Can restrictive cardiomyopathy lead to cardiomegaly?

Restrictive Cardiomyopathy and Cardiomegaly

No, restrictive cardiomyopathy typically does not lead to cardiomegaly, as it is characterized by normal or near-normal ventricular chamber sizes with preserved systolic function. 1

Cardiac Anatomy in Restrictive Cardiomyopathy

Restrictive cardiomyopathy (RCM) has distinct anatomical features that differentiate it from other cardiomyopathies:

• Left and right ventricular chamber sizes are usually normal
• Ventricular wall thickness is normal or only mildly increased
• Systolic function (ejection fraction) is typically preserved
• Massive biatrial enlargement is common due to chronically elevated ventricular filling pressures 1

The classic morphological pattern in restrictive cardiomyopathy includes:

• Normal or reduced ventricular size
• Biatrial dilation (often massive)
• Absence of cardiomegaly on chest radiography 1, 2

Pathophysiology of Restrictive Cardiomyopathy

The defining characteristic of restrictive cardiomyopathy is impaired ventricular filling during diastole due to:

• Increased myocardial stiffness
• Rapid rise in ventricular pressure with only small increases in filling volume
• Restrictive ventricular filling pattern 2

This pathophysiology results from:

1. Interstitial fibrosis and intrinsic myocardial dysfunction
2. Infiltration of extracellular spaces
3. Accumulation of storage material within cardiomyocytes
4. Endomyocardial fibrosis 2

Common Etiologies of Restrictive Cardiomyopathy

Restrictive cardiomyopathy can be caused by various conditions:

• Infiltrative diseases: Amyloidosis, sarcoidosis
• Storage diseases: Hemochromatosis, Fabry's disease, Gaucher's disease
• Fibrotic conditions: Radiation-induced fibrosis, endomyocardial fibrosis
• Connective tissue disorders: Scleroderma
• Idiopathic: No identifiable cause 1, 3, 4

Clinical Presentation

Patients with restrictive cardiomyopathy typically present with:

• Dyspnea due to elevated diastolic pressures
• Prominent signs of fluid retention
• Fatigue and weakness from impaired cardiac output reserve
• No evidence of cardiomegaly on chest radiography 1

Diagnostic Considerations

When evaluating a patient with suspected restrictive cardiomyopathy:

• Echocardiography will show normal ventricular size with preserved systolic function
• Doppler studies demonstrate restrictive filling pattern
• Cardiac MRI may help identify specific etiologies
• Differentiation from constrictive pericarditis is crucial, as the latter is potentially surgically correctable 5, 2

Prognosis and Treatment

Restrictive cardiomyopathy generally has a poor prognosis:

• 50% survival at 5 years after diagnosis 1
• Treatment is challenging and often ineffective
• Disease-specific therapies may be available for certain causes (iron chelation for hemochromatosis, targeted therapy for amyloidosis) 5, 3
• Heart transplantation may be considered in appropriate candidates 6

Common Pitfalls

1. Confusing restrictive cardiomyopathy with constrictive pericarditis, which has similar hemodynamics but different treatment
2. Failing to identify potentially treatable causes of restrictive cardiomyopathy
3. Assuming cardiomegaly is present when it typically is not
4. Overuse of diuretics, which can reduce stroke volume and cardiac output 5

In summary, while restrictive cardiomyopathy causes significant cardiac dysfunction, it does not typically cause cardiomegaly, as the ventricles maintain normal or reduced size. The hallmark finding is biatrial enlargement with normal-sized ventricles.