Diagnostic and prognostic value of Technetium-99m pyrophosphate uptake quantitation for transthyretin cardiac amyloidosis

99mTc-pyrophosphate imaging has emerged as an important non-invasive method to diagnose transthyretin cardiac amyloidosis (ATTR-CM). Quantitation of 99mTc-pyrophosphate activity, on SPECT images, could be a marker of ATTR-CM disease burden. We assessed the diagnostic accuracy and clinical significance of 99mTc-pyrophosphate quantitation. Patients who underwent 99mTc-pyrophosphate imaging for suspected ATTR-CM were included. Using SPECT images, radiotracer activity in the myocardium was calculated using cardiac pyrophosphate activity (CPA) and volume of involvement (VOI), with thresholds for abnormal activity derived from LVBP activity. Diagnostic accuracy was assessed using area under the receiver operating characteristic curve (AUC). In total, 124 patients were identified, mean age 73.9 ± 11.4, with ATTR-CM diagnosed in 43 (34.7%) patients. CPA had the highest diagnostic accuracy (AUC .996, 95% CI .987-1.00), and was significantly higher compared to the Perugini score (AUC .952, P = .016). In patients with ATTR-CM, CPA was associated with reduced left ventricular ejection fraction (adjusted odds ratio 1.28, P = .035) and heart failure hospitalizations (adjusted hazard ratio 1.29, P = .006). Quantitative assessment of myocardial radiotracer activity with CPA or VOI have high diagnostic accuracy for ATTR-CM. Both measures are potential non-invasive markers to follow progression of disease or response to therapy. Las imágenes de 99mTc-pirofosfato han surgido como un importante método no invasivo para diagnosticar la amiloidosis cardíaca por transtiretina (ATTR-CM). La cuantificación de la actividad del 99mTc-pirofosfato, en las imágenes de SPECT, podría ser un marcador de la carga de enfermedad de ATTR-CM. Evaluamos la precisión diagnóstica y la importancia clínica de la cuantificación del 99mTc-pirofosfato. Se incluyeron pacientes que se sometieron 99mTc-pirofosfato por sospecha de ATTR-CM. Utilizando imágenes de SPECT, se calculó la actividad del radiotrazador en el miocardio utilizando la actividad cardiaca del pirofosfato (CPA) y el volumen del involucro (VOI), con umbrales para la actividad anormal derivados de la actividad del LVBP. La precisión diagnóstica se evaluó utilizando el área bajo la curva (AUC) de las características del funcionamiento del receptor. En total, se identificaron 124 pacientes, edad media 73,9 ± 11,4, con ATTR-CM diagnosticado en 43 (34,7%) pacientes. La CPA tuvo la mayor certeza diagnóstica (AUC 0.996, IC del 95% 0.987 – 1.00),