SCMR 22nd Annual Scientific Sessions
Description of Clinical Presentation: We describe a case of a 68-year-old man who presented to the outpatient clinic with palpitations and dyspnea. He had a past medical history of permanent atrial fibrillation (AF) and polycystic kidney disease (PKD) diagnosed in 1994, for which he underwent two renal transplants. His family history was unremarkable.
Diagnostic Techniques and Their Most Important Findings:
Blood tests showed polycythemia (Hb 17.4g/dL) and elevated serum free kappa light chains, but normal kappa/lambda ratio. His transthoracic echocardiogram demonstrated normal biventricular size and systolic function, with LVH and increased wall thickness towards the apex (Figure 1 – A, diastole B, systole).
Differentials for this presentation included hypertrophic cardiomyopathy (HCM) and cardiac amyloidosis; thus a CMR scan was performed (Aera 1.5T, Siemens). Extracardiac findings included multiple liver and kidneys cysts in keeping with PKD (Figure 2, A). LV was normal in size with preserved ejection fraction (LVEF=71%). There was marked apical hypertrophy (16mm) and asymmetrical septal hypertrophy (18mm in the basal anterior septum) (Figure 2, diastole B, systole C) with systolic mid-to-apical cavity obliteration, but no LV outflow tract obstruction at rest. T1 mapping showed several myocardial areas of extremely low native T1 (360-460ms, normal 1020±60ms MOLLI, Figure 2, D); native T1 values were within normal range elsewhere. Myocardial T2 mapping was normal (Figure 2, E). Post-contrast, a TI scout revealed simultaneous nulling of the myocardium and blood pool (Figure 2, F). There was dense late gadolinium enhancement (LGE) (Figure 3, A-D) and elevated extracellular volume fraction (ECV) in the same areas as low T1 (Figure 3, E and F).
In summary, there was pronounced fatty infiltration of the hypertrophied segments, with matching LGE. Amyloid infiltration was unlikely as T1 values were normal outside of the fatty infiltration areas. Simultaneous signal nulling in TI scout was thought to be not specific for amyloid and may also be seen in cases of polycythemia when hematocrit has a similar cell fraction (and therefore ECV) as the myocardium.
There was no clear explanation for this fatty infiltration of the myocardium. Differentials include Anderson-Fabry disease (AFD) with an atypical appearance and fatty metaplasia in the context of apical HCM, although extremely unusual. However, during follow-up serum alpha-galactosidase levels were normal, making AFD unlikely. An endomyocardial biopsy was recommended but declined by the patient. Apical HCM with fatty metaplasia was considered the most likely hypothesis
Learning Points from this Case:
- Simultaneous nulling of myocardium and blood pool is not specific for cardiac amyloidosis.
- Native T1 mapping allowed the detection of fatty infiltration in a patient who otherwise would be labelled as apical HCM with scar alone.
- Areas of scar with fatty metaplasia result in high ECV values.