Helically cut vascular strip preparation: geometrical considerations.

The present study examines certain constraints associated with the use of helically cut strips obtained from the rat aorta. The angle (phi) at which a strip is cut from a vessel segment is intimately related to the strip width as well as the vessel circumference. Quantitatively, the relationship can be expressed by the equation cos phi = strip width/vessel circumference. To obtain strips of equal width from vessels of different diameters, the angle (phi) at which the strips are cut must differ. The stress developed by vascular strips was found to be a function of phi. Strips cut transverse to the long axis developed approximately 20 times more stress than strips cut parallel to the long axis. Strips cut at other angles developed intermediate stresses. This study demonstrates that helically cut strips lend themselves to artifact with respect to the tension-generating capacity of vascular smooth muscle if the geometrical considerations of strip width, vessel diameter, and the pitch of the helix are ignored.