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Atrial masses postcardiac transplant are not well reported and their diagnosis and treatment can be challenging. In the asymptomatic patient, differentiating thrombus from cardiac tumor can sometimes be difficult and the use of multiple imaging modalities is recommended. Accurate diagnosis is imperative to inform a treatment plan that balances the benefits and risks of a medical versus surgical approach. We present three cases of atrial masses postcardiac transplant to illustrate this clinical dilemma.
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Most atrial masses postcardiac transplant are discovered on routine TTE or DSE. Infective endocarditis should always be considered in the differential diagnosis, though this is more likely when the patient's clinical status is consistent with an infective process. In the asymptomatic patient, thrombus or tumor is more probable, but can be difficult to distinguish.
Virchow's triad still holds true postcardiac transplantation, and any factors that cause a hypercoagulable state, disruption to flow, or endothelial or vessel wall injury can promote thrombus formation. Patients with atrial fibrillation, large LA, low cardiac output states (possibly due to rejection or CAV) and absence of anticoagulation are at increased risk of thrombus formation. Thrombus should be suspected when masses form in close proximity to suture lines or foreign objects (e.g. pacing wires or catheters), and when they develop in a relatively short time period. Operative technique is also important as patients who undergo the preferred ‘bicaval’ anastamotic technique rather than the more traditional ‘bi-atrial’ approach tend to have smaller LA size with less spontaneous echo contrast (SEC), thrombus and embolic events (1–3).
In nontransplant patients, cardiac tumors are more likely to be secondary than primary with autopsy studies reporting a frequency of 8.4% (in patients with known cancer) and up to 0.03%, respectively (4,5). Most primary tumors are benign myxomas or papillary fibroelastomas, while malignant primaries are predominantly sarcomas, with occasional lymphomas and mesotheliomas (Table 1). Although malignancy postcardiac transplantation occurs more commonly than the general population, the reporting of primary cardiac malignancies is limited to individual case reports. Apart from our Case 1, there are two other documented cases of pathologically proven myxoma postcardiac transplant (11,12). In both cases, the myxoma was attached via a pedicle arising from a left atrial suture line rather than the classical location on the IAS, highlighting potential diagnostic pitfalls. When a primary cardiac tumor is suspected, definitive treatment is often sought since approximately 25% present with embolic events (more likely with small tumors involving the aortic valve or left atrium) (13).
Table 1. General features and imaging characteristics of common atrial masses6–10
| ||General Considerations||Thrombus||Myxoma||Papillary fibroelastoma||Sarcoma|
|General features||Thrombi > tumors Secondary > primary tumors 75–94% primary tumors are benign||Homogenous appearance Suture/foreign body sites Rapid onset Coagulopathic AF, LV dysfunction, large LA||50–80% of benign tumors 75% in LA Attached to fossa ovalis (IAS) Attached via stalk/pedicle Typically ovoid/spherical Heterogenous appearance||10–25% of benign tumors Small (<1 cm) usually solitary Affects left sided heart valves “Flower-like” with fronds||95% of primary malignancies Most common in RA Broad based Locally invasive/metastases Poor prognosis|
|ECHO (TTE/TEE)||Cost-effective Easily available Hemodynamic assessment Contrast/3D add information||Best for PM lead assessment TEE assesses SEC, LAA, IAS well No contrast uptake No color flow within mass||Pedicle often best seen on TEE Assesses tumor mobility well Hemodynamic effects||Modality of choice “Shimmering” appearance Valvular function spared||Hemodynamic effects Pericardial effusion|
|CT||Best for thoracic extension Coronary artery assessment Radiation Contrast nephrotoxicity||Low attenuation mass Possible calcific foci if chronic No contrast uptake||Low attenuation Heterogenous contrast uptake||Often difficult to visualize||Heterogenous contrast uptake Tumor extension/spread|
|MRI||Best tissue characterization No radiation/contrast safer Cardiac device incompatible Availability/cost possible issue||T1/T2 dependent on clot age No contrast uptake||Isointense in T1 Hyperintense in T2 Heterogenous contrast uptake||Often difficult to visualize||Heterogenous in T1 Hyperintense in T2 “Cauliflower” appearance Enhances with contrast|
TTE is a noninvasive, readily available and cost-effective imaging modality that can inform on mass morphology, location and hemodynamic consequences. TEE is a useful adjunct to provide additional resolution and information about SEC, the left atrial appendage and the IAS. However, for cardiac transplant patients, relying solely on echocardiography to differentiate intra-cardiac masses can result in misdiagnoses (14,15). Cardiac MRI (with contrast) adds significant diagnostic accuracy for intra-cardiac masses, and is highly recommended as a complementary imaging modality when available (9,16). CT can also be helpful when MRI is contra-indicated, especially for coronary artery assessment and extra-cardiac thoracic evaluation (8,9; Table 1).
When malignancy is suspected, transvenous cardiac biopsy can be utilized to obtain pathology, especially when complete surgical resection is thought not possible or too risky. Biopsy guidance with TTE, TEE or intracardiac echocardiography (ICE) improves diagnostic sampling and safety, and right sided masses are preferred due to a lower risk of systemic embolization (17–19).
Treatment plans for atrial masses postcardiac transplant should be individualized given the lack of clinical trial information. Most benign atrial tumors will need consideration for surgical removal to avoid complications of mass effect or embolization (6,20). Most posttransplant atrial thrombi can safely undergo a trial of anticoagulation, although there is little evidence to support the best approach in large ‘ball-like’ thrombi, or when anticoagulation fails to have effect (21,22). When diagnostic uncertainty exists, a trial of anticoagulation of at least 4 weeks with repeat imaging to examine for a response seems prudent (23) The chosen treatment course should balance the risk of conservative treatment/anticoagulation with the operative risk of surgical intervention, whilst considering patient preferences.