What Is the Best Initial Imaging for Suspected Restrictive or Infiltrative Cardiomyopathy?

A 62-year-old patient presents with several months of progressive dyspnea on exertion and bilateral lower extremity edema. An ECG shows low voltage in the limb leads, and a prior limited cardiac ultrasound noted a preserved ejection fraction. You’ve already ruled out significant coronary artery disease. Now, faced with a clinical picture of heart failure with preserved ejection fraction (HFpEF), your differential narrows to restrictive or infiltrative cardiomyopathies. What is the most appropriate initial, comprehensive imaging study to order to clarify the diagnosis and guide the next steps in management?

According to the American College of Radiology (ACR) Appropriateness Criteria, a US echocardiography transthoracic resting is Usually appropriate as the initial imaging test in this specific clinical scenario. This article provides a detailed workflow for this presentation, explaining the rationale for this choice, the key differential diagnoses, and the critical downstream decision-making that follows the initial study.

Who Fits This Clinical Scenario for Suspected Restrictive Cardiomyopathy?

This guidance applies to patients presenting with signs and symptoms of heart failure—such as dyspnea, fatigue, and peripheral edema—where initial evaluation suggests preserved or near-normal left ventricular systolic function. The core of the clinical suspicion is diastolic dysfunction, where the ventricles are stiff and do not relax properly to allow for adequate filling. A crucial prerequisite for this scenario is that ischemic cardiomyopathy has already been reasonably excluded through prior stress testing, coronary computed tomography angiography (CTA), or invasive coronary angiography.

It is essential to distinguish this presentation from similar, yet distinct, clinical situations that require different imaging pathways:

• Suspected hypertrophic cardiomyopathy: If the patient’s primary feature is significant, unexplained left ventricular hypertrophy on ECG or a prior study, particularly with a family history, the workup should follow the specific guidance for hypertrophic cardiomyopathy.
• Suspected arrhythmogenic cardiomyopathy: If the dominant clinical features are ventricular arrhythmias, syncope, or a family history of sudden cardiac death, especially with ECG findings suggestive of right ventricular pathology (e.g., epsilon waves), the investigation should align with the arrhythmogenic cardiomyopathy scenario.
• Suspected inflammatory cardiomyopathy: If the patient has a recent history of a viral prodrome, fever, and chest pain, suggesting acute myocarditis, the imaging workup for inflammatory cardiomyopathy is more appropriate.

This article is focused squarely on the patient where the leading hypothesis is an infiltrative process (like amyloidosis or sarcoidosis) or an idiopathic restrictive state causing diastolic heart failure.

What Diagnoses Are You Working Up in Suspected Restrictive or Infiltrative Disease?

When ordering imaging for suspected restrictive cardiomyopathy (RCM), you are investigating a specific set of conditions that cause the myocardium to become stiff and noncompliant. The goal of imaging is to identify features that can differentiate among these possibilities.

Cardiac Amyloidosis is a primary concern and one of the most common causes of infiltrative cardiomyopathy. This condition involves the extracellular deposition of misfolded proteins (amyloid fibrils) within the myocardium. This infiltration thickens the heart walls, impairs relaxation, and leads to progressive diastolic and, eventually, systolic dysfunction. The two most common types affecting the heart are light-chain (AL) and transthyretin (ATTR) amyloidosis, which have vastly different treatments and prognoses.

Cardiac Sarcoidosis is another key consideration. This is a multisystem inflammatory disease characterized by the formation of noncaseating granulomas. When these granulomas infiltrate the myocardium, they can cause a restrictive physiology, but also conduction system disease (heart block) and life-threatening ventricular arrhythmias.

Hemochromatosis represents a storage disease rather than a classic infiltrative one, but it can produce a restrictive phenotype. Excessive iron deposition in cardiomyocytes is toxic, leading to diastolic dysfunction. If left untreated, it typically progresses to a dilated cardiomyopathy with systolic failure.

Constrictive Pericarditis is the great mimic of RCM. While the pathophysiology is external (a thickened, fibrotic, and sometimes calcified pericardium encasing the heart), the clinical presentation of impaired ventricular filling is nearly identical to RCM. Differentiating these two is a critical function of initial imaging, as constrictive pericarditis is often surgically treatable.

