A valve-spreading catheter capable of producing graded reversible acute aortic regurgitation has been described. We modified this device to improve its safety and steerability. The modified valve-spreading catheter was composed of a removable core flexible guidewire and a caged catheter. The guidewire could easily and safely be steered into the left ventricle. The caged catheter could then be advanced over the guidewire to the aortic valve area with greater safety and ease. Opening of the caged catheter resulted in graded reversible acute aortic regurgitation. The modified valve-spreading catheter was used in 5 anesthetized mongrel dogs to create reversible graded acute aortic regurgitation, demonstrating its safety, and thus its utility. This device qualifies as an ideal instrument for creating variable and transient acute aortic regurgitation in intact animals.