REVIEW OF THE PUBLISHED LITERATURE WITH MCE USED FOR WALL MOTION
EVALUATION
The use of rest MCE in the context of chest pain was evaluated in
different studies either or both for WM and MP assessments. The studies
that evaluated only MP were not included in our review.
Rinkevich et al. 1 studied the MCE in predicting
events in pts with CP who presented to the ED with non ST-elevation at
the ECG; in particular they analysed 1017 pts, assessing both regional
WM and MP with MCE in addition to the standard ECG evaluation, with a
mean follow-up of 7.7 months. Considering only rest WM data, which is
the main purpose of the current review, 43 pts with normal WM had events
and 249 events (85% of all events) took place in patients with rest WM
abnormalities assessed with contrast.
On the multivariable Cox regression analysis, history of hypertension
(P=0.028), ECG (P=0.0001), WM (P<0.0001), and MP
(P<0.0001) were significant predictors of cardiac events.
Abnormal WM increased the risk of events by five-fold when compared with
normal WM (95% CI: 3.4–7.2), whereas abnormal MP increased the risk by
only twofold
when compared with normal MP (95% CI: 1.5–2.7).
They concluded that early assessment of WM (and MP) on MCE added
significant diagnostic and prognostic value to routine evaluation in pts
presenting to the ED with suspected cardiac CP and no ST-segment
elevation. There was no standard (without contrast) echocardiography
included in the standard clinical comparison control, so that MCE for
rest WM assessment was compared to clinical assessment and ECG only.
Furthermore, Troponin assessment was not included in the study.
Tong et al. 2 compared WM and MP analysis with
modified TIMI risk score (mTIMI, which is TIMI score not including
troponin levels) in 957 pts presenting to the ED with CP and a
nondiagnostic ECG. Cumulative pts outcomes were determined at three time
points: early (within 24 hours), intermediate (up to 30 days), and late
(>30 days). On the basis of their mTIMI or TIMI scores, pts
were categorized as either low (score<2), intermediate (score
of 3 or 4), or high (score >5) risk. The mTIMI score was
unable to discriminate between intermediate- compared to high-risk pts
at any follow-up time point, whereas only 2 of 523 pts with normal WM
had an early primary event. WM evaluation provided incremental
prognostic value over mTIMI scores for predicting intermediate and late
events. But it should be emphasized that rest MCE WM was not assessed
with very low mechanical index imaging but rather with harmonic low
mechanical index, which has lower yield to detect WM abnormalities
compared with very low mechanical index imaging. The full TIMI score
could not improve upon these results at any follow-up time point.
Wei et al. 3 enrolled 1166 pts (cohort 1) with a
validation cohort (cohort 2) of 720 pts; all pts presented to ED with CP
lasting 30 minutes or more and there wasn’t any ST-segment elevation on
the ECG. Wall motion (WM) and myocardial perfusion (MP) were separately
assessed by MCE. Any abnormality or ST changes on ECG (odds ratio
[OR] 2.5; 95% confidence interval [CI], 1.4-4.5, P = 0.002, and
OR 2.9, 95% CI, 1.7-4.8, P < 0.001, respectively), abnormal
WM with normal MP (OR 3.5, 95% CI, 1.8-6.5, P < 0.001), and
abnormal WM with abnormal MP (OR 9.6, 95% CI, 5.8-16.0, P <
0.001), so that either or both WM and MP were found to be significant
multivariate predictors of nonfatal myocardial infarction or cardiac
death. Apparently, there was no comparison between WM assessed with MCE
and without contrast, so that in this well-conducted study, there
remains the clinical question whether contrast WM assessment is superior
or not to standard WM assessment without contrast.
Kalvaitis et al. 4 explored the effect of time
delay of the use of MCE in the ED. In particular 957 pts were enrolled,
they presented to ED with CP and no ST-elevation at the ECG and were
divided into 4 quartiles depending on the time between their last
episode of CP and the MCE evaluation. Pts in quartile I had MCE during
ongoing CP (time delay of 0 minutes). The time delays in quartiles II,
III, and IV were 54 ± 44, 213 ± 54, and 556 ± 184 minutes, respectively
(P < 0.001). In each quartile, pts with normal WM had the
lowest incidence of events, whereas those with both abnormal WM and MP
had the highest incidence of events. Pts with abnormal WM but normal MP
had an intermediate event rate. They concluded that timing of MCE did
not affect the ability to predict event rate at 24 hours in pts with CP.
Again, it should be emphasized that rest MCE WM was not assessed with
very low mechanical index imaging but rather with harmonic low
mechanical index, which has lower capability to detect WM abnormalities
compared with very low mechanical index imaging.
Wyrick et al. 5 analysed the cost-efficiency of
MCE in 957 pts presenting to ED with CP and no ST-elevation at the ECG,
but this analysis is most probably conducted on the same patient cohort
studied by Kalvaitis et al,4 so we did not include it
in our review.
Finally, Porter et al. 6 compared patient
outcome after stress real-time MCE (RTMCE), using very-low mechanical
index, versus conventional stress echo with low mechanical index and
harmonic imaging (CSE). Outpatient and inpatient subjects admitted for
chest pain with normal or equivocal troponin were referred for
dobutamine or exercise stress echocardiography were prospectively
randomized to either RTMCE or CSE. Definity contrast was used for CSE
only when endocardial border delineation was inadequate (63% of
studies). 2014 pts were evaluated with a mean follow-up of 2.6 years. An
abnormal RTMCE was more frequently observed than an abnormal CSE at peak
stress (p < 0.001), and more frequently resulted in
revascularization (p = 0.004). Resting WM abnormalities were also more
frequently seen with RTMCE (p < 0.01), and were an independent
predictor of death/nonfatal MI (p = 0.005) for RTMCE, but not CSE. This
is a signal that RTMCE, as now supported by European and American
guidelines,7,8 is superior to standard
contrast-echocardiography-using higher mechanical index (0.2-0.4) and
harmonic imaging- to detect mild WM abnormalities.