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Association between mean hemodynamic variables during the first 24 h and outcomes in cardiogenic shock: identification of clinically relevant thresholds
Critical Care volume 29, Article number: 137 (2025)
Abstract
Purpose
Cardiogenic shock (CS) remains a critical condition with high mortality rates despite advances in treatment. This study aims to comprehensively evaluate both macrocirculatory and tissue perfusion variables over the initial 24 h post-admission to determine their impact on patient prognosis and identify potential hemodynamic thresholds for optimal outcomes. Secondary aims were to explore the correlation between macrocirculatory and tissue perfusion variables.
Design
This is a post hoc analysis of data from two prospective studies, OptimaCC (NCT01367743) and MicroShock (NCT03436641), involving only patients with CS. Both studies applied regular assessment of hemodynamic variables at specific time points (admission, 6, 12, and 24 h) to ensure consistency in data collection, enrolling 118 patients between September 2011 and July 2021, with similar inclusion criteria and care processes.
Results
The median age of the cohort was 69 years, 59% being male. The primary outcome, 30-day mortality, occurred in 37% of patients. Average macrocirculation variables over the first 24 h of CS such as mean arterial pressure (MAP), cardiac output (CO), cardiac index (CI), and cardiac power index (CPI) were significantly lower in patients meeting the primary outcome. Accordingly, average tissue perfusion variables (ΔPCO2 and ΔPCO2/C(a-v)O2) over the first 24 h of CS were also consistently impaired in patients meeting the primary outcome. The optimal clinically relevant thresholds of the first 24 h time course for poor outcomes, closely approximating the optimal values identified in the analysis, were: mean SAP < 95 mmHg, MAP < 70 mmHg, CO < 3.5 L/min, CI ≤ 1.8 L/min/m2, CPI < 0.27 W/m2, ScvO2 < 70%, ΔPCO2 ≥ 9 mmHg, and ΔPCO2/C(a-v)O2 ≥ 1.5 mmHg/mL.
Conclusions
This study is the first to identify critical hemodynamic thresholds, encompassing both macrocirculatory and tissue perfusion variables, within the initial 24 h of CS that are associated with adverse outcomes. The identified thresholds suggest specific hemodynamic targets that may guide resuscitation strategies.
Take-home message
This study introduces two novel contributions in cardiogenic shock management: a comprehensive longitudinal assessment of macrocirculatory variables during early treatment and the first-ever longitudinal evaluation of tissue perfusion variables in early cardiogenic shock. These findings offer new hemodynamic targets for optimizing early intervention.
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Introduction
Cardiogenic shock (CS) presents a significant challenge, requiring a thorough approach to guide resuscitation strategies [1, 2]. Understanding both macrocirculatory and tissue perfusion variables is crucial for gaining insights into hemodynamic intricacies [3]. Despite advancements in pharmaceuticals and acute mechanical circulatory support (aMCS), mortality rates in CS patients remain high at 30–50% at 6 to 12 months [4]. To address this, the Shock Academic Research Consortium (SHARC) has proposed a refined definition of CS as a cardiac disorder characterized by clinical and biochemical evidence of sustained tissue hypoperfusion [5]. Diagnosis includes systolic blood pressure (SBP) < 90 mmHg for ≥ 30 min or the need for vasopressors, inotropes, or mechanical circulatory support to maintain systolic blood pressure ≥ 90 mmHg, with additional hemodynamic criteria such as cardiac index (CI) < 2.2 L/min/m2 measured by invasive or non-invasive methods. This definition completes the recently updated Society for Cardiovascular Angiography and Interventions (SCAI) Shock classification [6].
While various hemodynamic variables, especially those related to prognosis, have shown utility in isolated analyses typically conducted upon admission, subsequent hemodynamic management remains a matter of debate [7, 8]. To date, no studies have accurately reported a temporal longitudinal assessment of these macrocirculatory and tissue perfusion variables correlated with prognosis during the first hours of patient care. Consequently, this study aims to comprehensively evaluate hemodynamic variables, including tissue perfusion variables, along with their mean values over the initial 24 h post-admission, elucidating their dynamic impact on patient prognosis. Secondary aims were to explore the correlation between macrocirculatory and tissue perfusion variables. We hypothesized that hospital mortality in CS patients would rise with progressively lower hemodynamic variables. Furthermore, we aimed to identify potential thresholds that might delineate optimal hemodynamic ranges.
