Sirs:
Assessment of individual patient risk for short-term outcomes following acute ST-elevation
myocardial infarction (STEMI) has focused on risk scores with high sensitivity to
identify high-risk patients [1]. By contrast, there is a lack of uniformly accepted
scores for predicting the absence of complications following primary percutaneous
intervention (pPCI), and current guidelines still recommend admission in intensive
care unit (ICU) during at least 24 h after symptoms onset in patients with uncomplicated
STEMI [1–3]. Minimizing ICU admissions, particularly in the current COVID-19 era,
is paramount for minimizing patient exposure and optimizing resource allocation [4–6].
We hypothesized whether in the era of regional pPCI reperfusion networks, uncomplicated
STEMI patients remaining event-free following prompt TIMI 3 flow restoration, would
facilitate early discharge from the ICU [7, 8]. The present study aimed to identify
predictors of very low-risk STEMI patients following uncomplicated pPCI, and to assess
the safety of an early ICU discharge strategy.
To test our hypothesis, we analyzed consecutive STEMI patients undergoing pPCI in
our referral area (~ 850,000 inhabitants) arriving within 12 h after symptom onset,
between 2012 and 2019 (n = 2185). Per protocol all patients received a loading dose
of 300 mg of aspirin plus 600 mg of clopidogrel or 180 mg of ticagrelor or 60 mg of
prasugrel before the procedure. We recorded in a prospective dedicated database clinical
characteristics, peri-procedural complications including arrhythmias, Killip-Kimball
class, reperfusion time, and procedural characteristics; 24-h ICU cardiac complications
including ventricular fibrillation/tachycardia, A-V block or asystole, acute pulmonary
edema, mechanical ventilation, shock, acute stent thrombosis and cardiac death; and
30-day cardiac death. Patients were divided in two cohorts: a derivation cohort (n = 1492;
years 2012–2016) to identify independent very low-risk predictors; and a validation
cohort (n = 693; years 2017–2019).
Univariate and multivariate logistic regression analysis were used to determine predictors
of 24-h cardiac complications and 30-day cardiac death. Multivariate analysis included
clinical and procedural predictors that exhibited a p value < 0.05 in the univariate
analysis. First, multivariable-independent predictors allowed patient stratification
in to very low-risk (odds ratio ≤ 0.85 for early cardiac complications and 30-day
cardiac death) and other risk groups. Next, cardiac events beyond the first 6 h in
the ICU were characterized in the very low-risk group. Finally, specificity to predict
early cardiac complications and 30-day cardiac death in the very-low risk group was
also assessed.
Derivation cohort independent predictors of very low-risk were age ≤ 75 years-old,
absence of primary malignant arrhythmias during the first assistance, Killip-Kimball
class I, radial access, absence of left main or three-vessel coronary disease, and
successful angioplasty-stenting (defined as final TIMI 3 flow), as shown in Table 1.
The same very low-risk predictors emerged in the validation cohort (data not presented).
