Incidental rib hotspots on 99mTc-pyrophosphate scintigraphy in a patient with transthyretin cardiac amyloidosis: cough-induced fractures unveiled

Abstract

Figures

Electrocardiography showed atrial fibrillation, low-voltage complexes, and right bundle branch block (A). Transthoracic echocardiography revealed increased left ventricular wall thickness of 12 mm (B) and increased left atrial volume index of 48 mL/m2 (C). Technetium-99 m pyrophosphate scintigraphy demonstrated Perugini Grade 3 myocardial uptake (D, yellow arrows). Unexpectedly, five focal extracardiac hotspots were observed: four along the anterolateral right third to sixth ribs and one at the lateral right ninth rib (D, red arrows). Chest computed tomography demonstrated focal sclerotic changes at the third to sixth rib sites on frontal and lateral images (E and F, arrows), consistent with healed rib fractures. At the ninth rib site, a fracture line was clearly visualized on lateral imaging (F, arrow), confirming an additional rib fracture.

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Case description

An 88-year-old woman was hospitalized for an asthma exacerbation. She had lumbar canal stenosis and bilateral carpal tunnel syndrome but no family history of heart disease. After a severe coughing episode, she was treated with intravenous corticosteroids. Two months later, she was readmitted for heart failure. Electrocardiography showed atrial fibrillation, low-voltage complexes, and right bundle branch block (Figure 1A). Transthoracic echocardiography revealed increased left ventricular wall thickness of 12 mm (Figure 1B), preserved ejection fraction of 58%, and increased left atrial volume index of 48 mL/m^2^ (Figure 1C), raising suspicion for cardiac amyloidosis. Technetium-99m pyrophosphate (99mTc-PYP) scintigraphy demonstrated Perugini Grade 3 myocardial uptake (Figure 1D, yellow arrows). Serum and urine immunofixation were negative for monoclonal proteins, and transthyretin genotyping was not performed. The diagnosis of transthyretin cardiac amyloidosis was made,^1^ and treatment with azosemide, dapagliflozin, and apixaban was initiated.

Electrocardiography showed atrial fibrillation, low-voltage complexes, and right bundle branch block (A). Transthoracic echocardiography revealed increased left ventricular wall thickness of 12 mm (B) and increased left atrial volume index of 48 mL/m2 (C). Technetium-99 m pyrophosphate scintigraphy demonstrated Perugini Grade 3 myocardial uptake (D, yellow arrows). Unexpectedly, five focal extracardiac hotspots were observed: four along the anterolateral right third to sixth ribs and one at the lateral right ninth rib (D, red arrows). Chest computed tomography demonstrated focal sclerotic changes at the third to sixth rib sites on frontal and lateral images (E and F, arrows), consistent with healed rib fractures. At the ninth rib site, a fracture line was clearly visualized on lateral imaging (F, arrow), confirming an additional rib fracture.

Unexpectedly, five focal extracardiac hotspots were observed: four along the anterolateral right third to sixth ribs and one at the lateral right ninth rib (Figure 1D, red arrows). Because of these hotspots, the heart-to-contralateral ratio could not be reliably measured. Chest computed tomography demonstrated focal sclerotic changes at the third to sixth rib sites on frontal and lateral images (Figure 1E and F, arrows), consistent with healed rib fractures. At the ninth rib site, a fracture line was clearly visualized on lateral imaging (Figure 1F, arrow), confirming an additional rib fracture. Although the exact timing of injury could not be confirmed, the fractures were suspected to be related to the recent coughing episode.

Cough-induced rib fractures are most commonly observed in postmenopausal women and are associated with risk factors such as asthma, osteoporosis, and corticosteroid use.^2,3^ This case underscores the importance of assessing extracardiac findings on 99mTc-PYP scintigraphy, as they may provide clinically meaningful insights beyond myocardial assessment.