You’re cruising through a cardio Q-bank and you hit a vignette that feels like heart failure… but the EF is normal. The stem is packed with clues, and the answer choices are all “reasonable.” This is exactly where restrictive cardiomyopathy (RCM) loves to hide—and where you can pick up easy points by learning to interrogate every distractor.
Tag: Cardiovascular > Heart Failure & Cardiomyopathies
The Clinical Vignette (Classic Q-bank Style)
A 64-year-old man presents with progressive exertional dyspnea and fatigue. He has bilateral leg edema and abdominal distension. Vitals are normal. Exam shows elevated JVP with prominent y descent, hepatomegaly, ascites, and mild bibasilar crackles. ECG shows low voltage. Echocardiogram shows:
- Normal or near-normal LVEF
- Normal LV size
- Biatrial enlargement
- Doppler: impaired ventricular filling (diastolic dysfunction)
He has a history of carpal tunnel syndrome and chronic back pain.
Question: What is the most likely underlying diagnosis?
Correct Answer: Restrictive Cardiomyopathy (Most commonly Amyloidosis)
Why it’s restrictive cardiomyopathy
RCM is fundamentally a diastolic filling problem: the ventricles are “stiff,” so they can’t fill, even though systolic function is often preserved early.
High-yield clues from the vignette:
- Right-sided heart failure features: JVP elevation, hepatomegaly, ascites, edema
- Preserved EF: points away from classic HFrEF causes (e.g., dilated cardiomyopathy, ischemic cardiomyopathy)
- Biatrial enlargement: atria dilate because they’re pushing against noncompliant ventricles
- Low voltage ECG + systemic findings (carpal tunnel, back pain): classic for amyloidosis (AL or ATTR)
Pathophysiology in one line
Infiltrative deposition (e.g., amyloid) → stiff ventricles → impaired diastolic filling → ↑ filling pressures → congestion (often right-sided prominent) with normal/near-normal EF.
What you should remember for Step exams
- RCM = HFpEF phenotype (but not all HFpEF is RCM)
- Echo: non-dilated ventricles + biatrial enlargement + diastolic dysfunction
- ECG: may show low voltage (especially amyloid) despite thick-looking walls on echo
- Hemodynamics: elevated filling pressures; can resemble constrictive pericarditis (key differentiator below)
The Distractors: Why Each One Is Tempting (and Why It’s Wrong)
Below is the typical answer-choice lineup and how to kill each option quickly.
1) Dilated Cardiomyopathy (DCM)
Why it tempts you: heart failure symptoms + edema + crackles.
Why it’s wrong here:
- DCM is primarily systolic dysfunction → reduced EF
- Echo would show dilated ventricles (increased LV end-diastolic volume) and often functional MR/TR
DCM high-yield associations:
- Alcohol, doxorubicin, viral myocarditis (Coxsackie B), peripartum, hemochromatosis, Chagas
- Leads to S3, displaced PMI, HFrEF
2) Hypertrophic Cardiomyopathy (HCM)
Why it tempts you: diastolic dysfunction can happen in HCM too.
Why it’s wrong here:
- HCM classically features asymmetric septal hypertrophy and dynamic LV outflow tract obstruction
- Symptoms often include exertional syncope, angina, palpitations; exam may reveal a systolic murmur that increases with Valsalva/standing and decreases with squatting/handgrip
- Echo would show septal hypertrophy and systolic anterior motion (SAM) of the mitral valve
HCM high-yield:
- AD mutation in sarcomere proteins (e.g., beta-myosin heavy chain)
- Risk of sudden cardiac death in young athletes
3) Constrictive Pericarditis
Why it tempts you: it mimics restrictive cardiomyopathy—right-sided failure, JVP elevation, ascites, preserved EF.
