It is well established that reperfusion therapy in
patients with ST-elevation acute myocardial infarction
(STEMI) has to be achieved as soon as
... [Show More] possible.
After 12h from symptom onset, reperfusion
therapy, on average, does not offer any benefit [1, 2].
Yet about one-third of STEMI patients are latecomers
with symptoms on admission lasting for
more than 12h [3]. An important confounder in
latecomers, however, is the difficulty in interpreting
symptom duration. The presence of Q waves on the
baseline electrocardiogram has been suggested to
provide additional information to that given by
symptom duration. In an analysis of the APEXAMI
trial, baseline Q waves but not time from
symptom onset significantly predicted mortality at
90 days in patients with STEMI treated by primary
percutaneous coronary intervention (pPCI) [4].
The causes responsible for a late presentation are
multiple, including painless ischemia and erroneous
interpretation of the symptom by the patient;
important predictors of late presentation are
diabetes, older age, and female gender [5].
Accordingly, previous studies have demonstrated
that latecomers are older, more often have comorbidities
and have a more adverse cardiovascular
risk profile than patients presenting earlier after
symptom onset. The associated comorbidities and
the worse cardiovascular risk profile may be factors
that contribute to the unfavorable outcome of this
patient population. The organization of hub and
spoke networks for pPCI also may contribute to
late presentation as suggested by the substantial
heterogeneity in the rate of patients receiving
pPCI, ranging from 92% in the Czech Republic to
8% in Turkey [6].
It is worth nothing that the threshold of 12h
for benefit related to pPCI is mainly based on the
fact that latecomers were not included in trials
showing superiority of pPCI over fibrinolysis.
Indeed, in trials of fibrinolysis versus placebo,
the prognostic advantage of fibrinolysis was limited
to patients presenting within 12h of pain onset.
In particular, in the Estudio Multicéntrico
Estreptoquinasa Repúblicas de América del Sur
(EMERAS) trial, which studied 4534 patients
entering hospital up to 24h after pain onset, no
benefit was observed among 1791 patients presenting
>12h from symptom onset [7]. Similarly, the
Late Assessment of Thrombolytic Efficacy (LATE)
study, a large trial of 5711 patients randomized to
intravenous alteplase or placebo between 6 and
24h from symptom onset, found that the benefit of
fibrinolysis with alteplase was confined to patients
presenting within 12h of symptom onset [8]. [Show Less]