Abstract |
We studied to investigate the predictive values of
gated SPECT for the improvement of wall motion after
bypass surgery. As we compared postoperative SPECT with
preoperative ones, we defined viability as wall motion
improvement. We performed rest T1-20l/stress Tc-99m-
MIBI gated SPECT in 25 patients before and 3 months
after bypass surgery. Myocardial wall motion was graded
as normal, hypokinesia, a kinesia, and dyskinesia by
pair-wise visual analysis of gated pre and
postoperative SPECT's on the same monitor wall motion
abnormalities before operation, 69 (75%) improved and
23 did not. Before operation, we could find segments
with good systolic thickenining 64 segments among total
92. Thickening of the remaining 28 was poor. Wall
motion improved postoperatively in 45 segments (70%)
among 64 with good thickening, Twenty four(86%) among
28 segments with poor thickening had also improved. We
grouped segments into mild(hypokinetic) and
severe(akinetic/dyskinetic) ones. Among 33 segments
with severe motion abnormalities, 14 had good
thickening and 19 did not. Nine(60%) improved out of 14
segments having severe abnormality with good
thickening. However, 16(84%) segments out of 19 having
severe abnormality with poor thickening also improved.
Neither degree of perfusion decrease nor severity of
wall motion abnormalities could explain the high rate
of false negatives. In conclusion, as we defined
viability as wall motion improvement by comparing pre
and postoperative SPECT, systolic thickening observed
by gated Tc-99m-MIBI SPECT in myocardial segments with
wall motion abnormalities predicted wall motion
improvement after bypass surgery. However, poor
thickening could not be referred as evidence of
nonviable myocardium both in mild and severe
contractile dysfunction, so that we might need
stimulation study such as dobutamine echocardiography
or dobutamine gated SPECT. |