Myocardial scintigraphy in suspected amyloidosis

A practical guide for referring physicians

Principle and method

amylo2Amyloidosis is a heterogeneous group of diseases characterised by extracellular deposition of fibrillar proteins, leading to progressive organ involvement. Cardiac amyloidosis, particularly transthyretin (ATTR) and AL (light-chain) amyloidosis, is associated with severe cardiomyopathy, heart failure and a poor prognosis.

Traditionally, the diagnosis of cardiac amyloidosis has been based on endomyocardial biopsy. In recent years, however, non-invasive diagnosis using phosphonate radiopharmaceutical scintigraphy has become established:

  • 99mTc-DPD (3,3-diphosphono-1,2-propanedicarboxylic acid),
  • 99mTc-PYP (pyrophosphate),
  • 99mTc-HMDP (hydroxymethylenediphosphonate).

amylo3These substances bind to amyloid fibrils in the myocardium and enable specific detection of TTR amyloidosis. Imaging is performed planarly and using SPECT/CT, which provides detailed anatomical and functional information.

Main clinical indications

  • Suspected cardiac amyloidosis in patients with:
    • hypertrophic cardiomyopathy of unclear aetiology,
    • restrictive cardiomyopathy,
    • heart failure with diastolic dysfunction,
    • unexplained left ventricular hypertrophy on echocardiography or MRI.
  • Differentiation of types of amyloidosis:
    • phosphonate scintigraphy is highly specific for ATTR,
    • AL amyloidosis usually does not show significant uptake.
  • Prognostic stratification – the extent of accumulation correlates with the severity of the condition and prognosis.
  • Monitoring the effect of therapy – especially with new drugs affecting transthyretin (tafamidis, patisiran, inotersen).

Interpretation and clinical significance

Evaluation of findings

  • Grade 0: no accumulation in the myocardium.
  • Grade 1: minimal uptake less than in the ribs.
  • Grade 2: accumulation similar to that in the ribs.
  • Grade 3: accumulation higher than in the ribs with clear visualisation of the myocardium.

The difference between ATTR and AL amyloidosis is significant:

  • ATTR: typically strong accumulation of radiopharmaceutical.
  • AL: mostly negative or only weak uptake.

The combination of scintigraphy with negative immunofixation testing of serum and urine allows for non-invasive confirmation of ATTR amyloidosis without the need for a biopsy.

Practical information for the referring physician

  • Patient preparation: no special diet or discontinuation of medication is necessary.
  • Examination procedure:
    1. intravenous administration of 99mTc-phosphonate,
    2. planar images of the heart and entire body approximately 1–3 hours after administration,
    3. supplemented by SPECT/CT for a more accurate assessment of accumulation and differentiation from bone activity.
  • Examination duration: 2–3 hours.
  • Contraindications: pregnancy; relative contraindication in breastfeeding women.

Summary for practice

Myocardial scintigraphy with phosphonate radiopharmaceuticals is:

  • a key method for diagnosing TTR amyloidosis,
  • capable of distinguishing TTR from AL amyloidosis in a non-invasive manner,
  • essential for early diagnosis and initiation of targeted therapy,
  • a safe, accessible and prognostically significant method.

Its introduction has fundamentally changed the approach to the diagnosis of cardiac amyloidosis – it allows for rapid and reliable diagnosis without the need for invasive biopsy, thereby improving patient care and prognosis.