Method and apparatus for examining vascular endothelial functions
Vascular endothelial function in terms of flow-mediated dilation (FMD) of peripheral arteries can be assessed reliably by measuring beat-to-beat pulse-wave conduction time (PCT) simultaneously for two symmetric segments of arteries locating on the right and left sides of body. When reactive hyperemia is induced in the peripheral tissues on one side, the time dependent changes in PCT caused by FMD on that side can be detected as the beat-to-beat differences in PCT between two sides (ΔPCT). ΔPCT would provide a sensitive and specific assessment of the FMD response, because the influences of the systemic changes in hemodynamic and neurohumoral factors common to both sides are subtracted out. In addition, measurement of PCT requires no skillful technique and is advantageous in that the apparatus is inexpensive.
1. An apparatus for assessing vascular endothelial function, comprising;
an arterial occlusion apparatus for occluding arteries in a specified region in a living body for more than a predetermined time,
a pulse-wave-conduction-velocity-relating information measurement apparatus for measuring successively a first pulse-wave-conduction-velocity-relating information which is a pulse-wave-conduction-velocity-relating information related to the velocity at which a pulse conducts through the artery in a first segment including a part or a whole of the specified region of said artery and the second pulse-wave-conduction-velocity-relating information which is a pulse-wave-conduction-velocity-relating information of the artery in a second segment almost symmetric to said first segment with respect to the median plane, and
comparative value calculating means for calculating a pre-ischemic comparative value representing a difference or ratio of said first pulse-wave-conduction-velocity-relating information to said second pulse-wave-conduction-velocity-relating information before ischemia by said arterial occlusion apparatus and also for calculating a post-ischemic comparative value representing a difference or ratio of said first pulse-wave-conduction-velocity-relating information to said second pulse-wave-conduction-velocity-relating information after release from ischemia (arterial occlusion) by said arterial occlusion apparatus.
2. The apparatus for assessing vascular endothelial function according to claim 1 wherein said first segment is a segment from the heart to a specified point on said artery and said second segment is a segment almost symmetric to a segment from the heart to a specified point on said artery with respect to the median plane.
3. The apparatus for assessing vascular endothelial function according to claim 1 , wherein
said comparative value calculating means is for calculating successively said post-ischemic comparative value, and further comprising
a vascular endothelial dysfunction judgment means for judging an impairment of vascular endothelial function on the basis of the fact that an absolute value of a difference between a peak value of the post-ischemic comparative value and the pre-ischemic comparative value calculated successively by the comparative value calculating means is at or lower than a predetermined judgment standard value.
4. The apparatus for assessing vascular endothelial function according to claim 1 , wherein
said comparative value calculating means is for calculating successively said post-ischemic comparative value, and further comprising
an output apparatus for illustrating graphically changes over time in comparative values calculated successively by said comparative value calculating means.
5. The apparatus for assessing vascular endothelial function according to claim 1 , wherein
said first segment is closer to the peripheral side than a region of arterial occlusion by said arterial occlusion apparatus,
said pulse-wave-conduction-velocity-relating information measurement apparatus is for measuring almost simultaneously a third pulse-wave-conduction-velocity-relating information which is said pulse-wave-conduction-velocity-relating information at a specified third segment closer to the central side rather than said arterial occlusion region and a fourth pulse-wave-conduction-velocity-relating information which is said pulse-wave-conduction-velocity-relating information at a fourth segment almost symmetric to said third segment with respect to the median plane, in addition to said first pulse-wave-conduction-velocity-relating information and the second pulse-wave-conduction-velocity-relating information, and
said comparative value calculating means is for calculating respectively a pre-ischemic comparative value on the central side representing a difference or ratio of said third pulse-wave-conduction-velocity-relating information to said fourth pulse-wave-conduction-velocity-relating information obtained before ischemia by said arterial occlusion apparatus, and a post-ischemic comparative value on the central side representing a difference or ratio of the third pulse-wave-conduction-velocity-relating information to the fourth pulse-wave-conduction-velocity-relating information obtained after release from ischemia (arterial occlusion) by said arterial occlusion apparatus, in addition to the pre-ischemic comparative value on the peripheral side representing a difference or ratio of said first pulse-wave-conduction-velocity-relating information to the second pulse-wave-conduction-velocity-relating information obtained before ischemia by said arterial occlusion apparatus and post-ischemic comparative value on the peripheral side representing a difference or ratio of said first pulse-wave-conduction-velocity-relating information to said second pulse-wave-conduction-velocity-relating information obtained after release from ischemia (arterial occlusion) by said arterial occlusion apparatus.