Suspected Cystic Tumor of Atrioventricular Node

Zehavit E Kirshenboim¹, Joan M Lacomis¹, Timothy Wong²

¹Department of Radiology, Division of Cardiothoracic Imaging, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
²University of Pittsburgh School of Medicine, Division of Cardiology, Pittsburgh, PA, USA.

Clinical History

A 56-year-old woman presented with palpitations and a recently diagnosed early-stage breast cancer. Her 12-lead electrocardiogram (ECG) did not show abnormalities (Figure 1).

Figure 1. 12-lead ECG at presentation.

A 7-day Holter monitor revealed rare ectopy, with <1% premature ventricular complexes (PVCs) and <1% premature atrial contractions (PACs), and no sustained ventricular or supraventricular arrhythmias. As part of the work-up, she underwent coronary artery calcium (CAC) scoring CT, which showed a calcium score of zero, and incidentally identified a hyperdense cardiac lesion. CAC unenhanced CT demonstrated a 1 cm hyperdense lesion at the interatrial septum (Figure 2). Transthoracic echocardiography (TTE) was performed but did not visualize the lesion.

Figure 2. Axial image of unenhanced coronary artery calcium score CT, shows a well circumscribed 1cm hyperdense lesion at the interatrial septum (arrow).

 

CMR Findings

CMR (Siemens Magnetom Sola 1.5T) demonstrated the lesion at the interatrial septum near the atrioventricular junction. It was hyperintense on T1-weighted images, on both pre-contrast (Figure 3) and post-contrast (Figure 4) images, with limited evaluation of enhancement.

Figure 3. Short axis oblique precontrast T1 image shows a hyperintense lesion (arrow).

 

Figure 4. Short axis oblique late gadolinium enhancement image shows a 1 cm hyperintense lesion (arrow).

Native T1 mapping demonstrated very low signal intensity (Figure 5), and on balanced steady-state free precession (bSSFP) was slightly hyperintense to the myocardium (Movie 1).

Figure 5. Four chamber view T1 mapping image of the lesion demonstrates low T1 value at 245 ms (arrow).

 

Movie 1. Four chamber view bSSFP shows the lesion is slightly hyperintense to the myocardium (arrow).

T2 mapping value was elevated at 70 ms (Figure 6).

Figure 6. Basal short axis T2 mapping with and without color mapping demonstrates elevated T2 values (70 ms).

Perfusion sequence was also performed, however the mass was not well seen. Visualization may be improved by thinner slices, overlapping slice spacing to ensure lesion coverage, multiple orthogonal views, and split-dose contrast protocols.

Conclusion

On 18F-fluorodeoxyglucose (FDG) PET/CT the cardiac lesion demonstrated no FDG avidity (Figure 7).  Given the lesion’s location, signal characteristics, non-FDG-avidity, and absence of aggressive features, a cystic tumor of the AV node (CTAVN) was favored. The differential diagnosis includes bronchogenic cyst, mesothelial cyst, teratomas and histiocytoid cardiomyopathy, which can be differentiated from cystic tumor of the AV node by histopathology. Cardiac surgery determined the lesion was too small for biopsy or resection, and the patient is therefore being managed with conservative monitoring.

Figure 7. FDG PET/CT demonstrating no FDG uptake in the hyperdense lesion at the atrioventricular node region (A, arrow), with corresponding CT (B) and attenuation-corrected PET images (C).

 

Perspective

Cystic tumors of the AV node are rare cardiac tumors that predominantly affect women (3:1 ratio). Despite being benign, CTAVN is associated with variable degrees of heart block that can progress to complete heart block and sudden cardiac death, with no relationship between size and occurrence of arrhythmia. Treatment includes tumor resection, although it is unclear if it would reduce the risk of sudden cardiac death. Permanent pacemaker implantation was used in several cases with varying degrees of heart block.[1,2] Given its subtle presentation, this tumor should be considered in patients—particularly young adults and females—presenting with heart block limited to the AV node or sudden cardiac death.[3]

This case highlights the value of multimodality imaging in the evaluation of an incidental cardiac mass with potential conduction system implications. The lesion’s characteristic location, T1 hyperintensity on CMR, and lack of FDG uptake strongly favored the diagnosis of a cystic tumor of the AV node. While not visualized on echocardiography and not amenable to biopsy or resection, careful correlation with rhythm monitoring and clinical context supported conservative management. Follow-up imaging and cardiology evaluation remain key components of monitoring in such cases, particularly given the potential for conduction disturbances development over time.

Click here for a link to the CMR scan on CloudCMR.

 

References

1. Giuliano K, Scully B, Etchill E, Lawton J. Cystic tumor of the atrioventricular node. Glob Cardiol Sci Pract. 2020 Nov 30;2020(2):e202028. doi: 10.21542/gcsp.2020.28. PMID: 33426045; PMCID: PMC7768629.
2. Abuzeid W, Myers RBH. Cystic tumour of the atrioventricular node: treatment dilemma. BMJ Case Rep. 2017 Apr 24;2017:bcr2017219314. doi: 10.1136/bcr-2017-219314. PMID: 28438795; PMCID: PMC5534749.
3. Luc JGY, Phan K, Tchantchaleishvili V. Cystic tumor of the atrioventricular node: a review of the literature. J Thorac Dis. 2017 Sep;9(9):3313-3318. doi: 10.21037/jtd.2017.08.101. PMID: 29221317; PMCID: PMC5708412.

Case prepared by Anna Baritussio, MD, PhD, FEACVI
Cases of SCMR, Editorial team
Department of Cardiac, Thoracic, Vascular Sciences and Public Health
Padua University Hospital, Padua, Italy