Why Is Transthoracic Echocardiography the Recommended First Study for Restrictive Cardiomyopathy?

The ACR designates US echocardiography transthoracic resting as Usually appropriate because it is a powerful, non-invasive, and widely accessible first step that can answer multiple key questions in this workup. It involves no ionizing radiation (0 mSv) and provides a wealth of functional and morphological information.

A comprehensive transthoracic echocardiogram (TTE) in this setting should assess:

• Ventricular Wall Thickness: Symmetrical biventricular thickening is a classic, though non-specific, sign of an infiltrative process like amyloidosis.
• Diastolic Function: This is the cornerstone of the diagnosis. Doppler imaging, including mitral inflow patterns and tissue Doppler imaging of the mitral annulus (e.g., E/e’ ratio), provides objective evidence of impaired ventricular relaxation and elevated filling pressures.
• Myocardial Strain: Speckle-tracking echocardiography to measure global longitudinal strain (GLS) is particularly valuable. A pattern of reduced basal and mid-ventricular strain with preserved apical strain (“apical sparing”) is a highly specific marker for cardiac amyloidosis.
• Atrial Size: Biatrial enlargement is a common consequence of chronically elevated ventricular filling pressures and is a hallmark of significant diastolic dysfunction.
• Pericardial Evaluation: The TTE can often identify pericardial thickening, an effusion, or the characteristic “septal bounce” and respiratory flow variations seen in constrictive pericarditis, helping to distinguish it from RCM.

While TTE is the best initial test, MRI heart function and morphology without and with IV contrast is also rated Usually appropriate. It is often considered the best second test or problem-solving tool when echo is inconclusive. Cardiac MRI excels at tissue characterization, using techniques like late gadolinium enhancement (LGE) to reveal patterns of fibrosis or infiltration that can be virtually pathognomonic for conditions like amyloidosis (diffuse subendocardial or transmural LGE) or sarcoidosis (patchy, mid-myocardial LGE).

In contrast, other imaging modalities are rated lower for this initial evaluation:

• US echocardiography transesophageal is rated Usually not appropriate. While providing superior images, it is invasive and unnecessary for the initial questions of wall thickness and diastolic function, which are well-answered by TTE.
• CTA coronary arteries with IV contrast is also Usually not appropriate. This scenario presumes ischemic disease has been excluded, making a dedicated coronary study redundant and exposing the patient to unnecessary radiation (☢☢☢ 1-10 mSv).

What’s Next After Echocardiography? Downstream Workflow for Restrictive Disease

The results of the initial transthoracic echocardiogram will guide the subsequent diagnostic pathway. The workflow is not linear and depends heavily on the specific echocardiographic findings.

If the TTE is highly suggestive of cardiac amyloidosis (e.g., biventricular thickening, severe diastolic dysfunction, and apical sparing on GLS), the workup proceeds to subtype the disease. This involves blood and urine tests (serum free light chains, serum and urine protein electrophoresis with immunofixation) to screen for AL amyloidosis. Concurrently, a technetium-99m pyrophosphate (PYP) scan is often performed. A positive PYP scan in the absence of a monoclonal gammopathy is diagnostic for ATTR cardiac amyloidosis, avoiding the need for a biopsy.

If the TTE findings are equivocal or non-specific, this is the primary indication to order the other Usually appropriate study: MRI heart function and morphology without and with IV contrast. Cardiac MRI can provide a definitive diagnosis by demonstrating characteristic LGE patterns, or it can rule out significant infiltration, pointing towards an idiopathic RCM or an alternative diagnosis.

If the TTE suggests constrictive pericarditis (e.g., septal bounce, respirophasic flow variation), cardiac MRI or CT heart function and morphology with IV contrast (May be appropriate) can be used to confirm the diagnosis by precisely measuring pericardial thickness and assessing for associated inflammation or calcification.

If the TTE is entirely normal, and clinical suspicion for a restrictive process remains high, further investigation may still be warranted, but it may also prompt a re-evaluation of the primary diagnosis to consider non-cardiac causes of the patient’s symptoms.

