Validation of gated myocardial perfusion SPECT wall thickening by cardiac magnetic resonance

Objectives The purpose of this investigation was to assess the degree to which regional myocardial wall thickening (WT) measured by gated myocardial perfusion (MP) SPECT agrees with cardiac magnetic resonance (CMR) measurement of WT.

Methods MP & ECG-gated True-FISP CMR data were analyzed for 20 pts evaluated after myocardial infarction (age 60±11 years; 95% males) by “Emory Cardiac Toolbox” & Medis “MASS” software. MP isolated myocardial counts & formed polar perfusion maps for each segment of the R-R interval, the systolic count changes of which were used to compute WT. CMR used manually drawn endocardial & epicardial contours to compute regional WT. CMR data were processed for 10 age-matched normal volunteers to define CMR WT threshold of abnormality. All computations were sampled into conventional 17 AHA LV wall segments.

Results Among the 20 pts, 24% of all segments had abnormally low WT by CMR. MP WT correlated significantly with CMR WT (r=0.73, p=0.0003). On a segment by segment basis abnormal regional MP WT predicted abnormal CMR WT (ROC area = 87±2%). Logistic regression indicated MP correctly characterized WT in 81% of cases (chi-square = 143.9, p<0.0001) while overestimating frequency of abnormal WT (8% McNemar's difference, p = 0.002).

Conclusions MP WT measurements correlated significantly with CMR values & provided a high degree of accuracy in detecting segments with abnormal WT, suggesting that finding abnormal WT by MP should be followed by further cardiac testing.