Cardiogenic shock (CS) is a state of severe hypoperfusion due to cardiac dysfunction that commonly leads to multiorgan failure. This diagnosis accounts for approximately 5% of admissions to general intensive care units, and its incidence has increased during the last few years.1 Despite the widespread use of revascularization in patients with ST-segment elevation acute myocardial infarction (STEMI) and other therapeutic advances in the management of critically-ill patients, in-hospital mortality due to CS remains very high (40%-50% in most series).2–4 Furthermore, mortality may change according to the volume of treating centers and the experience of medical teams.5 Current guidelines recommend centralizing the care of these patients in high-volume centers, with 24/7 availability of the catheterization laboratory (cathlab), and short-term mechanical circulatory support.6

Significant heterogeneity has been reported in the management of CS. To the best of our knowledge, no study has assessed the impact of (hospital departments) where patients are treated, and the structure and organization of treating centers on clinical outcomes in this clinical scenario.

The aims of this study were the following: a) To describe the temporal trends in management patterns and outcomes in patients with STEMI-related CS; b) to characterize the type of treating centers where STEMI-related CS patients are admitted throughout the Spanish National Health System (SNHS), and c) to assess the potential association between changing patterns of care and in-hospital mortality.

A total of 392 169 STEMI episodes were identified during the study period (2003-2015), of which 60 976 (15.5%) were excluded because they did not meet the inclusion criteria (not mutually exclusive). A total of 19 963 (6.03%) of the remaining 331 193 episodes were STEMI-related CS. The proportion of women was 28.8% for non–CS-STEMI and 38.8% for CS-STEMI (P <.001). The mean age was 67.2±13.8 years for non–CS-STEMI and 73.4±11.8 years for CS-STEMI (P <.001). The CS-STEMI group showed a higher degree of comorbidity than the non–CS-STEMI group (Charlson index ≥ 3 points 82.1% vs 50.1%, P <.001), except for cardiovascular disease-related comorbidities (table 2).

The absolute number of in-hospital deaths was 25 949/311 230 (8.3%) for STEMI without CS and 14 627/19 963 (72.9%) for STEMI-related CS. The mean length of stay was 8.6 days for STEMI without CS and 9.9 days for STEMI-related CS. Excluding deaths, the mean length of hospital stay was 9±7.3 days for patients with STEMI without CS and 21.1±19.2 days for patients with STEMI-related CS (P <.001).

Clinical and demographic variables independently associated with in-hospital mortality in the multilevel risk adjustment model are shown in table 3, with CS being the most important variable (OR, 14.6; 95% CI, 14.2-15). This model showed good discriminative ability (AUROC, 0.89; 95%CI, 0.887-0.891). The specific model for in-hospital mortality for the CS-STEMI group is shown in table 2 of the supplementary data. The AUROC for this model was 0.72; 95%CI, 0.71-0.73).

This model showed acceptable calibration, with optimal agreement between observed and expected in-hospital mortality (first tertile: 0.54 vs 0.55, respectively, second tertile: 0.78 vs 0.77; and third tertile: 0.88 vs 0.88) and a significant decrease in the statistical likelihood ratio test compared with the null model (P <.001)

In the CS-STEMI group, the performance of revascularization procedures during hospitalization, either PCI or CABG, was independently associated with a lower in-hospital mortality risk (OR, 0.29; 95%CI, 0.26-0.31; P <.001 and OR, 0.25; 95%CI, 0.19-0.32; P <.001, respectively; AUROC, 0.76; 95%CI, 0.75-0.77) (table 3 of the supplementary data). The RSMR was significantly lower in type 3 and 4 hospitals with an ICCU than in type 3 and 4 hospitals without ICCU (65.3%±7.9 vs 72±11.7; P <.001).

Time trends in CS incidence, management, mortality, and RSMR by hospital types (2003-2015)

The incidence rate of CS in STEMI did not change significantly during the study period (lowest rate, 5.7%, in 2015; highest, 6.4%, in 2008) (IRR, 1; P=.62). The performance of PCI increased during the study period, from 19.2% in 2003 to 59.5% in 2015 (P for trend <.001) while there was no statistically significant change in the trend for CABG use (mean rate, 1.9%; P for trend=.35).

The proportion of type 4 hospitals (table 1 of the supplementary data) remained stable at 19.8±0.7% from 2005 to 2015 (figure 1 of the supplementary data). A total of 7807 patients with STEMI-related CS discharged from 2005 to 2015 (48%) were admitted to type 4 hospitals, while 74.2% were treated at type 3 or type 4 hospitals. The proportion of patients treated at type 4 hospitals significantly increased (P <.005) from 38.4% in 2005 to 52.9% in 2015.

