Successful Cardiac Arrest Resuscitation?
Congratulations, but You're Not Done
BY JAMES R. ROBERTS, MD
The goal of cardiac arrest resuscitation is to minimize downtime and obtain and support the return of spontaneous circulation. Once the heart is beating and the patient has at least a palpable blood pressure, most emergency physicians think their clinical tasks are essentially finished, congratulating themselves on a successful resuscitation.
But the next step should be an attempt to ferret out the cause of the cardiac arrest, obtain basic blood work, repeat the electrocardiogram, perhaps initiate hypothermia, consult cardiology, and expedite transfer to the coronary care unit. Other interventions, such as IV fluids, vasopressors, and antiarrhythmics, are occasionally required, but unfortunately, the long-term survival rate for out-of-hospital cardiac arrest patients with normal neurologic function is quite poor.
Approximately 350,000 patients experience out-of-hospital cardiac arrest (OHCA) in the United States each year. (Circulation. 2018;137: e67; http://bit.ly/2Z51wVb.) They have a plethora of causes, some directly related to the heart but others with the heart as a target of other dysfunctions, such as cardiac arrest after pulmonary arrest. It may not be possible to determine the cause of cardiac arrest in the ED. Acute myocardial infarction is one common cause of OHCA, and this is more common in patients who have post-arrest cardiac arrhythmias, a new left bundle branch block, or an obviously abnormal ECG suggesting acute MI. Coronary angiography and revascularization are the standard of care for an acute MI, but the efficacy of these interventions is uncertain when performed in the absence of hard data confirming acute MI as the cause of arrest. Even when the cardiac arrest is due to myocardial infarction, it is not uncommon for the initial post-resuscitation ECG to lack obvious or classic findings.
A number of studies have attempted to clarify the role of acute cardiac angiography after out-of-hospital cardiac arrest, but this is a difficult concept to study with rigor. Data on pre-arrest symptoms or even a medical history and accurate downtime are difficult to obtain. Some studies of post-arrest cardiac catheterization have included in-hospital cardiac arrest or patients without definite evidence of acute MI on a post-resuscitation ECG. Another confounding variable is that an ECG suggestive of an acute MI post-arrest does not necessarily mean coronary occlusion, and a nonspecific ECG can initially be seen after a bona fide MI. Suffice it to say that acute coronary artery occlusion is poorly predicted by clinical and ECG findings in the immediate post-arrest scenario. Some studies have also considered an intervention within 24 hours similar to one performed immediately after resuscitation.
Read a fantastic recent article discussing these concepts in detail: Circulation. 2019;139:e530; http://bit.ly/2IpOOe0.
Early Coronary Angiography and Survival after Out-of-Hospital Cardiac Arrest: A Systematic Review and Meta-Analysis
Khera R, CarlLee S, et al.
This recent review addresses immediate cardiac catheterization to evaluate patients who have been resuscitated from OHCA. This intervention has been studied in some depth in the past, and it has generally been concluded that such early intervention is worthwhile and associated with improved long-term survival in those with an acute MI. Data and consensus on non-STEMI arrest are less robust, so the role of cardiac catheterization remains uncertain, though numerous articles of varying quality deal with the subject. These authors searched electronic databases from 1990 to 2017 that included early coronary angiography, defined as within one day of cardiac arrest, compared with a control group that did not have this intervention. The goal was to evaluate rapid cardiac catheterization with survival outcome. More than 8,000 studies were identified, but only 17 were selected for meta-analysis because of various exclusions.
The use of this early invasive strategy for patients with OHCA is a particularly difficult subject in resuscitated patients who are without obvious signs of ischemia on a post-resuscitation ECG. In fact, an immediate 12-lead ECG is unreliable in diagnosing AMI in resuscitated patients. False-positive and false-negative ECGs may be seen. And merely restoring myocardial perfusion does not necessarily mean better neurological outcome. Subjects were those resuscitated from OHCA who received cardiac catheterization within 24 hours of onset, particularly evaluating final neurological outcome. The control group did not undergo early cardiac catheterization, but they could have had the procedure more than 24 hours after cardiac arrest. The authors looked at in-hospital survival, 30-day survival, and in-hospital survival with favorable neurological outcome. Neurological outcome was evaluated via a modified Rankin scale and a cerebral performance category score, which are commonly used to assess neurological outcome at discharge.