Materials and methods
Study design and study settings
We performed a post hoc analysis of data collected prospectively in two studies of CS: OptimaCC [9] and MicroShock [10]. These two studies were chosen because they enrolled similar populations of patients with CS, with closely regular assessment of hemodynamic variables at the same time point (admission i.e. H0, H6, H12, H24). Also, the process of care and the inclusion window were similar in the two studies. OptimaCC was conducted in nine French intensive care units (ICUs) and MicroShock in two ICUs. The two trials enrolled 118 patients between September 2011 and July 2021, namely 57 patients from the OptimaCC study and 61 patients from the MicroShock study.
Ethics
The protocol of each of the two studies was approved by the appropriate ethics committees. OptimaCC (NCT01367743) received the approval of the Nancy Hospital Institutional Review Board, France. MicroShock (NCT03436641) received approval from the Comité de Protection des Personnes, Sud-Est V, France (Comité de Protection des Personnes, Sud-Est V; reference 18-STRA-01).
Study population
All patients admitted to the participating centers during each trial period were screened for eligibility. Inclusion criteria were age 18 years or older and ICU admission for CS. We did not include data from patients who withdrew consent after initial inclusion.
While OptimaCC included only acute myocardial infarction complicated by CS (AMI-CS), the MicroShock study included all types of CS except CS following cardiac arrest.
Study definitions
Definitions of CS were nearly identical in the two studies. In OptimaCC, CS was defined by simultaneous presence of all the following criteria: (1) CS due to acute myocardial infarction (AMI) successfully revascularized by using percutaneous coronary intervention (PCI); (2) SBP < 90 mmHg or mean arterial pressure (MAP) < 65 mmHg without a vasopressor agent or need for vasopressor therapy to correct hypotension; (3) CI < 2.2 l/min/m2 in the absence of vasopressor or inotrope therapy; (4) pulmonary artery occlusion pressure > 15 mmHg or echocardiographic evidence of high pressure; (5) echocardiographic left ventricular ejection fraction (LVEF) < 40% without inotrope support (this criterion was not taken into account in instances of treatment with dopamine, norepinephrine, epinephrine, dobutamine, or milrinone); (6) at least one evidence of tissue hypoperfusion (e.g., skin mottling, oliguria, elevated lactate level, altered consciousness) and (7) an inserted pulmonary artery catheter. All these seven criteria had to be met for a patient to be included in the study. In MicroShock, CS was defined according to the definition used in the FRENSHOCK registry which considers all CS shock regardless of the etiology [11], and patients were included if they met at least one criterion of each of the following three main components: (1) Low cardiac output, defined by systolic blood pressure < 90 mmHg and/or the need for amines (dobutamine and/or norepinephrine and/or epinephrine) to maintain systolic blood pressure > 90 mmHg and/or cardiac index < 2.2 L/min/m2 on echocardiography or right heart catheterization; (2) Elevation of left and/or right heart pressures, defined by clinical signs, radiology (overload signs on chest X-ray or computed tomography scan), biological tests (natriuretic peptide elevation), echocardiography (usual signs of left ventricular filling pressure elevation) or invasive hemodynamic overload signs (elevation of mean pulmonary artery pressure or pulmonary capillary wedge pressure); (3) Signs of malperfusion, which could be clinical (oliguria, mottling, confusion) and/or biological (lactate > 2 mmol/L, hepatic insufficiency, renal failure).
The SCAI shock classification was evaluated at admission for all patients enrolled in the MicroShock study. In contrast, for the patients included in the OptimaCC study, the classification was retrospectively and independently determined in a blinded manner by two expert authors based on admission characteristics. The vasoactive-inotropic score (VIS) was calculated based on its latest version [12].
