Abstract Body (Do not enter title and authors here): Introduction
In cases of cardiogenic shock, the transaortic micro-axial flow pump (Impella) improves systemic circulation and increases coronary perfusion pressure (CPP) while reducing myocardial oxygen consumption (MVO₂) via its left ventricular (LV) unloading effect. The Impella 5.5, in particular, enables stronger LV unloading due to its higher flow capacity. Physiologically, coronary blood flow (CBF) increases with CPP, while reduced MVO₂ may activate autoregulatory mechanisms that limit CBF.
Hypothesis
We hypothesized that a marked reduction in MVO₂ by the Impella 5.5 may attenuate CBF. This study evaluates the impact of Impella 5.5 support on CBF in normal and post-reperfusion coronary arteries using a goat model of ischemia-reperfusion.
Methods
Saanen goats (N=8, BW: 61.6±4.5 kg) were used under general anesthesia. The Impella 5.5 was inserted via the carotid artery into the LV. We measured blood pressure, LV pressure, pulmonary artery flow, arterial and coronary sinus oxygen saturation, and CBF in the left anterior descending artery (LAD) and left circumflex artery (LCX). We occluded the proximal LAD with a 3 mm balloon for 90 minutes, then deflated for reperfusion (Fig. A). At 30-min after reperfusion, Impella support was set at three stages: Control (P1), Partial support with residual native cardiac output (P3-7), and Total support (P6-9).
Results
Increasing Impella support augmented CPP (37.8 ± 10.6 vs. 47.1 ± 8.5 vs. 75.2 ± 12.7 mmHg, P < 0.05) and reduced MVO₂ (298.3 ± 161.0 vs. 257.9 ± 122.2 vs. 161.0 ± 121.6, P < 0.05) (Fig. B). Total support with the Impella 5.5 suppressed MVO₂ by 53.0 ± 18.8% compared to the Control condition. LCX flow decreased with increasing Impella support (46.9 ± 26.6 vs. 45.0 ± 28.5 vs. 37.8 ± 31.0 mL/min, P < 0.05). Similarly, LAD flow was significantly reduced under Total support (30.9 ± 11.4 vs. 28.5 ± 11.7 vs. 23.7 ± 12.2 mL/min, P < 0.05) (Fig. C).
Conclusion
In a goat model of ischemia–reperfusion, total support with the Impella 5.5 reduced CBF in both the normal LCX and the injured LAD. These results may be influenced by factors such as the severity of coronary injury, the timing of measurement, and the specific animal model used. Nevertheless, the findings suggest that autoregulatory mechanisms triggered by suppressed MVO₂ play a critical role in determining CBF, even in post-reperfusion setting, and should be carefully considered when evaluating the effects of Impella5.5 support on coronary circulation.