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. 2023 Aug 4;60(3):385–391. doi: 10.1097/SHK.0000000000002184

INTRA-AORTIC BALLOON PUMP REDUCES 30-DAY MORTALITY IN EARLY-STAGE CARDIOGENIC SHOCK COMPLICATING ACUTE MYOCARDIAL INFARCTION ACCORDING TO SCAI CLASSIFICATION

Da Luo ∗,†,‡, Rihong Huang §, Xiaoying Wang ∥, Jing Zhang , Xinyong Cai ∗∗, Fuyuan Liu ††, Yuhua Lei ‡‡, Dongsheng Li §§, Wenjie Zhou ∗,†,‡, Changwu Xu ∗,†,‡, Bing Huang ∗,†,‡, Hong Jiang ∗,†,‡, Jing Chen ∗,†,‡
PMCID: PMC10510821  PMID: 37548623

ABSTRACT

Background: Cardiogenic shock complicating acute myocardial infarction (AMICS) remains a high 30-day mortality. Mechanical circulatory support devices are increasingly used in AMICS, but their effects on mortality vary partly because of shock severity. Aims: This study aimed to evaluate the association between intra-aortic balloon pump (IABP) and 30-day mortality in patients with early-stage AMICS. Methods: We retrospectively analyzed patients with ST-segment elevation myocardial infarction (STEMI) based on a multicenter clinical trial (NCT04996901). Patients were stratified by IABP use, and shock severity was classified according to the Society for Cardiovascular Angiography and Interventions (SCAI) SHOCK stages. The primary outcome was 30-day all-cause mortality. The association between IABP and 30-day mortality was evaluated across shock stages using propensity score matching, weighting, and logistic regression. Results: Five thousand three hundred forty-three patients were included, and 299 received IABP. The SCAI SHOCK stage was associated with 30-day mortality (odds ratio [OR], 20.19; 95% confidence interval [CI], 13.60–29.97; P < 0.001). In the 580 matched patients, a significant interaction between IABP and 30-day mortality at different shock stages was observed (P = 0.005). Intra-aortic balloon pump was associated with lower 30-day mortality among patients with shock stage A/B (5.8% vs. 1.2%; OR, 0.19; 95% CI, 0.03–0.73; P = 0.034) but not stage C/D/E (29.3% vs. 38.1%; OR, 1.49; 95% CI, 0.84–2.65; P = 0.172). These results were confirmed by sensitivity analyses of the weighted cohort. Conclusions: Intra-aortic balloon pump reduced 30-day mortality in patients with early-stage AMICS. The SCAI SHOCK stage provides risk stratification for patients with STEMI and helps identify those who may respond well to IABP.

KEYWORDS/ABBREVIATIONS: Intra-aortic balloon pump, cardiogenic shock, acute myocardial infarction, mortality, SCAI shock stage, AMICS—cardiogenic shock complicating acute myocardial infarction, CI—confidence interval, CS—cardiogenic shock, IABP—intra-aortic balloon pump, MCS—mechanical circulatory support, OR—odds ratio, PPCI—primary percutaneous coronary intervention, PSM—propensity score matching, SCAI—Society for Cardiovascular Angiography and Interventions, STEMI—ST-segment elevation myocardial infarction, TIMI—thrombolysis in myocardial infarction

INTRODUCTION

Cardiogenic shock (CS) complicating acute myocardial infarction (AMICS) remains poor clinical outcomes, with a high 30-day mortality of approximately 40% to 45%, despite early initiation of primary percutaneous coronary intervention (PPCI) (1). Mechanical circulatory support (MCS) devices are increasingly used in AMICS, but their effect on mortality varies partly because of the severity of shock and the timing of device insertion, emphasizing the importance of early recognition and the golden hour of shock management (2,3).

Conventional shock criteria cannot accurately identify the preshock phase and fail to implement timely interventions to prevent hemodynamic deterioration. Therefore, a more detailed classification of CS is urgently required to guide treatment and predict outcomes. More recently, the 2022 Society for Cardiovascular Angiography and Interventions (SCAI) SHOCK stage classification scheme has been proposed to further define shock severity by using a uniform framework with specific criteria (4). The SCAI SHOCK stages A to E indicate a dynamic nature of shock, including at risk, beginning, classic, deteriorating, and extremis for the shock stage continuum, providing a mortality risk stratification for shock patients. Recent retrospective and prospective studies have established incremental mortality across the SCAI SHOCK stages among patients with AMICS (5,6). Thus, classifying shock patients may provide insight into a better understanding of the prerequisites for effective device therapies, as no MCS device has been demonstrated to improve the outcomes of AMICS patients in contemporary MCS trials (7–11).

