Epidemiology of Shock in Contemporary Cardiac Intensive Care Units

Abstract

Background Clinical investigations of shock in cardiac intensive care units (CICUs) have primarily focused on acute myocardial infarction (AMI) complicated by cardiogenic shock (AMICS). Few studies have evaluated the full spectrum of shock in contemporary CICUs. Methods and Results The Critical Care Cardiology Trials Network is a multicenter network of advanced CICUs in North America. Anytime between September 2017 and September 2018, each center (n=16) contributed a 2-month snap-shot of all consecutive medical admissions to the CICU. Data were submitted to the central coordinating center (TIMI Study Group, Boston, MA). Shock was defined as sustained systolic blood pressure <90 mm Hg with end-organ dysfunction ascribed to the hypotension. Shock type was classified by site investigators as cardiogenic, distributive, hypovolemic, or mixed. Among 3049 CICU admissions, 677 (22%) met clinical criteria for shock. Shock type was varied, with 66% assessed as cardiogenic shock (CS), 7% as distributive, 3% as hypovolemic, 20% as mixed, and 4% as unknown. Among patients with CS (n=450), 30% had AMICS, 18% had ischemic cardiomyopathy without AMI, 28% had nonischemic cardiomyopathy, and 17% had a cardiac cause other than primary myocardial dysfunction. Patients with mixed shock had cardiovascular comorbidities similar to patients with CS. The median CICU stay was 4.0 days (interquartile range [IQR], 2.5-8.1 days) for AMICS, 4.3 days (IQR, 2.1-8.5 days) for CS not related to AMI, and 5.8 days (IQR, 2.9-10.0 days) for mixed shock versus 1.9 days (IQR, 1.0-3.6) for patients without shock ( P<0.01 for each). Median Sequential Organ Failure Assessment scores were higher in patients with mixed shock (10; IQR, 6-13) versus AMICS (8; IQR, 5-11) or CS without AMI (7; IQR, 5-11; each P<0.01). In-hospital mortality rates were 36% (95% CI, 28%-45%), 31% (95% CI, 26%-36%), and 39% (95% CI, 31%-48%) in AMICS, CS without AMI, and mixed shock, respectively. Conclusions The epidemiology of shock in contemporary advanced CICUs is varied, and AMICS now represents less than one-third of all CS. Despite advanced therapies, mortality in CS and mixed shock remains high. Investigation of management strategies and new therapies to treat shock in the CICU should take this epidemiology into account.

Keywords: North America; cardiogenic shock; epidemiology; hypotension; intensive care units.

Figure 1.. Shock type.

A, All patients meeting criteria for shock (n=677) were classified according to shock type. B, Patients with cardiogenic shock (n=450) were further divided according to the cause of cardiogenic shock. Patients with cardiogenic shock from an ischemic cause were categorized according to whether or not the shock presentation was precipitated by acute myocardial infarction (AMI). AMICS indicates acute myocardial infarction cardiogenic shock.

Figure 2.. Mortality by shock type.

Cardiac intensive care unit (CICU) and in-hospital mortality rates are summarized for patients with acute myocardial infarction cardiogenic shock (AMICS), cardiogenic shock without acute myocardial infarction (AMI), and mixed shock. Absolute binomial 95% CIs are shown. In-hospital mortality rates between mixed shock vs AMICS and mixed shock vs cardiogenic shock (CS) without AMI were not statistically different when adjusted for age, sex, and severity of illness (P=0.50 and P=0.87, respectively).