CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 9, October 2012
498
AFRICA
mortality more than double compared to patients who presented
with STDMI (risk ratios 2.03, 95% CI: 1.46–2.83,
p
<
0.001)
or STEMI (risk ratios 2.36, 95% CI: 1.83–3.04,
p
<
0.001).
On the other hand, patients presenting with minor or no ECG
abnormalities (without ST-segment shifts and without bundle
branch block/s) had a significantly lower risk (acute heart failure
was rare and in-hospital mortality was very low). The in-hospital
mortality in this group of patients was 2.9% (
p
<
0.001).
Fig. 2 presents a comparison between patients with minor or
no ECG changes and each of the other groups (STEMI, STDMI,
LBBB, RBBB).
Discussion
STEMI and STDMI have a common pathogenesis: vulnerable
plaque erosion or rupture followed by thrombus formation,
resulting in impaired vessel patency. Impaired or no flow in a
coronary artery causes ischaemic symptoms and ECG changes.
The release of myocardial necrosis markers defines the diagnosis
of myocardial infarction.
The current guidelines recommend different reperfusion
approaches based on the admission ECG in patients with acute
MI. On the other hand, ECG changes can be altered by a bundle
branch block, previous MI and other conditions. Also, the infarct-
related artery and infarct-related segment can influence the final
ECG pattern. For example, acute occlusion of the circumflex
artery may have no ST-segment elevation on a 12-lead ECG.
Instead, ST-segment depressions are frequently present – this is
sometimes called a hidden STEMI.
In our registry the most common IRA in STDMI patients
was the circumflex branch. Moreover, nearly one-third of all
STDMI patients had a TIMI grade 0 flow before PCI. Infarction
in the circumflex artery bed is very often under-diagnosed and
these patients undergo coronary angiography very late or not
at all. Based on these facts, there is an increasing effort to find
real differences or similarities between STEMI and STDMI
regarding their risk factors, prognosis, mortality and appropriate
revascularisation strategy.
In previously published studies, baseline characteristics of
patients with STEMI compared to those without ST-segment
elevation were significantly different, and the same was true in
this study. Patients with STEMI were younger and had less often
had a previous MI and/or diabetes mellitus. Cardiogenic shock
was also found to be more common in STEMI patients.
Rosenberger
et al
.
23
investigated whether risk factors were
related differently to ST-elevation and non-ST-elevation ACS.
The main finding from this large survey of more than 10 000
patients was that different risk factors were related to different
types of ACS. Smoking was related to STEMI patients, whereas
obesity and high blood pressure were more common among MI
patients without ST-elevation.
Our findings confirm the results of the Opera registry.
24
The
primary objective of the nationwide Opera study was to describe
the in-hospital management and cardiovascular outcomes (at one
year) of MI patients. The results show that patients suffering from
MI with and without ST-elevation had comparable in-hospital
(4.6
vs 4.3%) and long-term prognoses (9% in STEMI vs 11.6%
in NSTEMI, log-range
p
=
0.09).
Cox
et al.
25
showed (in the Comparative early and late
outcomes after primary percutaneous coronary intervention
in ST-segment elevation and non-ST-segment elevation acute
myocardial infarction from the CADILLAC trial) that patients
with myocardial infarction without ST-elevation tended to have
lower mortality rates than those with STEMI (0.4 vs 2.2%,
p
=
0.06).
Similarly, the mortality rates at one year were comparable
in STEMI and NSTEMI patients (3.4 vs 4.4%, respectively,
p
=
0.43).
In a study by Savonitto
et al
.,
26
the 30-day mortality rate
between STEMI and STDMI was not statistically different (5.1
vs 5.1%, respectively).
Granger
et al
.
27
attempted to develop a single model to assess
the risk for in-hospital mortality of ACS patients. Killip class
was the most powerful predictor with a two-fold increased risk of
death with each worsening class. Age was associated with nearly
the same prognostic significance, with a 1.7-fold increased risk
for every 10 years’ increase in age.
The next most important variables were systolic blood
pressure, resuscitated cardiac arrest and initial serum creatinine
levels. The strongest predictors of one-year mortality in the
Opera study were heart failure and age. Moreover, similar
predictors were found in STEMI and NSTEMI patients.
24
The
same was true in our registry, with age and heart failure being
strong independent in-hospital mortality risk factors.
There is no doubt that timely reperfusion of STEMI patients
is critical. The current guidelines of the European Society of
Cardiology appropriately recognise acute myocardial infarction
with ongoing or recurrent chest pain and ST-segment depressions
as the highest-risk subgroup and an indication for emergency
coronary angiography, followed by revascularisation when
appropriate.
Chan
et al
.
28
investigated mortality differences and timing of
revascularisation of patients undergoing cardiac catheterisation
for STEMI and NSTEMI. During the six-year accrual period,
a total of 1 974 patients were classified as having STEMI, and
2 413
patients as having NSTEMI. NSTEMI was associated with
a higher risk of long-term mortality (unadjusted mortality at one
year for STEMI was 9.5 vs 14.3% for NSTEMI). Compared
with no or late revascularisation, early revascularisation was
associated with a similar reduction in long-term outcomes for
both STEMI and NSTEMI (lower adjusted risk of mortality for
STEMI and NSTEMI,
p
=
0.22).
The Fragmin and Fast Revascularisation during InStability in
Coronary artery disease (FRISC-2) invasive trial showed for the
first time a significant event rate (MI, death or both) reduction,
favouring the invasive over the non-invasive strategy at six months
in the NSTE-ACS population. The greatest benefit of invasive
treatment, when evaluated using electrocardiography, was seen
in the subset of patients with ST-segment depression MI.
19
The
Treat Angina with Aggrastat and Determine Cost of Therapy
with an Invasive or Conservative Strategy (TACTICS-TIMI)
trial revealed that the greatest benefits of invasive treatment were
achieved in patients presenting with cardiac enzyme elevation
and ST-segment changes,
20
i.e. in STDMI patients. Also, a meta-
analysis of seven randomised trials that included a total of 9 212
patients showed that invasive management should be considered
for all patients with NSTEMI, and in particular those with
ST-segment depression.
21
In our study, there was no difference related to in-hospital
mortality between STEMI and STDMI patients treated by
emergency PCI (5.3 vs 6.78%, respectively,
p
=
0.274).
There was
a significant in-hospital mortality reduction in STDMI patients
