Systems of Care and Team-Based Approach to the Management of Mechanical Complications Following Acute Myocardial Infarction

The uniform adoption of primary percutaneous coronary intervention (PCI) and integration of regionalized systems of ST-elevation myocardial infarction (STEMI) care have reduced mortality following acute myocardial infarction (AMI) to <5% in the current era¹. These advances have been accompanied by substantial declines in the incidence of post-MI mechanical complications (MCs-AMI), a heterogenous cohort of catastrophic sequelae stemming from extensive myocardial necrosis typically seen within the first week following an AMI^{2, 3}, but fortunately now uncommon. A recent analysis of over 9 million hospitalizations for acute coronary syndrome from the National Inpatient Sample between 2003 to 2015 reported the incidence of MCs-AMI following STEMI to be 0.27%, a nearly 6-fold decline from the pre-thrombolytic era ^{4, 5}. The prognosis of those afflicted by MCs-AMI, however, remains dismal with the majority progressing to cardiogenic shock and in-hospital mortality rates approaching 50%. ^{4, 6}. One of the unforeseen consequences of the global COVID-19 pandemic has been an increase in the incidence of these deleterious complications, due to delayed presentations of AMIs stemming from public avoidance of hospitals^7-9. This phenomenon occurred worldwide, with a 30-50% decline in STEMI presentations and an increase in out-of-hospital cardiac arrest¹⁰.

The care of patients with MC-AMI is inherently time sensitive and resource intensive¹¹. While clinical guidelines recommend prompt surgical repair, especially in patients with hemodynamic and electrical instability, there remain clinical gaps in knowledge regarding the optimal timing of intervention and utilization of novel percutaneous technologies. This is particularly true in patients with post-infarct ventricular septal defects (VSDs), given registry data suggesting improved survival associated with early hemodynamic stabilization and delayed surgery to allow time for infarcted cardiac tissue to fibrose and stabilize^{12, 13}. It is also known that up to 20% of patients with MCs-AMI may be deemed to be of prohibitive surgical risk due to deteriorating CS⁶. As a result, consideration is often given to alternative percutaneous interventions, such as transcatheter edge-to-edge repair in the case of mitral regurgitation due to papillary muscle rupture and transcatheter closure of VSDs using the Amplatzer^TM post-infarct muscular VSD occluder (Abbott Laboratories, Chicago, IL) ^14-16. While technically feasible, decision making around percutaneous options for MCs-AMI is complex, often requiring the integration of invasive hemodynamics, multi-modality imaging, and input from a multidisciplinary heart team. In addition, short-term outcomes are significantly worse when compared to similar non-surgical interventions performed under more stable conditions, perhaps in part due to higher risk patients tending to undergo percutaneous intervention^{17, 18}. Thus given the paucity of direct comparative data, there remains considerable controversy regarding the management of MCs-AMI and significant regional variations in expertise, treatment and outcomes.¹⁹

In this issue of Circulation, Damluji et al present an American Heart Association (AHA) Scientific Statement entitled “Mechanical Complications of Acute Myocardial Infarction.”²⁰ This document provides the most comprehensive and up-to-date expert review of the various syndromes that comprise this highly morbid and precarious disease space. At the outset, the authors submit three plausible reasons to account for the stable incidence of MCs-AMI seen today: 1) An at risk aging population with associated co-morbidities and frailty syndromes; 2) Technologic advances in dedicated cardiac imaging modalities; and 3) Increase in the number of tertiary and quaternary care institutions with advanced cardiac expertise. In systematic fashion, the authors examine the epidemiologies, risk factors, clinical features, and multimodality imaging tools required for the timely diagnosis of the five cardinal MCs-AMI: 1) Acute mitral regurgitation due to papillary muscle rupture; 2) VSDs; 3) Left ventricular (LV) free wall rupture; 4) LV pseudoaneurysms; and 5) LV aneurysms. The statement also provides a meticulous and well-researched analysis of the varying surgical and percutaneous treatment strategies that have been studied and are currently implemented in clinical practice.

