Electrocardiographic Features in Transthyretin Cardiac Amyloidosis

<b>Background:</b>^99mTc pyrophosphate scintigraphy (^99mTc-PYP) is useful for diagnosing transthyretin amyloid cardiomyopathy (ATTR-CA). We examined the characteristics of ^99mTc-PYP-positive patients at our institution. <b>Methods:</b> A total of 76 patients who underwent ^99mTc-PYP from December 2020 and March 2022 were grouped into ^99mTc-PYP-positive (P) and -negative (N) groups and compared. <b>Results:</b> Nine of seventy-six patients were positive (11.8%), and all patients were diagnosed with ATTR-CA by myocardial biopsy or clinical findings. The heart-to-contralateral lung ratio in the P group was significantly higher (N Group: 1.15, P Group: 1.92, <i>p</i> < 0.001). In the P group, the left ventricular posterior wall thickness was significantly thickened (N Group; 12.5 mm, P Group; 15.5 mm, <i>p</i> = 0.003). Electrocardiogram showed left ventricular hypertrophy (LVH) was observed more frequently in the N group (N Group; 30 patients (44.8%) and the P Group; 1 patient (11.1%), <i>p</i> < 0.001). In addition, the QTc interval was significantly prolonged in the P group (N Group; 422 msec, P Group; 456 msec, <i>p</i> = 0.001). <b>Conclusions:</b> In patients who have significant LVH on echocardiogram but not on electrocardiogram, ^99mTc-PYP may be useful for diagnosing ATTR-CA. However, the present study is a single-center retrospective study with a small number of patients, and the results are exploratory and hypothesis-generating. Prospective studies with a larger number of subjects are needed.