An apparatus (100), control system (150) and methods are provided for directlymeasuring a pressure gradient, i.e. byreal-time pressure measurements, with particular application for in situmeasurement of transvalvular blood pressure gradients forthe aortic valve and other heart valves, using minimally-invasive techniques.The apparatus takes the form of a multi-sensor assembly,e.g. enclosed within a micro-catheter or a steerable guidewire, and comprisesa plurality of optical pressure sensors (10) isarranged along a length of the distal end portion (101), for measuringpressure simultaneously at each sensor location. For example,four MOMS optical pressure sensors (10), and optionally, a flow sensor (20),are incorporated into a distal end portion (101) havinga diameter of 0.89 mm or less, and preferably 0.46 mm or less. Beneficially,all sensors are optically coupled, via respective opticalfibers (11), to an optical coupler (112) at the proximal end of the multi-sensor apparatus, without requiring electrical connections.
