DEVICE OF DETERMINING THE ELASTICITY OF THE ARTERIAL WALL

Abstract: The present invention relates to a device for determining the elasticity of the arterial wall by measuring pulse wave velocity. The device is a metallic plate attached to a pick-up microphone of an oscillograph. The device is placed over the left external carotid and the left dorsalis pedis arteries to record pulse waves. By simultaneously recording an ECG, the pulse wave velocity can be determined.

Description: DEVICE OF DETERMINING THE ELASTICITY OF THE ARTERIAL WALL S P E C I F I C A T I O N The present invention relates to medical technology but more particularly, to a device and method of determining the elasticity of the arterial wall. BACKGROUND OF THE INVENTION. I have been working on the oscillographic method of recording the arterial pulse ever since I did my research work on my thesis "Aortic Stenosis by Indirect Oscillography" for my Degree of Doctor of Medicine from the University of Geneva. This continued to be my field of interest for many years while working as Research Assistant to Professor Pierre Duchosal of the Department of Cardiology, University of Geneva and then with the famous Director of the Institute of Cardiology of London, Dr. Paul Wood. The problem then for some years was to record an arterial pulse wave, which very closely resembled the intra- arterial pulse with the use of a high frequency oscillograph. By repeated trials, I was able to design an attachment to the pick-up of the microphone of the NEP pulse recording unit (Type A-643) of Sanborn. This is described below. Having devised this attachment to record the desired arterial pulse and using a method which I also designed and described below, I planned a research work on normal and hypercholesterolaemic subjects at the Brompton Hospital in London. For this, I was awarded the Alice Hamilton Fellowship for research on haemodynamics for two years by the US based International Federation of University Women - a lone award given annually to one female University graduate chosen from candidates from over the world and this was the first time that Greece won the award. In the recent 2 nd International Symposium on Diseases of the Aorta held in Athens, Greece in April 1996, great interest was shown on the elasticity of the arterial wall as shown by the number of research papers read but with the use of more sophisticated invasive and non-invasive methods. In the discussions wherein I participated, it came out that my method, which was much simpler and least expensive had comparable results. I was invited to present my work on normal subjects of different age groups in the 20 th Annual Congress of the South African Cardiological Society in October 1996. Communication with a top world authority on pulse wave velocity, Professor Michael F. O'Rourke of the University of South Wales, Australia, also confirmed the consistency of this method compared with more sophisticated techniques (Doppler Flow and tonometry) and giving the same results. BRIEF SUMMARY OF THE INVENTION. It is the primary object of the present invention to provide for indirectly determining the elasticity of the arterial wall. This method is based on the speed of the transmission of the pulse wave through the arteries. The more elastic the arteries, the slower will be the transmission time and as the elasticity decreases, the faster will be the transmission time. Indirect oscillography is the technique used to measure the speed of the flow of blood as indicated by the pulse wave velocity. The time interval for the pulse wave to be recorded between two points in the arterial system can be determined by recording the pulse in a "central artery" and a "peripheral artery" which in my method are the left external carotid and left dorsalis pedis arteries, respectively. These arteries are well exposed, easily located and the distance between them is long enough so that a longer segment is measured and the statistical margin of error is less. The subjects used in this study are within a specific height range. It is essential that the pulses recorded resemble as closely as possible the intra-arterial pulse and this has been achieved by designing a special device attached to the pick-up of the microphone of the high frequency oscillograph. This device is a circular metallic plate, one centimeter in diameter and one millimeter thick whose center is welded to the center of the pick-up microphone with a metallic rod one centimeter long and two millimeters in diameter. BRIEF DESCRIPTION OF FIGURES. FIGURE 1/4 - Perspective view of the device used in the invention. FIGURE 2/4 - Recording of the pulse pattern on the oscilloscope screen of the left carotid and left dorsalis arteries . FIGURE 3/4 - Figure of the location of the attachments of electrodes of the ECG placed on a patient. FIGURE 4/4 - Recording of the left carotid and left dorsalis pedis arteries pulse wave simultaneously with the Std. Lead II of the ECG. Referring to Fig. 1/4, the device used in the present invention is a circular metallic plate welded to the center of the pick-up microphone of a high frequency oscillograph and is attached on a patient as shown in Fig. 3/4. With this attachment placed over the arteries, nice pulses of the left external carotid and left dorsalis pedis arteries are obtained (Fig.2/4). With the subject in the semirecumbent position and the surrounding room temperature kept as constant as possible, the ECG (Std. II) is recorded simultaneously with the left external carotid artery and the left dorsalis pedis arterial pulses (Fig.3/4). Recordings were made in some subjects at intervals of six, twelve and eighteen months and the results were the same. Q is the start of the isometric ventricular contraction, A - the foot point of the anacrotic arterial pulse (left external carotid artery), and Al the foot point of the anacrotic arterial pulse (left dorsalis pedis artery) (Fig.4/4). So, the difference between QAl and QA is a measure of the time interval between the instant that the pulse is recorded from the "central artery", i.e., the left external carotid artery and the instant that the same pulse is recorded from the "peripheral artery, i.e., the left dorsalis pedis artery (Fig. 4/4). This method is simple, inexpensive, reproducible and non-invasive. Its results are similar to more sophisticated and expensive methods. It is very applicable for mass screening of big populations (normal and high-risk subjects) especially in developing countries.

Claims: I CLAIM This device is a metallic plate attached to the pick-up microphone of a high frequency oscillograph. This device enables us to record a pulse, which very closely resembles the intra arterial pulse. This device is placed on the skin over the left external carotid and the left dorsalis pedis arteries and the pulses are recorded simultaneously with the Std lead II of the ECG measuring the time in seconds. With these recordings we get the difference between the time the blood travels from the central artery to the peripheral artery.

Inventors: MARCOYANNOPOULOU-FOJAS HELEN, MARCOYANNOPOULOU-FOJAS, HELEN
Applicants: MARCOYANNOPOULOU FOJAS HELEN, MARCOYANNOPOULOU-FOJAS, HELEN
Application year: 1999
Main classification: A61B5
IPC codes: A61B5, A61B7