Validation of [99mTc]Tc-HMDP SPECT/CT Myocardium-to-blood Ratio for the Detection of ATTR Cardiomyopathy.

Background: This study validates the accuracy of ^99mTc-hydroxymethylene diphosphonate ([^99mTc]Tc-HMDP) single-photon emission tomography / computed tomography (SPECT/CT) in the diagnosis of transthyretin amyloidosis (ATTR) cardiomyopathy using myocardium-to-blood ratio (MBR).

Methods: The final study population was 80 patients who underwent [^99mTc]Tc-HMDP SPECT/CT for suspected ATTR cardiomyopathy at Helsinki University Hospital or Jorvi Central Hospital in Finland. Patients were diagnosed according to the currently accepted European Society of Cardiology criteria as either non-ATTR (n=48) or ATTR cardiomyopathy patients (n=32). The left ventricular (LV) MBR was calculated by dividing LV maximal myocardial uptake with maximal left atrial uptake. Right ventricular (RV) uptake was calculated as the maximal uptake ratio on the RV free wall and right atrium. Data are presented as mean ± standard deviation.

Results: The LV MBR was higher in ATTR patients than non-ATTR patients (4.6 ± 1.2 vs. 0.9 ± 0.2, p<0.001). The LV MBR of 1.5 identified ATTR cardiomyopathy with 100% accuracy. LV MBR was associated with LV wall thickness on echocardiography in univariable analysis but not with LV ejection fraction or E/e'. The RV MBR was higher in ATTR patients (2.9 ± 1.0 vs. 0.8 ± 0.2, p<0.001). Neither LV nor RV MBR were associated with the clinical severity of ATTR cardiomyopathy in univariable analysis.

Conclusions: LV myocardium-to-blood ratio (MBR) greater than 1.5 was 100% accurate for detecting ATTR cardiomyopathy using [^99mTc]Tc-HMDP SPECT/CT. Left ventricular MBR was associated with wall thickness on echocardiography but not with the clinical severity of ATTR cardiomyopathy.