Does restrictive cardiomyopathy often present with syncopal episodes?

Syncope in Restrictive Cardiomyopathy

Syncope is not a common presenting symptom of restrictive cardiomyopathy but may occur due to conduction system disease, arrhythmias, or impaired cardiac output from the restrictive physiology. Based on the most recent guidelines, syncope in restrictive cardiomyopathy is typically associated with specific underlying mechanisms rather than being a predominant presenting feature of the disease itself.

Mechanisms of Syncope in Restrictive Cardiomyopathy

Syncope in restrictive cardiomyopathy can occur through several mechanisms:

1. Arrhythmias:

   • Atrioventricular (AV) block is the most common cause of syncope in certain types of restrictive cardiomyopathy 1
   • Ventricular arrhythmias, particularly in amyloidosis and sarcoidosis 1
   • Atrial fibrillation, which is common in many etiologies of restrictive cardiomyopathy 1

2. Hemodynamic Causes:

   • Impaired cardiac output due to restrictive physiology 1
   • Inability to augment cardiac output during exertion 1
   • Fixed stroke volume with limited ability to increase during demand 1

3. Specific Etiologies:

   • Amyloidosis: Syncope may be due to conduction system disease, arrhythmias, impaired cardiac output, or neurological involvement 1
   • Fabry disease: Syncope usually due to AV block 1
   • Hemochromatosis: Myocardial involvement more common than conduction system disease 1

Clinical Presentation and Diagnosis

When evaluating syncope in a patient with suspected restrictive cardiomyopathy:

• Look for other signs of heart failure with preserved ejection fraction but normal or reduced ventricular volumes
• Assess for atrial enlargement, which indicates sustained elevated ventricular filling pressures 1
• Evaluate for conduction abnormalities on ECG
• Consider the specific etiology of restrictive cardiomyopathy, as this may guide the likely mechanism of syncope

Management Approach

Management should be directed at:

1. Treating the underlying cause of restrictive cardiomyopathy when possible 1

   • Iron chelation therapy for hemochromatosis
   • Stem cell transplantation and/or chemotherapy for some cases of cardiac amyloidosis

2. Addressing the specific mechanism of syncope:

   • For arrhythmia-related syncope:
     • ICD implantation is recommended for patients with restrictive cardiomyopathy and sustained ventricular arrhythmias causing hemodynamic instability who are expected to survive >1 year with good functional status 1
     • Pacemaker implantation for high-grade AV block

3. Managing heart failure symptoms:

   • Diuretics for volume overload
   • Heart rate control to optimize left ventricular filling 1
   • Anticoagulation for all patients with atrial fibrillation 1

Prognosis

Restrictive cardiomyopathy generally has a poor prognosis:

• Survival is approximately 50% at 5 years after diagnosis 1
• The presence of syncope, particularly if unexplained, may indicate a higher risk of sudden cardiac death in certain forms of cardiomyopathy

Important Considerations

• Unlike hypertrophic cardiomyopathy, where syncope is more common (occurring in about 15.8% of patients) 2, syncope is not listed as a primary presenting feature of restrictive cardiomyopathy in major guidelines
• When syncope does occur in restrictive cardiomyopathy, it should prompt a thorough evaluation for arrhythmias and conduction system disease
• The timing of syncope may be important for risk stratification, as demonstrated in hypertrophic cardiomyopathy where recent unexplained syncope carries a higher risk of sudden death 3

Restrictive cardiomyopathy with syncope often requires a multidisciplinary approach involving cardiology, electrophysiology, and sometimes specialty care depending on the underlying etiology (e.g., hematology for amyloidosis).