Considering that the intra-aortic balloon pump (IABP) has the advantages of fast insertion, ease of use, and low complication rates, it remains the most commonly used MCS device compared with Impella and extracorporeal membrane oxygenation (ECMO) in China. Although the recommendation for the routine use of IABP in patients with AMICS is downgraded in the current guidelines, IABP is still the most widely used in clinical practice (12–14). The considerable gap between practice and guidelines is driving us to identify the right patient population that may respond particularly well to IABP in the setting of AMICS. To address these concerns, this study aimed to evaluate the association between IABP use and 30-day mortality in patients with early-stage (SCAI SHOCK stage A/B) AMICS.

MATERIALS AND METHODS

Study population

This study was a post hoc analysis based on an observational, multicenter clinical trial (The Chinese STEMI PPCI Registry [CSPR], ClinicalTrials.gov number, NCT04996901) and was performed under a waiver of informed consent as the nature of a retrospective study. In brief, the CSPR trial is aimed at developing and validating a feasible risk score to identify patients at high risk of 30-day major adverse cardiac events in 5,594 patients presenting with STEMI aged ≥18 years who were treated with PPCI at seven large centers in China between December 2015 and April 2021. Considering that the medical level was relatively comparable among the three official economic-geographic regions of Mainland China (East, Central, and North), we intended to involve hospitals in these regions to reflect the average treatment capacity. We included patients admitted to the seven largest interventional cardiology centers in China. Each center was the largest local hospital with the greatest clinical capacity for ST-segment elevation myocardial infarction (STEMI) treatment. The study conformed to the principles outlined in the Declaration of Helsinki. ST-segment elevation myocardial infarction was diagnosed based on the fourth universal definition of MI (15). All patients received evidence-based medical management of STEMI according to the current guidelines (12,16). The timing of IABP insertion (pre-, during, or post-PPCI procedure) was left to the discretion of the operating physician. We excluded 251 patients with symptom-to-balloon time >24 h and those who did not have any available data to determine the SCAI shock stage or mortality status (Fig. 1).

Fig. 1.

Fig. 1

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Study flow chart. PPCI, primary percutaneous coronary intervention.

Data sources, outcome measures, and study definition

Patient demographic and clinical characteristics were routinely extracted from electronic medical records and collected in a dedicated central database. The values of all vital signs and clinical measures reported most recently before IABP insertion were recorded. The accuracy of the data was checked by simple random sampling at the 5% level, and the medical records were reviewed again if the accuracy was inadequate at 98%.

The primary outcome measure was 30-day all-cause mortality. Mortality status was obtained through telephone interviews and hospital discharge summaries. For those lost to follow-up, queries in the Household Registration System were applied to determine mortality. Cardiogenic shock complicating acute myocardial infarction, equivalent to the SCAI SHOCK stage C/D/E group, was defined as meeting at least one of the following criteria: receiving mechanical ventilation or ultrafiltration and/or presenting with Killip class 3/4 and intravenous administration of vasoactive drugs. Other patients were defined as non-AMICS, equivalent to the SCAI SHOCK stage A/B group (4,11). Multivessel disease was defined as significant stenosis (>70% by visual assessment) in two or more major epicardial coronary arteries (17).

