BACKGROUND: The microaxial flow pump (mAFP) improves survival in selected patients with ST-segment elevation myocardial infarction-induced cardiogenic shock (STEMI-CS). Understanding the impact on cardiac output (CO), cardiac power output (CPO), and pulmonary artery pressure (PAP) provides insight into the potential unloading effect of the device, which is a reduction in total intrinsic mechanical work of the heart.

OBJECTIVE: This study sought to determine the effect of mAFP on hemodynamics in STEMI-CS.

METHODS: This substudy of the DanGer (Danish-German) shock trial randomized patients with STEMI-CS to mAFP or standard of care. Patients were monitored using a pulmonary artery catheter. Outcome measures were CO, CPO, and mean PAP during the first 48 hours.

RESULTS: Of 324 patients admitted to the cardiac intensive care unit (CICU), 223 patients (68%) had data on hemodynamic monitoring: 98 patients (63%) in the standard of care, and 125 (74%) patients in the mAFP group. The median first measured CO after CICU admission was 3.4 L/min (Q1-Q3: 2.6-4.4 L/min) in the control vs 3.7 L/min (Q1-Q3: 3.2-4.5 L/min) in the mAFP group; P = 0.13. After 6 hours, the CO increased in and was consistently higher in the mAFP group from 12 hours until 48 hours. The first measured mean PAP in the CICU had a median value of 31 mm Hg (Q1-Q3: 29-39 mm Hg) in the standard of care group compared with 27 mm Hg (Q1-Q3: 23-33 mm Hg) in the mAFP group (P < 0.001) and remained lower at all time points in the mAFP. Also, the first measured PCWP was lower in mAFP vs standard of care (18 mm Hg [Q1-Q3: 14-22 mm Hg] vs 22 mm Hg [Q1-Q3: 20-26 mm Hg]; P < 0.001) and remained lower until 48 hours. The median first measured CPO was 0.56 W (95% CI: 0.41-0.76 W) in the control vs 0.68 W (95% CI: 0.51-0.85 W; P = 0.01), in the mAFP group, and remained higher in the mAFP group until 48 hours.

CONCLUSIONS: 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 LV filling pressures while maintaining hydraulic power output delivered to the body by the heart and mAFP (CPO). (Danish Cardiogenic Shock Trial [DanShock]; NCT01633502).