Abstract
3362
Introduction: Consensus statements now advocate that, on SPECT or SPECT/CT, diffuse left ventricular myocardial (LVM) uptake of 99mTc-PYP that is at least as intense as rib uptake is diagnostic of cardiac transthyretin amyloidosis (ATTR). There are few data available about right ventricular myocardial (RVM) uptake. The objectives of this retrospective investigation were to determine the frequency of RVM uptake in pts undergoing PYP SPECT/CT, & to determine the relationship between RVM uptake & ATTR.
Methods: Data were reviewed for 318 pts with suspected ATTR, who underwent PYP SPECT/CT 3 hrs after injection of 555 MBq of 99mTc-PYP. An image format display that simultaneously showed transaxial, sagittal & coronal projections of SPECT tracer distribution alone, CT scans alone, & fused images was used for analysis. One physician, experienced in interpretation of 99mTc-PYP SPECT/CT, without knowledge of clinical data, visually compared LVM uptake & RVM uptake to rib uptake, & graded this uptake on a 4-point scale: 0 = no uptake, 1 < rib, 2 = rib or 3 >rib. A LVM uptake score ≥ 2 was considered positive for ATTR.
Results: 78 of the 318 (25%) pts were positive for ATTR. RVM uptake was present in 39 of the 318 pts (12%), including 38 (49%) of the 78 pts who had LVM uptake. All but 1 of the 39 pts with RVM uptake were positive for ATTR (97%). LVM uptake was greater than RVM uptake (2.9±0.5 versus 1.8±0.6, p < 0.0001) (see Table). LVM ≥ 2 was associated with RVM uptake (ROC AUC = 93±2%), & RVM uptake predicted ATTR confidence ≥ 2 (χ2 = 115.7, odds ratio = 227.0).
Conclusions: Even though right ventricular myocardial thickness is only about 10% of that of the left ventricular myocardium, right ventricular myocardial uptake of PYP may be present in as many as 50% of pts with ATTR, & has a very high positive predictive value (>97%). Future investigations will focus on the relationship between RVM uptake & cardiac dysfunction, as well as its prognostic significance, & its value for monitoring treatment response.