Absolute induction angiometer.

The objective of this method is the continuous recording of vascular diameters and their measurement in absolute terms. This can be accomplished by percutaneously introduced intravascular sensors (IVS) or surgically implanted perivascular sensors (PVS). Both types of sensor are made of bifilar insulated wires forming a bifilar loop. One wire of the bifilar loop acts as a transformer primary inducing an electromotive force (EMF) in the secondary loop wire. The latter EMF is a measure of the vascular diameter. The IVS loop is made of resilient wire and is disposed across a vascular diameter in the central plane of a blood vessel. The sensitivity is such that phasic variations of a few micrometers in the diameter of a major blood vessel (such as the aorta or a coronary artery) can be measured and recorded. The surgically implanted perivascular loop sensor permits observation of vasomotion in a conscious, unrestrained animal. Both IVS and PVS permit observation of coronary vasomotion in the beating heart. Unlike the relative induction angiometer, the present device does not require an extracorporeal magnet.