At each time point (admission i.e. H0, H6, H12, H24), variables reflecting macrocirculation and tissue perfusion were collected. Data used at H0 were obtained from the measurement closest to the time of admission, typically within the first hour, even for variables derived from pulmonary artery catheter or central venous catheters implanted in the superior vena cava territory. Macrocirculation was assessed using invasive blood pressure monitoring (intra-arterial catheter), heart rate, LVEF, and CI by echocardiography for the MicroShock study and pulmonary artery catheters for the OptimaCC study. Echocardiography variables were assessed by physicians with adult echocardiography certification [13, 14] using the Vivid-S5 or S70 system (General Electric). Cardiac index (L/min/m2) assessment with echocardiography was calculated by using standard formulae, as CI is the quotient of the cardiac output (CO) divided by the body surface area. The CO is the product of the stroke volume by the heart rate. Stroke volume is calculated as the product between aortic velocity–time integral (measured using pulsed-wave Doppler) and aortic cross-sectional area. The latter is calculated in the long-axis parasternal window using the left ventricular outflow tract diameter measurement. Thus, stroke volume = [(3.1416) × (left ventricular outflow tract diameter/2)2] × aortic velocity–time integral. Cardiac power index (CPI, W/m2) is the cardiac power output indexed to body surface area and was calculated as MAP × cardiac index/451 [15]. In the OptimaCC cohort, pulmonary artery catheter variables have been collected, such as right atrial pressure (RAP), pulmonary artery systolic pressure (PASP), pulmonary artery occlusion pressure (PAOP), systemic vascular resistance index (SVRI), pulmonary vascular resistance index (PVRI) and pulmonary artery pulsatility index (PAPi) was calculated as followed [PASP–diastolic pulmonary arterial pressure]/right atrial pressure.
Tissue perfusion variables were assessed using pairs of arterial and central venous blood samples to determine the following variables: arterial partial pressure of oxygen (PaO2), arterial partial pressure of carbon dioxide (PaCO2), central venous partial pressure of oxygen (PvO2), central venous partial pressure of carbon dioxide (PvCO2), arterial oxygen saturation (SaO2), and central venous oxygen saturation (ScvO2). In order to use the measurement values from the central venous catheter implanted in the superior vena cava territory as a reference, a correction factor was therefore applied to the OptimaCC data (obtained via a pulmonary artery catheter) by adding 5% from the raw values of SvO2, based on previous data showing a mean difference of 5% between mixed venous oxygen saturation (SvO2) and ScVO2 with minimal impact regarding the CO [16, 17]. The hemoglobin (Hb) and lactate concentrations were measured from the arterial blood. The arterial oxygen content (CaO2), central venous oxygen content (CvO2), C(a-v)O2, P(v-a)CO2, and ratio of venous-arterial carbon dioxide tension difference to arterial-venous oxygen content difference i.e. P(v-a)CO2/C(a-v)O2 ratio were defined as follows:
-
CaO2 = (1.34 × SaO2 × Hb) + (0.0031 × PaO2)
-
CvO2 = (1.34 × ScvO2 × Hb) + (0.0031 × PvO2)
-
C(a-v)O2 = CaO2–CvO2
-
P(v-a)CO2 = ∆PCO2 = PvCO2–PaCO2
-
P(v-a)CO2/C(a-v)O2 ratio = ∆PCO2/C(a-v)O2 = (PvCO2–PaCO2)/(CaO2–CvO2)
As mentioned, Pv-aCO2, also named PCO2 gap or ∆PCO2, was calculated by subtracting arterial partial pressure of carbon dioxide (PaCO2) from partial pressure of CO2 in superior vena cava blood (PvCO2) measured in arterial and central venous samples taken simultaneously. However, in the OptimaCC cohort, PvCO2 was collected via the pulmonary artery catheter and thus corresponded to mixed venous partial pressure of CO2 (PmvCO2), whereas, in the MicroShock cohort, it was collected via a central venous catheter implanted in the superior vena cava territory and thus corresponded to PcvCO2, which may be overestimated according to literature data [18]. In order to use the measurements values from the central venous catheter implanted in the superior vena cava territory as a reference, a correction factor was therefore applied to the OptimaCC data (obtained via a pulmonary artery catheter) by adding 2.7 mmHg from the raw values of PvCO2, based on data from the work of Cavaliere et al. [18].
In the supplementary material, data were analyzed using the pulmonary artery catheter as a reference by subtracting 5% from the raw ScvO2 values and subtracting 2.7 mmHg from the raw PcvCO2 values.
In the MicroShock study, skin mottling of the anterior aspect of the knee was assessed visually on both legs, as a variables of tissue hypoperfusion. Patients were placed supine with the legs straight and at the level of the heart. Mottling score which describes the extent of the mottled area on the knee and thigh was determined on a 6-point scale ranging from 0 to 5 in the MicroShock cohort as described previously [19, 20]. If mottling was present, then the leg with more prominent mottling was chosen for scoring.
If patients were put under VA-ECMO support within the first 24 h, the hemodynamic variables were no longer taken into account for the analysis once they were under VA-ECMO support.
