Respiratory Issues Dominate NACMI Risk Score for COVID/STEMI Mortality

Eight clinical variables can serve as useful predictors of in-hospital mortality in STEMI patients with a current or recent COVID-19 infection, new data from the North American COVID-19 Myocardial Infarction (NACMI) registry suggest.

The predictors provide a reference tool, which investigators led by Payam Dehghani, MD (Regina General Hospital, Canada), say could help in allocation of resources.

“The pandemic has unsurfaced critical stress points within the healthcare system forcing clinicians to triage patients that are more likely to survive so that resources can be allocated accordingly,” they write in the paper, published online July 9, 2022, in JSCAI. While there are other scores for predicting in-hospital mortality in patients with COVID-19, the NACMI score is the first to focus on those who are also hospitalized with STEMI.

Of 24 clinical variables identified, the ones most associated with in-hospital mortality were: respiratory rate > 35 breaths/minute, cardiogenic shock, oxygen saturation < 93%, age > 55 years, infiltrates on chest X-ray, kidney disease, diabetes, and dyspnea.

Commenting for TCTMD, Jay Giri, MD (Hospital of the University of Pennsylvania, Philadelphia), noted that the risk score is the latest of several unique contributions that the NACMI registry has made to furthering understanding of patients with STEMI and COVID, including a recent paper documenting atypical rates of nonculprit STEMI in women.

“One of the advantages with this registry is that the elements are more clinically rich than in much of the other literature around COVID, although the registry is on a much smaller scale,” he said. As for the clinical usefulness of the score, Giri said while it is about as solid as a risk score derived from a cohort can be, it lacks both internal and external validation, which perhaps could be a future goal for these or other investigators.

“While this is great to have, we find that very few of the risk scores that end up out there in the literature are being used in everyday clinical practice,” Giri added. “That’s not unique to this score, it’s just something that plagues risk scores in general.”

Senior study author Timothy Henry, MD (The Christ Hospital, Cincinnati, OH), told TCTMD that as long as COVID continues to stick around, knowing whether a patient is low or high risk for in-hospital mortality speeds up decision-making in a way that wasn’t possible 2 years ago.

“If we had this score in March 2020, it would have been hugely helpful,” Henry said. “COVID has changed, and the good news is there's not as many very sick people with COVID and STEMI in the hospital, but not everything about COVID and STEMI is self-evident. We believe the score is helpful and reliable for clinicians.”

NACMI Score Derivation and Performance

Dehghani and colleagues analyzed baseline demographic, clinical, and procedural data from 425 patients (72% male; 46% white) with COVID-19 and STEMI from 64 sites in the US and Canada who were enrolled in the NACMI registry between April 2020 and June 2021. All had tested positive for COVID-19 during or within 4 weeks before their index STEMI hospitalization.

The in-hospital mortality rate was 28%. Patients who survived the hospitalization (n = 307) were less likely than those who did not survive (n = 118) to be diabetic, hypertensive, or have a history of stroke. They also were less likely to have cardiogenic shock or cardiac arrest prior to PCI and to have developed STEMI while hospitalized for COVID. Overall, survivors were more likely than those who died to have received primary PCI (68% vs 46%; P < 0.001).

We find that very few of the risk scores that end up out there in the literature are being used in everyday clinical practice. Jay Giri

The eight clinical variables predictive of mortality were each given a weighted integer, which ranged from a low of 3 for diabetes and dyspnea to a high of 8 for respiratory rate > 35 breaths/minute and cardiogenic shock.

A total score of < 6 indicated a low risk of in-hospital mortality, while scores of 6 to 11 indicated moderate risk, 12 to 16 indicated high risk, and > 17 reflected a very high risk. In-hospital mortality occurred a rate of 3.6% in the low-risk group, 15% in the moderate-risk group, 35% in the high-risk group, and 60% in the very-high-risk group.

Dehghani and colleagues say the risk model works well in comparison with similar tools used to predict ACS outcomes, including the ACTION Registry-Get With the Guidelines (GWTG) risk score and a model derived from the Global Registry of Acute Coronary Events (GRACE).

Respiratory Issues Driving Risk?

Prior to COVID, contemporary analyses suggests that in-hospital STEMI mortality was approximately 2%, but increased to 20% or more when complicated by cardiogenic shock, cardiac arrest, or both, the researchers note. In the NACMI registry, cardiogenic shock was present in 16% and cardiac arrest in 9%.  

Giri said that the all-comer STEMI mortality rate in the National Cardiovascular Data Registry (NCDR) is under 4%. Getting it down to that rate “has been one of the biggest successes in cardiovascular care over the last four decades,” he said. “What these NACMI data have demonstrated is that the mortality rate in these patients with COVID is insanely higher, but . . . it’s not just being driven by patients experiencing cardiogenic shock. That’s where the risk factors that compile this score really stand out. It seems like the respiratory issues are potentially driving this risk, with four of the eight factors they identified being respiratory issues.”

Dehghani and colleagues note that some have “suggested that this is a unique STEMI phenotype in patients with COVID-19 in which cardiac disease is a secondary manifestation of a systemic pulmonary disease pattern.” Furthermore, they say there appears to be an interplay of multiple pathobiological pathways “that are concomitantly activated” in patients who have both STEMI and COVID-19.

“One of the things we’ve learned is that a main reason why COVID-positive patients have such higher mortality with STEMI is because they don’t just have cardiac disease,” Henry said. “They have multisystem disease.”

We believe the score is helpful and reliable for clinicians. Tim Henry

Given the fact that the risk score was derived from a patient cohort between spring 2020 and the summer of 2021, the next question is whether it would have the same weight in today’s patients, many of whom have been vaccinated and/or exposed to COVID or have tested positive for COVID a previous time, Giri observed.

“It's really hard to believe that the numbers would hold up exactly the same right now as they did earlier in the pandemic, but it's impossible to know that for sure,” he said.

Henry agreed it’s too early to know if the score will need to be adjusted due to the changing populations, though he said the current evidence suggests that while COVID STEMI patients in 2022 are typically lower risk than those in 2020 and 2021, the risk factors themselves haven’t changed.

“The score remains predictive even though the risk in the population has changed,” he observed. “I think that validates the [strength of] the score. We do plan to look at it again, though, once we have over 800 patients enrolled.”