Increased Mortality Risk Posed by Shock May Not Affect Long-term Survival

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Elderly patients with non-ST-segment elevation myocardial infarction (NSTEMI) who present with cardiogenic shock have an early increased risk of death through 6 months post-discharge, according to a study published online June 10, 2013, ahead of print in the American Heart Journal. However, beyond that time frame, mortality rates are comparable to patients without shock.

Matthew T. Roe, MD, MHS, of Duke Clinical Research Institute (Durham, NC), and colleagues evaluated data from 42,656 NSTEMI patients older than 65 years who were enrolled in the CRUSADE National Quality Improvement Initiative and received treatment at 448 US hospitals from 2003 to 2006. Patients were categorized according to whether they had cardiogenic shock (n = 2,001) or not (n = 40,655).

Less Revascularization, More Early Death for Shock Patients

In-hospital mortality was higher in patients with cardiogenic shock vs. no shock (39.1% vs. 4.5%; P < 0.001). Similarly, 4-year survival rates were lower in those with shock compared to those without shock (48.1% vs. 56.5%; P < 0.001). While survival curves diverged early after discharge with lower survival for patients with shock, the curves appeared to become parallel at approximately 6 months with only a modest divergence thereafter (log-rank P = 0.02).

In sensitivity analysis of survival, the risk of mortality through 6 months post-discharge was higher for patients who developed in-hospital shock (HR 1.65; 95% CI 1.40-1.93); however, conditional on 6-month survival, long-term mortality risk was similar between those who did and did not develop shock (HR 1.02; 95% CI 0.88-1.19).

The mean number of days out of the hospital was lower through 4 years for patients with shock compared with those without shock (829 ± 537 days vs. 929 ± 498 days; P < 0.001). However, there was no difference between the 2 groups for those who survived past 6 months (904 ± 423 days vs. 932 ± 428 days; P = 0.13).

Compared with patients presenting without shock, those with shock were less likely to undergo diagnostic cardiac catheterization and PCI, but more likely to undergo CABG (table 1).

Table 1. Treatment Differences

Cardiogenic Shock
(n = 2,001)

No Shock
(n = 40,655)

Cardiac Catheterization

53.0%

60.6%

PCI

25.5%

31.9%

CABG

13.4%

8.6%


P < 0.001 for each comparison.

Revascularization use was more frequent in patients who survived to discharge than in those who died (44.5% vs. 41.4%; P = 0.02), but the use of evidence-based secondary prevention therapies at discharge, including aspirin, statins, beta-blockers, and ACE inhibitors, or angiotensin receptor blockers, was lower in the shock group.

Six-Month Window Critical for Survival

"We know that there certainly is increased risk for patients with cardiogenic shock that persists even after discharge," study coauthor Akshay Bagai, MD, MHS, also of Duke Clinical Research Institute, told TCTMD in a telephone interview. "However, this study demonstrates that those who survive the high-risk period have a risk of death similar to heart attack patients who never had shock. So, that’s good news because I think we really have not known until now whether the risk for these patients continued indefinitely."

The study authors say the vulnerability that shock patients experience during the first 6 months may be due to having lost a large amount of viable myocardium, as well as to the deleterious effects of being in an acute inflammatory state.

"Why it’s 6 months and not 9 months or a year is hard to speculate on, but that is what the data show and that’s where the curves start to become parallel," Dr. Bagai said. "The resolution of the inflammatory state is what lowers the risk. Also, the fact that they have survived the 6 months indicates that they are in a good overall health state with regard to future outcomes."

Dr. Bagai said more research is needed to find ways to lower the early risk and give patients a greater chance of surviving beyond the 6-month window.

"We should invest in more treatments that would lower the risk of death early on after cardiogenic shock," he said. These may be supportive therapies or medical therapies aimed at either preventing or managing shock, he added.

Dr. Bagai said he believes studies like this are important because patients with cardiogenic shock are not well represented in clinical data due to their frequent exclusion from a wide variety of trials and interventions.

Data Magnify Poor Prognosis for NSTEMI Patients

In a telephone interview with TCTMD, Kishore J. Harjai, MD, of Columbia University Medical Center (New York, NY), said he was most struck by the fact that even among those without shock, only 60% received cardiac catheterization.

"That is kind of an eye-opener and it makes you wonder why [they] are not getting a cardiac catheterization during their hospital stay in the face of so many randomized trials showing that invasive therapies are very clearly beneficial in this patient population," he said. "Also, I think another big message from this is that even if you don’t have cardiogenic shock, the long-term outcome for NSTEMI is very poor."

The study authors hypothesize that advanced age and greater comorbidities, as well as reluctance on the part of clinicians to perform invasive procedures in the absence of long-term survival data or recommendations from national guidelines likely contribute to the low utilization of invasive therapies.

Dr. Harjai said he agrees with the study authors, however, that age-specific recommendations for the treatment of patients with NSTEMI and shock are not a reasonable approach and guideline recommendations should reflect that point. Both the 2013 ACCF/AHA and ESC guidelines for the management of STEMI no longer differentiate the recommendation for emergency revascularization in cardiogenic patients with shock based on age, according to Dr. Roe and colleagues. However, there are no recommendations for specific treatment approaches for patients with NSTEMI and shock in the unstable angina/NSTEMI guidelines.

 


Source:
Bagai A, Chen AY, Wang TY, et al. Long-term outcomes among older patients with non-ST-segment elevation myocardial infarction complicated by cardiogenic shock. Am Heart J. 2013;Epub ahead of print.

Disclosures:

Dr. Roe reports receiving research funding from Eli Lilly, KAI Pharmaceuticals, and Sanofi-Aventis; participating in educational activities for AstraZeneca and Janssen Pharmaceuticals; and serving as a consultant for Bristol Myers Squibb, Daiichi-Sankyo, Eli Lilly, GlaxoSmithKline, Janssen Pharmaceuticals, Merck, and Regeneron.

Drs. Bagai and Harjai report no relevant conflicts of interest.

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