Cardiac Amyloidosis Screening Protocol
Screen patients ≥65 years old (≥60 years for African Americans) with left ventricular wall thickness ≥12 mm using echocardiography, followed by nuclear scintigraphy with bone tracers (99mTc-PYP/DPD/HMDP) combined with serum/urine immunofixation and free light chain assay to differentiate ATTR from AL amyloidosis. 1, 2
Target Populations for Screening
The 2021 ASNC/AHA/ASE expert consensus identifies specific high-risk groups requiring systematic screening 1:
Asymptomatic Individuals Requiring Assessment:
- Age threshold: ≥65 years (≥60 years for African Americans) 3
- Structural criteria: Interventricular septal wall thickness ≥12 mm on echocardiography 1, 3
- Red flag symptoms: Unexplained bilateral carpal tunnel syndrome, biceps tendon rupture without trauma, lumbar spinal stenosis 1, 2
Symptomatic Heart Failure Patients:
- Disproportionately elevated NT-proBNP relative to degree of heart failure 2
- Low QRS voltage on ECG despite increased left ventricular wall thickness 2
- Pseudoinfarct pattern (Q waves without prior myocardial infarction) 2
Diagnostic Algorithm
Step 1: Initial Echocardiographic Screening
Perform echocardiography looking for these specific features 1:
- LV wall thickness >12 mm
- Relative apical sparing (apical longitudinal strain/combined mid+basal longitudinal strain >1.0)
- Grade ≥2 diastolic dysfunction
- Biatrial enlargement
- Granular sparkling myocardial appearance
- Small LV cavity with preserved ejection fraction
Critical pitfall: 69.5% of cases are identified during noncardiac admissions where screening would typically be overlooked 3. Implement technologist-driven daily screening protocols rather than relying solely on physician-ordered studies.
Step 2: Simultaneous Laboratory Workup
Immediately order both tests together (do not wait for sequential results) 1, 2:
Monoclonal protein assessment (detects AL amyloidosis in 98-100% of cases) 4:
- Serum and urine immunofixation electrophoresis
- Serum free light chain (FLC) assay with κ/λ ratio
- Critical: Use the same FLC assay method consistently; assays are not interchangeable 4
Nuclear scintigraphy with bone tracers 1, 2:
- 99mTc-PYP, 99mTc-DPD, or 99mTc-HMDP
- Grade 2 or 3 myocardial uptake confirms ATTR amyloidosis
Step 3: Diagnostic Interpretation
For ATTR cardiac amyloidosis diagnosis (noninvasive pathway) 1:
- Grade 2 or 3 uptake on bone tracer scintigraphy AND
- Absence of monoclonal protein on immunofixation/FLC AND
- Typical cardiac imaging features present
For AL cardiac amyloidosis diagnosis 1:
- Extracardiac biopsy proven AL amyloidosis AND
- Either typical cardiac imaging features OR abnormal cardiac biomarkers (NT-proBNP or troponin)
Critical caveat: Up to 40% of ATTR patients have concurrent monoclonal gammopathy of undetermined significance (MGUS) 2. In this scenario, scintigraphy alone cannot ensure 100% specificity—proceed to endomyocardial biopsy with mass spectrometry for definitive typing 1.
Advanced Imaging Considerations
Cardiac MRI (if available and no contraindications):
Use when echocardiography is suggestive but inconclusive 1:
- LV wall thickness above upper limit of normal for sex
- Global extracellular volume (ECV) >0.40
- Diffuse late gadolinium enhancement
- Abnormal gadolinium kinetics (myocardial nulling prior to blood pool)
Contraindication: Estimated GFR <30 mL/min/1.73 m² (nephrogenic systemic fibrosis risk) 1
Implementation Strategy
Recent evidence demonstrates that systematic screening protocols dramatically improve detection rates from near-zero baseline to 7.3% diagnostic yield 3. Key innovations include:
- Daily technologist-driven screening at point of image acquisition
- Holographic visual aids and educational interventions for sonographers
- Standardized strain imaging application for all eligible patients
- Structured communication pathways for high-risk findings
Most impactful change: Empower echocardiography technologists to flag high-risk patients immediately rather than waiting for physician report interpretation, as this captures cases during incidental imaging that would otherwise be missed 3.
Follow-up After Positive Screen
Once cardiac amyloidosis is confirmed:
- Genetic testing for TTR gene mutations (differentiates hereditary from wild-type ATTR) 2
- Multidisciplinary evaluation including hematology-oncology (for AL), neurology (for neuropathy assessment), and cardiology 5
- Immediate consideration for disease-modifying therapy, as FDA-approved treatments can reduce disease progression and heart failure hospitalizations 5, 6