By Van Selby, MD

Assistant Professor of Medicine, University of California, San Francisco Cardiology Division, Advanced Heart Failure Section

Dr. Selby reports he is a consultant for Alnylam Pharmaceuticals and Akcea Therapeutics.

SYNOPSIS: Implementation of a standardized, team-based approach to cardiogenic shock resulted in improved 30-day survival compared to historical controls.

SOURCE: Tehrani BN, Truesdell AG, Sherwood MW, et al. Standardized team-based care for cardiogenic shock. J Am Coll Cardiol 2019;73:1659-1669.

Cardiogenic shock (CS) remains a leading cause of cardiovascular mortality. There is growing interest in the use of multidisciplinary “shock teams” to rapidly identify and treat CS using standardized algorithms. While several centers have demonstrated the feasibility of a shock team approach, none have shown whether this is associated with improvements in clinical outcomes.

In 2017, the Inova Heart and Vascular Institute introduced a shock team approach based on a clinical algorithm for the management of CS. The team focused on five primary goals: rapid identification of CS, use of invasive hemodynamic monitoring, minimization of vasopressor and inotrope use, early mechanical circulatory support (MCS), and facilitating cardiac recovery.

CS was defined according to criteria used in previous clinical trials, including systolic blood pressure < 90 mmHg, evidence of end-organ hypoperfusion, and serum lactate > 2 mmol/L. When a patient with suspected cardiogenic shock was identified, the treating team makes a single phone call to gather physicians from interventional cardiology, heart failure, cardiothoracic surgery, and critical care for a multidisciplinary conversation. The patient would be transferred to either the catheterization laboratory for acute myocardial infarction (AMI) or to the cardiac ICU for acute decompensated heart failure (ADHF). All patients underwent right heart catheterization. Patients were determined to meet hemodynamic criteria for CS when the following were present: cardiac index < 1.8 L/min/m2 without inotropes or < 2.2 with inotropes, pulmonary capillary wedge pressure > 15 mmHg, cardiac power output (CPO) < 0.6 W, or a pulmonary arterial pulsatility index (PAPi) < 1.0. In patients meeting hemodynamic criteria for CS, the use of early MCS was recommended, with an Impella CP (Abiomed) as the standard support device and others available as appropriate.

During the study period (2017-2018), 204 patients were admitted for CS. The cause of shock was AMI in 82 patients and ADHF in 122 patients. Compared to a baseline 30-day survival of 47% in 2016 (before introduction of the shock team), there was an increase in survival to 58% in 2017 and 77% in 2018 (P < 0.01). A clinical risk score was developed that included all variables found to be associated with 30-day mortality: age ≥ 71 years, diabetes, dialysis, use of vasopressors ≥ 36 hours at time of diagnosis, lactate ≥ 3.0 mg/dL, CPO < 0.6 W, and PAPi < 1.0 at 24 hours after diagnosis.

The authors concluded that a standardized team-based approach may improve outcomes in CS. Furthermore, a score that incorporates demographic, laboratory, and hemodynamic variables can risk-stratify patients with CS and guide clinical decision-making.

COMMENTARY

Despite advances in revascularization and MCS, data from registries and clinical trials continue to show poor outcomes for patients hospitalized with CS, with mortality rates often around 50%. There are multiple contributing factors, including delayed recognition of CS and wide practice variation that often includes high doses of medications with substantial adverse effects (e.g., vasopressors and inotropes) or support devices that do not provide substantial hemodynamic improvement (intra-aortic balloon pumps). The authors of multiple single-center studies have reported implementation of a standardized “shock team” approach to facilitate rapid identification and treatment of CS. The Tehrani et al study is the first to associate a shock team with improved CS survival. The Inova shock team approach may serve as a template for clinicians at other centers to use when developing their own approach for CS.

There are several important aspects of this program to highlight. First, the importance of an easy-to-activate multidisciplinary shock team. Patients with CS are medically complex and require multispecialty care. In the model used by Inova providers, activate the shock team with a single phone call as soon as CS is suspected (with easy-to-use criteria). The initial providers often were at regional referring hospitals. Contacting the shock team not only helped guide initial management but also facilitated transfer to Inova for more advanced care. This “hub and spoke” system provides prompt access to expert consultation and helps patients move to higher-level care as quickly as possible.

Second: The importance of hemodynamic monitoring in CS. Use of the Swan-Ganz catheter declined after clinical trials failed to show benefit in a general acute heart failure population. However, since then, several observational reports have shown benefit from right heart catheterization in CS. Current American Heart Association guidelines suggest it can be helpful in this situation. Right heart catheterization is essential for identifying hemodynamic abnormalities and guiding decision-making regarding the need for MCS.

Third, the shock team model emphasizes the early use of MCS. The authors found that every 60-minute delay in insertion of MCS was associated with a 9.9% increase in mortality. Generally, the Inova model recommended the Impella CP (Abiomed) as the standard device used for left ventricular support, although several devices were used according to the needs of the patient. In addition to interpretation of standard data obtained during right heart catheterization, practitioners involved in the management of CS should be familiar with the CPO and PAPi. These are novel hemodynamic parameters that are used commonly in contemporary shock algorithms to determine whether left- and/or right-sided mechanical support is needed.

This was a single-center observational study with the usual associated limitations; the use of a historical control group is suboptimal. Future multicenter studies will help refine the optimal use of shock teams. Despite these limitations, the study by Tehrani et al represents a major advancement in our understanding of the optimal approach to treating cardiogenic shock.