PET May Differentiate Cardiac Amyloidosis, Hypertensive Heart Disease

PET imaging can accurately identify and differentiate between cardiac amyloidosis and hypertensive heart disease, according to a study in The Journal of Nuclear Medicine.

Researchers from Australia performed a small study to determine the feasibility of using 18F-florbetaben PET to diagnose cardiac amyloidosis.

“Currently, there is no definitive test to diagnose cardiac amyloidosis other than an invasive biopsy of the heart muscle,” coauthor W. Phillip Law, a radiology, nuclear medicine and molecular imaging specialist at Princess Alexandra Hospital in Brisbane, Australia, said in a release. “Cardiac amyloidosis is often not diagnosed until late in the course of the disease, as the typical appearance of the infiltrated myocardium on echocardiography and MRI can be mistaken for other more prevalent disorders."[[{"type":"media","view_mode":"media_crop","fid":"53631","attributes":{"alt":"W. Phillip Law","class":"media-image media-image-right","id":"media_crop_1927998018879","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"6714","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 113px; width: 170px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"W. Phillip Law","typeof":"foaf:Image"}}]]

The researchers performed 18F-florbetaben PET on 14 patients: five with amyloid light chain, five with amyloid transthyretin, and four control with hypertensive heart disease. Earlier studies with amyloid radiotracers in the heart  used normal subjects as controls. This study differed because it compared subjects with thickened heart muscle secondary to amyloid deposition to those with thickened myocardium due to hypertensive heart disease.

Qualitative and quantitative assessments of 18F-florbetaben activity were performed using the SUV_mean of the left ventricular myocardium and blood pool and calculation of target-to-background SUV ratio. Myocardial 18F-forbetaben retention was also calculated as the percent- age mean myocardial SUV change between 0 and 5 minutes and 15 and 20 minutes after radiotracer injection. Global left ventricular longitudinal and right ventricular free wall longitudinal strain were calculated using two-dimensional speckle-tracking echocardiography.

The results showed that target-to-background SUV ratio and percentage myocardial 18F-forbetaben retention were higher in amyloid patients than in hypertensive controls. A cut-off value of 40% was able to differentiate between cardiac amyloid patients and hypertensive control subjects. Percentage myocardial 18F-forbetaben retention was an independent determinant of both global left ventricular longitudinal and right ventricular free wall longitudinal strain via an inverse curve relationship.

"The relationship of PET quantification of florbetaben retention in the heart, with histological amyloid plaque burden, may provide another means of monitoring disease and could also be useful in monitoring response of cardiac amyloid to treatment, but further research needs to be undertaken to investigate this relationship," Law concluded.