A Methodological Approach to Non-invasive Assessments of Vascular Function and Morphology

The overall goal of the following experiment is to examine subclinical arthrosclerosis in different vascular territories. First, laser doppler imaging with iontophoresis of vasodilating drugs is used to examine microvascular endothelial function. Next, flow mediated dilatation and glycerin, tritrate mediated dilatation are used to examine large vessel endothelial function.

Lastly, the carotid intimate media thickness is analyzed for advanced morphological changes. The results show changes in microvascular and large vessel endothelial function in response to stimulation. In addition, the vessel wall of the carotid artery is also characterized.

These methods can help answer key questions in the field of cardiovascular physiology, such as determining the impact of interventions on vascular health in different clinical populations. First, prepare the laser doppler imager. Let it warm up for half an hour or longer.

Calibrate the machine and get the software ready to use. Also, prepare the solutions in the perspex chamber. Then bring the study participant to the imager seat, the participant slightly reclined, and on a firm pillow with one elbow bent at 90 degrees and that forearm comfortably positioned on a black mat.

Be sure to secure the forearm to the pillow so that it stays in place on the mat. Next, prepare the perspex chambers. First, attach their plugs to the iontophoresis controller.

Then attach the chamber containing acetylcholine to the Anodal connection, and attach the chamber containing sodium nitro perside to the catheter connection. Then connect the two chambers to the voler aspect of the secured forearm using double-sided adhesive pads. Also, cover the chambers with 32 millimeter cover slips.

Now in the scanner software, open the scanner setup window located on the top left of the home screen. Select the image scan tab and determine the area that is to be scanned by clicking the mark button in the bottom right corner of the window. Carefully position the scanner head so that it accurately scans the area of interest if needed.

Manually change the region of interest by entering in the size of the scanning area into the scan area section near the top of the window. Ensure that the region of interest includes the diameter of each of the iontophoresis chambers and is large enough to limit variability in skin blood flow. The scan can now be started following completion of the scan.

Use LDI image analysis software. To open the data file. Select the image review option in the main window.

Now mark out a region of interest around the outer diameters of each chamber. Then click the statistics icon and a column containing the median perfusion units for each chamber will be displayed from each of the 12 scans of each chamber. Take note of the baseline perfusion unit and the highest perfusion unit.

Begin with setting up the Doppler ultrasound machine and live imaging vascular image analysis software. Then introduce the participant to the setup and have the participant relax in the chair. Ask the test participant to remove any jewelry from the wrist and use a pillow for them to rest their arm comfortably.

Then put a blood pressure cuff around the participant's wrist. It must be held as still as possible. Next, secure the linear transducer array from the machine to a stereotactic clamp.

Then tighten the clamp on the transducer. Next, access the menu on the ultrasound machine there. Set the scanning frequency to five megahertz and set the depth to about 3.5 centimeters.

Now using the transducer, locate the brachial artery with longitudinal scanning. It is usually two to 10 centimeters above the antecubital fossa. Then set the gain for a symmetrical brightness in the near and far wall of the vessel.

Color doppler will show the arterial blood pulsing through the artery, which will distinguish it from any veins. Set the view of the brachial artery so it is clearly seen and horizontal on the screen. It should appear as two solid parallel lines separated by a clear area between the lines in the software.

Use the cursor to mark the region of interest and the via software will automatically record. The vessel diameter adjustment of the area can be done with the X and Y buttons on the main screen. Now, click the start button and image the artery for two minutes.

Then press inflate to record for five minutes while inflating the blood pressure cuff to S systolic pressures. Blood flow to the hand should be occluded by the cuff after the cuff deflates. Continue recording for three minutes.

At this point, hyperemia is induced, which stimulates nitric oxide mediated vasodilation. Then provide a 10 minute rest. Next, relocate the brachial artery and make a new baseline recording of the artery's diameter for two minutes.

Now, ask the participant to sublingually ingest a 500 gram glycerol tritrate tablet and continue recording for five minutes. After five minutes, the tablet should be removed and the participant should be monitored for adverse effects. When analyzing the data, be sure to check the baseline region for artifacts, exclude any artifacts before averaging the remaining values to get a baseline diameter.

Also, during the flow mediated dilation analysis, inspect the automatically detected region of peak dilation. If it is misidentified, manually select a more confined region, which contains the peak. For this measurement, have the participant lie down comfortably on a bed with a pillow.

Then set up the ECG leads for a basic trace. Attach them to both arms and to the left ankle. Next, go to the menu and set the scanning frequency to 10 megahertz and the recording depth to three to four centimeters.

Then adjust the gain as before. Now, ask the participant to roll their head slightly to the left and use the linear array transducer to scan the right carotid artery. Search for a bifurcation point in the vessel as this shows the common carotid artery bifurcating into the internal and external carotid arteries.

Scan the carotid artery along all its sections in a longitudinal plane. Identify the common internal and external artery if any plaque is seen. Save the images now.

Take at least three images of a section that is free of plaque and is about a centimeter from the carotid bulb. Have the participant roll their head to the other side and repeat the procedure to document the left carotid artery.Later. Analyze the images offline using the artery measurement software package while collecting the values for CIMT and lumen diameter.

Be aware that accurate readings from the near wall can't be made so only analyze readings from the far wall. Laser Doppler imaging with iontophoresis was used on a healthy middle-aged woman without cardiovascular disease. There was a marked increase in median blood flux with both stimuli.

Peak blood flux reached 455 perfusion units for acetylcholine and 446 perfusion units for sodium nitro proxide. Flow mediated dilation and glycerol tritrate mediated dilation were both investigated in a healthy young woman free of cardiovascular disease. The flow mediated dilation test increased artery diameter by about 10%and the glycerol tritrate mediated dilation increased artery diameter by about 30%Carotid intimate media thickness was looked at in the left carotid artery of a healthy individual.

The CIMT value for the far wall was 0.83 millimeters and the lumen diameter was 7.71 millimeters. The same measurements on the right carotid artery were 0.87 millimeters and 7.8 millimeters After their development. These techniques paved the way for researchers in cardiovascular physiology to understand the mechanisms of cardiovascular disease in different clinical populations.