We investigated clinical characteristics and predictors of clinical outcomes in CS patients treated with contemporary management from a large-scale, multi-center registry. This study demonstrated the actual state of CS in Korea. The major findings of this study were: (1) in-hospital mortality of CS patients remains high, (2) dopamine and norepinephrine were used as first-line vasopressors, (3) more than half of the patients required MCS devices, and (4) old age, cardiac arrest, high-dose vasopressor, and organ failure were independent predictors of in-hospital mortality.
Cardiogenic shock is a critical illness with a very high rate of fatality. However, most treatment modalities have been tested only empirically with no solid supporting evidence because randomized controlled trials are very difficult to perform in this vulnerable patient subset. For example, over 20 years, there have been only three major randomized controlled trials, mostly in the AMI patients. The Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock (SHOCK) trial established the role of early coronary revascularization in AMI patients complicated by CS (10). The Intra-aortic Balloon Pump in Cardiogenic Shock II (IABP-SHOCK II) trial showed that routine IABP did not reduce patient mortality. The Culprit Lesion Only PCI versus Multivessel PCI in Cardiogenic Shock (CULPRIT-SHOCK) trial showed that multi-vessel PCI did improve clinical outcome.(11, 12)
On the contrary, the registry studies cover a variety of causes of CS. However, those previous studies were relatively small in sample size or were associated with a lower rate of MCS device use, which does not reflect current practice. The CardShock study, a European, multi-center registry, was conducted between 2010 and 2012 but included only 219 patients, 13 of whom were treated with ventricular assist device or ECMO. (13–15) The Japanese Circulation Society Cardiovascular Shock registry conducted between 2012 and 2014 was the largest registry of CS, enrolling 979 patients, (16) but that study did not collect information on vasopressor or MCS usage. The RESCUE study is the largest multi-center, real-world registry of CS patients with a broad spectrum of etiologies. More than half of enrolled patients have received either IABP or ECMO, representing contemporary management of more severe forms of CS. Still, in this study, a total of 419 patients (33.6%) died at index hospitalization, which is consistent with the 30–40% mortality reported in other studies performed in the early 2010s. These findings suggest that the mortality rate of AMI patients complicated by CS may plateau over time despite introduction of new devices and techniques improving coronary artery revascularization. Further, beneficial hemodynamic support may be masked by MCS-related complications such as limb ischemia, systemic embolization, and fatal bleeding in CS patients treated with MCS.
The prognostic factors found in this study were consistent with those reported in previous studies. Indices of organ failure such as acute kidney injury requiring continuous renal replacement therapy and respiratory failure requiring mechanical ventilator were significant prognostic factors for in-hospital mortality.(15, 16) Cardiac arrest was also a prognostic factor for in-hospital mortality. Our group showed that extracorporeal cardiopulmonary resuscitation had a survival benefit over the conventional approach used in a previous study.(17) Future research regarding optimal strategy of extracorporeal cardiopulmonary resuscitation is needed to improve the mortality rate seen with this RESCUE registry. High vasoactive-inotrope score was a powerful indicator of in-hospital mortality in this study. Recently, our group showed that a high level of vasoactive inotropic support during the first 48 hours was significantly associated with increased in-hospital mortality in adult CS patients.(18) Basically, inotropes or vasopressors can improve hemodynamics in the acute stage through increased myocardial contractility or modification of vascular tone. However, these agents can also be related to adverse cardiovascular events such as hypertension/hypotension, arrhythmias, peripheral, and cardiac ischemia, which may be fatal.(19) Accordingly, the decision whether to increase vasopressor dosage or apply advanced MCS in patients who have already received high-dose vasopressor should be carefully weighed after considering a risk-benefit analysis.
Our study has several limitations. First, most patients presented with an ischemic etiology, and patients with non-ischemic cause were heterogeneous and of limited sample size. Second, this registry did not include all mechanical circulatory support because Impella is not currently available in Korea. Third, treatment of CS such as type and amount of fluids and vasopressor/inotropes administered and type and timing of MCS were left to the physician’s discretion, although coronary intervention was based on the guidelines of the Korean Circulation Society.