Out of Hospital Cardiac Arrest – The Role of The Cardiac Catheterization Laboratory

From Christian Eriksen during the 2020 European Football Championship, to Damar Hamlin during the National Football League regular season in January 2023, and Bronny James during a practice session in July 2023; all were notable events that have contributed to public awareness on out of hospital cardiac arrest (OHCA). Despite the rapid and continued advances in modern medicine, prognosis remains poor in the absence of high-quality bystander cardiopulmonary resuscitation (CPR), a shockable rhythm, prompt return of spontaneous circulation (ROSC), and evidence of ST-elevation acute coronary syndrome (ACS) on post-arrest electrocardiogram (ECG) prompting rapid revascularization. Many of these factors relate to underlying coronary artery disease and shock, highlighting the importance of early integration of the cardiac catheterization laboratory into the post-arrest protocol. The American Heart Association (AHA) Scientific Statement, titled "The Cardiac Catheterization Laboratory Management of the Comatose Adult Patient with an Out of Hospital Cardiac Arrest" aims to provide contemporary data as a guide for clinicians when approaching the post-cardiac arrest patient, and the role of the cardiac catheterization laboratory in OHCA. The authors review current guidelines and clinical trials evaluating outcomes following OHCA based on different patient characteristics and clinical risk profiles, utilization of the cardiac catheterization laboratory, and mechanical circulatory support-associated CPR.

Sudden cardiac arrest remains a leading cause of death in the United States, with about 357,000 annual events, accounting for almost 50% of all cardiovascular deaths.^(1-3) Although the rate of survival to discharge remains low, there is significant variation in the true survival rate by both demographic (e.g., gender, ethnicity) and clinical (e.g., early high-quality bystander CPR, the presence of a shockable rhythm, prompt ROSC, and ST segment elevation of post-arrest ECG prompting rapid revascularization) factors.^{(4, 5)} Clinical risk prediction tools, including the Cardiac Arrest Hospital Prognosis (CAHP) score, Targeted Temperature Management (TTM) score, and MIRACLE₂ score, have been created to aid in prognostication around the time of OHCA, but are limited given the heterogeneity of patients presenting with OHCA and their dynamic clinical course.^(6-8)

Early invasive assessment of patients who have achieved ROSC and found to have ST elevation on their post-arrest ECG is guideline-recommended, and in those otherwise viable patients with cardiogenic shock, ongoing electrical instability, or suspicion for ongoing infarction, there is less ambiguity, and an early invasive strategy should strongly be considered. The decision is difficult in many cases for patients who have not achieved ROSC or who remain comatose given unknown neurological prognosis.^{(9, 10)} A low CAHP score, early bystander CPR, time to ROSC <30 minutes, initial shockable rhythm, and younger age without significant renal dysfunction are all favorable prognostic indicators of good neurological recovery and should be considered when evaluating those patients with unknown neurological prognosis and ST elevations on post-arrest ECG but the majority of patients do not present with many or all of these positive findings.⁽⁶⁾

The authors also aim to offer guidance in these difficult circumstances, where the role of the cardiac catheterization laboratory is unclear, and the decision of action or inaction must be made based on incomplete or conflicting information. Among patients without ST elevation on post-arrest ECG, observational studies suggest benefits associated with early invasive management, but these have been limited by selection bias. Randomized controlled trials overcome such biases and have shown no significant difference comparing early vs. delayed invasive assessment in that subset of patients. Such differences in outcomes highlight the challenge of bedside decision-making in OHCA and suggest the need for individualized clinical judgement which will result in some success, but unfortunately coupled with inevitable errors of commission or omission.^(11-15)

Current capabilities of the cardiac catheterization laboratories vary by location and institution. Most provide diagnostic coronary angiography, revascularization, and perhaps intracardiac hemodynamic assessment, but not all offer the full gamut of services, including mechanical circulatory support, such intra-aortic balloon pump (IABP), percutaneous right- and left-sided mechanical ventricular assist devices (VADs), and emergent extracorporeal membrane oxygenation (ECMO). As such, all individuals participating in the resuscitation and management of OHCA patients must be aware of the respective local expertise in order to make appropriate decisions when faced with an OHCA case.

While IABP use has declined in OHCA, the use of mechanical assist devices such as Impella and ECMO has increased, in particular the use of ECMO as part of extracorporeal CPR (ECPR) for refractory cardiac arrest or for profound cardiogenic shock post-ROSC.^(16-18) Nevertheless, the technical and financial resources to develop and maintain quality in such programs is immense. Proceduralists recognize that cannulation for ECPR is not exceptionally challenging, and the main limitation of wide dissemination of ECPR as a viable strategy is the resources necessary to achieve the extremely rapid cannulation times as suggested by international consensus guidelines.^(19-21) ECPR programs are further challenged by the considerable multidisciplinary expertise and infrastructure necessary to subsequently manage these patients. As such, the observational data supporting the use of ECPR must be interpreted with caution given the lack of generalizability to most hospitals.

Studies assessing the benefit of ECPR in cardiogenic shock and OHCA are ongoing. Until these findings are unveiled, the AHA guidelines continue to provide a class IIb indication for ECPR, stating it can be considered as a rescue therapy in select patients if the suspected etiology of cardiac arrest is potentially reversible and it can be performed expeditiously by providers who are adequately trained in its use.⁽⁹⁾ If we are to improve outcomes in OHCA, we must commit to and emulate the success of such programs by properly resourcing specialized in-hospital teams with a centralized emergency medical services, and alert programs to coordinate rapid triage and transfer of potentially eligible patients.

The assessment for obstructive coronary artery disease and initiation of mechanical circulatory support will remain the most common roles for the cardiac catheterization laboratory in OHCA, but consideration must also be given to other disease processes, beyond coronary artery disease, where advanced resuscitation can occur. These include cardiac tamponade and catheter-based therapies for pulmonary embolism. Systemic administration of tissue plasminogen activator (tPA) remains a cornerstone of treatment of massive pulmonary embolism with or without cardiac arrest, however a growing body of evidence suggests the need for percutaneous mechanical thrombectomy or catheter-directed thrombolysis in select patients who are not candidates for systemic tPA,^{(22, 23)} with the possibility of right ventricular or biventricular mechanical circulatory support, if required.

In a patient-centered and practical approach, those seeking to develop ECPR programs should consider a stepwise approach and consider that there are many patients who decompensate in the hospital. For these, there is less ambiguity in decision-making and greater clarity on how to treat. Rapid response teams can bring the full institutional capabilities to the patient regardless of whether the arrest occurs on the wards, intensive care unit, operating room, or during a pulmonary embolectomy in the interventional radiology suite. Providing such expertise 24 hours a day and 7 days a week is certainly a prelude to creating such programs and provide an opportunity to develop the necessary collaborations.

OHCA remains a catastrophic condition. The cardiac catheterization laboratory has become a critical component in the chain of survival in select patients, whether it be through coronary angiography and percutaneous coronary intervention, mechanical circulatory support, or other invasive procedures. The AHA Scientific Statement, titled "The Cardiac Catheterization Laboratory Management of the Comatose Adult Patient with an Out of Hospital Cardiac Arrest" provides a concise summary of consensus guidelines and available data on OHCA to help guide both individual and multidisciplinary decision-making.