Stress Thallium Vs CT Angiogram - Which is best?

Hello all,

My mom (58 yrs) had a mild positive during treadmill test. She has been adviced for a stress thallium test (Nuclear) to rule out any benefit of doubts. She is a bit obese.

I have been hearing quite a lot about CT angiogram as well.

Can one of you suggest, which of these two would be best suitable in determining blocked arteries?

Thanks much in advance.

Gany

[kenkeith]

CT 64 slice scan angiogram will include the anatomy of the vessels, chest, and aorta vessel (ascending, arch and descending).  The scan will show any layers of soft plaque outside the lumen, and it is the soft plaque that has a higher risk of rupturing, clotting  and causing an MI.  The scan and stress test are about equal in determing the plaque within the lumen that may cause ischemia (blocked, partially blocked vessels.

Obesity, unable to hold one's breath for several seconds, and inability to reduce the heart rate below 63 bpm, etc. may preclude the option of CT.

[oldie]

I've been re-reading your posts on 64 slice CT. In my most recent talks with cardios they still insist that catheterisation is the 'gold standard' for discovering and meauring the extent of obstruct in coronary arteries and that  the CT shows it  but doesn't measure it ie., 50% or 70%    or whatever.  You are well-read in this. Can you please give us all your latest view?

[kenkeith]

The CT scan 64 slice angiogram may have become obsolete and cath angiogram was better, but the new technology, called 256-slice CT, provides a quantum leap in imaging and is now being used to diagnose heart disease.

"This advanced scanner achieves whole imaging of the heart within a short time span using low dose radiation, providing much more visual detail about the heart's function and structures. The images are then reconstructed in 3D format to help determine strength of the heartbeat and plaque deposits within the coronary arteries. These deposits may eventually block one or more coronary arteries and cause chest pain or even a heart attack. That's why physicians may use the 256-slice CT scanning device as a means of diagnosing early or advanced coronary artery disease".  Additionally, it is a much faster dx in an emergency for possible heart attack, etc. and that may save a life.

My CT scan angioplasty  took images of the pulmonary system and the lung and aorta... had some minor lung defect...unwanted information!  As well, the scan involves the aorta (root, ascending, arch and descending portions; the test is more inclusive. The scan also, views soft plaque (plaque that resides between vessel lining as well as the hard plaque within the lumen (vessel channel).  The cath can also visualize for soft plaque by including an ultra sound unit at the end of the cath.

An angiogram whether ct or cath  involves medium (dye) injection to view any blockages.  It seems to me that a ct score involves the degree of soft plaque,  and provide percentages, doesn't make sense there is an inability to not be able to determine the degree of blockage within the lumen.

I know that a 3D (current state of art) provides a view similar to what is seen with a view during open heart surgery. The degree of stenosis can be very accurate with just a visual view of the lumen.  It seems the ct  would be able to calculate the degree of blockage with the state-of-art technology?

[ed34]

There is also that the standard angiogram doesn't see all vessels as it has to have a flow of blood to be seen. When my triple bypass failed, one of the veins wouldn't show up on the angiogram and cardiologists couldn't figure out where the surgeon had put it. Even though the surgical notes stated the position, it was totally invisible. A CT scan taken, a week later, showed the vein very clearly.

[kenkeith]

Very good reply and the additional information should be very helpful to many.

[ed34]

"The CTA is essentially a useless bit of technology that was first touted because of its high resolution.  Without exercise testing, the CTA shows a great picture of anatomy, but is useless in giving us any information whether the patient will benefit.
I would recommend nuclear stress testing, followed by angiogram if she fails"

Now this is where I get a bit confused. If a nuclear scan shows an area of the heart defecit in oxygen supply, and the vessel/s responsible are very small, then will the angiogram actually see them? I see the validity in the nuclear scan being in stress/rest modes. Is it worth the risk of a stroke/heart attack to possibly find the blockage cannot be seen? Maybe this never occurs, but as I stated in my case, they couldn't locate a blocked vein in my case using an angiogram.

[kenkeith]

"The CTA is essentially a useless bit of technology that was first touted because of its high resolution.  Without exercise testing, the CTA shows a great picture of anatomy, but is useless in giving us any information whether the patient will benefit".

>>>>What benefit is the expectation??? What are you talking about? Unclear.  I can tell you the CT scan is not useless.  It can dx a condition in ER within minutes that often took hours and sometimes days.  It is undisputable that it has saved lifes.

What is " heart defecit "?  Never heard of that!. We can all see the validity of testing for blood perfussion through heart tissue at rest and exercise...that's basic and been around a long time.

"Is it worth the risk of a stroke/heart attack to possibly find the blockage cannot be seen? Maybe this never occurs, but as I stated in my case, they couldn't locate a blocked vein in my case using an angiogram."
>>>>The significance in the ability to see microvessels, if that is want you are referring to in your case, can be helpful to manage and diagnose variant angina. Is it worth the risk of stroke/MI to do a cath angiogram!?  Maybe I miss your point.

