Implantation of the Impella CP micro-axial flow pump may increase survival at six months among patients with STEMI complicated by cardiogenic shock (CS), according to the results of the DanGer Shock study, presented during a Late-Breaking Clinical Trial session at ACC.24 and published simultaneously in the New England Journal of Medicine.

The international, open-label trial conducted over 10 years at 14 centers in Denmark, Germany and the U.K., analyzed data from 355 patients treated for STEMI with cardiogenic shock (median age 67 years, 79.2% men) randomized to standard of care or standard of care plus an Impella CP pump before, during or up to 12 hours after receiving treatment in the cardiac catheterization laboratory.

Results showed that the primary endpoint, death from any cause, occurred in 82 of 179 patients (45.8%) in pump group and 103 of 179 (58.5%) patients in the standard care group (hazard ratio, 0.74; 95% CI, 0.55-0.99; p=0.04). The number needed to treat to avoid one death was eight.

There was also a reduction in the composite secondary endpoint of additional mechanical heart support, heart transplant or death with the heart pump, which occurred in 94 (52.5%) patients in that group compared with 112 (63.6%) in the standard care group (HR 0.72; CI 95%, 0.55-0.95, p=0.04). The mean number of days alive and out of hospital was similar between the pump and standard care groups at 82 and 73 days.

The composite safety endpoint of severe bleeding, limb ischemia, hemolysis, device failure or worsening of aortic regurgitation, occurred in 43 patients in the pump group and 11 in the standard care group (relative risk, 4.74; 95% CI, 2.36-9.55). In the pump group, the number needed to harm was six. The relative risk of moderate or severe bleeding was 2.06, of limb ischemia was 5.15, renal replacement therapy 1.98 and sepsis with a positive blood culture was 2.79. A subgroup analysis indicated that patients with low blood pressure at baseline may see greater benefit from the pump, a finding the authors say is in line with experimental data.

"What was a surprise for us was that the benefit seems to persist beyond 30 days," said the study's lead author, Jacob E. Møller, MD. "It's not only that we are saving lives, it looks like we are also saving myocardium [heart muscle] so the patients keep surviving, and the survival curves continue to separate beyond the first 30 days." However, the authors noted that it doesn't come without a cost. "We see significantly more serious complications in the Impella-treated patients," said Møller. "Overall, we have more complications, but we also save lives." He noted the need for further studies to assess the benefits in more diverse patient populations and to examine how the duration of mechanical support might affect the rate of severe complications and identify opportunities to further optimize practices to minimize complications.

In an accompanying editorial comment, Sunil V. Rao, MD, FACC, wrote that "The results of the DanGer Shock trial are clear in that the microaxial flow pump reduced mortality among selected patients with AMI-CS. However, given the rapidly evolving nature of mechanical circulatory support use, other unresolved issues remain." These include, he wrote, the timing of microaxial-flow-pump placement (before primary [PCI] or after opening the infarct-related artery), the incorporation of shock protocols or a "shock team" as a standardized approach, and the combined use of the microaxial flow pump with other mechanical circulatory support such as venoarterial extracorporeal membrane oxygenation.