7th March 2024

Investigations

Echocardiography will typically show thickened myocardium and thickened valves with small ventricular cavity sizes. It will also demonstrate impaired filling with diastolic dysfunction due to impaired relaxation caused by the increase in myocardial stiffness.

ECG findings in RCM will typically include low voltage QRS complexes, as well as varying blocks including bundle branch block or complete heart block. Atrial fibrillation is common and, thus, this may also be seen on the ECG. You may also see ‘pseudo-infarction’ Q waves present.

RCM is typically idiopathic in nature, though amyloid is the commonest identifiable cause in the western world. Other causes can include Sarcoidosis and infiltrative diseases such as haemochromatosis or Fabry’s disease.

Sarcoid would be suggested by the presence of systemic granulomas seen on imaging with elevated serum ACE levels and hypercalcaemia. Fabry’s can be diagnosed by assessing for low levels of alpha-galactosidase A on blood tests. Haemochromatosis can be diagnosed through assessment of ferritin and transferrin saturation, while suspicion of a genetic inheritance should lead to assessment for mutation of the HFE gene.

Given that amyloid is a significant and treatable cause of RCM, its presence or absence should be investigated. There are two commonly acquired types, AL and AA amyloid – the former caused by light chain deposition and the latter by overproduction of acute phase proteins, typically in chronic inflammation. AL more commonly affects the heart and is the more common of the two subtypes.

Investigation for AL amyloid should include a myeloma screen with protein electrophoresis and urinary Bence-Jones protein analysis. 

Investigation for AA amyloid include amyloid scintigraphy (a nuclear imaging modality) to assess organ distribution, while fat biopsy can confirm presence when it demonstrates red-green birefringence under polarised light after staining with congo red.

Transthyretin amyloidosis is the most common inherited systemic form of amyloidosis and if suspected after imaging tests then genetic testing can be performed.