Timely Question

[KimC]

Hi --

I'm at SHANDS, scheduled for a 7AM cath tomorrow. I had my bloodwork, stress, echo and tonometry tests today. The good news is that I performed well on my stress test, and the tonometry results were slightly better compared to the last time. I'm feeling confident.

My question relates to the tonometry test. First, has anyone had one? I know very little about it. What I know is that the test measures aortic pressure. Mine was high. What kind of numbers are important to know, and what do they indicate?

I SHOULD have asked the cardio during the test what his comments meant, but I didn't. I smiled and nodded, like an idiot. He compared me to his daughter. I hate it when doctors do that. They get this look on their face ...

I should've said, "Look, I have an MA from Columbia Univ., worked on the Hill and have a curious mind. Please answer my questions in the most direct scientific terms, so that I won't go online later and look them up myself. I can handle it."

Help, please! What kind of questions should I ask tomorrow before I leave?

Many thanks,

 

[tobagotwo]

Tonometry

Tonometry

A tough one to find, as tonometry is more often related to pressures inside the eye than with measuring the stiffness of arteries. The particualr study I found most elucidating was done on diabetic children, as arterial damage is a problem for them. But it should apply equally to you, as it's the function of tonometry we're interested in, not the results of the study itself.

The results of tonometry appear to be measured as an Augmentation Index (AI), and then refined to an Augmentation Index corrected to a heart rate of 75 beats per minute (AI75), to standardize the findings, and reduce the scoring variations created by different patient states and heart rates.

If I understand it, the augmentation level is how much the "bounce" off the artery wall increases the pressure of the fluid (blood) within the artery, as shown by changes in the energy waveform measured from the artery. A stiffer arterial wall creates a larger bounce, and a higher AI. This will also yield a higher AI75.

From http://care.diabetesjournals.org/cgi/content/full/27/12/2911

Diabetes Care 27:2911-2917, 2004 © 2004 by the American Diabetes Association, Inc.

Pathophysiology/Complications Original Article

Radial Artery Tonometry Demonstrates Arterial Stiffness in Children With Type 1 Diabetes
Michael J. Haller, MD1, Margaret Samyn, MD2, Wilmer W. Nichols, PHD3, Todd Brusko, MD4, Clive Wasserfall, MS4, R. Fletcher Schwartz, BS4, Mark Atkinson, PHD4, Jonathan J. Shuster, PHD5, Gary L. Pierce, MS6 and Janet H. Silverstein, MD1

In brief, a high-fidelity micromanometer (blood pressure gauge - RDH) with a frequency response of >2 kHz (Millar Instruments, Houston, TX) was placed on the right radial artery, and gentle pressure was applied until a consistent waveform was produced.

After 10?20 sequential waveforms had been acquired, the integral software was used to generate an averaged peripheral and corresponding central waveform that was used for the determination of the AI and AI75. The algorithm used to convert the radial pulse wave to an aortic waveform was derived from invasive pressure and flow data obtained by cardiac catheterization and has been validated in several adult studies (6?8)...

...AI is defined as the difference between the first and second peaks of the central arterial waveform, expressed as a percentage of the pulse pressure, and measures the contribution that the wave reflection makes to the arterial pressure waveform. The amplitude and timing of the reflected wave depends largely on the stiffness of the small and large arteries; thus, AI provides a measure of systemic arterial stiffness. AI75. allows for a true comparison of the augmentation of central pressure between study subjects by discounting differences related to heart rate variation (9). An elevated or positive AI suggests stiffer arteries than a low or negative AI.

In the study, the "normal" group had an average AI of ?0.47 ± 9.79, and an average AI75 of ?3.31 ± 10.36. The negative numbers on the control subjects would suggest (to me) that the arterial walls were more supple and relaxed, and thus had a damping effect on the pressure wave. In the study, those with arterial problems had positive AI and AI75 measurements.

I hope this helps you to form some questions for tomorrow.

Best wishes,

 

[Phyllis]

Hi Kim,
I've been trying to get some answers by searching the web for the tonometry test, but haven't come up with any information on standard values. Maybe somebody else will come up with the answers before the night is over. Why not take the time tonight to write your questions out so that you are satisfied with the answers before you leave tomorrow. I find it always helps to have a list!
I'm glad the stress test went well and we wish you the same good results with the cath tomorrow.

 

[Phyllis]

Ah, Bob to the rescue. Maybe that link should be posted in reference sources in case anyone else has the question in the future! Good luck, Kim.

 

[PJmomrunner]

Hi Kim:

This is a challenging post. I certainly can't say I understand much about the indices used in tonometry, but it appears I'm not alone. I found two papers I thought you might be interested in:

http://www.ncbi.nlm.nih.gov/entrez/...d&dopt=Abstract&list_uids=12204510&query_hl=7

http://hyper.ahajournals.org/cgi/content/full/43/4/e25

I hope they help some. Are these tests being done as part of some sort of evaluation of the meds you are on?

I hope you are doing well.

P. J.

 

[Marguerite53]

Hi Kim.

Hi Kim.

Hi. Hope your tests/doctor visit went well. Just wanted to chime in to get you back on the top of the "new posts" list so we can follow your journey.

I think you should use the "look, I have an MA......." line on doctors!! Certainly as patient you can command the same respect that they demand! It's the gumption part that's hard to muster, isn't it? They just seem to have more of that during those visits.....better rehearsed, they are.

Anyway, please let us know what you are learning about yourself and I truly hope the news is all good.

Best Wishes! Marguerite

 

[gijanet]

Kim

Kim

Hoping all went well with your cath today. A little belated, but I'm praying that it went smoothly and that you got some answers. Sending hugs, too. Janet

 

[Sherry]

Hi, Kim. I am also keeping you in my thoughts as you go through this testing. Hope to hear from you soon.