniques and Their Most Important Findings: Transthoracic echocardiography revealed a large (1.1 x 1.4cm), nonmobile mass on the posterior tricuspid leaflet and mild to moderate tricuspid regurgitation (TR). The bubble study was negative. Transesophageal echocardiography (TEE) found moderate TR with perforation of the posterior leaflet and a sessile vegetation (0.72 cm) on the atrial side of the posterior tricuspid leaflet. Additionally, there was a round, homogenous mass, measuring 1.5x1.4 cm, in the anterior and superior portion of the interatrial septum. Color doppler revealed flow within the structure. Cardiac MRI characterized the mass as isointense on T1, hyperintense on T2, and did not take up contrast on perfusion or delayed imaging. Extracardiac MRI found numerous round nodules throughout the lungs, as well as large T2 hyperintense nodules throughout the liver and spleen.

Learning Points from this Case: Intra-cardiac masses are commonly categorized into three main groups: thrombus, vegetation, or neoplasm. Echocardiography remains the initial imaging test of choice, as it provides mass size, location, and mobility. The addition of ultrasound enhancing agents can help delineate a vascular tumor from that of thrombus. Cardiac MR can further characterize different tissues, especially with regards to patterns of contrast enhancement, and is especially useful when looking at tumors. Frequently, neoplasms are highly vascular and often take up contrast. The tumor in our patient did not enhance in post gadolinium imaging; however, this can be seen in rectal carcinomas. The location of the mass lesions, the presence of two intra-cardiac and multiple extra-cardiac lesions with similar tissue characteristics makes them more likely to be metastatic lesions. Unfortunately, metastatic disease to the heart often portends a poor prognosis, with variable response to chemotherapy.

4-chamber Cine demonstrating the interarterial septal rounded mass
Short axis of the inter-atrial septal mass
Transesophageal echocardiogram showing homogenous mass within the inter-atrial septum (left). Transesophageal echocardiogram demonstrating tricuspid vegetation (right).