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

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 [PYP1] or PYP-negative [PYP2]) 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 6 13.0 y, and 57 (89.1%) were male. Comparing the PYP1 to the PYP2 group, the left ventricular global longitudinal strain was significantly worse in the former (PYP1 vs. PYP2, 210.5 6 2.6 vs. 213.1 6 4.1; P 5 0.003). PYP1 patients also had worse regional basal strain (24.6 6 2.6 vs. 28.8 6 4.0, P, 0.001) and a trend toward worse midventricular strain (29.6 6 4.0 vs. 211.7 6 4.4, P 5 0.07), but there was no statistical difference in the apical region (217.6 6 4.73 vs. 219.0 6 6.46, P 5 0.35). This is consistent with an apex-sparing pattern shown by the relative apical longitudinal strain index (1.3 6 0.5 vs. 1.0 6 0.3, P 5 0.008). Segment-to-segment analysis demonstrated a significant difference in strain between PYP1 and PYP2 segments in 4 segments: basal inferior (P 5 0.006), basal anterolateral (P 5 0.01), apical septal (P 5 0.002), and apical inferior (P 5 0.001). Left ventricular diastolic dysfunction was significantly different, with 17 (77.3%) patients in the PYP1 group versus 15 (36.6%) in PYP2 participants (P 5 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.