Heart pump helps prevent death after severe heart attack

Patients with ST-segment elevation myocardial infarction (STEMI)-related cardiogenic shock may benefit from a significantly higher survival rate at 6 months through the routine use of a microaxial flow pump in combination with standard care as compared with standard care alone, as shown in a study presented at the recent ACC.24.

However, use of the microaxial flow pump is associated with a markedly higher incidence of a composite of adverse events.

“This is the first time in a very long time that we have a positive study for managing cardiogenic shock,” said lead author Jacob E Møller, MD, professor in the Department of Cardiology at the Odense University Hospital in Denmark, in a press release. “I think this will be a routine device that will be used in these desperately ill patients.” [https://tinyurl.com/2dhzputd]

Møller and his team randomized 360 patients with STEMI and cardiogenic shock to receive either a microaxial flow pump (Impella CP) plus standard care or standard care alone. Of the participants, 355 (median age 67 years, 79.0 percent men) made it to the final analysis: 179 in the microaxial flow pump arm and 176 in the standard care arm. [N Engl J Med 2024;doi:10.1056/NEJMoa2312572]

All-cause mortality at 180 days was the primary endpoint, while safety endpoints included a composite of severe bleeding, limb ischaemia, haemolysis, device failure, or worsening aortic regurgitation.

Of the 179 patients who underwent implantation with microaxial flow pump, 82 (45.8 percent) died from any cause within 6 months. This was substantially lower than the 103 (58.5 percent) patients who suffered the same fate in the standard care group (hazard ratio, 0.74, 95 percent confidence interval [CI], 0.55‒0.99; p=0.04). [Møller JE, et al, ACC 2024]

In terms of safety, a composite of adverse events occurred more frequently in the heart pump-treated group than in the standard care group (24.0 percent vs 6.2 percent; relative risk [RR], 4.74, 95 percent CI, 2.36‒9.55). Additionally, 75 patients (41.9 percent) in the microaxial flow pump arm received renal replacement therapy relative to 47 (26.7 percent) in standard care (RR, 1.98, 95 percent CI, 1.27‒3.09).

“Routine use of microaxial flow pump led to an absolute 13-percent reduction in death at 180 days,” Møller said. “This was associated with increased risk of complications.”

Lesser myocardium stress

In the subgroup analysis, Møller and colleagues found a potentially greater benefit with the microaxial flow pump if the patient’s blood pressure was low prior to randomization. This finding was consistent with experimental data, which showed that the heart pump did not work well if the left ventricular afterload was amplified by vasoconstriction. [Crit Care 2020;24:95]

Furthermore, the microaxial flow pump unburdens the left ventricle by reducing wall stress, leading to a decrease in myocardial oxygen consumption. [JACC Heart Fail 2015;3:873-82; EuroIntervention 2019;14:e1585-e1592]

Experimental studies demonstrated reduced myocardial injury when unloading the left ventricle. However, it remained unclear whether this therapeutic effect transpired in the current study. [J Am Coll Cardiol 2003;41:1087-1095]

“What was a surprise for us was that the benefit seems to persist beyond 30 days,” Møller said in a press release. “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.”

“It doesn’t come without a cost—we see significantly more serious complications in the Impella-treated patients,” he said. “Overall, we have more complications, but we also save lives.” [https://tinyurl.com/2dhzputd]