Statistical analysis

Categorical variables were reported as frequencies (percentages), and continuous variables were presented as mean ± SD or median (interquartile range). Normally distributed continuous variables were compared using Student t test, and nonnormally distributed variables were compared using Mann-Whitney U test. Two-group comparisons of categorical variables were performed using chi-square test, and Fisher exact test was performed if the approximation method was inadequate. Propensity score matching (PSM) was performed between the IABP and no IABP groups based on the estimated propensity scores using nearest neighbor matching (1:1) within a caliper of 0.2 and no replacement (MatchIt R package, version 4.5.1, Stanford, CA, USA). The propensity scores were calculated using nine baseline characteristics, including age, sex, systolic and diastolic blood pressure, heart rate, Killip class, cardiac arrest, anterior myocardial infarction, post-PPCI thrombolysis in myocardial infarction (TIMI) flow grade, and multivessel disease, according to the discretion of the operation. After PSM, the efficacy of balancing the baseline characteristics was estimated using absolute standardized differences of <10%. The association between IABP use and crude 30-day mortality was assessed using univariate logistic regression models that were fitted in the unmatched and matched cohorts. In addition, demographic and clinical characteristics were screened using the least absolute shrinkage and selection operator, and logistic regression models were constructed to evaluate independent predictors associated with 30-day mortality before and after PSM. Odds ratios (OR) with 95% confidence intervals (CIs) were calculated from these models. To evaluate the relationship between IABP use and 30-day mortality in the various subgroups of interest, logistics regression models were fitted, and P values for interaction were analyzed in the matched study cohort. Kaplan-Meier curves were used to estimate the 30-day mortality risk in patients treated with IABP versus medical therapy alone at different shock stages in the matched cohort. Furthermore, the robustness of the results was confirmed by performing covariate balancing propensity score (CBPS) weighting as a sensitivity analysis (WeightIt R package, version 0.13.1, Stanford, CA, USA). Outcomes were evaluated again using logistic regression analysis as described previously. Statistical significance was defined as a two-sided P value of <0.05. All statistical analyses were performed using R version 4.2.0 (R Foundation for Statistical Computing, Vienna, Austria) and RStudio version 2023.03.0+386.

RESULTS

Baseline characteristics of study population

Table 1 presents an overview of the baseline characteristics of the population stratified by IABP application. A total of 5,343 patients were included in this study (Fig. 1). Among them, 299 received IABP support. The mean age of the participants was 61 ± 12 years, and 20.3% were women. The median symptom-to-balloon time was 5 h, 49.1% had hypertension, and 18.3% had diabetes. Before PSM, patients in the IABP group were more likely to be older, women, and have lower blood pressure, higher heart rates, longer symptom-to-balloon time, and higher Killip class (all P < 0.05), whereas they had similar comorbidity burdens, such as hypertension, diabetes, hyperlipidemia, atrial fibrillation, heart failure, myocardial infarction, and stroke. At the lesion level, there were significant differences between the two groups in anterior myocardial infarction, post-PPCI TIMI flow grade, stent implantation, multivessel disease, and complete revascularization (all P < 0.05). Baseline characteristics considered to affect IABP implantation were well balanced, with no differences between the two groups in the matched cohort (both N = 290, Supplemental Fig. 1, http://links.lww.com/SHK/B745) or in the weighted cohort (Supplemental Table 1, http://links.lww.com/SHK/B745).

Table 1.

Clinical and lesion characteristics of the patients at baseline before and after PSM