Pitfalls to Avoid (and When to Get Help)

When working up suspected restrictive or infiltrative cardiomyopathy, several common pitfalls can delay diagnosis or lead to misinterpretation.

• Underutilizing Strain Imaging: Failing to obtain or correctly interpret global longitudinal strain can cause you to miss the classic “apical sparing” sign of cardiac amyloidosis, one of the most specific echocardiographic markers.
• Confusing RCM with HCM: Mistaking the biventricular thickening of amyloidosis for asymmetric septal hypertrophy of hypertrophic cardiomyopathy can lead to incorrect genetic counseling and therapy.
• Overlooking Constriction: Not carefully assessing for the hemodynamic signs of constrictive pericarditis on every study for suspected RCM is a major pitfall, as constriction is a potentially curable condition.
• Stopping the Workup Too Early: A “normal” ejection fraction on a limited study can be falsely reassuring. In a patient with clear heart failure symptoms, a normal EF should increase, not decrease, suspicion for a restrictive process and prompt a full diastolic assessment.

If the diagnosis remains unclear after both advanced echocardiography and cardiac MRI, or if there is discordance between imaging and clinical findings, escalation to a cardiologist with expertise in advanced heart failure and cardiomyopathies is essential. This may lead to consideration of endomyocardial biopsy, the ultimate gold standard for diagnosis.

Related ACR Topics and Tools

For further exploration of imaging guidelines and related clinical scenarios, the following resources are available:

• For breadth across all scenarios in Nonischemic Myocardial Disease with Clinical Manifestations (Ischemic Cardiomyopathy Already Excluded), see our parent guide: Nonischemic Myocardial Disease with Clinical Manifestations (Ischemic Cardiomyopathy Already Excluded): ACR Appropriateness Decoded.
• Imaging Appropriateness Selector — for adjacent scenarios
• Imaging Protocol Library — for technique on the recommended study
• Radiation Dose Calculator — for cumulative dose conversations

Frequently Asked Questions

Why is cardiac MRI also ‘Usually Appropriate’ if echocardiography is the recommended first step?

While echocardiography is the best initial screening tool due to its accessibility and cost-effectiveness, cardiac MRI with gadolinium is superior for tissue characterization. It can often provide a more definitive diagnosis by identifying specific patterns of late gadolinium enhancement (LGE) characteristic of diseases like amyloidosis or sarcoidosis. It is often used as the second step when echo is suggestive but not diagnostic, or when findings are unclear.

Can a normal ejection fraction rule out restrictive cardiomyopathy?

No, a normal or even super-normal left ventricular ejection fraction (LVEF) is a characteristic feature of early-to-moderate restrictive cardiomyopathy. The primary hemodynamic problem is diastolic dysfunction (impaired filling), not systolic dysfunction (impaired pumping). Heart failure symptoms with a preserved EF should raise suspicion for a restrictive process.

What is the role of FDG-PET/CT in this workup?

According to the ACR, FDG-PET/CT is rated ‘May be appropriate.’ Its primary role in this specific scenario is in the evaluation of suspected cardiac sarcoidosis. It is highly sensitive for detecting active myocardial inflammation, which can guide therapy and assess treatment response. It is not a first-line test for a general RCM workup but is a key tool when sarcoidosis is high on the differential.

If ischemic disease is excluded, is there any role for coronary imaging?

Generally, no. The scenario explicitly states that ischemic cardiomyopathy has been excluded. Therefore, modalities like coronary CTA or invasive angiography, which are rated ‘Usually not appropriate,’ would be redundant and add unnecessary risk, cost, and radiation exposure. The focus is entirely on evaluating the structure and function of the myocardium itself.

Does the workup change if the patient has a known systemic disease like rheumatoid arthritis or lupus?

Yes, the pre-test probability of certain infiltrative diseases may change. For example, sarcoidosis and amyloidosis can be associated with other systemic inflammatory or hematologic conditions. While the initial imaging study (echocardiography) would likely remain the same, the interpretation and downstream testing would be heavily influenced by the patient’s known comorbidities.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 26, 2026