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Transthyretin cardiac amyloidosis prevalence in the transcatheter aortic valve replacement population is lower than previously described, and NT-pro BNP can guide screening, according to a recent study.

Transthyretin cardiac amyloidosis (ATTR-CA) prevalence in aortic stenosis patients is 5–20%, with higher rates in those who underwent transcatheter aortic valve replacement (TAVR) vs. surgical aortic valve replacement (SAVR). Recently, the indication for TAVR has changed to include low-risk patients. 

A study in the European Journal of Nuclear Medicine and Molecular Imaging evaluated ATTR-CM prevalence in a contemporary TAVR population and assessed high-risk features to guide screening.

Study Subjects

A total of 380 patients from a TAVR clinic were enrolled and underwent a technetium-99m pyrophosphate (99mTc-PyP) scan. The mean age was 83 years; most patients were White (95%). At the time of analysis, 304 (80%) patients had undergone TAVR, 29 (7.6%) had undergone SAVR, 2 (<1%) had had balloon valvuloplasty, and 45 (11.8%) had not undergone any procedure.

ATTR-CA Prevalence

The overall positivity rate was low (5.3%, n=20). Of the 20 patients with the positive 99mTc-PyP scan, ATTR-CA was confirmed in 17; one deferred confirmatory testing; one had light-chain amyloidosis; and one had a negative biopsy result.

Characteristics of Patients With Positive 99MTC-Pyp Scans

Patients who had a positive 99mTc-PyP scan were older (88 vs. 83 years, p=0.001) and had a higher carpal tunnel syndrome (CTS) prevalence (50% vs. 15%, p=0.001) than those with a negative scan. No other significant differences in comorbidities were observed between the two groups.

Regarding echocardiography, patients with a positive 99mTc-PyP scan had higher left ventricular mass index (136 vs. 103 g/m2, p=0.002), a lower ejection fraction (53% vs. 61%), and a lower stroke volume index (29 vs. 37 mL/m2) than those with a negative scan. The global longitudinal strain was more impaired (−9.3% vs. −15.1%, p<0.001), and low-flow low-gradient aortic stenosis (LFLG-AS) was more common (65% vs. 30%, p=0.003) in patients with a positive scan.

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Positive 99mTc-PyP Scan Predictors

Raised N-terminal pro-B-type natriuretic peptide (NT-proBNP) was highly associated with a positive 99mTc-PyP scan, with an odds ratio (OR) of 10.8 and 10.2 for >500 and >1000 ng/L NT-proBNP, respectively. Relative apical sparing (RAS, OR: 7.1) and CTS (OR: 5.7) were also highly associated with a positive scan.

Elevated NT-proBNP demonstrated the highest sensitivity and negative predictive value for a positive 99mTc-PyP scan, with reasonable specificity. An NT-proBNP cutoff value of 1000 ng/L yielded 90% sensitivity and 99% negative predictive value. This cutoff would have resulted in 51% fewer cardiac scintigraphy referrals in this population. CTS, RAS, and LFLG-AS had higher specificity but lower sensitivity than NT-proBNP.

In conclusion, ATTR-CA prevalence is lower in a contemporary TAVR population than previously documented. Of the parameters assessed, NT-proBNP can judiciously guide referral for a 99mTc-PyP scan for ATTR-CA screening.

Source:

Abadie, B., Ali, A. H., Martyn, T., Higgins, A., Krishnaswamy, A., Reed, G. W., Puri, R., Yun, J., Cremer, P., Hanna, M., Tang, W. W., Kapadia, S., & Jaber, W. A. (2023). Prevalence of ATTR-CA and high-risk features to guide testing in patients referred for TAVR. European Journal of Nuclear Medicine and Molecular Imaging. https://doi.org/10.1007/s00259-023-06374-2