Measure Overall Unmatched cohort Propensity-score matched cohort
No IABP IABP P No IABP IABP P
N = 5,343 n = 5,044 n = 299 n = 290 n = 290
Age, years 61 ± 12 61 ± 12 64 ± 13 <0.001 64 ± 12 64 ± 13 0.745
Female 1,085 (20.3) 1,007 (20.0) 78 (26.1) 0.013 81 (27.9) 76 (26.2) 0.709
Systolic BP, mm Hg 123 ± 23 124 ± 22 113 ± 26 <0.001 115 ± 23 114 ± 25 0.590
Diastolic BP, mm Hg 77 ± 15 77 ± 15 70 ± 17 <0.001 71 ± 15 71 ± 16 0.932
Heart rate, bpm 79 ± 16 78 ± 15 88 ± 22 <0.001 89 ± 19 88 ± 21 0.471
Symptom-to-balloon time, h 5 (3–8) 5 (3–8) 5 (3–8) 0.005 5 (3–8) 5 (3–8) 0.115
Smoking history 2,735 (51.2) 2,608 (51.7) 127 (42.5) 0.002 130 (44.8) 122 (42.1) 0.558
Hypertension 2,622 (49.1) 2,476 (49.1) 146 (48.8) 0.978 141 (48.6) 140 (48.3) 1
Diabetes 980 (18.3) 921 (18.3) 59 (19.7) 0.574 57 (19.7) 57 (19.7) 1
Hyperlipidemia 368 (6.9) 346 (6.9) 22 (7.4) 0.831 21 (7.2) 21 (7.2) 1
Previous atrial fibrillation 126 (2.4) 117 (2.3) 9 (3.0) 0.570 12 (4.1) 9 (3.1) 0.657
Previous heart failure 25 (0.5) 23 (0.5) 2 (0.7) 0.930 4 (1.4) 2 (0.7) 0.682
Previous myocardial infarction 182 (3.4) 167 (3.3) 15 (5.0) 0.157 10 (3.4) 15 (5.2) 0.413
Previous PCI 250 (4.7) 231 (4.6) 19 (6.4) 0.204 15 (5.2) 19 (6.6) 0.596
Previous stroke 338 (6.3) 322 (6.4) 16 (5.4) 0.555 29 (10.0) 15 (5.2) 0.041
Cardiac arrest before PCI 60 (1.1) 46 (0.9) 14 (4.7) <0.001 14 (4.8) 13 (4.5) 1
Killip class <0.001 0.928
 1 4,014 (75.1) 4,001 (79.3) 13 (4.3) 13 (4.5) 13 (4.5)
 2 826 (15.5) 703 (13.9) 123 (41.1) 126 (43.4) 123 (42.4)
 3 245 (4.6) 170 (3.4) 75 (25.1) 77 (26.6) 73 (25.2)
 4 258 (4.8) 170 (3.4) 88 (29.4) 74 (25.5) 81 (27.9)
Anterior myocardial infarction 2,683 (50.2) 2,463 (48.8) 220 (73.6) <0.001 211 (72.8) 211 (72.8) 1
Postprocedural TIMI flow grade 5,261 (98.5) 4,974 (98.6) 287 (96.0) 0.001 281 (96.9) 279 (96.2) 0.820
Stent implantation 4,915 (92.0) 4,665 (92.5) 250 (83.6) <0.001 252 (86.9) 243 (83.8) 0.348
Multivessel disease 2,748 (51.4) 2,575 (51.1) 173 (57.9) 0.026 157 (54.1) 167 (57.6) 0.452
Complete revascularization 3,114 (58.3) 2,959 (58.7) 155 (51.8) 0.024 155 (53.4) 151 (52.1) 0.803
Mechanical ventilation 272 (5.1) 160 (3.2) 112 (37.5) <0.001 77 (26.6) 105 (36.2) 0.016
CRRT 36 (0.7) 22 (0.4) 14 (4.7) <0.001 5 (1.7) 13 (4.5) 0.094
Vasoactive agents during hospitalization 522 (9.8) 394 (7.8) 128 (42.8) <0.001 82 (28.3) 125 (43.1) <0.001
Discharge medications
 DAPT 5,282 (98.9) 4,995 (99.0) 287 (96.0) <0.001 279 (96.2) 279 (96.2) 1
 Beta-blocker 4,372 (81.8) 4,136 (82.0) 236 (78.9) 0.208 228 (78.6) 230 (79.3) 0.919
 ACEi/ARB/ARNi 3,460 (64.8) 3,298 (65.4) 162 (54.2) <0.001 157 (54.1) 159 (54.8) 0.934
 Aldosterone antagonist 1,253 (23.5) 1,097 (21.7) 156 (52.2) <0.001 130 (44.8) 153 (52.8) 0.068
 Statin 5,278 (98.8) 4,994 (99.0) 284 (95.0) <0.001 283 (97.6) 276 (95.2) 0.182
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ACEi, angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blocker; ARNi, angiotensin receptor-neprilysin inhibitor; BP, blood pressure; CRRT, continuous renal replacement therapy; DAPT, dural antiplatelet therapy; IABP, intra-aortic balloon pump; PCI, percutaneous coronary intervention; TIMI, thrombolysis in myocardial infarction.

