Usefulness of relative apical longitudinal strain index to predict positive 99m Tc-labeled pyrophosphate scintigraphy findings in advanced-age patients with suspected transthyretin amyloid cardiomyopathy.

BACKGROUND We previously reported that a high score (2 or 3 points) according to the Kumamoto criteria, a combination of high-sensitivity cardiac troponin T (hs-cTnT) ≥0.308 ng/mL, the length of QRS ≥ 120 ms in electrocardiogram, and left ventricular (LV) posterior wall thickness ≥ 13.6 mm, increases the pretest probability of 99m Tc-labeled pyrophosphate (99m Tc-PYP) scintigraphy in patients with suspected transthyretin amyloid cardiomyopathy (ATTR-CM). However, some patients with a low score (0 or 1 point) show positive findings on 99m Tc-PYP scintigraphy. Therefore, we evaluated the usefulness of additional examinations, including echocardiographic assessment of myocardial strain, to raise the pretest probability of 99m Tc-PYP scintigraphy for these patients. METHODS AND RESULTS We examined 109 consecutive patients aged ≥70 years with low scores according to the Kumamoto criteria who underwent 99m Tc-PYP scintigraphy. Nineteen patients (17%) had positive 99m Tc-PYP scintigraphy findings. The relative apical longitudinal strain (LS) index (apical LS/ basal LS + mid LS) (RapLSI) was significantly higher in patients with positive than negative 99m Tc-PYP scintigraphy findings (1.04 ± 0.37 vs 0.70 ± 0.28, P < .01). Multivariable logistic regression analysis revealed that a high RapLSI (≥1.04) was significantly associated with 99m Tc-PYP positivity (odds ratio, 14.14; 95% confidence interval, 3.36-59.47; P < .01). The sensitivity, specificity, and accuracy of the diagnostic model using the RapLSI for identification of 99m Tc-PYP positivity were 53%, 94%, and 87%, respectively. CONCLUSIONS A high RapLSI can raise the pretest probability of 99m Tc-PYP scintigraphy in patients with a low score according to the Kumamoto criteria. The RapLSI can assist clinicians in determining strategies for these patients.