Table 1
Univatiate and multivariate analysis of predictors of very low-risk of 24-h cardiac
events and 30-day cardiac death following primary percutaneous coronary intervention
Clinical and procedural predictors
No complication (n = 1348)
Complication (n = 144)
p
Early complication* [OR, 95% CI]
p
30-day cardiac death [OR, 95% CI]
p
Age ≤ 75 year old
1074 (80)
88 (61)
< 0.01
0.56 [0.37–0.84]
< 0.01
0.10 [0.04–0.20]
< 0.01
Female gender
296 (22)
41 (29)
010
Diabetes mellitus
328 (24)
44 (31)
0.12
Previous vascular disease (any)
274 (20)
43 (30)
0.01
Anterior myocardial infarction
546 (41)
75 (52)
0.01
Killip class I at presentation
1179 (88)
59 (41)
< 0.01
0.14 [0.10–0.22]
< 0.01
0.12 [0.06–0.26]
< 0.01
No arrhythmia first assistance†
180 (13)
59 (41)
< 0.01
0.32 [0.21–0.21]
< 0.01
0.36 [0.17–0.76]
< 0.01
Radial access
1320 (98)
125 (87)
< 0.01
0.50 [0.24–1.04]
0.06
0.18 [0.07–0.46]
< 0.01
No three vessel/LM disease
283 (21)
46 (32)
< 0.01
0.85 [0.56–1.30]
0.40
0.51 [0.25–1.00]
0.05
Stent implanted
1321 (98)
144 (100)
0.20
Successful angioplasty-stenting‡
1263 (94)
121 (84)
< 0.01
0.42 [0.10–0.21]
< 0.01
0.16 [0.07–0.37]
< 0.01
Complete revascularization
519 (39)
46 (32)
0.16
Reperfusion time (minutes)
191 (130–309)
181 (129–299)
0.60
IIb/IIIa inhibitors use
547 (41)
50 (34)
0.36
Dual antiplatelet load
1348 (100)
144 (100)
NA
Baseline oral anticoagulation
44 (3)
12 (8)
0.02
ICU cardiac predictors**
LVEF < 40%
1166 (86)
77 (54)
< 0.001
NA
NA
Creatinin clearance (ml/min)
92 (42)
68 (38)
< 0.001
NA
NA
Values presented as n (%) or mean (SD) or median (Q1–Q3)
ICU intensive care unit, NA not assessed, LM left main, LVEF left ventricular ejection
fraction
*Including 24-h cardiac death, malignant arrhythmias, severe heart failure, stent
thrombosis/re-acute myocardial infarction
**Intensive Care Unit predictors were not included in the multivariate analysis
†Including atrial or ventricular fibrillation, ventricular tachycardia, A-V block
or asystole appeared until the end of primary percutaneous coronary intervention procedure
‡Defined as final TIMI 3 flow without major procedural complications
In the derivation cohort, 144 of 1492 (9.7%) patients had a 24-h-cardiac event (21
patients with stent thrombosis); 50 (3.4%) suffered a 30-day cardiac death; and 638
(43%) met very-low risk criteria. In the very-low-risk group, seven patients (1.1%)
had a 24-h-cardiac event, all due to stent thrombosis, one with concomitant ventricular
fibrillation (specificity = 0.95, p < 0.01). No 30-day cardiac deaths were recorded
in the very low-risk group (specificity = 1, p < 0.01).
In the validation cohort, 78 of 693 (11.3%) patients had a 24-h-cardiac event (16
of them stent thrombosis); 17 (2.5%) suffered a 30-day cardiac death; and 369 (53%)
met criteria of very-low risk. In the very-low risk group, ten patients (2.7%) had
a 24-h-cardiac event, nine due to stent thrombosis, (one with concomitant ventricular
fibrillation) and one due to heart failure (patient with active hemolytic anemia complicated
with systemic inflammatory syndrome) (specificity = 0.88, p < 0.01). No 30-day cardiac
deaths were recorded in the very low-risk group (specificity = 1, p < 0.01).
The 6-h ICU cut-point analysis performed in the very-low risk group only revealed
one stent thrombosis event beyond the 6 h (0.9 ‰), without other complications (specificity ≈ 1,
p < 0.01).
This is the first study to focus on predictors of very low-risk of complications following
STEMI in the pPCI reperfusion era. We found that younger patients with uncomplicated
STEMI without complex coronary anatomy are highly likely to remain uncomplicated providing
the infarct related artery is successfully opened via transradial pPCI. Importantly,
the identified variables may be easily recorded upon completion of the pPCI procedure.
Proper identification of such very low-risk patients should improve current post-procedural
decision-making algorithms, including very early (within 6 h) patient transfer from
the intensive care to a conventional ward, thus optimizing intensive care resources
for other life-threatening pathologies.
Stent thrombosis is always concerning, and in this very-low risk stratification model,
it was the least accurate event to predict; nevertheless, stent thrombosis usually
manifests early post-pPCI. Indeed, only one patient presented stent thrombosis beyond
6 h after ICU admission. These data should be interpreted in the context of a regional
pPCI reperfusion network that includes a high percentage of radial access and stenting,
and short reperfusion delay [2]. Nevertheless, pending confirmation in larger prospective
studies, an early discharge strategy from the ICU within 6 h post-successful pPCI
may be a reasonably safe option in almost half of STEMI patients.