ATTR-CM: Early Diagnosis and Risk Stratification Essential

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive, infiltrative cardiomyopathy caused by the deposition of misfolded transthyretin (TTR) protein in the myocardium. This deposition leads to myocardial thickening, restrictive physiology, and ultimately heart failure. The disease manifests in two primary forms: wild-type ATTR-CM (wtATTR-CM), which typically affects older males, and hereditary ATTR-CM (hATTR-CM), caused by TTR gene mutations and presenting with variable age of onset and penetrance. The non-specific nature of early symptoms, such as dyspnoea, fatigue, and peripheral oedema, often leads to misdiagnosis or delayed diagnosis, frequently as heart failure with preserved ejection fraction (HFpEF).

The diagnostic pathway for ATTR-CM has evolved significantly. Historically, endomyocardial biopsy was the gold standard, but non-invasive imaging techniques have largely superseded it. Technetium-99m pyrophosphate (Tc-99m PYP) scintigraphy, when performed in conjunction with serum and urine monoclonal protein screening to rule out light chain (AL) amyloidosis, offers high sensitivity and specificity for ATTR-CM. A Perugini score of 2 or 3 on Tc-99m PYP scintigraphy, in the absence of a monoclonal gammopathy, is diagnostic for ATTR-CM. Cardiac magnetic resonance imaging (CMR) can also provide supportive evidence, demonstrating characteristic findings such as diffuse subendocardial late gadolinium enhancement and increased extracellular volume.

Optimising Patient Outcomes Through Risk Stratification

Once diagnosed, accurate risk stratification is paramount for guiding treatment and predicting prognosis. Several factors contribute to the risk profile of ATTR-CM patients. These include New York Heart Association (NYHA) functional class, N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, and estimated glomerular filtration rate (eGFR). Elevated NT-proBNP levels reflect increased myocardial wall stress and are consistently associated with worse outcomes. Similarly, declining renal function, indicated by a low eGFR, is a marker of advanced disease and higher mortality risk. The presence of specific TTR gene mutations in hATTR-CM also influences disease progression and phenotype, necessitating genetic counselling and cascade screening for at-risk family members.

Beyond these established markers, ongoing research explores additional prognostic indicators. These include measures of cardiac strain by echocardiography, which can detect subtle myocardial dysfunction even in early stages, and advanced CMR parameters. The goal is to identify patients at higher risk of rapid progression or adverse events, allowing for more aggressive or tailored therapeutic strategies. For instance, patients with more advanced disease or rapidly progressing symptoms may benefit from earlier initiation of TTR stabilisers or silencers. The current therapeutic landscape includes TTR stabilisers, such as tafamidis, which prevent the dissociation of the TTR tetramer, and TTR silencers, like patisiran and inotersen, which reduce the production of TTR protein. The efficacy of these agents is greatest when initiated early in the disease course, underscoring the importance of timely diagnosis and precise risk assessment.

Limitations in current practice include the continued under-recognition of ATTR-CM, particularly in primary care settings, and the need for broader access to diagnostic imaging. While Tc-99m PYP scintigraphy is highly effective, its availability can be a barrier in some regions. Furthermore, the long-term comparative effectiveness of different therapeutic agents across various ATTR-CM subtypes and risk profiles continues to be an area of active investigation. Future directions include the development of novel biomarkers for earlier detection and monitoring of disease progression, as well as combination therapies to further improve patient outcomes.

Another crucial area of development involves refining risk stratification models to incorporate a wider array of clinical, imaging, and biochemical parameters. Machine learning algorithms are being explored to integrate these diverse data points, potentially offering more granular and predictive risk scores than current methods. This could lead to truly personalised treatment pathways, optimising the balance between therapeutic benefit and potential side effects for each patient.

Furthermore, the role of multidisciplinary teams in managing ATTR-CM is gaining increasing recognition. Collaboration between cardiologists, neurologists (especially for hATTR-CM with neurological manifestations), nephrologists, genetic counsellors, and palliative care specialists is essential to address the multifaceted nature of the disease and provide comprehensive patient support. This integrated approach is vital for improving quality of life and extending survival in this challenging patient population.