Global and Regional Variations in Transthyretin Cardiac Amyloidosis: A Comparison of Longitudinal Strain and 99mTc-Pyrophosphate Imaging

Abstract

There are limited data on the head-to-head comparison of ^99mTc-pyrophosphate (^99mTc-PYP) and echocardiographic strain imaging in the assessment of transthyretin (TTR) cardiac amyloidosis. Methods: At Mayo Clinic Arizona, patients who had undergone both a ^99mTc-PYP scan and a transthoracic echocardiogram within a 90-d period were retrospectively identified for chart review and strain imaging analysis. Patients were divided into 2 groups according to their ^99mTc-PYP results (PYP-positive [PYP+] or PYP-negative [PYP-]) for the comparison. A standard 17-segment model was used for segmental, regional, and global longitudinal strain comparison. A P value of less than 0.05 was deemed significant. Results: In total, 64 patients were included, the mean age was 75.1 ± 13.0 y, and 57 (89.1%) were male. Comparing the PYP+ to the PYP- group, the left ventricular global longitudinal strain was significantly worse in the former (PYP+ vs. PYP-, -10.5 ± 2.6 vs. -13.1 ± 4.1; P = 0.003). PYP+ patients also had worse regional basal strain (-4.6 ± 2.6 vs. -8.8 ± 4.0, P < 0.001) and a trend toward worse midventricular strain (-9.6 ± 4.0 vs. -11.7 ± 4.4, P = 0.07), but there was no statistical difference in the apical region (-17.6 ± 4.73 vs. -19.0 ± 6.46, P = 0.35). This is consistent with an apex-sparing pattern shown by the relative apical longitudinal strain index (1.3 ± 0.5 vs. 1.0 ± 0.3, P = 0.008). Segment-to-segment analysis demonstrated a significant difference in strain between PYP+ and PYP- segments in 4 segments: basal inferior (P = 0.006), basal anterolateral (P = 0.01), apical septal (P = 0.002), and apical inferior (P = 0.001). Left ventricular diastolic dysfunction was significantly different, with 17 (77.3%) patients in the PYP+ group versus 15 (36.6%) in PYP- participants (P = 0.002). Conclusion: Our study suggested that ^99mTc-PYP uptake is related to overall worse LV segmental, regional, and global longitudinal strain function, as well as diastolic function, compared with patients without ^99mTc-PYP uptake. These data are important for helping clinicians learn about the echocardiographic function features related to ^99mTc-PYP uptake and can help generate hypotheses for future studies.

Keywords: 99mTc-pyrophosphate imaging; cardiology; correlative imaging; longitudinal strain; transthyretin cardiac amyloidosis.