The microaxial flow pump (mAFP) unloads the heart in STEMI-cardiogenic shock (CS) patients undergoing hemodynamic monitoring with a pulmonary artery catheter (PAC) by reducing native cardiac output (CO), pulmonary pressures and left ventricular filling pressures, while maintaining hydraulic power output delivered to the body by the heart and the device, according to a substudy of the DanGer Shock trial published June 23 in JACC. Furthermore, the higher cardiac power output (CPO) in the mAFP group required less reliance on vasoactive drugs.

In this analysis of the open-label trial, Jacob E. Møller, MD, et al., analyzed data from 324 patients with STEMI-CS admitted to the cardiac intensive care unit (CICU) in 14 centers in Demark, Germany and the U.K. from January 2013 to July 2023 who were randomized to mAFP or standard of care. Of them, data on hemodynamic monitoring was available for 223 patients (68%): 125 in the mAFP group and 98 in the standard of care group. The authors note that patients monitored with a PAC were predominantly men and had a median age of 67 years.

Outcome measures were CO, CPO and mean pulmonary artery pressure (PAP) during the first 48 hours, and the primary endpoint was mortality at 180 days.

Results showed that the median first measured CO was 3.4 L/min in the control group vs. 3.7 L/min in the mAFP group (p=0.13). In the mAFP group, the CO was consistently higher from 12 hours until 48 hours. Additionally, in the mAFP group, the first measured mean PAP in the CICU remained lower at all time points. The first measured pulmonary capillary wedge pressure remained lower in the mAFP group until 48 hours, and the median first measured CPO was 0.56 W in the control group vs. 0.68 W in the mAFP group (p=0.01) and remained higher in the mAFP group until 48 hours.

"The mAFP reduces intrinsic mechanical work of the heart in STEMI-CS patients enrolled in the DanGer Shock trial by reducing native CO, pulmonary pressures and [left ventricular] filling pressures while maintaining hydraulic power output delivered to the body by the heart and mAFP," write the authors.

"By reducing myocardial work and wall stress, unloading may be protective in stunned, postischemic myocardium vulnerable to further insult," write P. Elliott Miller, MD, et al., in an accompanying editorial comment. "It remains unclear how the timing of mAFP placement relative to revascularization could further impact these findings, and this remains an area of active investigation."