In the absence of clinical guidelines, Damluji et al propose patient-centered treatment pathways for MCs-AMI, predicated on time-sensitive triage, upstream hemodynamic stabilization and regionalized inter-institutional collaboration. Analogous to systems of care models currently in place for other emergency cardiovascular conditions, the management of MCs-AMI should ideally be centralized to Level 1 cardiac centers capable of providing longitudinal and full spectrum care^21-24. The authors further dichotomize MCs-AMI treatment based on the presence or absence of refractory circulatory collapse. In both circumstances, the acuity and co-morbidities associated with these syndromes merit the expertise of multiple disciplines, including critical care cardiologists who serve as the “quarterbacks” of modern era high intensity cardiac intensive care units (CICU’s) and help to consolidate input from other specialties.²⁵ In the management of hemodynamically unstable patients, recent data from North American registries suggest that the implementation of dedicated “Shock Teams” with well-defined algorithms can improve short-term outcomes by facilitating timely diagnosis and implementation of medical and device-based therapies tailored to the individual CS phenotype^26-29. As patients with MCs-AMI often present at the extremes of the CS severity spectrum, a team-based approach incorporating the expertise of interventional cardiologists, cardiac surgeons, advanced heart failure specialists, imaging cardiologists, and CICU intensivists is key to ensuring appropriate patient selection for advanced therapies to maximize benefit and mitigate the risk of adverse clinical events, including complications of the therapies.³⁰

For MCs-AMI patients with persistent CS, the benefits derived from surgical or percutaneous repair of the mechanical defects may be limited given the large amount of non-viable myocardium and associated metabolic and end-organ impairments. Damluji et al highlight the need to incorporate the expertise of advanced heart failure specialists into the multidisciplinary team for consideration of destination therapies, including durable left ventricular assist devices and orthotopic heart transplantation (OHT). Historically, patients with Interagency Registry for Mechanically Assisted Circulatory Support Class 1 heart failure requiring full circulatory support have fared poorly following OHT, with 1 year survival rates of 58%.³¹ Following updates to the United Network for Organ Sharing allocation system in 2018 which now prioritizes patients supported with veno-arterial extracorporeal membrane oxygenation for OHT, data suggests improved short-term survival compared to the old system due to expedited wait times, and a potentially larger shared pool of donors. Given the myriad organ system complexities often seen in patients with MCs-AMI, the authors also advocate for early engagement of palliative services to help address not only physical and emotional symptoms, but to facilitate discussions with patients and their surrogates regarding their health values and goals of care. This is particularly important for patients deemed ineligible for advanced therapies, and in whom further escalation in management may be futile and/or inconsistent with the health values of the patient.³²

The 2021 Scientific Statement on MCs-AMI provides timely and clinically relevant guidance for physicians and other clinicians involved in the management of this extremely high-risk patient population. The authors are to be congratulated for putting forth guidance for managing such a complex disease space with a limited evidence base on which to put forth effective treatment strategies. The rarity and high mortality of these conditions do not readily lend them to the constructs of randomized controlled trials. Therefore, the clinical gaps in knowledge that persist across the severity spectrum of MCs-AMI should spur the development of innovative methods in how we garner reliable and high quality data to advance patient care. Building on more than two decades of efforts to enhance care delivery models for various cardiovascular conditions, through Get With The Guidelines® and other quality improvement initiatives, the AHA is ideally suited to be at the forefront in developing a national initiative for MCs-AMI. In this model, real time de-identified data from hospitals caring for patients afflicted with these syndromes would contribute to a collaborative registry (Figure 1). Knowledge gathered from this information has the potential to facilitate the development of pragmatic clinical trial designs ultimately to better inform clinical practice. Through the continued collaboration between professional societies, industry, payers and regulatory stakeholders, such an initiative could serve as an invaluable resource for current and emerging therapies in a disease space that continues to be challenged by poor outcomes. Perhaps, this remains the strongest message left behind from this comprehensive guidance document.

Figure