Striking the balance in admissions with non-ST-segment elevation myocardial infarction requiring advanced respiratory support

This editorial refers to ‘Incidence, predictors andprognosis of respiratory supportin non-ST segment elevationmyocardial infarction’, by T. Mektus et al. https://doi.org/10.1177/2048872620919947. Respiratory insufficiency is the most common indication for cardiac intensive care unit (ICU) admission and is associated with poor outcome, comprising over 25% of admissions with a mortality of over 20%.1 Although these data are intuitive given the burden of out-of-hospital cardiac arrest and cardiogenic shock in the cardiac ICU, the impact of advanced respiratory support on outcome persists even once the adjustment is made for these diagnoses and severity of illness.2 In acute coronary syndrome specifically, advanced respiratory support is associated with increased length of stay and mortality.2,3 Metkus and colleagues conducted a retrospective cohort study of 4 152 421 NSTEMI hospitalizations who required either non-invasive or invasive ventilatory support during the first 24 h of admission for non-ST-segment elevation myocardial infarction (NSTEMI) using the US National Inpatient Sample database.2 The authors demonstrate that although respiratory support is required in the minority of patients, the need for non-invasive ventilation (NIV) or invasive mechanical ventilation (IMV) in patients with NSTEMI is both increasing in incidence and associated with an adverse prognosis. The need for ventilation correlated closely with other factors known to confer a worse prognosis or ICU admission in NSTEMI.4 Notably, despite the role of early coronary angiography, with follow on revascularization where appropriate, being well established in international guidelines,5,6 patients receiving respiratory support were less likely to undergo revascularization. Moreover, those patients that underwent revascularization despite advanced respiratory support had significantly lower mortality. The requirement for respiratory support in NSTEMI is a surrogate for both comorbid disease and severity of illness. In a non-randomized group, the reduced rates of coronary angiography reported in this study may reflect selection bias, with coronary angiography being denied to the patients who are most unwell. However, when patients with in-hospital cardiac arrest and cardiogenic shock were excluded from the analysis, access to coronary revascularization independently reduced the odds of mortality by 67%. These data may also reveal discrepancies in care with regards to patients being admitted to a facility with no coronary angiography capability, and/or patients being deemed too unwell to transfer to a percutaneous coronary intervention (PCI) centre; respiratory support, specifically non-invasive support can present logistical challenges around patient transfer both to the catheter lab and between hospitals. Nonetheless, if we believe that early angiography and revascularization reduces the burden of mortality in this group of high-risk patients, then models of care that deliver NSTEMI patients to centres that are able to provide both ventilatory support and early revascularization and to support them whilst in the catheter lab would seem desirable. It is important to also consider the impact of ICU admission in itself, by virtue of the requirement for advanced respiratory support. Increasingly, intensive care management is shifting towards a ‘less is more’ mantra. Sequential randomized trials have demonstrated that an intensive management approach may not confer outcome benefit but merely increase potential harm.7 However, the ICU community must be careful to balance limiting iatrogenic harm through exuberant ventilation, fluid resuscitation, and sedation whilst ensuring that those interventions that confer true outcome benefit such as early coronary revascularization in high-risk NSTEMI are considered. Specialist intensive care is needed to both optimize ventilation and manage the associated pneumonia and sepsis identified in this study. However, admission to a non-cardiac ward is associated with a lower rate of angiography following admission with NSTEMI8 and early involvement of a cardiologist is associated with the increased use of guideline-recommended management.9 It is imperative that, as many intensive care units move towards a ‘closed’ model of care, evidence-based interventions are considered through close collaboration with specialty cardiology where this is not embedded in routine practice. The authors note that the use of NIV and IMV in NSTEMI is increasing over time after a period of initial decline at the national level. During the timescale of this study the ‘early invasive’ approach to NSTEMI, characterized by early angiography and revascularization with PCI or CABG, has been widely adopted across healthcare systems.10 In parallel to this, the complexity of cases that may gain access to the cardiac catheter laboratory has increased.11 The improving outcomes in the non-invasively ventilated cohort in this study likely point to better patient selection and multi-professional care of these patients at an ICU level. The poor outcomes in the invasively ventilated population may highlight an opportunity to better identify those patients who are unlikely to benefit from IMV in the context of NSTEMI or in whom early revascularization is imperative to optimize outcome. Future studies may also examine methods to mitigate ventilator-associated pneumonia and optimal ventilatory strategies in the IMV supported patients. In essence, these data speak to the need for clinicians and healthcare systems alike to provide specialist cardiac critical care, through the growth of cardiovascular critical care units staffed by acute cardiovascular care specialists, that this Journal12 and others1,13 have described. Whilst the majority of patients with NSTEMI are unlikely to require critical care, for those who do, expertise in interventional cardiology, heart failure, and critical care will be required given the burden of cardiac and non-cardiac respiratory failure and the complexities of management.1,2 Regional networks need to ensure equity of access to these specialized units and the associated multi-professional team for patients at highest risk of poor outcome i.e. those with ACS requiring IMV (Figure 1). Only with hybrid training in acute cardiovascular care will we account for the broad spectrum of expertise required in the contemporary intensive cardiovascular care unit to strike the balance between evidence-based practice in both the cardiology and critical care space and improve outcomes for our patients. Model NSTEMI network. ACCU, acute cardiovascular care unit; ICU, intensive care unit; IMV, invasive mechanical ventilation; NIV, non-invasive ventilation; PCI, percutaneous coronary intervention. Model NSTEMI network. ACCU, acute cardiovascular care unit; ICU, intensive care unit; IMV, invasive mechanical ventilation; NIV, non-invasive ventilation; PCI, percutaneous coronary intervention. Conflict of interest: none declared. The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal: Acute Cardiovascular Care or of the European Society of Cardiology.