7.1 / IAGS 2019
Session 7: Hemodynamics Session 1
Hemodynamic Support for AMI with Cardiogenic Shock: Which Device is Best? Are We Ready for Primetime? Do We Need Systems of Care?
Problem Presenter: Srihari S. Naidu, MD
Statement of the problem
Despite major advances in the treatment of acute myocardial infarction (AMI), including primary percutaneous coronary intervention (PPCI), adjunctive pharmacotherapy and judicious use of intra-aortic balloon counterpulsation, the incidence and associated mortality of cardiogenic shock has seen little decline. Indeed, after adjustment for comorbidities, there has been a two-fold increase in the incidence of cardiogenic shock in AMI, and this is similar for both males and females, and in those over and under the age of 75. Mortality with cardiogenic shock has improved from roughly 45% to 35% in this time span, representing a 25% improvement in survival, but has hit a plateau despite high penetration of PPCI and IABP use (roughly 70% and 50%, respectively) within the United States. Although higher penetration of PPCI may improve survival incrementally, further use of the IABP would be unlikely to improve outcomes based on the randomized IABP-SHOCK II trial.
Gaps in knowledge
Goals for the management of cardiogenic shock would include decreasing both the incidence of shock as well as its associated mortality. While there is good reason to believe that improvements in symptom-onset-to-PCI time will reduce infarct size and reduce both electrical and mechanical complications, this has not yet been proven in prospective fashion. In addition, early recognition of cardiogenic shock, and those patients at risk of developing cardiogenic shock in various clinical settings, remains problematic. Next, although mechanical support has theoretic benefits in this population through ventricular unloading and possible reductions in infarct size, as well as hemodynamic support to prevent and/or reverse end-organ damage, there exists no completed and adequately powered randomized trial with supportive data. In this context, it is difficult to know whether the increasing penetration of these mechanical support devices is helping or hurting this population. Finally, although systems of care and heart teams for identification, triage, and rapid stabilization and transfer of patients in a so-called hub-and-spoke model are emerging, data showing this to improve mortality remain absent.
Possible solutions and future directions
Much discussion among the IAGS delegates revolved around the fact that cardiogenic shock is both a time-based and an anatomy-based modifiable variable. That is, the risk of developing shock from extensive myocardial damage increases based both on the extent of myocardium at risk and the duration from symptom onset to PCI. Indeed, shock typically develops more than 12 hours after infarction begins, and can be as late as 1-2 days, and it may be even exacerbated in some cases by PPCI reperfusion injury. Accordingly, defining cardiogenic shock in all clinical settings becomes paramount to early identification and treatment. To this end, the group discussed the SCAI/HFSA Clinical Expert Consensus Document on Defining Cardiogenic Shock. This document is a multi-society definitions paper to be released during the SCAI 2019 scientific sessions which creates a universal lexicon for the stages of cardiogenic shock. Such a definition is anticipated to aid in rapid identification of shock and its severity, as well as those at risk of shock, whether the stage modifies through time and intervention, and whether the patient should be transferred to another facility and/or escalated in terms of hemodynamic support. The definition and stages can then be prospectively and retrospectively validated as a tool to improve outcomes.
Second, the group supported a systems of care approach to hospitals, where community hospitals (level 3) would identify and stabilize patients but have a system in place for rapid transfer to either level 2 hospitals (those with PPCI and minimally-invasive MCS) or directly to level 1 hospitals (those with ECMO, temporary VAD and heart transplantation) depending on the clinical picture and response to initial intervention. Models of such a hub-and-spoke protocol exist in various regions of the country and outcomes data are needed from these hospitals to validate this approach. In addition, each hospital and system should create heart teams of heart failure, interventional cardiology, critical care, surgical and nursing providers in order help identify these patients and rapidly determine strategy and disposition.
Finally, the group strongly supported the objective that more data are needed to guide choice and escalation of MCS devices in patients with cardiogenic shock. In addition, more algorithm-based management protocols should be developed and validated prospectively. To this end, the national Cardiogenic Shock Initiative (CSI) was discussed. This algorithm which is utilized in multiple hospitals across the United States as an IRB-based research protocol employs a model of MCS (in this case, Abiomed’s Impella CP) prior to PPCI and right heart catheterization to guide escalation of devices and weaning of vasopressors prior to the patient leaving the catheterization laboratory. In preliminary data, survival in patients within CSI appears excellent at >70%, but ranges from 30% to 96% based on biochemical (lactate) and hemodynamic (cardiac power output) variables over the initial 24 hours. Other algorithms are needed, with an aim to prospectively test different algorithms in randomized fashion or between networks. To this data should be added further randomized controlled trials of MCS in shock, such as the DANGER trial currently underway in Europe.