Restrictive cardiomyopathy (RCM) is one of those Step questions that loves to “look like” constrictive pericarditis or HFpEF—until you notice the key clue: the ventricles can’t fill because the myocardium is stiff, not because systolic squeeze is weak. If you can picture noncompliant ventricles + biatrial enlargement + right-sided congestion, you’ll crush most RCM vignettes.
Where Restrictive Cardiomyopathy Fits in Step Heart Failure
RCM is primarily a diastolic dysfunction problem:
- Systolic function (EF): often preserved early
- Diastolic filling: impaired due to decreased ventricular compliance
- Chamber size:
- Ventricles: usually normal size (can be mildly thickened depending on cause)
- Atria: enlarged (key board-style finding)
Step framing: RCM is a classic cause of HFpEF with prominent signs of systemic venous congestion.
First Aid cross-reference: Cardiovascular → Cardiomyopathies (RCM: infiltrative diseases like amyloidosis, sarcoidosis; storage diseases like hemochromatosis)
Definition (One Sentence You Should Memorize)
Restrictive cardiomyopathy is a cardiomyopathy characterized by stiff, noncompliant ventricles causing impaired diastolic filling and elevated filling pressures, typically with preserved systolic function early and biatrial enlargement.
Pathophysiology: Why Filling Fails
The unifying mechanism is reduced ventricular compliance. That leads to:
- ↑ LVEDP / RVEDP (elevated end-diastolic pressures)
- ↓ ventricular filling during diastole
- Pulmonary and systemic venous congestion
- Atrial dilation from chronically high filling pressures → predisposes to atrial fibrillation
Common Etiologies (High-Yield)
Most Step etiologies are infiltrative, storage, or fibrotic:
| Etiology | Mechanism | Step clues |
|---|---|---|
| Amyloidosis (AL, ATTR) | Extracellular amyloid deposition → stiff ventricles | Older adult; nephrotic syndrome, neuropathy; echo “sparkling”; low-voltage ECG (classic association) |
| Sarcoidosis | Noncaseating granulomas + conduction system infiltration | Young/middle age; pulmonary sx, hilar adenopathy; AV block/arrhythmias |
| Hemochromatosis | Iron deposition (heart, liver, pancreas) | Bronze diabetes, cirrhosis; dilated or restrictive phenotype; arrhythmias |
| Endomyocardial fibrosis / Löffler endocarditis | Fibrosis ± eosinophils → stiff ventricles | Eosinophilia, asthma/allergy/parasites; mural thrombi; embolic events |
| Radiation-induced heart disease | Fibrosis of myocardium/pericardium | Cancer history (breast/lymphoma), years later |
| Scleroderma | Fibrosis | Raynaud, skin thickening; pulmonary HTN commonly coexists |
First Aid cross-reference:
- Amyloidosis: Pathology → Amyloidosis (Congo red, apple-green birefringence) + Cardio → Cardiomyopathies
- Sarcoidosis: Pulm/Immune → Sarcoidosis (noncaseating granulomas, ACE ↑)
- Hemochromatosis: GI → Hemochromatosis
Clinical Presentation: What the Patient Looks Like
RCM often presents like right-sided heart failure and HFpEF:
Symptoms
- Dyspnea on exertion, orthopnea (from ↑ left-sided filling pressures)
- Peripheral edema, ascites, abdominal discomfort (congestion)
- Fatigue/exercise intolerance
- Palpitations (atrial fibrillation is common)
Physical exam findings
- JVD
- Hepatomegaly, ascites, peripheral edema
- S3 may be present due to rapid early filling into a stiff ventricle (can also hear S4 in diastolic dysfunction, but atrial fibrillation removes S4)
- Kussmaul sign (JVP rises with inspiration) can occur—also seen in constrictive pericarditis
High-yield vibe: If you see HF symptoms + preserved EF + big atria, think RCM.
