Usefulness of relative apical longitudinal strain index to predict positive <superscript>99m</superscript>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 99mTc‐labeled pyrophosphate (99mTc‐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 99mTc‐PYP scintigraphy. Therefore, we evaluated the usefulness of additional examinations, including echocardiographic assessment of myocardial strain, to raise the pretest probability of 99mTc‐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 99mTc‐PYP scintigraphy. Nineteen patients (17%) had positive 99mTc‐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 99mTc‐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 99mTc‐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 99mTc‐PYP positivity were 53%, 94%, and 87%, respectively. Conclusions: A high RapLSI can raise the pretest probability of 99mTc‐PYP scintigraphy in patients with a low score according to the Kumamoto criteria. The RapLSI can assist clinicians in determining strategies for these patients. [ABSTRACT FROM AUTHOR]

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