Abstract Body (Do not enter title and authors here): Mechanical circulatory support (MCS) devices, such as the Impella cardiac pump, improve haemodynamics in left ventricular systolic dysfunction, but their effects on renal tissue oxygenation have not been explored. This study investigated whether Impella support improved renal tissue perfusion and oxygenation in an ovine model of acute ischemia-induced left ventricular systolic dysfunction. We hypothesised that MCS via the Impella CP would increase renal tissue oxygenation and facilitate renal recovery.
Experiments were performed in anaesthetised female Romney sheep. Cortical and medullary oxygenation and perfusion were measured using fibreoptic probes (n=8). Acute myocardial infarction was induced via coronary microembolisation using polystyrene microspheres. All parameters were monitored for 60 minutes following embolisation. The Impella device was inserted into the left ventricle under echocardiographic guidance and operated at maximum tolerated speed for 60 minutes (P7–P9). The pump was withdrawn for the last 30 minutes of the protocol.
Ejection fraction (EF), mean arterial pressure (MAP) and medullary oxygenation were significantly reduced following embolization (Δ EF 36 ± 7%; p<0.001, Δ MAP 14.9 ± 1.9 mmHg; post hoc; p<0.001 and Δ medullary oxygenation 23.9 ± 7.2 mmHg; post hoc; p<0.001). Renal cortical oxygenation did not change following embolization (p>0.05). Renal cortical and medullary perfusion did not significantly change across the time points examined. Impella CP support increased MAP by 7.4 ± 4.0 mmHg compared to the end of embolisation (p=0.023). Cortical tissue oxygenation improved from 84.6 ± 14.0 mmHg (post embolization) to 117.7 ± 16.3 mmHg (post hoc; p=0.008). Medullary tissue oxygenation also improved from 56.5 ± 8.1 mmHg to 72.7 ± 8.0 mmHg (post hoc; p=0.006). Withdrawal of the pump support did not change renal cortical tissue oxygenation at 30 minutes (post hoc, p>0.05), but medullary tissue oxygenation reduced by 13.9 ± 4.4 mmHg at 30 minutes (post hoc, p=0.002).
These results provide the first direct evidence that unloading the heart using the Impella device improves renal medullary and cortical oxygenation in acute myocardial infarction-induced left ventricular systolic dysfunction. These observations suggest that unloading the left ventricle may protect the kidney in acute ischemia-induced left ventricular systolic dysfunction by improving renal oxygenation, particularly to the renal medulla.