The association between shock stages and 30-day mortality

The SCAI SHOCK stage was strongly associated with 30-day mortality in both the unmatched and matched cohorts (OR, 20.19; 95% CI, 13.60–29.97; P < 0.001; and OR, 13.53; 95% CI, 7.16–25.58; P < 0.001, respectively; Supplemental Table 2, http://links.lww.com/SHK/B745). As expected, a higher SCAI SHOCK stage was accompanied by higher illness severity and greater use of IABP (Supplemental Fig. 2, http://links.lww.com/SHK/B745). In addition, the 30-day mortality rates at SCAI SHOCK stage A/B and C/D/E in the unmatched cohort were 3.5% and 36.2%, respectively. In the matched cohort, 13 (3.6%) and 74 (34.1%) patients died during the 30-day follow-up period at stages A/B and C/D/E, respectively. Additional IABP support did not improve 30-day mortality in general population without distinguishing shock severity compared with medical therapy alone (both P > 0.05 in the matched and weighted cohorts, Supplemental Table 3, http://links.lww.com/SHK/B745).

IABP and 30-day mortality in early-stage AMICS

Associations between IABP use and 30-day mortality in the subgroups of the matched cohort are shown in Figure 2. There was a significant interactive effect of IABP use and SCAI SHOCK stage on 30-day mortality (P for interaction = 0.005), whereas no significant differences were found between IABP and 30-day mortality concerning age, sex, diabetes, hypertension, Killip class, anterior myocardial infarction, and symptom-to-balloon time (all P > 0.05). Implantation of IABP was associated with lower 30-day mortality rather than 7-day mortality among patients at SCAI SHOCK stage A/B (OR with IABP, 0.19; 95% CI, 0.03–0.73; P = 0.034) but not at SCAI SHOCK stage C/D/E (OR, 1.49; 95% CI, 0.84–2.65; P = 0.172; Table 2). A similar result was observed in the sensitivity analysis of the weighted cohort (Table 2 and Supplemental Fig. 3, http://links.lww.com/SHK/B745). The Kaplan-Meier estimate of the mortality of patients with SCAI SHOCK stage A/B at 30 days was 1.2% (95% CI, 0.97–1.00) in the IABP group and 5.8% (95% CI, 0.91–0.98) in the medical therapy alone group (P = 0.019 by log-rank test, Fig. 3), whereas there was no significant difference between the two groups in patients with advanced SCAI SHOCK stage C/D/E.

Fig. 2.

Fig. 2

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Subgroup analyses for 30-day mortality of the matched cohort. The forest plot displays the OR and 95% CIs of 30-day mortality according to the subgroups of interest in the matched cohort. The P value for interaction was 0.005 for SCAI SHOCK stage A/B versus SCAI SHOCK stage C/D/E. CI, confidence interval; IABP, intra-aortic balloon pump; OR, odds ratio.

Table 2.

Seven- and 30-day mortality associated with IABP in patients with AMICS at different SCAI SHOCK stages

7-day mortality 30-day mortality
OR (95% CI) P OR (95% CI) P
PSM
 SCAI SHOCK stage A/B 0.31 (0.05–1.30) 0.147 0.19 (0.03–0.73) 0.034
 SCAI SHOCK stage C/D/E 1.39 (0.76–2.59) 0.287 1.49 (0.84–2.65) 0.172
CBPS
 SCAI SHOCK stage A/B 0.32 (0.07–1.51) 0.148 0.22 (0.05–0.97) 0.045
 SCAI SHOCK stage C/D/E 1.50 (0.84–2.70) 0.171 1.55 (0.90–2.67) 0.110
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CBPS, covariate balancing propensity score; CI, confidence interval; IABP, intra-aortic balloon pump; OR, odds ratio; PSM, propensity score matching.

Fig. 3.

Fig. 3

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Kaplan-Meier curves for cumulative event rate stratified by treatment strategy at different SCAI SHOCK stages in the matched cohort. Kaplan-Meier curves present the time-to-event mortality up to 30 days after admission in patients treated with IABP versus without IABP at (A) SCAI SHOCK stage A/B and (B) SCAI SHOCK stage C/D/E, respectively. IABP, intra-aortic balloon pump.

DISCUSSION

In this retrospective and multicenter study, we evaluated the association between the use of IABP and survival of patients in early-stage AMICS. The propensity-matched comparison from our analysis indicated that IABP support was associated with a 4.6% lower 30-day mortality in patients with SCAI SHOCK stage A/B when compared with those with medical therapy only, whereas patients with advanced SCAI SHOCK stages above C did not respond well to IABP.

