A method of measuring differential pressure between a left ventricle and an aorta across an aortic valve for diagnosis of aortic stenosis using a coaxial dual lumen pigtail catheter that utilizes coaxial construction incorporating a thin wall guiding catheter technology for the outer lumen and using a strong braided diagnostic technology for the central lumen to accommodate high-pressure injections. The catheter includes a manifold body to provide for connection to each of the dual lumens. The distal end of the coaxial dual lumen pigtail catheter tapers to a more flexible portion that is perforated by spiral side holes to provide for more undistorted pressure readings in the left ventricle. The coaxial dual lumen pigtail catheter also utilizes proximal straight sideholes at the end of the dual lumen portion and a taper between the dual lumen portion and the single lumen portion.