Data collection
For each patient in each study, a dedicated study nurse or investigator at each participating center collected the baseline clinical data and comorbidities; characteristics of the CS; clinical and laboratory features at ICU admission; treatments delivered in the ICU; ICU length of stay; invasive mechanical ventilation duration; and vital and functional status at ICU discharge, hospital discharge and at long-term follow-up.
Outcome measures
For the present study, the primary outcome was the 30-day mortality. The 30-day mortality was a secondary outcome in the MicroShock study and OptimaCC study. As objective judgment criteria, these elements were collected in a precise manner in both studies.
Statistical analysis
Continuous variables were expressed as medians with interquartile ranges and categorical variables as frequencies and percentages. Baseline characteristics were compared between the two cohorts using Wilcoxon test for continuous variables and Fisher’s exact test for categorical variables. The hemodynamic variables were also compared between patients who experienced the primary outcome (death at 30 days) and those who did not, using the same tests. The mean value of each hemodynamic variable was calculated from the 4 measurements at H0, H6, H12, and H24 when at least one of the four measurements was available. Missing values were not imputed and were not accounted for in the analyses. However, missing data were rare during the study period. For each hemodynamic variable, most patients had all four measurements.
The association between hemodynamic variables and the outcome was assessed using univariable Cox model. Hazard Ratios (HR) are reported with 95% confidence interval (CI 95%). For each hemodynamic variable, an optimal threshold was determined by maximizing the Harrell’s C-index in univariable Cox model.
Kaplan–Meier analyses were performed to provide event-free survival curves based on the optimal thresholds for hemodynamic variables. Differences between the curves were analyzed using the log-rank test.
The relationship between macrocirculation indices and tissue perfusion variables was assessed by calculating Spearman’s rank correlation coefficients.
The two-tailed significance level was set at p < 0.05. All statistical analyses were performed using R software version 4.1.2 (R Foundation for Statistical Computing, Vienna, Austria).
Results
Baseline characteristics
Data from 118 patients were analyzed in two pooled prospective multicenter observational cohorts. The comprehensive characteristics are summarized in Table 1. The median age of our cohort was 69 (60–77 years) years. The study population consisted predominantly of males (59%). The median LVEF was 30% (IQR 20–40). Admission lactate level was 3.4 mmol/l (IQR 1.9–6). At admission, the median SAPS II score was 61 (45–74) points, median SOFA was 9 (7–11) points, and median VIS was 39 (13–83). The distribution of post-hoc calculated SCAI shock classification at admission was as follows: B (2%), C (53%), D (29%), and E (16%). A total of 90% of the patients were under mechanical ventilation. Prior to study enrollment, 28% of patients had experienced a cardiac arrest event necessitating cardiopulmonary resuscitation.
Primary outcome
The primary outcome, 30-day mortality, occurred in 44 patients (37%) (Table 1). When analyzing the average values over the first 24 h of CS, the mean of macrocirculatory variables were consistently and significantly lower in the group meeting the primary outcome criteria (except for CI; p = 0.07 and ScVO2 ; p = 0.09) (Table 2). Conversely, the average values for tissue hypoperfusion variables, ∆PCO2, ∆PCO2/C(a-v)O2, and arterial lactate, during the first 24 h were significantly higher (i.e. worst) in the group meeting the primary outcome criteria (except for ∆PCO2/C(a-v)O2; p = 0.05) (Table 2). In Table S1, the primary outcome was analyzed using the pulmonary artery catheter as a reference, showing almost similar results.
Exclusively within the OptimaCC cohort, where pulmonary artery catheter variable were prospectively measured in nearly all patients at each time point (H0, H6, H12, and H24), comparisons of the mean of these variables (during the first 24 h) between 30-day survivors and non-survivors are presented in Table S2. Notably, a lower mean PAOP during the first 24 h was significantly associated with improved 30-day survival.
Exclusively within the MicroShock study cohort, where mottling scores were prospectively assessed (as a clinical sign of tissue hypoperfusion) in nearly all patients at each time point, the mottling score was consistently and significantly associated with 30-day mortality across all time points within the first 24 h (Table S3, Fig. S1).
