Exercise stress test ( Also called treadmill test ) is an important investigation not only in patients with suspected CAD but also in established CAD . In the former group , it helps us to exclude CAD in patients with chest pain and in the later group , it helps us to assess functional capacity , risk stratification and to detect any additional ( New or residual ) ischemia.
Stress test being a physiological test , has a huge advantage of assessing the adequacy of myocardial blood flow without even knowing the coronary anatomy , while Coronary angiogram (CAG) has a zero physiological value* in spite of excellent assessment of the coronary anatomy !
It is an irony , in the assessment of angina we are expected to assess the physiological adequacy of myocardial blood flow , we have kept coronary angiogram as a gold standard over and above the much neglected physiological stress test.
Of course, the limitation of stress test is that , it has only 75% specificity( to rule out CAD ) and about 80% sensitivity (To detect CAD ) .In simple terms stress test is likely to miss 20% times to miss a CAD in patients with CAD and 25% of times falsely diagnose CAD in patients without CAD.
In the above statistics , coronary angiogram was considered gold standard . The problem with this data is that , CAG is not the real gold standard ,but it was nominated as a gold standard . We now know normal coronary angiogram is not equivalent to normal coronary arteries and vice versa.
While both test have limitations , it is logical to believe CAG has an edge over stress test since it visualises the anatomy. But , once an obstruction is demonstrated by CAG, stress test scores over in assessing the physiological impact of the lesion.
Is a 70% LAD lesion significant or not ?
Stress test will give vital information to answer this question.If this patient performs 10-12Met exercise without symptoms it means , the obstruction is not impeding the flow even during stress. He may do well with medical therapy.
What does a positive stress *mean for the patient and for the physician ?
(* A false positive EST in LVH, anemia, baseline ST shifts are included in discussion )
- A positive stress test with or without angina at low workload <5 METS indicates very significant obstructive CAD either in left main , or proximal LAD/LCX. They should get immediate CAG.
- A positive stress test at load 5-10METS is again significant and patients should get early CAG
- A positive stress test with angina at good work load >10-12 mets would indicate insignificant or minimally obstructive CAD.
- A positive stress test at the peak of exercise at good work load > 10-12METS without angina could indicate a false positive or very minimal CAD.
For the physician , the proper way of interpretation should be , the fact that a person performs 10-12 METS indicate the myoacardial blood flow would be more than adequate in most life situations. Knowing the coronary anatomy serves no purpose here, as no revascularisation will be attempted even if he is going to have a significant CAD ( Which again , is also highly unlikely ) .He should be managed with appropriate lifestyle (Diet, activity, relaxation ) anti anginal drugs, aspirin , good lipid control and plaque stabilisation with statins .
Can a patient with critical left main or proximal LAD perform >10METS in exercise stress test ?
No , large clinical experience (Also refered to Class C evidence by ACC/AHA!) indicate no patient with critical left main or equivalent disease can perform 10 METS excercise
While , EST may be less hyped investigation, but it is the only noninvasive test , ( that too , simple and cheap ) that can rule out * a significant left main or equivalent almost 100% correctly .
Now that, the results of COURAGE and BARI 2D have clearly indicated medical therapy is best form of management in chronic CAD , ( except in severe obstructive CAD in vital locations) a positive EST at > 10-12Mets , has absolutely no indication* to for doing a CAG.
*Some would advocate a policy of doing a CAG as a baseline investigation in all patients with positive EST to know the coronary anatomy and will not proceed onto revascularisation if there is insignificant lesions.
Further , real life experience has taught us , routine CAG in these patients
- Increases patient anxiety as he is given a report with a diagram of obstructed heart vessels
- Leads to multiple cardiac consultations
- Divergence of opinions
- Finally end up in the likely hood of a inappropriate revascularisation for a insignificant distal CAD.
Final message
Every patient, who has positive stress test , ( Please note , it could even be true positive ) need not undergo CAG . Most interventional cardiologists could feel otherwise , but one should also remember , There is one more role for the interventional cardiologist ie , to intervene when inappropriate interventions are done to their patients.