The IABP-SHOCK II trial, the largest random controlled trial of AMICS associated with IABP use to date, found that IABP negatively affected 30-day, 1-year, or 6-year all-cause mortality in patients with AMICS (8,9,18). Therefore, contemporary clinical guidelines have downgraded the class of recommendations for routine use of the IABP in the management of STEMI (class IIb and class III, respectively) (12,19). Nevertheless, approximately 70% of all patients using MCS devices were still receiving IABP support by 2020, according to the study by Dhruva et al. (20). A possible explanation for this might be that clinicians believe its potential benefit because it can enhance coronary blood flow, ameliorate myocardial ischemia, and reduce LV afterload and myocardial oxygen consumption. In addition, alternative MCS devices such as Impella and ECMO were not associated with lower mortality but rather higher complication rates when compared with IABP in patients with CS in clinical practice (7,10,20,21). Given that, IABP remains the most commonly used MCS device for patients with AMICS.

Although high-quality evidence from the powered IABP-SHOCK II trial demonstrated no significant mortality benefit of IABP support for patients with AMICS, we think this technique is not really outdated and could not be replaced nowadays, especially in hospitals where advanced MCS devices are unavailable. According to the SCAI SHOCK stage classification expert consensus, it enrolled patients with myocardial infarction at advanced SCAI SHOCK stages (classic shock or a more severe shock status) and did not determine the association between IABP use and survival across the spectrum of shock severity in the IABP-SHOCK II trial (4,22). As a heterogeneous population, the prognosis of patients with CS may vary widely along with the severity of the shock. Meanwhile, the timing of IABP insertion was late in the IABP-SHOCK II trial, typically after percutaneous revascularization or in the presence of impaired end-organ perfusion, as additional IABP insertion did not provide significant hemodynamic support (23). On the other hand, it remains uncertain whether the duration of IABP use affects clinical outcomes. The median duration of IABP support was 3 days in the IABP-SHOCK II trial. Interestingly, at days 2 and 3, but not at baseline or day 4, patients receiving IABP presented with a significantly lower Simplified Acute Physiology Score II, which indicated the severity of disease. In general, myocardial stunning and short-term hibernation are characterized by long-lasting contractile dysfunction and recovery over a time frame of hours to 1 week after reperfusion or revascularization (24). It seems that an appropriately prolonged duration of IABP implantation may help improve prognosis.

To determine the specific population that responds well to IABP, van Nunen et al. (25) investigated the impact of IABP support in extensive STEMI with persisting ischemia post-PCI. They assumed that IABP only works in the presence of intact coronary autoregulation, as the use of IABP was associated with a reduction in 6-month mortality in the substudy. However, no significant improvement in the 6-month outcome was observed in the subsequent pilot study (26). Similar to these studies, our findings showed IABP did not reduce the 30-day mortality in the subgroups with anterior and nonanterior STEMI (P > 0.05). Hence, further research is needed to determine the specific population, optimal timing, and duration of IABP insertion in the context of AMICS.

With respect to the aforementioned uncertainty, the importance of early IABP support is now being evaluated with favorable outcomes in patients with AMICS. The current study indicates that IABP may be helpful in patients with lower shock severity (SCAI SHOCK stage A/B). In patients with advanced SCAI SHOCK stages, the hemodynamic improvement supported by IABP is relatively negligible. It may be insufficient to reverse the severe damage that has already occurred due to not merely impaired cardiac output but diminished end-organ perfusion and systemic inflammatory response (7). As reported by Hanson et al. (5), less than 20% of patients who progressed to SCAI SHOCK stage E 24 h after admission survived, regardless of baseline stage, emphasizing the importance of early recognition and the golden hour of shock management. A retrospective study from Gul and Bellumkonda (27) encouraged early delivery of IABP in patients with CS. The study indicated that the 30-day mortality was 24% in the setting of using IABP within 1 h of onset of CS, whereas the mortality was notably higher as 49% when delayed implantation occurred ≥1 h after recognition of CS. Similarly, several studies have reported that early IABP implantation before PCI was associated with lower in-hospital mortality or improved myocardial perfusion, even though long-term mortality was not affected (28–31). Apart from patients who received early implantation during the preshock stage, there was no mortality advantage observed in other patient categories who underwent IABP implantation compared with those who did not in this study. Thus, early initiation of IABP may be considered for high-risk patients who exhibit preshock status and are at high risk of shock deterioration.