[oldie]

I am following your posts with the concentration your joint experience merits. Please keep it going. Your differing views are priceless information for us all.
For exampl,. I hope you will return to ED324's assertion:     'There is also that the standard angiogram doesn't see all vessels as it has to have a flow of blood to be seen'  So does the flow of blood stop in a straight angiogram? Isn't it the blood that carries the iodine through  the vessels so they can be seen?.

[kenkeith]

QUOTE:'There is also that the standard angiogram doesn't see all vessels as it has to have a flow of blood to be seen'  So does the flow of blood stop in a straight angiogram? Isn't it the blood that carries the iodine through  the vessels so they can be seen?.

>>>>>Yes, blood flow moves the injected agent through the tissues.  CTA and cath angiogram by definition are perfusion tests looking for blockage, etc.  Total blockage would stop the blood flow to a portion of the heart unless there are collateral vessels bypassing and feeding blood into the area formerly fed by the blocked vessel.  Collateral vesses can develop slowly as the bockage inceases.  Increase of blockage, increases the gradient pressure across the blocked vessel.  With the higher pressure, blood flow will flow to the area of least resistance and often open the previously unopened vessels (collateral vessels).  There is some evidence with an acute blockage there can be some opening of collateral vessels.

With my CTA. the report indicates there are images that show blood flow to the stented RCA 6 years ago, and good outflow from the stent implant.  Conjecture on my part, if there is a reduced output from a stent,  that reduced volume output can provide a calculation of percentage of blockage with a ratio of blood volume in vs. out.

A cath angiogram as far as I know doesn't see any microvessels, but microvessels can be problematic causing chest pain (angina), and the problem apparently viewed according to ed with the CT 256 slice (if I understand the comment correctly)... the CTA technology is not very useful because it doesn't provide therapy.  We all know tests are diagnostic and not therapy so I don't really understand what is implied.

A CTA that can view microvessels, may give the treating doctor some insight how to treat the variant angina. Usually that is medication (calcium antagonist and nitrate).  There are results with this therapy for angina, and often in about 6-12 months there is a gradual reduction of symtoms (symptoms).  Being able to image microvessels is a major step to treat variant angina, so I am somewhat at a loss regarding the comment technology doesn't benefit the patient!  There requires a dx before treatment so it really doesn't make sense to say the technology doesn't benefit the patient!?

[ed34]

I think people are confusing who said what in their post. So, perhaps I should clear up my points. A vein which was grafted during my bypass completely blocked and no blood was flowing through the vessel, hence no trace material for the scanner to pick up. This rendered the vein invisible during the angiogram. However, a CT scan did pick up the vein, supposedly because it slices the actual anatomy of the heart using different tissue densities to create an image. So, my point was, if a coronary artery is completely blocked, hence no blood flowing, it will be invisible on the angiogram. However a CT scan will see it. It could be any diagonal or branch, but what benefit could an angiogram possibly have over an angiogram when a CT scan sees more? I'm not referring to micro vessels, the vein in my case is certainly not micro.
(Oldie) an angiogram can only see the dye injected directly into the vessels from the catheter during the procedure. When you lay on the table, you see the dye squirting into the coronary arteries and they suddenly appear on the monitor. Once the dye has passed through the artery, which it does very quickly, it becomes invisible again. This is why a technician has to take a snapshot of the image and can freeze frame it for close analysis.
Imagine a clear plastic tube with clean water flowing quickly through it. You can't see the water. You inject some dye and you see it. However, the dye soon washes through and the tube once again becomes clear again, the water is invisible. This is a rough idea how it works. So if you have a blocked tube, dye will never enter it, so it will never be seen.
Experts can obviously see if certain vessels are blocked, such as the LAD because they know where the vessel is expected to be and how far down it should run. The same with the circumflex and right coronary artery. But, when you get into slightly smaller vessels, I was asking if the situation would become confusing because our arteries tend to be mapped differently. How would you know if a smaller branch was blocked and should exist if it's invisible?

[kenkeith]

"This is a rough idea how it works. So if you have a blocked tube, dye will never enter it, so it will never be seen".  Not the same as there is missing the relevant dynamics.

Blood will show in a blocked vessel.  For instance consider fluid dynamics as it relates to hemodynamics (it is fluid, degrees of viscosity).  For an anology there is water flow down a channel (river) and the banks of the river have different sized barriers.  The river flows with a given velocity (movement) and it will have a different sectional  flow patterns and velocity based tortuousity,etc.  Add volume and pressure at the mouth of the river and because of tortuosity, shear stress, velocity, etc. the banks of the river become less of a barrier and a dam develops and as the river flows there will be more deposits of material that blocks the normal flow of the river. What happens?  The river flow meets higher resistance at the dam site and the river backs up and tributaries develop. Put oil in the water at the appropriate location and oil will show at the dam site and move into the branches as well

Another example consider a garden hose that has holes and at the end there is an outlet with some resistance to the water flow.  Increase the water supply and the resistance increases at the outlet and water will leak out of the holes as there is less resistance.  Fluids flow to area of least resistance.  The examples, don't include the viablity of the human system and that adds other dimensions.