An ICCU was available in 23 Spanish hospitals in 2005 and in 28 hospitals in 2015. The proportion of type 3 and 4 hospitals with an ICCU in 2015 is shown in table 1 of the supplementary data. There was an increase in the proportion of patients with STEMI-related CS admitted to type 3 and 4 hospitals (figure 1A), with no significant differences in age and sex in patients with STEMI-related CS according to ICCU availability. A Charlson index value ≥ 3 was more common in patients treated in type 3 and 4 hospitals with an ICCU (83.4% vs 85.1%; P=.02), although the prevalence of other comorbidities was similar according to ICCU availability (table 4). PCI in STEMI-related CS was more often performed in type 3 and 4 hospitals with ICCU than in hospitals without ICCU (60.1% vs 52.8%; P <.001) (figure 1B). The in-hospital risk-adjusted mortality rate was 65.3% in patients admitted to type 3 and 4 hospitals with an ICCU vs 72% in those without ICCU (P <.0001; figure 1C).

Figure 1.

A: proportion of patients treated at type 4 hospitals across the study period. B: proportion of patients undergoing percutaneous coronary intervention in patients admitted to type 3 and 4 hospitals. C: risk-standardized mortality rates according to ICCU availability. ICCU, intensive cardiac care unit.

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Table 4.

Clinical characteristics of patients with cardiogenic shock due to acute coronary syndrome treated at hospitals type 3 and 4

Variable	No ICCU	ICCU	P
No.	7086	3951
Age, y	71.6±12.2	71.8±12.5	.885
Male sex	63.9	65.3	.128
Charlson index group 2	83.4	85.1	.02
History of PTCA (ICD-9 codes V45.82)	6.3	4.5	<.001
History of CABG surgery (ICD-9 codes V45.81)	1.6	1	.02
Congestive heart failure (CC 80)	46.1	47.7	.12
Other acute/subacute forms of ischemic heart disease (CC 82)	8.3	11	<.001
Coronary atherosclerosis or angina (CC 83-84)	63.8	69.6	<.001
Valvular or rheumatic heart disease (CC 86)	15.4	18.7	<.001
Hypertension (CC 89, 91)	49.2	44.1	<.001
Stroke (CC 95-96)	1.70	2.00	.15
Cerebrovascular disease (CC 97-99, 103)	3.3	3.9	.17
Renal failure (CC 131)	31.5	29.60	.03
Chronic obstructive pulmonary disease (CC 108)	7.5	8.1	.25
Pneumonia (CC 111-113)	10.80	12.20	.001
Diabetes mellitus or diabetes mellitus complications except proliferative retinopathy (CC 15-20, 120)	35.5	28.9	<.001
Protein-calorie malnutrition (CC 21)	0.8	0.5	.06
Dementia or other specified brain disorders (CC 49-50)	8.6	8.4	.72
Hemiplegia. paraplegia. paralysis. functional disability (CC 67-69, 100-102, 177-178)	4.3	2.9	<.001
Vascular disease and complications (CC 104-105)	0.9	0.8	.61
Metastatic cancer. acute leukemia and other severe cancers (CC 7-8)	1.1	1.6	.02
Trauma in last year (CC 154-156, 158-162)	0.8	1	.32
Major psychiatric disorders (CC 54-56)	1	0.8	.25
Chronic liver disease (CC 25-27)	0.7	0.6	.66

CABG, coronary artery bypass graft; CC, condition categories; ICCU, intensive cardiac care unit; ICD-9, International Classification of Diseases-9th Revision; PTCA, percutaneous transluminal coronary angioplasty.

Unless otherwise indicated, values are expressed as mean±standard deviation or percentage.

Secondary diagnoses grouped in risk factors (Pope et al.).15

Among patients treated at type 3 and 4 hospitals, the proportion of patients undergoing revascularization procedures was similar regardless of whether they were initially admitted to that hospital or transferred from other hospitals (PCI rates, 55.2% for nontransferred patients vs 52.9% for transferred-in patients, P=.66; CABG rates, 2.5% for nontransferred vs 3.4% for transferred-in patients, P=.48). RSMRs were similar in both groups of patients (69.6%±10.8 for nontransferred patients and 70.4±10.2 for transferred-in patients, P=.46).

There was a 35% relative reduction in the unadjusted mortality rate during the study period (from 10.5% in 2003 to 6.8% in 2015) for non-CS-STEMI while the relative reduction for STEMI-related CS was 17% (from 82% in 2003 to 67.1% in 2015). The mean RSMR also decreased significantly, from 10.9% in 2003 to 6.7% in 2015 for non–CS-STEMI (IRR per year, 0.958; P <.001) and from 82.7% in 2003 to 66.8% in 2015 (IRR per year, 0.978; P <.001, figure 2).

Figure 2.