Conventional shock criteria fail to accurately identify the preshock stage, making early intervention impossible to prevent hemodynamic deterioration. Since 2019, the SCAI SHOCK stage classification has been developed to address the spectrum of shock severity, stress the patient trajectories, and gradations of risk within each shock stage (4,22). Consistent with the literature, this study validated that higher SCAI SHOCK stages were associated with higher 30-day mortality (32). A recent scientific statement on invasive management of AMICS from the AHA recommended the applications of SCAI SHOCK stage classification to therapeutic critical pathways, including consideration of early MCS (3). As recently presented from a retrospective study by Jentzer et al. (33), IABP use was associated with lower crude in-hospital mortality, without differences at SCAI SHOCK stages B to D, which differs in part from our findings presented here. This discrepancy could be attributed to the study population with different etiology of shock and a clear distinction between stages C to E rather than ambiguous stages C/D/E in this study. Overall, the SCAI shock classification provides a reproducible framework for individualized assessment of patients with STEMI. The interaction between IABP implantation and survival across SCAI shock stages supports our hypothesis that patients presenting with STEMI would benefit from early recognition of CS and prompt delivery of IABP.

Given the ease of use, low complication rates, and less medical expenses of IABP implantation in comparison to Impella and ECMO, IABP may maintain a certain or greater practical value as the specific population is identified. The results of this study highlight the potential value of IABP in the early stage of shock management, especially in developing countries where medical resources are relatively scarce and advanced MCS devices may be unavailable. The clinical implications of this study will be strengthened if the findings are confirmed in a larger prospective study.

LIMITATION

The generalizability of these results is subject to certain limitations. First, this study was a retrospective, non-prespecified subgroup analysis of the CSPR trial, implying that these results should be interpreted with caution. Second, the follow-up period was only 30 days. Thus, the long-term outcomes associated with IABP use remain unknown. Third, lack of lactate values limits our ability to accurately differentiate preshock and classic shock, as a lactate level of ≥2 mmol/L is a key biochemical marker for SCAI SHOCK stage C. Different stages of AMICS, specifically SCAI SHOCK C, D, and E, could not be well distinguished in this study. Therefore, it remains unknown whether IABP implantation affects clinical outcomes in patients with specific shock stages above C. Finally, progression across the SCAI shock stage is a dynamic process. The evolving trajectories of the patient were not well captured as hemodynamic data were only presented at a single time point.

CONCLUSION

In a cohort of patients with STEMI, the SCAI SHOCK stage provides stepwise mortality risk stratification and helps to identify those who may respond to IABP insertion. Patients with additional IABP support at SCAI SHOCK stage A/B had a lower observed 30-day mortality than those with medical therapy alone.

Supplementary Material

shock-60-385-s001.docx (96.6KB, docx)
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shock-60-385-s002.docx (604.5KB, docx)
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ACKNOWLEDGMENTS

None.

Footnotes

Drs Luo, Huang, and Wang contributed equally to this work and are joint first authors.

Funding support and author disclosures: This work was supported by the Chinese Society of Cardiology's Foundation (CSCF2021A02). All authors have reported that they have no relationships relevant to the contents of this article to disclose.

The authors report no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal’s Web site (www.shockjournal.com).

Contributor Information

Da Luo, Email: luoda@whu.edu.cn.

Rihong Huang, Email: huangrihong_dl@163.com.

Xiaoying Wang, Email: 439710966@qq.com.

Jing Zhang, Email: zhangjing_yczx@163.com.

Xinyong Cai, Email: Caixinyong0403@163.com.

Fuyuan Liu, Email: liufuyuan_xy@163.com.

Yuhua Lei, Email: leiyuhua_es@163.com.

Dongsheng Li, Email: lidongsheng_wh3@163.com.

Wenjie Zhou, Email: wenjie210@163.com.

Changwu Xu, Email: xuchangwu@whu.edu.cn.

Bing Huang, Email: binghuang@whu.edu.cn.

Hong Jiang, Email: hong-jiang@whu.edu.cn.

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