How to separate from RCM (extremely high-yield):
| Feature | Restrictive CM | Constrictive Pericarditis |
|---|---|---|
| Primary problem | Myocardium stiff | Pericardium stiff |
| Biatrial enlargement | Common | Can occur but less classic |
| Pericardial calcification | No | Often present (CXR/CT) |
| Kussmaul sign (↑ JVP on inspiration) | Can be present | Classic |
| Response to pericardiectomy | No | Often improves |
| Doppler/pressures | Similar “dip-and-plateau” can occur | Similar |
Best practical test-day clue:
- History of TB, prior cardiac surgery, mediastinal radiation → constrictive pericarditis
- Low voltage + infiltrative systemic findings → restrictive cardiomyopathy (amyloid)
4) Cardiac Tamponade
Why it tempts you: elevated JVP and heart failure-ish presentation.
Why it’s wrong here:
- Tamponade is usually acute/subacute and classically causes Beck triad: hypotension, muffled heart sounds, JVD
- Would expect pulsus paradoxus and tachycardia
- Echo would show pericardial effusion with diastolic collapse of right-sided chambers
Key distinction: tamponade is a pressure-on-the-heart emergency; restrictive CM is a stiff-heart chronic diastolic failure pattern.
5) Concentric LV Hypertrophy from Longstanding Hypertension (HFpEF)
Why it tempts you: preserved EF + diastolic dysfunction = HFpEF.
Why it’s wrong here:
- HTN-related HFpEF typically shows LV wall thickening from hypertrophy and often a history of long-standing hypertension
- This vignette points more toward an infiltrative process (low voltage ECG + systemic symptoms)
High-yield:
HFpEF is a syndrome; restrictive CM is a specific cause of HFpEF.
6) Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
Why it tempts you: right-sided findings.
Why it’s wrong here:
- ARVC is primarily an electrical disease with ventricular arrhythmias (e.g., VT), syncope, and sudden death
- Often younger patients; ECG may show epsilon waves
- Not primarily a diastolic filling pathology causing biatrial enlargement
Restrictive Cardiomyopathy: The High-Yield Core You Need
Common causes (Step favorites)
- Amyloidosis (AL or ATTR): restrictive physiology + low voltage ECG + thick walls on echo
- Sarcoidosis: can cause restrictive features + conduction block/arrhythmias
- Hemochromatosis: can be restrictive or dilated; think “bronze diabetes,” liver disease, cardiomyopathy
- Endomyocardial fibrosis / Loeffler endocarditis (eosinophilic): rare but classic board concept
- Radiation-induced myocardial fibrosis
Typical findings
- Symptoms: exertional dyspnea, fatigue, edema, ascites (often prominent right-sided congestion)
- Echo: normal LV cavity size, preserved EF early, biatrial enlargement, Doppler diastolic dysfunction
- ECG: low voltage (amyloid), conduction abnormalities (sarcoid), atrial arrhythmias due to atrial dilation
Amyloidosis pearl: “Thick heart, quiet ECG”
A classic Step clue is the mismatch:
- Echo: thickened ventricular walls (infiltration)
- ECG: low voltage (because it’s not true myocyte hypertrophy)
How to Approach These Questions in 15 Seconds
- Is EF preserved? If yes, think diastolic dysfunction (HFpEF spectrum).
- Is LV dilated? If no, DCM is unlikely.
- Any “infiltrative” clues?
- low voltage ECG
- systemic symptoms (carpal tunnel, neuropathy, proteinuria, back pain)
- biatrial enlargement
→ Restrictive CM (amyloid until proven otherwise)
- Could it be constrictive pericarditis? Look for TB, surgery, radiation, pericardial calcification.
Rapid-Fire NBME-Style Takeaways
- Restrictive CM = impaired filling + normal/near-normal EF + biatrial enlargement.
- Amyloidosis is the prototypical cause: low voltage ECG + thick walls on echo + systemic signs.
- Constrictive pericarditis is the main mimic; history and imaging (calcification) help.
- DCM = systolic dysfunction with dilated ventricles (reduced EF).
- HCM = asymmetric septal hypertrophy + dynamic obstruction (Valsalva increases murmur).