Monitoring and Staging ATTR Cardiomyopathy

Key Takeaways:

• The National Amyloidosis Centre (NAC/UK) stage, built on NT-proBNP and eGFR thresholds, stratifies prognosis at diagnosis and frames how closely to follow a patient.
• Serial NT-proBNP, high-sensitivity troponin, 6-minute walk distance, NYHA class, and a quality-of-life score together signal whether disease-modifying therapy is holding the disease stable.
• Genotype guides family screening and counseling in hereditary disease but does not change the monitoring plan itself.

Once transthyretin amyloid cardiomyopathy (ATTR-CM) is diagnosed, attention turns to 2 linked questions: how advanced is the disease, and is treatment holding it stable? Both wild-type (ATTRwt-CM) and hereditary (ATTRv-CM) disease are progressive, and both are now addressed by disease-modifying therapy in the United States, which makes serial, structured follow-up the backbone of care.¹

Staging systems and prognosis

The most widely used tool for ATTR cardiomyopathy staging is the National Amyloidosis Centre (NAC) staging system, also called the UK staging system, which applies to both subtypes. It rests on 2 thresholds – N-terminal pro-B-type natriuretic peptide (NT-proBNP) greater than 3,000 ng/L and estimated glomerular filtration rate (eGFR) less than 45 mL/min/1.73 m². Stage 1 exceeds neither threshold, Stage 2 exceeds 1 threshold, and Stage 3 exceeds both thresholds, with reported median survivals of 69.2, 46.7, and 24.1 months, respectively.¹

A separate Mayo (Grogan) staging system for wild-type disease uses NT-proBNP and troponin T: Stage 1 is defined by NT-proBNP ≤3,000 pg/mL and troponin T ≤0.05 ng/mL, with higher stages as these cutpoints are exceeded. Baseline stage anchors prognosis and sets the intensity of follow-up.¹

Serial biomarkers

Between staging assessments, NT-proBNP and high-sensitivity troponin are the workhorse measures; the consensus identifies both troponin and NT-proBNP as powerful prognostic markers, and it is their trajectory over time – not any single value – that gauges stability. A steadily rising NT-proBNP or troponin signals that the disease is progressing despite therapy and warrants reassessment.¹

Imaging for follow-up

Imaging complements the laboratory picture. The consensus recognizes an abnormal global longitudinal strain (GLS) with a characteristic apical-sparing pattern on echocardiography, and increased extracellular volume (ECV) with diffuse late gadolinium enhancement on cardiac magnetic resonance (CMR), as features of the amyloid phenotype.¹

These measures are well established for recognizing that phenotype; their role in routine serial follow-up is less standardized, and they are generally used to corroborate the biomarker and functional trajectory rather than to drive decisions on their own.¹

Signals of treatment response

Treatment response is judged by whether these same measures hold steady rather than decline. For ATTR-CM, the United States has approved TTR stabilizers (tafamidis and acoramidis) and one TTR-lowering silencer (vutrisiran) for both wild-type and hereditary disease; their trials define the endpoints now used to track response.^2-4

In the stabilizer class, a 30-month trial (ATTR-ACT) reduced the decline in 6-minute walk test (6MWT) distance by 75.68 m and the decline in Kansas City Cardiomyopathy Questionnaire (KCCQ) overall summary score by 13.65 points versus placebo, alongside lower all-cause mortality.²

A second stabilizer trial (ATTRibute-CM) used a hierarchical win-ratio endpoint of death, cardiovascular hospitalization, NT-proBNP, and 6MWT distance: death and cardiovascular hospitalization together accounted for more than half of the pairwise comparisons (58 percent), while NT-proBNP produced the highest ratio of wins to losses (23.3 percent versus 7.0 percent). Serious adverse events were no more frequent on active treatment than on placebo (54.6 percent versus 64.9 percent).³

In the silencer class, HELIOS-B reduced a composite of all-cause mortality and recurrent cardiovascular events, with a hazard ratio of 0.72 (95% CI, 0.56 to 0.93).⁴

Trial evidence from an agent not approved for ATTR-CM also informs which measures to track: APOLLO-B studied patisiran – which did not receive a United States cardiomyopathy indication – with 6MWT distance as its primary endpoint and KCCQ as a secondary endpoint, although it did not show a benefit on its second secondary endpoint.⁵

No head-to-head trials compare these agents, so it is a rising NT-proBNP, a falling walk distance, a worsening New York Heart Association (NYHA) functional class, or a declining KCCQ score – not the choice of class – that should prompt reassessment. Genotype, once assigned, guides family screening and counseling in hereditary disease but does not itself alter the monitoring schedule.¹