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Dr.S.Venkatesan MD 
I had a positive reading. I believe it was some activity when I was recovering after I was on the treadmill for 7 minutes. I have low blood pressure, my total cholesterol is 205 and am 57 years old. I was told that I might have narrowing of an arterie and if they find something on the next test they would put a stent in. I can’t imagine that with low blood pressure and never being on cholesterol meds that this could happen. Any opinion will be appreciated.
The data you have given is limited , still I would advice you will require coronary angiogram and decide thereafter.
Please consult your cardiologist.
Dr Venkatesan Chennai,India
Dear Dr. Venkatesan
Thank you for this useful article giving insights into Stress test. I am a 54 year old former smoker (quit smoking in July 2016) . as apart of my annual check up recently I did Treadmill test and test was positive. My exercise time was about 5.8 minutes and i achieved 85 % of heart rate. However towards the end of test I felt slight heaviness in chest but no pain. My recovery was also normal and BP behavior during test was also normal.
I have been doing treadmill test every year and earlier results were all normal and negative.My cholesterol tested for last 20 years is always normal at around 4.2 with both HDL and LDL with in normal limits. TGL is also always normal. I am on Blood pressure medications since about 20 years but BP is well controlled at 120/80. I do not have diabetes.
I walk for 45 minutes on daily basis since many years and my weight is about 78 kgs and height is 172 cm.
I have never experienced any chest pain or shortness of breath while walking. I do suffer from GERD and am taking pantazole 20 mg.
I am quite puzzled as to how a stress test can change with in one year from Negative to positive (Test was done on same machine) with no change in lifestyle.
my Cardiologist is recommending Angiography. However I am reluctant to go for angiography and instead want try out medication/lifestyle change option.Currently I have started LIpitor (10 mg) and Plavis(75 mg) as advised by Doctor.
Would appreciate your advise about path forward. I do not have any symptoms of CAD.
Regards
Hi,
Medical management is possible for you.Please have periodic consultations with your cardiologist.
Venkatesan
Dear Dr. Vankatesan
will follow your advice. Thank you for your time.
54 old male hypertensive,non diabetic, dyslipedimia under control,ecg resting normal,echo normal,TMT strongly positive, completed 9minutes in TMT and achieved a 10 Mets had mild angina at TMT dukes score of + 4 .what is the ideal route is it Medical or angiogram.pl comment.
Dr Venkatesan replies , this patient requires early coronary angiogram and further assessment.
Very Nicely said sir.
Respected Sir, my father(age 61 years) is regular walker and has experienced no symptoms like breathlessness or pain or sweating but his TMT has come out to be positive. It says significant ST depression in II,III, AVf & V5-V6 starting 3rd stage of exercise and persisting till 6 minutes of recovery. Exercise duration:9:29 min, METS:10.8, MHR:87%. His ECG is completely normal, cholesterol is 200, Triglyceride is 285 and blood sugar 103. Doctor is suggesting Angiography. In your opinion can this situation be controlled through diet and medicine or Angiography is mandatory. Your response will be very valuable for decision making. Thanking you
Dr Venkatesan replies TMT file need to be seen before commenting.
Thank you so much Sir for your reply. In fact your above article has been very helpful and encouraging. Is there any way I can share the file with you in order to get your valuable opinion?
Hello Sir, I am a 48 year old female. I play lawn tennis regularly. When I had my stress test in 2016 at FORTIS it was normal with 11.6 METS. Recently I got the stress test done again from a different hospital (MEDANTA) and it shows borderline positive for reversible myocardial ischemia. it says >1mm depression seen in 2,3 avF , V5-V6 at peak of exercise which reverted in 1 minute of recovery. My cholestrol is borderline high at 211 and HDL is 43.
Please advise my next step.
Dr Venkatesan replies, need to see the patient and the complete file to give a proper opinion.