Diagnosis: How Step Questions Want You to Prove It
ECG
- Nonspecific ST-T changes, conduction abnormalities
- Amyloidosis: may show low-voltage QRS, pseudo-infarct patterns
- Sarcoid: AV block, ventricular arrhythmias
Chest X-ray
- Pulmonary congestion; sometimes cardiomegaly from atrial enlargement
Echocardiogram (Most Tested)
Key findings:
- Biatrial enlargement
- Normal or near-normal ventricular size
- Diastolic dysfunction:
- Often restrictive filling pattern (rapid early filling with high E wave, shortened deceleration time)
- Depending on cause: increased wall “thickness” in amyloid (actually infiltrate)
Cardiac MRI
- Helpful for infiltrative disease:
- Amyloidosis: diffuse subendocardial late gadolinium enhancement (classic teaching)
- Sarcoid: patchy enhancement
Endomyocardial biopsy
- Not always required, but it’s the definitive test in select cases (especially infiltrative causes)
The Classic Step Trap: RCM vs Constrictive Pericarditis
These can look extremely similar (both cause impaired filling + right-sided congestion). A few high-yield distinctions:
| Feature | Restrictive cardiomyopathy | Constrictive pericarditis |
|---|---|---|
| Primary problem | Myocardium is stiff | Pericardium is rigid |
| Echo | Biatrial enlargement; restrictive filling | Septal “bounce” may be seen; pericardial thickening sometimes |
| Imaging | MRI suggests infiltrate | CT/MRI may show pericardial calcification/thickening |
| Hemodynamics | Elevated diastolic pressures | Elevated diastolic pressures + ventricular interdependence |
| Treatment | Diuretics + treat cause; transplant sometimes | Pericardiectomy can be curative |
Test-taking tip: If the stem mentions radiation/TB, think constrictive pericarditis—but radiation can also cause myocardial fibrosis → RCM. In that case, look for imaging clues (pericardial thickening/calcification vs infiltrative myocardial features).
Treatment: What You Actually Do
RCM management is mostly:
- Treat congestion
- Treat the underlying cause (if possible)
- Manage arrhythmias
- Consider advanced therapies in severe disease
Symptomatic management (core)
- Diuretics (loop diuretics) for volume overload
- Use carefully: stiff ventricles depend on adequate preload; over-diuresis can drop CO.
- Salt restriction, fluid management
Rhythm management
- Atrial fibrillation is common due to atrial enlargement:
- Rate/rhythm control as appropriate
- Anticoagulation often indicated (especially if AF)
Cause-directed treatment (high-yield associations)
- Amyloidosis: chemo for AL; transthyretin stabilizers for ATTR (Step usually focuses more on diagnosis than drug names)
- Hemochromatosis: phlebotomy/chelation
- Sarcoidosis: corticosteroids (plus ICD consideration if ventricular arrhythmias)
- Eosinophilic (Löffler): treat underlying eosinophilia; steroids depending on cause
Advanced
- Heart transplant for refractory cases (selected patients)
High-Yield “Buzz Phrases” and Associations (USMLE Favorites)
Restrictive cardiomyopathy = think:
- Infiltrative disease
- HFpEF
- Biatrial enlargement
- Right-sided failure signs (JVD, edema, ascites)
Amyloidosis associations (super high-yield)
- Restrictive cardiomyopathy
- Low-voltage ECG despite “thick” ventricular walls on echo
- Multisystem clues: nephrotic syndrome, neuropathy, macroglossia, carpal tunnel (AL)
Sarcoidosis associations
- Noncaseating granulomas
- Conduction abnormalities (AV block), ventricular arrhythmias
- Pulmonary findings (bilateral hilar adenopathy)
Hemochromatosis associations
- “Bronze diabetes” + cirrhosis + cardiomyopathy (restrictive or dilated)
- Arrhythmias
First Aid cross-reference list (quick):
- Cardio → Cardiomyopathies: RCM causes + phenotype
- Path → Amyloidosis: Congo red, apple-green birefringence
- Pulm/Immune → Sarcoidosis: noncaseating granulomas
- GI → Hemochromatosis: iron overload systemic findings
Rapid-Fire Step 1/2 Checkpoints
- RCM is primarily diastolic dysfunction; EF often preserved early.
- Biatrial enlargement is a key echo clue.
- Amyloid: thick-looking walls + low-voltage ECG = classic pairing.
- AF is common because chronically elevated filling pressures stretch the atria.
- Differentiate from constrictive pericarditis (pericardial thickening/calcification; potential surgical cure).