Extent of regional wall motion abnormalities by gated spect in patients with Q-wave myocardial infarction

Abstract

Background: Regional wall motion abnormalities (RWMA) on post stress gated SPECT enhance detection of myocardial ischemia. However, the extent of RWMA in patients (pts) with a prior electrocardiography (EKG) Q-wave myocardial infarction (Q-MI) on gated SPECT is not known. We studied this on post stress gated SPECT myocardial perfusion (MPI) studies in pts with a Q-MI by EKG. Methods: Thirty pts with EKG criteria of Q-MI, as defined by the presence of a Q or Qs wave of > 40 msec (± height > 1/3 rd of the R-wave) in two consecutive leads of a major epicardial coronary artery were analyzed. Quantitative post stress gated SPECT (Autoquant -QGS®) functional raw data for motion (mm) and thickening (%) on a four region polar map was analyzed. The maximum endocardial wall motion from end diastole to end systole on the brightest colour scale was 10 mm. The wall thickening form end diastole to end systole expressed as a percentage (%), with twice the end diastolic thickness at end systole equal to 100%. A 17-segment, 5-point scale sum rest score (SRS) and sum motion score (SMS) were calculated on the gated MPI. Twenty-three pts with a normal rest EKG and a MPI study were compared as a control group. Results: Mean age was 61 ± 10 years, 56% males. The individual regional (n=43) scores corresponding to the Q-MI location and that of the control group are shown on table. 24 of 30 pts (80 %) and 33 of 43 (78%) regions with a Q-MI had RWMA by gated SPECT. Q-MI pts showed significantly lower mean wall motion and wall thickening scores compared to the control group (p<0.001, Table). A QGS® mean wall motion score of < 5 mm and wall thickening of ≤ 30% had 76% sensitivity and 78–80% specificity for a regional Q-MI by EKG. 15 of 33 (45%) regions were akinetic (motion ≤ 1 mm ± ≤ 10% thickening) by gated SPECT. The mean SMS and SRS were significantly higher with Q-MI (17 ± 10 and 22 ± 10 respectively, P<0.001). SPECT Variables Q - MI (n = 30) Control Group (n = 23) p value Motion (mm) Septum (n = 11) 2.0 ± 1.7 6.5 ± 1.6 <0.001 Lateral (n = 5) 5.0 ± 2.6 9 ± 1.4 <0.001 Anterior (n = 3) 4.2 ± 2.0 9.2 ± 1.5 <0.001 Inferior (n = 24) 4.7 ± 2.0 7.6 ± 1.7 <0.001 Thickening (%) Septum 22 ± 12 44 ± 11 <0.001 Lateral 10.5 ± 5 42 ± 12 <0.001 Anterior 10.5 ± 9 40 ± 10 <0.001 Inferior 18 ± 9 39 ± 11 <0.001 SMS 17 ± 10 0.5 ± 1.2 <0.001 SRS 22 ± 10 1.2 ± 1.3 <0.001 Conclusions: Pts with Q-MI have about 20% normal, 45% akinetic and remaining hypokinetic regions by gated SPECT. Gated SPECT MPI motion of ≤ 5 mm, wall thickening ≤ 30%, mean SMS ≥ 7 and mean SRS ≥12 were markers of a Q-MI by EKG.