Cardiac amyloidosis - ATTR wild-type

Case contributed by Dr Joachim Feger

Presentation

Fatigue, dyspnea on exertion. Non-obstructive hypertrophic cardiomyopathy with reduced ejection fraction (EF) in cardiac echo. History of bilateral carpal tunnel syndrome.

Patient Data

Age: 75 years
Gender: Male

Findings:

Heart rate:  68 bpm, body surface area (BSA) 2.03 m²

Hematocrit:  0.39

Image quality: no limitations

Morphology and functional analysis:

  • LV-EDVI: 91 mL/m²
  • LV-ESVI: 49 mL/m²
  • LV-SVI: 42 mL/m²
  • LV-EF: 46%
  • cardiac output: 6.3 L/min
  • cardiac index: 3.1 L/min/m²
  • LV-ED wall + papillary mass index: 151 g/m²
  • Septum thickness: 20 mm

Global hypokinesia, pronounced in the thickened basal inferoseptal and inferior segments.

Mildly increased left atrium. Thickened atrial septum. Persistent foramen ovale (PFO).

Aortic valve insufficiency with a diastolic jet in the left ventricular outflow tract (LVOT).

No intracavitary thrombi were found.

Myocardial tissue properties

Increased myocardial signal intensity in the apical segments, probably due to stagnant blood.

Difficulties in nulling the myocardium with the look locker sequence.

PSIR and IR-GE sequences show a dark blood pool and a subendocardial late gadolinium enhancement in a non-coronary arterial distribution with a lesser extent in the apical segments, together with a transmural enhancement of the basal segments.

T1 mapping native: 1170-1250 ms [950-1060ms*], extracellular volume (ECV): ≥60% 

*reference range based on local data

No pericardial enhancement. Minimal pericardial effusion.

Impression:

Non-obstructive left ventricular hypertrophy with mild systolic dysfunction.

Cardiac MRI findings are consistent with cardiac amyloidosis. 

The high values in extracellular volume (ECV) and the distinct thickening of the interventricular septum favor ATTR over AL cardiac amyloidosis.

Annotated image

Cine images, T2 black-blood and STIR imaging:

Thickening of the interventricular septum (orange measurement >20mm) and the interatrial septum (blue measurement ≈ 8mm).

T2 ratio was <1.9 – a T2 ratio of ≥2 is considered abnormal.

Minimal pericardial effusion (blue arrowhead).

Look-Locker:

Images sorted by acquisition time.

On close inspection, the myocardium passes through the zero-point before the blood pool. Usually, this is the other way around.

Late gadolinium enhancement (LGE):

It is conspicuous, that the blood pool has an even darker signal than the "nulled" myocardium not only on the inversion recovery gradient echo images but also on the PSIR image. This is due to high myocardial gadolinium uptake and fast blood washout referred to as abnormal blood-pool gadolinium kinetics 1.

There is subendocardial late gadolinium enhancement in a non-coronary arterial distribution (red arrowheads) in midventricular and basal segments, and faint transmural enhancement of the septal and inferior basal segments (red arrows).

T1 mapping native and postcontrast:

Obviously increased native T1 here measured in the basal inferoseptal segment (z-score of 6.3). Native T1 measured in other segments ranged from 1170-1250 ms.

Decreased postcontrast T1.

Massively increased calculated extracellular volume (ECV) by ≥60%.

Case Discussion

This case illustrates and reviews the MR imaging features of cardiac amyloidosis:

  • left ventricular hypertrophy, increased indexed mass, thickened interatrial septum
  • faster myocardial nulling than the blood pool 2,3
  • dark blood pool and subendocardial late gadolinium enhancement (LGE) in a non-coronary distribution with transmural pattern 1-4
  • high values in native T1 and extracellular volume (ECV) 5-9

Higher values in extracellular volume (ECV) 5-9 wall thickness and mass have been reported for ATTR amyloidosis, whereas higher native T1 values 5-9 and higher T2 values the latter as a biomarker for myocardial edema 7 have been reported for cardiac AL amyloidosis. This is, why ATTR is in favor over AL amyloidosis in this case.

An endomyocardial biopsy obtained about six months after the cardiac MRI revealed cardiac interstitial ATTR amyloidosis. Subsequent genotyping lead to the diagnosis of wild-type ATTR amyloidosis.

Also of note is that myocardial edema is of worse prognosis in cardiac AL amyloidosis 7.

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