My cath angiogram showed/shows a comletely blocked LAD as well as the CTA as one would either have died or there are tributaries feeding into that would have been supplied by the LAD.

[ed34]

I'm sorry but I have to disagree with this. If we forget all the rivers and dams, tubes, hosepipes, stress, resistance etc and go back to real basics we can see why. There are many people with dead areas of heart muscle. This obviously means that muslce is receiving no oxygen, which means no blood. If you inject dye into the Left coronary artery or the right coronary artery, none of the vessels in those areas would show up on an angiogram because it's impossible. It's impossible because it would suggest blood flow to that area, which would suggest oxygen supply, which would suggest the tissue cannot be dead. That would lead to millions of people being misdiagnosed which I doubt.
I can see your point with regards to collateral development for example, but we do know not everyone develops them, or in time. My LAD was too blocked 100% in the proximal section, but the remainder of the vessel appeared on the angiogram, although very thin. This was because it had a feed coming in from the very distal section, just enough to keep my heart muscle alive but not enough to allow exertion. So yes, if we develop natural bypasses, then the dye will find a way through but it can only flow within the blood. So no blood, no dye, no image. The Vein I mentioned in my case was closed, it was not able to accept blood from either end, hence it was empty. This is why is wouldn't show up on a standard angiogram. Empty vessels in dead areas of a heart would not show up on an angiogram or thallium perfusion scan because they rely on blood flowing.
Anyway back to my point. I think a CT scan is far more accurate than an angiogram because it detects all vessels and it is much lower risk. The newer scanners are much quicker also, much quicker than an angiogram. My wife went for a follow up CT scan last week for her cancer, which usually took 30 minutes. She went in the room and just as I picked up a magazine and started to flick through the pages, she was back out. I thought it had been cancelled and I was amased to hear the scan was finished so quick.

[kenkeith]

I am providing some insight to an understanding of fluid dynamics as it relates to blood flow.  I have not been specific to any particular heart disease, test, etc. that's another subject.  Before there can be any assessment of a condition, there needs to be an understanding of the NORMAL functionality.  You have a problem of going from general to specific, and specific to general, have conclusions based on conjecture what you believe is to be true without providing a basis, etc.  We all know necrotic cells don't pass a perfussion test nor electrical impulses and that realization stems from the knowledge we know about how cells behave normally! etc.  

We have had discussions related to statistics and probability....you don't seem to understand that either?  Arteriogenises was argued by you and you didn't realize your information was related to angiogenesis.etc. etc.  I don't mean to be rude to you but you don't seem to understand.
I am providing a link to help undertand vessel anatomy.
http://www.medhelp.org/posts/Heart-Disease/Angiogenesis-a-bypass/show/1066312

[ed34]

You have evaded the question, do you believe blood vessels never become empty and don't show up on angiograms or nuclear scans, where for example there has been tissue death.

[kenkeith]

I am happy to answer your questions (relevant or not) with pm.  It is my opinion further discussion on the subject is not in the best interest of the forum.  When I have time I will respond to any and all questions. Today I have matters that will take up most of my time.

[kenkeith]

Oldie asked my opinion so I should conclude with answer that may not be clear.

I stated in prior post, that necrotic (dead) cells are unable to pass blood (no perfusion) or electrical impulses so that should answer previous post.

A cath can be attached at the tip with ultra sound device but no transducer. The ultra sound is able to view the anatomy of the vessel for any soft plaque as does a CTA, and can also distinquish any total blockage to be hard plaque and often it can get to the core of necrotic cells

[oldie]

Eight months ago I had a dubotamine stress test which showed weakness at three points in the heart walls ‘suggesting’ CAD, ‘probably’ trivascular.  The doctors said I should get catheterization.  Now, the forums have convinced me I must do it. I had chosen the medication, diet exercise route. I feel the same as before – good days and bad hours.
The postings that decided me were those that said that without an angio one cannot know to what extent the arteries are blocked and that meanwhile they could be getting worse. If anyone approves or disagrees please say so.

[kenkeith]

If the protocol regimen that you have been following is not effective, then follow the doctor's recommendations, it his/her responsibility for your well being.  You should not take anything said on any forum. That is exactly what should not happen!  If you don't have confidence in your doctor's advice, you should find another doctor.  

[Gilaman]

I have angiogram scheduled Friday morning and I am terrified but the stress test showed a possible problem and I have been having a irregular pulse and pvcs and possible supra ventricular tachycardia. I had calcium score of 236 and I had plaque on the back of my heart. Saw a cardiac electrophysialogist and he was worried it was a plumbing problem rather then electrical. I am a 64 year old female with diabetes , IGA Deficiency, high blood pressure and a family history of mother with dissecting thoracic aortic aneursyms 3 and two angioplasties for one blocked vessel. Help am terrified. Also allergic to shellfish and IVP dye.