Cardiac catheterization was obtained in 44 percent of the 14,972 patients with OHCA; 66 percent of patients did not undergo the procedure. The age range was 57 to 67, with a median age of 62. Patients with an initial shockable rhythm ranged from 26 percent to 100 percent. The rate of STEMI was 32 percent, but it ranged from zero to 100 percent. Cardiac catheterization was performed in about 18 percent of patients who did not have a STEMI on their presenting ECG.
The analysis demonstrated a statistically significant positive association from the use of early cardiac catheterization and survival to discharge, as well as survival with a favorable neurological outcome, though a wide range of variables were noted. Early cardiac catheterization in studies that only included patients with an initial shockable rhythm was associated with a twofold increase in the odds of survival to discharge and a 50 percent increase in the odds of a favorable neurological outcome.
The authors stated that patients with OHCA caused by an initial shockable rhythm, such as ventricular fibrillation, were more likely to have an MI as the underlying ideology and would have a greater benefit from cardiac catheterization. Likewise, they felt that patients with STEMI would also have a better outcome because this would include only those with treatable coronary lesions. This was not a randomized study, but the authors said their findings support early cardiac catheterization to improve survival in patients with OHCA.
Comment: I could not ascertain in this study if a stent or angioplasty was performed whenever angiography identified a discrete coronary lesion. I would assume so. I also could not figure out how patients were chosen to include only those with a presumed cardiac cause for their cardiac arrest, how many patients with non-STEMI were included, and whether post-cardiac arrest hypothermia was a concomitant intervention. The time from cardiac arrest to intervention was not discussed either. Nonetheless, it is the largest analysis to date, and it showed a favorable outcome for post-cardiac arrest.
Using cardiac catheterization immediately or within 24 hours for survivors of OHCA has been evolving since the 1990s. It does not seem that waiting 24 hours v. immediate cardiac catheterization makes much of a difference. Spaulding, et al., performed angiography on 84 consecutive patients who had no obvious noncardiac cause for the arrest; 48 percent had coronary artery occlusion. These authors treated all comers, and found that clinical evaluation and ECG findings were poor indicators of significant coronary artery occlusion. Twenty-eight percent of patients in this study had normal coronary arteries or clinically insignificant lesions. (New Engl J Med. 1997;336:1629; http://bit.ly/2G7CFHJ.)
Cardiac catheterization following cardiac arrest for all subjects except those with obvious noncardiac causes (trauma, respiratory arrest) is an increasingly common intervention that is not reserved only for patients with obvious STEMI on post-arrest ECG. Some facilities perform catheterization for all patients with ROSC. Studies have shown that about 70 percent of patients with VF have significant coronary lesions upon catheterization regardless of post-arrest ECG. Some centers do angiography even for comatose patients when a cardiovascular etiology is suspected, performing cardiac catheterization in patients who are hemodynamically unstable.
It should be noted, however, that the results of cardiac catheterization in those without obvious acute MI on ECG have not been so impressive. (Intensive Care Med. 2015;41:856, New Engl J Med. 2019;380:1397; http://bit.ly/2G4dDJE.) Dumas, et al., in the widening PROCAT registry found a culprit coronary lesion requiring angioplasty in nearly one-third of patients with OHCA without STEMI on ECG. In patients with no STEMI on post-resuscitation ECG, cardiac catheterization was associated with a nearly twofold increase in favorable outcomes. Note that a shockable rhythm was more highly associated with a culprit lesion that could be fixed by stenting. (JACC Cardiovasc Interv. 2016;9:1011; http://bit.ly/2GfBAid.)
The role of cardiac catheterization post-recovery from OHCA is quickly evolving to the point where it is reasonably supported in all patients except those with an obvious noncardiac cause. The benefit of immediate cardiac catheterization rather than within 24 hours of arrest is unclear, but it appears reasonable that the emergency clinician should initiate contact with cardiology and the cardiac catheterization laboratory following resuscitation of all eligible patients.
This protocol is not widely disseminated and often not even considered in the ED once ROSC has been established. It is also unclear what to do in hospitals without cardiac catheterization capability, but immediate cardiac catheterization after ROSC has significant support in the medical literature, and organizing this may become yet another new task for first-line providers. Why not do it directly from the ED as we do with acute MI?
Dr. Roberts is a professor of emergency medicine and toxicology at the Drexel University College of Medicine in Philadelphia. Read the Procedural Pause, a blog by Dr. Roberts and his daughter, Martha Roberts, ACNP, PNP, at http://bit.ly/EMN-ProceduralPause, and read his past columns at http://bit.ly/EMN-InFocus.
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