Critical threshold for longitudinal time course of hemodynamic variables
To identify the best thresholds for predicting the primary outcome, univariate Cox regression analysis was performed on mean macrocirculatory variables measured within the first 24 h. The optimal clinically relevant thresholds, closely approximating the optimal values identified in the analysis, for predicting the primary outcome were as follows: a mean SAP in the first 24 h < 95 mmHg with a Hazard Ration (HR): 2.1 (95% CI 1.1–3.9), a mean MAP in the first 24 h < 70 mmHg with a HR: 1.9 (95% CI 1.04–3.4), a mean ScvO2 in the first 24 h < 70% with an HR: 1.8 (95% CI 0.9–3.3), a mean CO in the first 24 h < 3.5 L/min with a HR: 2.4 (95% CI 1.3–4.3), a mean CI in the first 24 h ≤ 1.8 L/min/m2 with a HR: 1.8 (95% CI 0.9–3.4), and a mean CPI in the first 24 h < 0.27 W/m2 with a HR: 2.4 (95% CI 1.2–4.6) (Table 3). Exclusively within the OptimaCC cohort, the optimal clinically relevant thresholds for pulmonary arterial catheter variables—closely aligning with the optimal values identified in the analysis—for predicting the primary outcome are presented in Table S4.
Regarding tissue perfusion variables, the optimal clinically relevant thresholds, closely approximating the optimal values identified in the analysis, for predicting the primary outcome were as follows: a mean ∆PCO2 in the first 24 h ≥ 9 mmHg with an HR: 2.7 (95% CI 1.5–5.02), a mean ∆PCO2/C(a-v)O2 in the first 24 h ≥ 1.5 mmHg/mL with an HR: 2.1 (95% CI 1.1–4.3) (Table 3).
Longitudinal time courses of hemodynamic variables and 30-day mortality
Figure 1 shows the statistically significant association between the average value of macrocirculatory hemodynamic variables over the first 24 h and 30-day mortality. During the first 24 h, an average SAP < 95 mmHg, MAP < 70 mmHg, ScvO2 < 70%, CO < 3.5 L/min, CI ≤ 1.8 L/min/m2, as well as CPI < 0.27 W/m2 were significantly associated with a worse prognosis (C-index = 0.58 (0.51–0.65), C-index = 0.58 (0.51–0.66), C-index = 0.58 (0.51–0.66), C-index = 0.62 (0.54–0.69), C-index = 0.57 (0.5–0.65) and C-index = 0.58 (0.51–0.65) respectively) (Table 3).
Kaplan–Meier showing 30-day mortality in cardiogenic shock according to mean macrocirculatory variables during the first 24 h. A Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean SAP during the first 24 h. B Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean MAP during the first 24 h. C Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean CO during the first 24 h. D Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean CI during the first 24 h. E Kaplan–Meier showing 30-day mortality support in cardiogenic shock according to the mean CPI during the first 24 h. F Kaplan–Meier showing 30-day mortality support in cardiogenic shock according to the mean ScVO2 during the first 24 h
Patients with an average ∆PCO2 over the first 24 h ≥ 9 mmHg were significantly more likely to achieve the primary outcome (p = 0.0005) (Fig. 2). Similarly, for an average ∆PCO2/C(a-v)O2 ≥ 1.5 mmHg/mL (p = 0.004) and an arterial lactate ≥ 3 mmol/L (< 0.0001) (Fig. 2).
Kaplan–Meier showing 30-day mortality in cardiogenic shock according to mean perfusion variables during the first 24 h. A Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean ∆PCO2 during the first 24 h. B Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean ∆PCO2/C(a-v)O2 during the first 24 h. C Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean arterial lactate level during the first 24 h
In Table S5 and Fig. S2, these hemodynamic variables were analyzed using the pulmonary artery catheter as a reference.
Interaction of out-of-hospital cardiac arrest (OHCA) status with hemodynamic variables on 30-day mortality
Interaction terms in Cox models revealed no significant difference in the effect of mean macrocirculatory hemodynamic and tissue perfusion variables during the first 24 h of CS on 30-day mortality between patients with and without OHCA. Indicating no difference in effect between the two groups, with one exception: mean SAP (over the first 24 h) as a continuous variable (interaction p = 0.017) which was associated with 30-day mortality in patients without OHCA, but not in those with OHCA (Table S6).
Correlations between macrocirculation and tissue perfusion variables
No relationship was observed between the longitudinal time courses of macrocirculatory variables and tissue perfusion variables, with correlation coefficients close to zero (Fig. 3). The macrocirculatory variables showed a strong correlation with each other (MAP, CO, CI, and CPI), as did those of tissue perfusion (∆PCO2 and ∆PCO2/C(a-v)O2), with correlation coefficients between 0.62 and 0.93.
