Clinical value of supine and upright stress only myocardial perfusion imaging in overweight patients

Objectives We have assessed in overweight patients whether additional upright imaging increases the confidence of interpretation of the stress only supine MPI, thus reducing the need for rest imaging.

Methods 101 consecutive patients (M=51, 62+12 yrs) with BMI >30 (median 36, IQR 36-39) who had one day (n=54, BMI<35) or 2-day Tc-MIBI pharmacological stress (adenosine=98, dobutamine=3) MPI on a solid-state dedicated cardiac camera (D-SPECT, Spectrum-Dynamics, Israel) were assessed. Two experienced Nuclear Medicine physicians blinded to the clinical information interpreted the studies in consensus: stress supine MPI first, then the gated data and finally the upright data were added. At each stage images were interpreted as diagnostic (normal or abnormal) or equivocal and the need for a rest study was recorded (abnormal and equivocal scans). Defects seen on supine but not on upright were defined as artefacts and persistent defects on both supine and upright were defined as abnormal.

Results On stress supine images there were 27 normal, 22 abnormal and 52 equivocal scans. Rest imaging was required in 74/101 patients. The median EF was 52% (IQR 52-68%), not changing the need for rest imaging. After adding the upright scan there were 59 normal, 28 abnormal and 14 equivocal studies. There was no change in interpretation of studies with a definitive diagnosis on supine, however, only 14/52 (27%) supine equivocals remained equivocal, whereas 32/52 (62%) were reclassified as normal and 6/52 (11%) as abnormal (p<0.001). Following the upright scan rest scan was needed in 42/101 (p<0.001 vs. supine). 26/40 (65%) LAD territory supine defects (78% female) and 17/48 (35%) RCA territory supine defects (80% male) (p<0.001) disappeared on upright imaging.

Conclusions In overweight patients undergoing gated stress MPI the addition of upright to conventional supine only imaging significantly increases the ability to interpret scans as diagnostic and may reduce considerably the need for rest imaging, thus enabling a reduction in radiation exposure