Spectrum of Shock Treated in Contemporary US Practice: Clues From the CCCTN

NEW ORLEANS, LA—Acute MI complicated by cardiogenic shock (AMICS) now makes up less than a quarter of shock cases admitted to cardiac intensive care units (CICUs) in North America, according to registry data from 2017 and 2018. In fact, even within the cardiogenic shock population, only 30% of cases in the database were related to acute MI.

The diversity of clinical presentations and the fact that in-hospital mortality remains high despite advanced therapies speaks to the need to better understand the range of shock types, researchers say.

“I think that this is the beginning of a lot more to come. In a lot of ways, this analysis really generates more questions than it answers,” lead author David Berg, MD (Brigham and Women’s Hospital, Boston, MA), told TCTMD. Still, the study does some hold some clues relevant to practice, he added. “What it tells us is that the paradigm we’ve all had . . . for a long time has been acute myocardial infarction leading to cardiogenic shock. [This analysis says] that’s not the complete picture of cardiogenic shock. It’s a pretty heterogeneous and diverse disease.

“Almost all clinical investigations up until now have really been in AMICS. To really improve outcomes and move the needle, we need to be thinking about these other [groups],” Berg said.

Berg presented the findings today at the American College of Cardiology 2019 Scientific Session and  they were simultaneously published online in Circulation: Cardiovascular Quality and Outcomes.

CCCTN Registry

For their study, the investigators looked at a 2-month “snapshot” of medical admissions from 16 centers participating in the Critical Care Cardiology Trials Network (CCCTN) registry between September 2017 and September 2018. CCCTN is a research network of American Heart Association Level 1 CICUs across the United States and Canada.

There were 3,049 CICU admissions, of which 22% involved shock, defined as sustained systolic BP < 90 mm Hg with end-organ dysfunction attributed to the hypotension.

As noted above, shock etiology was quite varied: though cardiogenic shock predominated at 66%, 7% of cases were distributive, 3% hypovolemic, 20% mixed, and 4% of unknown cause. Cardiovascular comorbidities were similar between patients who had mixed versus cardiogenic shock.

Three in 10 of the cardiogenic shock patients had presented with acute MI, 28% had nonischemic cardiomyopathy, 18% had ischemic cardiomyopathy but not acute MI, and 17% had a cardiac cause apart from primary myocardial dysfunction.

Median CICU stay was significantly longer for patients with shock—whether mixed shock (5.8 days), cardiogenic shock not related to acute MI (4.3 days), or AMICS (4.0 days)—than for those admitted without shock (1.9 days; P < 0.01 for all). In cardiogenic and mixed shock patients, some form of invasive monitoring was employed in two-thirds and a pulmonary-artery catheter in one-third. Almost all patients received vasoactive medications, regardless of whether they had AMICS (92%), cardiogenic shock without acute MI (93%), or mixed shock (98%). Mechanical circulatory support (MCS) was more commonly used in AMICS patients (61%) than in those with cardiogenic shock without acute MI (26%) or mixed shock (23%; P < 0.01).

In-hospital mortality rates were 39% for mixed shock, 31% for cardiogenic shock without acute MI, and 36% for AMICS.

Among the cardiogenic shock patients, those who received MCS—a mix of intra-aortic balloon pump, Impella (Abiomed), TandemHeart (LivaNova), and extracorporeal membrane oxygenation—tended to have worse indices of illness severity. “Consistent with these findings, cardiogenic shock patients treated with MCS versus without MCS had higher in-hospital mortality rates [40% vs 28%], even after adjusting for differences in age, sex, and SOFA score (P < 0.01),” the researchers report.

Targeted Therapy the Goal

Dirk Westermann, MD, PhD (University Heart Centre Hamburg, Germany), commenting on the findings for TCTMD, said that the study gives a broad view of what’s happening across North America.

For him, the most interesting aspect of this data set is the patients with nonischemic cardiomyopathy or ischemic cardiomyopathy without acute MI—together, these make up 46% of the cardiogenic shock group.

“Why is it interesting? Because the way we might treat those people might be completely different,” Westermann said, adding, “When we speak about treatment, be it medical, interventional, or device-related, we obviously need to differentiate and not treat all patients similarly. I think it might be very wise to assess hemodynamics and see where the real problem for the patient is.”

Berg agreed, noting that the new data indicate “there are a lot of patients with preexisting heart failure, underlying cardiomyopathies, that are decompensating further and that’s a huge portion of shock.”

With AMICS, primary PCI is what’s most key, Westermann stressed. “That improves outcome. We know that. . . . But in these patients [without acute MI] primary PCI might not help.”

Asked what might be most helpful for this subgroup, and whether there have been recent advances in their care, Berg said that despite an overall shift towards percutaneous mechanical circulatory support, little is known about the use of these devices in patients whose cardiogenic shock isn’t due to acute MI. “I’m hopeful that those are the kinds of questions that we’re going to start to answer through the CCCT Network,” he said. “It’s all investigator-initiated. Everybody’s literally doing this out of the goodness of their heart. Sites aren’t getting paid to capture data.”

Ideally, he said, this analysis will bring more focus on “these other groups of shock that have kind of been underappreciated, I think, and how we better phenotype those shock patients and target therapies specifically to that.”