Correlation between longitudinal trends of macrocirculatory hemodynamic variables and tissue perfusion variables. Spearman rank correlation between longitudinal trends of macrocirculatory hemodynamic variables and tissue perfusion variables. MAP, mean arterial pressure; CO, cardiac output; CI, cardiac index; CPI, cardiac power index; ∆PCO2, delta PCO2; ∆PCO2/C(a-v)O2, ratio of venous-arterial carbon dioxide tension difference to arterial-venous oxygen content difference
Discussion
Our study is among the first to longitudinally evaluate macrocirculatory and tissue perfusion variables within the first 24 h of CS admission, addressing a critical gap as over 50% of randomized controlled trials in AMICS don’t even report cardiac index [21]. We found that specific thresholds of systemic hemodynamics, such as a mean MAP < 70 mmHg, a mean CO < 3.5 L/min and a mean CI ≤ 1.8 L/min/m2, were significantly associated with increased 30-day mortality. Additionally, tissue hypoperfusion variables such as ∆PCO2 ≥ 9 mmHg and ∆PCO2/C(a-v)O2 ≥ 1.5 mmHg/ml emerged as significant predictors of poor outcomes.
Mean arterial pressure threshold in cardiogenic shock
Our results identified a critical MAP threshold of 70 mmHg during the first 24 h, below which outcomes were poorer. These findings highlight the importance of early hemodynamic monitoring and target-setting in managing CS, given the lack of international consensus on hemodynamic targets in CS. Some guidelines advise using inotropes in CS patients with SBP < 90 mmHg [22], while others suggest a MAP target ≥ 65 mmHg in all circulatory shock states [23], but these targets lack validation in randomized clinical trials to date [24]. Recent retrospective studies indirectly provide evidence supporting a MAP target of 65 mmHg during the first 24 h after ICU admission for CS [25], or a MAP target of 70 mmHg during the first 36 h after ICU admission [26], due to poorer outcomes associated with MAP below these thresholds.
Mean ScvO2 threshold in cardiogenic shock
Few studies have precisely addressed the prognostic value of ScvO2 (or SvO2) in CS. Traditionally, a decrease in ScvO2 has been primarily attributed to inadequate oxygen delivery due to low CO [27, 28]. However, a recent study found a weak correlation between CO and ScvO2 in CS patients [29]. Interestingly, in line with our results, this study also showed a strong association between an early increase in ScvO2 (> 60% at 24 h) and improved patient outcomes.
Cardiac output/cardiac index threshold in cardiogenic shock
There is no consensus on target CO or CI during the initial hours of CS, even though improving these variables has long been a primary goal since Gunnar et al. reported a low CO in patients with CS following AMI in their pioneering work of 1966 [30]. One major limitation, however, is that most studies used a single value (CO, CI, CPO, or CPI) assessed at admission, neglecting the dynamic nature of hemodynamic variables in CS [30,31,32,33,34,35]. Historical studies have used various thresholds for CI, but precise cut-offs have been considered impractical due to cases of end-organ hypoperfusion with higher CI values. A sub-analysis of the SHOCK trial describes cardiac power output (CPO) as one of the best hemodynamic variables for predicting mortality in CS [15]. In our analysis, a CPI threshold of 0.27 W/m2 within the first 24 h was associated with increased mortality at day 30.
CO2-derived threshold in cardiogenic shock
In patients experiencing circulatory shock states, an elevation in tissue partial pressure of CO2 is observed, reflecting impaired tissue perfusion. This might result from higher CO2 production without a corresponding increase in blood flow to wash it out (due to increased heterogeneity of blood flow and/or a reduction in functional capillary density), or it could also result from anaerobic metabolism and elevated lactate production, which requires bicarbonate buffering, leading to increased CO2 production. In septic shock, a ΔPCO2 > 6 mmHg has been associated with higher mortality, reflecting inadequate CO [36]. Studies have shown inconsistent correlations between ΔPCO2 and macrocirculatory hemodynamics, but significant associations with microcirculatory perfusion have been noted [10, 37], even in a cohort of patients under VA-ECMO support [38]. The ΔPCO2/C(a-v)O2 ratio, also named PCO2 gap/Da-vO2, usually studied in septic shock, is another relevant variable reflecting tissue perfusion. By quantifying the relationship between the venous-to-arterial PCO2 difference and the arterial-to-venous oxygen content difference, this index offers earlier and potentially more dynamic insights into the adequacy of tissue oxygenation and perfusion in critically ill patients [39]. Our study found a mean above 1.5 mmHg/ml during the first 24 h to predict 30-day mortality, indicating increased anaerobic metabolism, as already described [40].
