By Jeffrey Zimmet, MD, PhD

Associate Professor of Medicine, University of California, San Francisco; Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center

SYNOPSIS: In a trial of immediate vs. delayed coronary angiography for resuscitated out-of-hospital cardiac arrest, researchers found no significant benefit on 30-day mortality.

SOURCE: Desch S, Freund A, Akin I, et al. Angiography after out-of-hospital cardiac arrest without ST-segment elevation. N Engl J Med 2021; Aug 29. doi: 10.1056/NEJMoa2101909. [Online ahead of print].

Myocardial infarction is the most common cause of out-of-hospital cardiac arrest (OHCA), in those cases for which a cardiac cause has been identified. One might expect expedient cardiac catheterization and intervention could affect mortality beneficially in this setting. In patients presenting with ST-elevation after successful resuscitation, immediate coronary angiography is the norm. What to do with the larger subset of patients without diagnostic ECGs has been the subject of considerable uncertainty. The authors of a prior study, the 2019 COACT trial, examined the effect of immediate angiography in patients with cardiac arrest with an initial shockable rhythm and demonstrated no improvement in survival at 90 days.1

Desch et al enrolled 554 patients with resuscitated OHCA who did not record ST-elevation on initial ECG. Of these, 281 were assigned to receive immediate angiography, which occurred in all but 13 of these patients, at a mean of 2.9 hours following cardiac arrest.

The remaining 273 patients were assigned to delayed angiography, which for the purposes of the trial meant transfer to the ICU for management and further diagnostics. These patients could be sent for cardiac cath after a minimum delay of 24 hours. In practice, 62.2% of patients in this group underwent coronary angiography, at a mean of 46.9 hours after cardiac arrest. Unlike the COACT trial, both shockable and non-shockable rhythms were included; just over half of the entire cohort presented with initial shockable rhythms. Interestingly, coronary lesions were identified that were “considered to be responsible for triggering cardiac arrest” in 38.1% of patients in the immediate angio group and in 43% of the delayed angio patients. Overall, 39.6% of patients underwent coronary revascularization by percutaneous coronary intervention (PCI). Most patients underwent targeted temperature management, with a longer time to initiation of temperature control in the immediate angiography group (median time = 153 minutes vs. 119 minutes for delayed angio patients).

At 30 days, the primary endpoint of all-cause mortality had occurred in 54% of patients in the immediate angio group vs. 46% in the delayed angio group, a difference that did not reach statistical significance. The cause of death was severe neurologic injury or circulatory collapse in most patients. The composite secondary endpoint of all-cause death or severe neurologic deficit was significantly more frequent in the immediate angiography group, with a hazard ratio of 1.16. Safety endpoints did not differ significantly between groups, including bleeding, stroke, or kidney failure, suggesting there was not an increase in harm associated with procedural complications of early angiography. The authors concluded that in patients successfully resuscitated from OHCA without ST-segment elevation, immediate coronary angiography did not show benefit over a delayed or selective approach in terms of 30-day mortality.

COMMENTARY

These authors did not address a sizable proportion of OHCA patients. Specifically, patients with ST-segment elevation after resuscitation or those who are hemodynamically unstable or record recurrent ventricular arrhythmias were excluded from this investigation. These patients almost certainly will continue to go to the cath lab early after presentation. For patients who do match the general inclusion criteria, several lessons are clear. Early mortality for these patients remains quite high, with most succumbing to the effects of anoxic neurologic injury. A minority of study patients were judged to have a culprit coronary lesion at the time of angiography. In this context, the neurologic damage may very well overwhelm any benefit of early coronary diagnostics.

Although approximately 40% of patients enrolled in this trial were labeled with a coronary culprit lesion, this conclusion is questionable and potentially misleading. A similar percentage of patients underwent PCI, but the authors did not explain how many of these presented with acute thrombotic coronary occlusion — the type of lesion where PCI might be expected to help prevent mortality early. In the similar COACT trial, where the inclusion of only shockable rhythms might be expected to result in a population enriched for acute myocardial infarction, only 5% of patients were reported to have acute thrombotic occlusion, with an additional 15% showing lesions that were judged to be acute but not occlusive. Indirect evidence suggests the numbers of patients in the Desch et al study who exhibited ongoing myocardial damage at the time of presentation was low. For example, peak biomarker values were modest, with a peak median troponin I in the delayed angiography group of only 1.10 micrograms/liter.

These observations only cement the overall takeaway message of these trials, which is that, in most cases of OHCA without ST-segment elevation or initial hemodynamic instability, patients can be stabilized in the ICU first, rather than rushing to the cardiac catheterization laboratory early in their course. Later selective coronary angiography after initial stabilization will continue to play a role in the management of these patients.

REFERENCE

  1. Lemkes JS, Janssens GN, van der Hoeven NW, et al. Coronary angiography after cardiac arrest without ST-segment elevation. N Engl J Med 2019;380:1397-1407.