Thrombus is the commonest mass and does not enhance; myxoma is a mobile left atrial mass on a stalk from the septum; metastases are far commoner than primary malignancy — CMR tissue characterisation and first-pass perfusion separate them.
Orient first
- Thrombus: next to akinetic segments, in the LA appendage, on lines; no enhancement on LGE with a long inversion time.
- Myxoma: interatrial septum (fossa ovalis), heterogeneous, bright on fluid-sensitive MRI, patchy enhancement.
- Malignant features: size > 5 cm, pericardial effusion, invasion, multiple chambers, perfusion.
Acquire the study
- Cine SSFP, T1 and T2 black-blood (± fat-saturated), first-pass perfusion, early and late gadolinium with a long inversion time.
The manoeuvre
- Cine: attachment, mobility, size in mm, chamber.
- T1/T2 with fat saturation: lipoma (fat), myxoma (T2 bright).
- First-pass perfusion series: enhancing (tumour) vs not (thrombus).
- LGE with a long inversion time (~600 ms): thrombus stays black.
- Pericardial effusion and infiltration.
What confirms it
- Tissue characterisation consistent with a named entity; histology for tumours.
What licenses you to exclude it
- A non-enhancing mass on long-TI LGE in an appropriate location is thrombus.
The classic misread
- Calling the crista terminalis, Chiari network or lipomatous hypertrophy of the septum a mass.