What are the characteristic echocardiographic findings in cardiac amyloidosis?

Characteristic Echocardiographic Findings in Cardiac Amyloidosis

The hallmark echocardiographic findings in cardiac amyloidosis are left ventricular wall thickness >12 mm, relative apical sparing of longitudinal strain (ratio >1.0), and grade ≥2 diastolic dysfunction, all occurring without alternative cardiac causes like hypertension. 1

Primary Diagnostic Echo Features

According to the 2021 ASNC/AHA/ASE expert consensus, the following echocardiographic findings are considered typical imaging features for both ATTR and AL cardiac amyloidosis:

Wall Thickness and Chamber Morphology

• LV wall thickness >12 mm without other known cardiac cause 1
• Normal or reduced LV cavity size (end-diastolic diameter typically 48±7 mm in CA vs 53±6 mm in non-CA) 2
• Biatrial enlargement, particularly right atrial area (27.4±8.4 cm² in CA vs 22.2±5.7 cm² in non-CA) 2
• Interventricular septum thickness typically 16±3 mm in CA patients 2

Strain Pattern: The "Apical Sparing" Sign

Relative apical sparing of global longitudinal strain is highly characteristic, defined as:

• Average apical LS divided by average of (mid + basal LS) >1.0 1
• This creates a distinctive "cherry on top" or "bull's eye" pattern on strain imaging
• Strain relative apical sparing ratio of 2.2±0.9 in CA vs 1.03±0.4 in non-CA patients 2

This finding reflects that the apex maintains relatively preserved contractility while the base and mid-ventricle are more severely affected by amyloid infiltration.

Diastolic Dysfunction

• Grade ≥2 diastolic dysfunction (restrictive filling pattern) 1
• This represents advanced diastolic impairment with elevated filling pressures

Additional Supportive Echo Findings

Right Ventricular Involvement

• Reduced TAPSE (16±5 mm in CA vs 20±4 mm in non-CA) 2
• RV wall thickening 2, 3
• These findings indicate biventricular involvement, which is common in cardiac amyloidosis

Classic Visual Appearance

• "Granular sparkling" appearance of the myocardium on 2D imaging 4
• Diffuse hyper-refractile texture due to amyloid infiltration
• This finding, while classic, is neither sensitive nor specific enough for diagnosis alone

Valvular Findings

• Thickened valve leaflets (aortic and mitral) without significant stenosis
• This reflects amyloid deposition in valvular tissue

Critical Diagnostic Algorithm

When evaluating suspected cardiac amyloidosis on echo:

1. Measure LV wall thickness: If >12 mm without hypertension or other cause → proceed
2. Assess strain pattern: Calculate apical-to-basal+mid ratio; if >1.0 → highly suggestive
3. Evaluate diastolic function: Grade ≥2 dysfunction supports diagnosis
4. Check for biatrial enlargement and RV involvement: Adds diagnostic confidence
5. Look for ECG-echo mismatch: Low voltage on ECG despite increased wall thickness on echo 3, 5

Important Clinical Pitfalls

The "Preserved EF" Trap

• Systolic function often appears preserved (EF ≥40%) until late-stage disease 1, 6
• Don't be falsely reassured by normal ejection fraction
• Longitudinal strain is abnormal even when EF appears normal, making strain imaging essential 6

Mimics to Exclude

Before diagnosing CA based on echo, reasonably exclude:

• Hypertensive heart disease (most common mimic)
• Hypertrophic cardiomyopathy (but can coexist with CA)
• Aortic stenosis (particularly low-flow AS can mimic CA) 1
• Chronic kidney disease with uremic cardiomyopathy

The ECG-Echo Mismatch

A powerful diagnostic clue is low QRS voltage on ECG (<0.5 mV in limb leads) despite increased wall thickness on echo 3, 5. This mismatch occurs because amyloid infiltration replaces contractile myocardium, reducing electrical voltage generation despite increased wall thickness.

Limitations and Next Steps

Echocardiography alone cannot definitively diagnose cardiac amyloidosis 4. When echo findings are suggestive:

• Proceed to 99mTc-PYP/DPD/HMDP bone scintigraphy for ATTR diagnosis 7, 1, 3
• Obtain serum free light chains and immunofixation to exclude AL amyloidosis 7, 1
• Consider cardiac MRI if bone scan is equivocal or contraindicated 1

The strength of echocardiography lies in its role as the first-line screening tool that raises suspicion and directs further diagnostic testing 8, 9. The combination of increased wall thickness, apical sparing pattern, and restrictive physiology should prompt immediate evaluation for cardiac amyloidosis, as early diagnosis is crucial for initiating disease-modifying therapies that improve outcomes 10, 11.