Temporal trends in CMR and RSMR in STEMI patients without CS (A), and STEMI-related CS across the study period (B). CMR, crude mortality rate; CS, cardiogenic shock; RSMR, risk-adjusted mortality rates; STEMI: ST-segment elevation myocardial infarction.

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Our study showed a progressive decline in crude and adjusted mortality rates in patients with STEMI-related CS at the national level in Spain during the study period. This seems to be a consequence, at least in part, of the increased proportion of patients admitted to hospitals with an ICCU and the greater use of coronary revascularization in these patients.

The incidence rate of CS among the patients with STEMI in our series was 6.03%. We used an administrative database for case identification. This may have led to an underestimation of the incidence of CS. However, the underestimation was not severe, since the rate of CS in our series falls within the lower range of previously reported incidence rates of CS in STEMI patients, between 5% and 10%.18–20

In-hospital mortality in CS remains very high and is the leading cause of death in STEMI patients.1,2,4 Patients included in our study were significantly older and had higher mortality compared with previously published CS series. Our study describes a large cohort of unselected CS patients admitted to hospitals with different resources and structures, which is in contrast with several prior publications, many of which were performed in highly selected tertiary centers, often referral centers for advanced care and therapies, and therefore included relatively younger and selected populations.1–4 This may explain the discrepancy in results as advanced age is consistently associated with worse outcomes in CS.1–3,21 More importantly, both crude and adjusted mortality progressively declined during the study period. This substantial improvement in outcomes can probably be explained by the widespread use of mechanical reperfusion in patients with STEMI during the last decade,22 along with the implementation of regional reperfusion networks in Spain.23 From 2009, 6 networks were created in 6 different regions. Similar results have been observed in other countries across Europe.24 Other factors, such as the improvement in life support techniques and overall critical patient care measures, may also have contributed to the substantial reduction in mortality observed in our study.

Current guidelines6 recommend centralizing the care of patients with CS in highly specialized centers, since this approach has been consistently associated with better outcomes in this clinical setting.5 Although the proportion of type 4 hospitals remained stable during the study period, our data show a progressive increase in the number of patients treated at these hospitals (roughly, from slightly more than one third to half), indicating a significant improvement in the organization of care for CS patients over time. The availability of an ICCU was associated with higher survival rates, probably reflecting the effect of specialized training and expertise in the diagnosis and management of CS, such as pulmonary artery catheterization, implantation of temporary pacemakers, echocardiography, and the use of mechanical support devices. In addition, ICCUs may have faster and easier access to coronary revascularization procedures. This hypothesis is supported by the 14% higher rate of PCI in patients admitted to hospitals with an ICCU in our series (60.1% vs 52.8%). Patients admitted to an ICCU also had a different profile, with a higher degree of comorbidity and cardiovascular risk and greater use of therapeutic procedures such as coronary revascularization.25 This finding aligns with the recommendation to centralize the care of patients with CS. In addition, our data might support the need to expand the establishment of ICCUs in hospitals with high volumes of ACS patients. Although the high clinical complexity of these patients requires a multidisciplinary approach, the results of this study highlight the importance of the leading role of highly trained cardiologists in the management of critically-ill cardiac patients, such as those with CS.26

One of the most important strengths of this study is its high external validity, since it allows us to obtain a real picture of clinical characteristics, management, and outcomes of patients with STEMI-related CS in our setting. However, several limitations should be acknowledged. First, it is a retrospective analysis of administrative data, with inherent drawbacks. However, the use of administrative records to estimate outcomes in health care services has been validated by comparison with data from medical records7,27 and has been applied to research on health service outcomes.28 The reliability of studies of this type enables the public comparison of hospitals in terms of outcomes.29 In contrast to the methodology used by the Centers of Medicare and Medicaid Services,11,27 we did not measure 30-day mortality but rather in-hospital mortality. Additionally, secondary diagnoses as potential confounders could have been present at admission or during admission, but can also reflect suboptimal management.27 Information about the use of all types of short-term circulatory support was not available. Finally, we cannot exclude the presence of unmeasured confounding factors that may adversely impact prognosis. Despite these limitations, our study, one of the largest series of CS, provides relevant information on the factors involved in the improvement of STEMI-related CS prognosis in the era of contemporary management, particularly the fact that the clinical care of these patients in ICCUs may improve the use of revascularization therapies and patient prognosis.

The proportion of patients with STEMI-related CS treated at hospitals with a cath lab and cardiac surgery facilities progressively increased during the study period, while there was a progressive reduction of both crude and adjusted mortality. Better outcomes were associated with the performance of revascularization procedures and the availability of an ICCU. These findings support the recommendation of centralizing the care of CS patients in highly specialized centers.

This work was supported by FIC (Fundación Interhospitalaria para la Investigación Cardiovascular) and Laboratorios Menarini (RECALCAR Project).

None declared.