Involves normal or decreased volume of both ventricles with bi-atrial enlargement, normal wall thickness, normal cardiac valves and impaired ventricular filling with restrictive physiology but near-normal systolic function

Aetiology

• Familial non-infiltrative cardiomyopathy (inherited genetic disorders)
• Infiltration of the myocardium by an invasive substance e.g. sarcoidosis, amyloid, tumours
• Fibrotic myocardium without an external invasive substance e.g. as a result of radiation exposure

Pathophysiology

• The walls of the ventricles become stiff, but not necessarily thickened
• Compliance of the ventricular walls during diastolic filling is reduced, resulting in the clinical features of heart failure

Clinical features

• As heart failure - dyspnoea, fatigue, elevated JVP, oedema
• AF develops in 75% of patients

Investigations

• ECG: reduced QRS, ST-segment and T wave changes
• Echocardiography: diagnostic, shows thickened ventricular walls
• Cardiac MRI: useful for distinguishing between restrictive cardiomyopathy and constrictive pericarditis

Management

• Manage heart failure
• Management of underlying cause if possible e.g. amyloidosis