By Jaime Warren, Ed.D, MBA, BHS, CNMT, NCT, FACC, and Mary Beth Farrell, EdD, CNMT, NCT, RT(N), FSNMMI-TS
Over the past year or two, you might have noticed an uptick in the use of 99mTc-pyrophosphate (PYP) [LA1] scans to diagnose cardiac amyloidosis. This trend prompts several questions: Why the renewed interest in a condition once considered rare? What is driving the increase in scan orders? And most intriguingly, will this upswing continue? Let’s dive into these queries to uncover the
answers.
What Is Cardiac Amyloidosis?
Cardiac amyloidosis, particularly the transthyretin variant (ATTR), is a systemic form of amyloidosis in which protein-based infiltrates are deposited in the myocardial extracellular
space (1). The accumulation of misfolded amyloid fibrils causes the myocardium to thicken and stiffen, leading to diastolic dysfunction and, eventually, heart failure.
Why Was Cardiac Amyloidosis Considered Rare?
Five to 10 years ago, few cardiologists were talking about amyloidosis because it was believed to be rare, affecting fewer than 200,000 people in the United States (2). Because it was considered rare, there was a general lack of awareness and recognition of the disease. In addition, recognizing cardiac amyloidosis was tricky since many of its signs and symptoms are similar to those of other, more common diseases such as hypertension, aortic stenosis, or hypertrophic cardiomyopathy. Cardiac amyloidosis often masquerades as heart failure with preserved ejection fraction (HFpEF). Furthermore, cardiac amyloidosis was often ignored because of the false perception that it could only be diagnosed by risky endocardial biopsy, and even if detected, the disease was incurable due to its rapid progression and lack of treatment options.
Why Is There a Resurgence of Interest in Cardiac Amyloidosis and 99mTc-PYP Imaging?
The resurgence of interest in cardiac amyloidosis can be attributed to a confluence of factors that have thrust the condition into the spotlight (3). First, advancements in noninvasive imaging technology, including nuclear medicine, echocardiography, and cardiac magnetic resonance, have significantly increased the ability to detect cardiac amyloidosis accurately. In particular, 99mTc-PYP scanning, which allows visualization and semi-quantification of amyloid burden, is becoming the predominant diagnostic method because of its high sensitivity and specificity (4). A second factor to explain the resurgence is evolving epidemiological evidence. With the increased ability to detect the disease, cardiac amyloidosis is now being diagnosed more frequently. Recent studies reveal a significant prevalence of the condition among heart failure patients, with approximately 16% exhibiting signs of cardiac amyloidosis (5). Complementary to these findings is an increase in life expectancy, contributing to a higher incidence of cardiac amyloidosis, which primarily affects the elderly.
The development of new therapies for treating cardiac amyloidosis has also spurred interest in diagnosis. The historical lack of effective treatments may have contributed to a lower perceived need for precise diagnosis. However, with the advent of several new medications that can significantly improve outcomes for patients with ATTR cardiac amyloidosis, such as tafamidis, there is now a greater incentive to identify and diagnose patients early in the disease course when treatment is most effective and can halt disease progression (6). Finally, increased education has expanded awareness of cardiac amyloidosis, leading to increased scan orders. Previously overlooked and misdiagnosed cases are now being identified through comprehensive clinical assessments, including ECGs and echocardiograms as initial screening tests leading to 99mTc-PYP scans for definitive diagnosis.
Future Trends: Will 99mTc-PYP Scan Orders Continue to Rise?
Why does the current trajectory suggest a continued increase in 99mTc-PYP scan ordering? As awareness of the benefits and implications of early and accurate diagnosis grows, so will the suspicion of ATTR amyloidosis in patients with unexplained cardiac symptoms. Correspondingly, the percentage of elderly patients continues to increase, thereby increasing the incidence and pool of patients to be evaluated. This demographic shift will push the demand for more specialized diagnostic tools, like the 99mTc-PYP scan, to effectively identify and manage age-related cardiac conditions. Finally, as treatment options for cardiac amyloidosis continue to evolve and improve, the need to accurately diagnose the condition early will become even more critical. Increases in the number of patients diagnosed with cardiac amyloidosis will likely influence research, funding, and the development of new technologies within the field of nuclear medicine (e.g., SPECT quantification, novel tracers).
In Conclusion: A Nuclear Cardiology Renaissance?
In conclusion, the rise in the use of 99mTc-PYP scans for cardiac ATTR amyloidosis reflects a paradigm shift in cardiovascular diagnostics. The interplay between historical rarity, technological advancements, treatment innovations, and evolving epidemiological trends has propelled these scans into a pivotal role in nuclear medicine. As professionals dedicated to this field, we must stay informed and adapt to these changes, ensuring that we continue to provide the best possible care for our patients.
References
- Embry-Dierson M, Farrell MB, Schockling E, Warren J, Jerome S. Cardiac amyloidosis imaging, part 1: amyloidosis etiology and image acquisition. J Nucl Med Technol. 2023;51(2);83-89.
- Jerome S, Farrell MB, Warren J, Embry-Dierson M, Schockling E. Cardiac amyloidosis imaging, Part 3: interpretation, diagnosis, and treatment. J Nucl Med Technol. 2023;51(2):102-116
- Satyavolu B, Dietz J, Soman P. The rise of cardiac amyloidosis imaging. J Nucl Med Technol. 2023;51(2):129-132.
- Poterucha TJ, Elias P, Bokhari S, et al. Diagnosing transthyretin cardiac amyloidosis by technetium Tc 99m pyrophosphate: a test in evolution. JACC Cardiovasc Imaging. 2021;14:1221–1231
- Castaño A, Narotsky DL, Hamid N, et al. Unveiling transthyretin cardiac amyloidosis and its predictors among elderly patients with severe aortic stenosis undergoing transcatheter aortic valve replacement. Eur Heart J. 2017;38:2879–2887.
- Ioannou A, Patel RK, Razvi Y, et al. Impact of earlier diagnosis in cardiac ATTR amyloidosis over the course of 20 years. Circulation. 2022;146(22):1657-1670.