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Stress MRI
Posted Jul 08, 2008
at 11:10 AM, EDT
Just curious - I train at a facility with "stress MRI" means dobutamine MRI, but last night was talking with a friend at another institution who said "dobutamine MRI - you can't do that, it's too hard to gate...stress MRI means adenosine MRI." A quick glance at the literature suggests that there's evidence for both approaches - I'm just curious what's used where, and why...does anyone know of places that routinely use both, or does the world divide into 2 clearly defined camps?
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The answer is: both types of stress MRI exist (adenosine and dobutmaine). Each one has its merits (just like when use with SPECT imaging). At the institution I trained, we used adenosine as the routine stress protocol and only used dobutamine if reuqested by the referring physician. Typical indications for dobutamine MRI (over adenosine): exercise induced symptoms, suspicion of ischemia from anomalous coronaries or ned to deonstrate contractile reserve in a hypokinetic/akinetic segment.
Adenosine is quicker and easier. Gating is NO problem with dobutamine CMR because the temporal resolution of SSFP (cine) sequences is very very low eg. 30-40ms.
Stress related wall motion abnormalities can also be assessed with dobutamine over adeonsine.
I am a private practice cardiologist in Scottsdale, AZ. A radiologist friend asked for "guinea pigs" to test their adenosine stress MRI protocol at a large imaging facility. I volunteered myself and my PA. I am a cool, calm and collected person normally. This test was not only LENGTHY (took over an hour and a half from image acquisition, total of 3 hours from IV start and skin prep) but sitting in the MRI scanner was indeed tough, both from a time duration and anxiety inducing standpoint.
I will mention this to you all for your benefit: I will not order this test on my worst enemy. Adenosine infuses per weight based protocol over 2 minutes. You cannot hear when the infusion starts, you notice an incredible vasodilation and racing heart, your respiratory drive increases, you feel like you are going to faint and then you open your eyes and you are stuck in a tube with "stabilizing" foam padding and wires on your chest, one IV in each antecubital fossa and then a voice says "breathe, don't breathe" and a loud honk sounds for 60 secs while you attempt to hold your breath and be a good patient but your heart is racing and you feel your diaphragm twitching from trying not to release your breath. NOW, how is a radiologist going to code a patient if truly an ischemic event or adenosine related issue happens? That is why I won't order this test, I find it not only impractical, it is not safe. Makes you also think twice about the use of adenosine.....good luck and ask your patients for feedback, no one will sign up twice, mark my words.
i did 1 year cardiac MRI. We do more than 1500 stress MRI per year. Compared to nuclear stress test, the adneosine infuison is only 2-3 min compared to 4-6 min (half the time) and therefore less side effects. It takes me on 30 to do the stress test including the Cines, delayed enhancement, assessesing the valves, regurgitaiton., looking for thrombus and ruling out dissection. In nuclear, you have to be scanned twice, rescanned if you didn't clear. MRI is by far one of the best stress perfusion studies and gives you detailed viability and scar assessement. When we did the test, the nurse is present during the adneosine infusion and guides you through it and i also talk to the pt while doing the test and warn him when the infusion starts.
The pts like it and we had no complaints.
i will definetly order it to most of my patients and myself if i need to.
I think the center wher eyou did it had limited experience with stress MRI.
I would like to add to the above fellow's comments. My institution does stress MRI as well. I suspect that the experience by the private practice cardiologist is at an institution that is still working out the protocol. Our scans take 40 minutes from start to finish. The adenosine infusion causes the same side effects as when you order an adenosine nuclear test. All of our cardiac MRIs are performed by cardiology only. We have 2 nurses present, a cardiologist and at least 1 extra MRI tech on hand. In just 40 minutes you obtain stress, rest and viability images. Additionally, I get all of my cine images including stacked short axis images to get an accurate 3D ejection fraction. During the adenosine infusion a nurse, a tech and the cardiologist are all standing at the patient's head talking them through the infusion, just like we do with a nuclear scan. The key is preparing your patients for the symptoms. I'm proud to say that we have not had any patients unable to complete the study. The results are instantaneous and the referring physicians have been thrilled with the image quality and the accuracy of the scan. We primarily use adenosine, but dobutamine is a definite option. The test is safe even in the early post MI setting.
Here are a few references if you would like:
J. Am. Coll. Cardiol. 2008;52;279-286
J. Am. Coll. Cardiol. 2007;50;1343-53
Circ. 2007;115;1769-76
From the above comments , Stress MRI seems to be an exciting new field in cardiac imaging which can give valuable informatins about myocardial ischemia & scarred myocardium in addition , the only problem if someting bad( cardiac arrest ) happened to the patient while inside MRI room, especially when long protocol 30-40 min dobutamine is used, of course the question of cost-effectivness is also another problem.
DR Ihab Suliman, Riyadh, KSA