Loss of hemodynamic coherence in cardiogenic shock
A key finding of our study is the notable dissociation between macrocirculatory and tissue perfusion variables in patients with CS. While strong correlations were observed within each variable group—macrocirculatory variables (MAP, CO, CI, CPI) and tissue perfusion variables (ΔPCO2 and ΔPCO2/C(a-v)O2)—the longitudinal trajectories of these two sets of variables showed no correlation. This dissociation suggests that optimizing macrohemodynamic variables, although essential for overall stabilization, does not necessarily equate to improved tissue perfusion, which is more strongly associated with CS outcomes [3]. This finding underscores the complexity of hemodynamic management in CS and highlights the need for comprehensive monitoring strategies that include direct assessment of tissue perfusion alongside traditional macrohemodynamic targets.
Strengths and study limitations
On the one hand, our results are consistent with recent studies emphasizing the benefits of longitudinal assessment of CS during the initial hours [41]. This approach refines classification and is strongly associated with in-hospital mortality. The identification of significant thresholds for tissue perfusion markers despite an absence of correlation with systemic markers indirectly but strongly argues for a multimodal monitoring. On the other hand, this study spans 10 years and includes CS patients from various causes, introducing some heterogeneity. The prolonged inclusion period partly resulted from logistical challenges. In the OptimaCC study, for instance, the final center was only initiated in June 2013, limiting early recruitment. Similarly, the MicroShock study faced multiple enrollment disruptions due to COVID-19. The OptimaCC study's criteria, requiring both successful PCI and a Swan-Ganz catheter, may have introduced selection bias by excluding more unstable patients, explaining the lower proportion of SCAI Stage E patients (4%) compared to MicroShock (28%). However, integrating both cohorts improves overall representation. Despite being one of the largest investigations of early hemodynamic variables in CS, the relatively small sample size limits statistical power. Although all C-index values achieved statistical significance, their relatively low magnitude indicates that the model had limited discriminatory power to differentiate between low- and high-risk subjects. Differences in measurement methods (pulmonary artery catheter in OptimaCC vs. echocardiography in MicroShock) and the evolving CS management over time are additional limitations. The use of a fixed correction factor constitutes another limitation of the study. Non-blinded measurements, reflecting clinical practice for CS management, likely introduced minimal bias. Due to the absence of standardized perfusion-based management guidelines, any bias from peripheral assessments was likely negligible. Finally, a more granular analysis incorporating time-based hemodynamic variables and threshold-exceedance durations could potentially refine our results. Lastly, as an observational study, it establishes associations rather than causality, emphasizing the need for prospective trials. Our work advocates for detailed and comprehensive hemodynamic assessment of CS patients, integrating its evolving nature during the crucial first few hours [41].
Conclusions
This study is among the first to identify critical hemodynamic thresholds within the initial 24 h of CS that are associated with adverse outcomes. Lower macrocirculatory variables and higher (i.e. worst) tissue hypoperfusion variables within the first 24 h are associated with increased mortality in CS patients. These findings highlight the importance of early, comprehensive hemodynamic monitoring and suggest specific thresholds that may guide resuscitation strategies. Further research is warranted to refine these thresholds and improve clinical outcomes in CS management.
What is new?
Monitoring the longitudinal average trend of hemodynamic variables during the first hours of cardiogenic shock significantly improved the ability to predict 30-day mortality.
What are the clinical implications?
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Defining hemodynamic targets: These new data might help define hemodynamic targets in the early management of cardiogenic shock.
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Evaluating future therapies: Better-defined hemodynamic targets, including both macrocirculatory and tissue perfusion variables, will aid in the design and evaluation of future therapies for cardiogenic shock, with greater precision.
Data availability
No datasets were generated or analysed during the current study.
Availability of data and materials
The study data will be shared with investigators upon reasonable request to the corresponding author.
