Assessment of Impella position on supine chest X-ray in the intensive care unit. Introduction and applicability of the Aortic Valve Location Ratio

Maintaining correct Impella position is a key factor for optimal functioning of the Impella device. The aortic valve is an important landmark for correct positioning. It would be of great value if the device position could be determined accurately by plain supine chest X-ray in the intensive care unit. The aim was to develop a ratio-based tool for determination of the aortic valve location on plain supine X-ray which can be used to monitor Impella position in the intensive care unit. Supine anterior-posterior chest X-ray of patients with an aortic valve prosthesis (n=473) were analyzed to determine the location of the aortic valve. We calculated several ratios with the potential to determine the position of the aortic valve. The Aortic Valve Location (AVL) ratio, defined as the distance between the carina and the aortic valve, divided by the thoracic width, was found to be the best performing ratio. The AVL ratio determines the location of the aortic valve caudal to the carina, at a distance of 0.25±0.05 times the thoracic width for male patients and 0.28±0.05 times the thoracic width for female patients. The AVL ratio was validated using computed tomography images of patients with angina pectoris without known valvular disease (n=95). There was a good correlation between the Impella position assessed with the AVL ratio and with echocardiography (n=53). The Aortic Valve Location Ratio enables accurate and reproducible localization of the aortic valve on supine chest X-ray. This tool is easily applicable and can be used for assessment of cardiac device position in patients on the ICU.