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     So You're going to have a (Nuclear) Cardiac Stress Test...




INTRODUCTION

   The usual reason for a nuclear cardiac stress test is to tell if 
your chest pain is caused by partial blockage of one or more arteries 
arteries of the heart.  Patients with this condition are said to have 
ischemic heart disease.

   Many patients will have a history of squeezing chest pain moving 
("radiating") down the left arm during physical stress.  Other 
patients do not have such classic complaints.  The idea behind the 
test is to stress the heart physically through exercise, and then 
image the response.

   If you want to participate in your own care, you will definitely 
want to speak with your doctor about why you are having this exam.



WHAT Will HAPPEN?

   It seems that no other nuclear medicine exam has more variation 
that a cardiac stress test.  There are, at present, two commonly used 
radiotracers -- the time-honored thallium and the newer technetium 
MIBI.  Either of these can be combined with either standard "planar" 
imaging or with the newer cross-sectional imaging ("SPECT"), in which 
the nuclear camera rotates around the patient's chest.  To complicate 
matters further, a patient can either undergo "real" exercise by walking 
on a treadmill or else receive an intravenous injection of dipyrdamole 
which dilates the arteries in the heart just as exercise would.

   Fortunately, some things are less variable.  You will have standard 
EKG leads attached to your chest just as for an electrocardiogram.  An 
intravenous line will be started in your arm.  There will be two sets of 
images (at least!).  One will be immediately after "stress," whether due 
to real exercise or simulated by dipyrdamole.  The other will be at "rest."



WHAT WILL HAPPEN? PART II (Only for the VERY interested!)

   If you are able to exercise, you will be shown how to walk on a 
treadmill.  At first the treadmill moves slowly and you may not have 
any problem "keeping up."  Then, as the test progresses, you will find 
yourself having to walk faster and faster.  Your blood pressure, heart 
rate and electrocardiogram will be monitored as you exercise.  The 
longer you can exercise, the better the test.   However, If you have 
chest pain or feel dizzy, you MUST inform the physician monitoring the 
examination.  When you feel you can exercise no longer, radiotracer 
will be injected through the I.V. line, and you will be helped onto a 
table where images of your heart will be taken by the nuclear medicine 
camera (stress images).

   If you are NOT able to exercise, you will be given dipyrdamole 
slowly through your I.V. line followed by radiotracer.  This simulates 
exercise.  Pseudo "stress" images of the heart are taken as above.

   In either case, you will be asked to return about 3 to 4 hours for 
repeat images (called variously delayed, rest or redistribution 
images).  Re-injection of additional radiotracer may be made depending 
on the radiotracer and the imaging protocol. 



HOW LONG WILL IT TAKE?

   The exercise, and the preparation for it, can take 20 to 40 
minutes or more depending on how much exercise you can tolerate.   
Imaging of your heart can take 30 minutes or more and there is a   
gap of 3 hours or so in between sets of images.

	All told, Nuclear Cardiac Stress Testing takes the better part 
of a day.



WHAT IS THE NUCLEAR PHYSICIAN LOOKING FOR?

   The nuclear physician is looking for areas of the heart that have 
decreased blood flow during exercise (or its equivalent) but normal 
flow during rest.  

	This decreased flow during physical stress, which is often associated 
with chest pain, is presumed due to narrowing or partial blockage of one 
or more (coronary) arteries in the heart.  The hope is, that with 
medication or with surgery, blood flow can be increased, thereby relieving 
chest pain and improving exercise tolerance.



WILL OTHER TESTS BE NEEDED?

   Depending on the results of your nuclear cardiac stress test AND 
your physical and clinical condition, coronary angiography and perhaps 
coronary artery dilation (angioplasty) may be performed.  

	Sometimes coronary artery bypass surgery is considered.  In other 
situations, medical management seems more appropriate.

   These alternatives should be discussed with your doctor when you 
get the results of your nuclear cardiac stress test.



WHAT PREPARATION IS SUGGESTED?

   Because there are so many different ways of going about nuclear 
cardiac stress testing, the best suggestion regarding eating is that 
you should contact the nuclear medicine department where your test will 
be done for their recommendations.  Diabetic patients on insulin merit 
special consideration, and the nuclear medicine department should know 
about this important information so that meals can be scheduled 
appropriately.

   Because various drugs can influence the stress test, you are 
encouraged to speak with your doctor to find out what cardiac 
medications you should be taking at the time of your examination.

   If you will be performing treadmill exercise, you would be 
advised to wear comfortable clothes including walking shoes or 
sneakers.

   A detailed note from your doctor which includes your current 
medications is very important.



FINAL WORDS

   Nuclear cardiac stress testing may seem complicated from the 
"WHAT WILL HAPPEN?" section above.  In practice, it is not  
complicated because a patient will simply follow whatever protocol 
(plan) is being used by the nuclear medicine department where the 
study is being done.  All approaches can yield excellent results if 
necessary care is taken.

   




                                    Michael Tobin, M.D.,Ph.D.

                                    Board Certified 

                                    American Board of Radiology

                                    American Board of Nuclear Medicine



copyright April, 1990

all rights reserved