Abbreviations
- AMI-CS:
-
Acute myocardial infarction complicated by cardiogenic shock
- CaO2 :
-
Arterial oxygen content
- CvO2 :
-
Central venous oxygen content
- CI:
-
Cardiac index
- CO:
-
Cardiac output
- CPI:
-
Cardiac power index
- CPO:
-
Cardiac power output
- CS:
-
Cardiogenic shock
- ∆PCO2 :
-
Delta PCO2
- LVEF:
-
Left ventricular ejection fraction
- MAP:
-
Mean arterial pressure
- OHCA:
-
Out-of-hospital cardiac arrest
- PaO2 :
-
Arterial partial pressure of oxygen
- PaCO2 :
-
Arterial partial pressure of carbon dioxide
- PvO2 :
-
Central venous partial pressure of oxygen
- PvCO2 :
-
Central venous partial pressure of carbon dioxide
- P(v-a)CO2/C(a-v)O2 ratio:
-
Ratio of venous-arterial carbon dioxide tension difference to arterial-venous oxygen content difference (or ∆PCO2/C(a-v)O2)
- SAPS II:
-
Simplified acute physiology score
- SCAI:
-
Society for cardiovascular angiography and interventions
- ScvO2 :
-
Central venous oxygen saturation
- SOFA:
-
Sequential organ failure assessment
- SvO2 :
-
Mixed venous oxygen saturation
- VA-ECMO:
-
Venoarterial extracorporeal membrane oxygenation
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BL, FM, and HM conceived the study. BL, AC, JD, JH, FM, AK, and HM have been involved in the care of patients and hemodynamic assessment. BL, AC, and HM collected the data and wrote the manuscript. KD and NG performed statistical analysis. BL, AC, JD, CD, NG, CEG, JH, FM, AK, and HM participated in the revising of a manuscript. All authors approved the final manuscript.
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The protocol of each of the two studies was approved by the appropriate ethics committees. OptimaCC (NCT01367743) received the approval of the Nancy Hospital Institutional Review Board, France. MicroShock (NCT03436641) received approval from the Comité de Protection des Personnes, Sud-Est V, France (Comité de Protection des Personnes, Sud-Est V; reference 18-STRA-01).
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Supplementary Information
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Supplementary Material 1: Figure S1. Comparison of the time course of mottling score from H0 to H24 between survivors and non-survivors at day 30, exclusively within the MicroShock cohort.
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Supplementary Material 2: Figure S2. Kaplan–Meier showing 30-day mortality in cardiogenic shock according to mean macrocirculatory and mean tissue perfusion variables during the first 24 h, using pulmonary artery catheter as reference. A Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean ScvO2 during the first 24 h. B Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean ∆PCO2 during the first 24 h. C Kaplan–Meier showing 30-day mortality in cardiogenic shock according to the mean ∆PCO2/C(a-v)O2 during the first 24 h. ∆PCO2: delta PCO2, ScvO2: central venous oxygen saturation, P(v-a)CO2/ C(a-v)O2 ratio: ratio of venous-arterial carbon dioxide tension difference to arterial-venous oxygen content difference (or ∆PCO2/C(a-v)O2).
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Supplementary Material 3: Table S1. Comparison of macrocirculatory hemodynamic and tissue perfusion variables between 30-day survivors and 30-day non-survivors, calculated using pulmonary artery catheter as reference.
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Supplementary Material 4: Table S2. Comparison of pulmonary artery catheter variables between 30-day survivors and 30-day non-survivors, exclusively within OptimaCC cohort.
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Supplementary Material 5: Table S3. Comparison of mottling score between 30-day survivors and 30-day non-survivors, exclusively within MicroShock cohort.
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Supplementary Material 6: Table S4. Association of pulmonary artery catheter variables with death at 30 days in univariable Cox model, exclusively within OptimaCC cohort.
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Supplementary Material 7: Table S5. Association of macrocirculatory hemodynamic and tissue perfusion variables with endpoints in univariable Cox model, calculated using pulmonary artery catheter as reference.
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Supplementary Material 8: Table S6. Association of macrocirculatory hemodynamic and tissue perfusion variables with death at 30 days in univariable Cox model and interaction with out-of-hospital cardiac arrest (OHCA).
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Levy, B., Curtiaud, A., Duarte, K. et al. Association between mean hemodynamic variables during the first 24 h and outcomes in cardiogenic shock: identification of clinically relevant thresholds. Crit Care 29, 137 (2025). https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s13054-025-05356-0
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DOI: https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s13054-025-05356-0