In the clinical practice of cardiology, some times, we are compelled to check our foundational concepts and refresh or reset the knowledge. Here is a two question challenge. The first question was in fact asked by one of my patients. Does negative TMT rule out CAD ? I thought it was a routine question, and told him no tests rule out CAD 100 % perfectly. It has only 70% accuracy. Some time later, after his consult , I was pondering over this 70 % accuracy . Very soon I realised , I was totally wrong with that answer as well. You can try to find the real truth about the validity of TMT in ruling out CAD.
1.Does negative TMT rule out CAD ?
A.No, It doesn’t
B.Yes, it rules out all significant CAD
C.Yes, it rules out obstructive CAD
D.No. It doesn’t rule out non-obstructive CAD .
Answer : To get the correct answer, go to the following question. (Response A,C,D are correct .B might appear right too , but it’s wrong.)
2.Which lesion often result in ACS in CAD population ?
A.Obstructive
B.Non obstructive
Answer : Both, (In fact, non obstructive CAD more often precipitates an ACS, because they are more in numbers)
So, what is the message from these two questions ?
TMT is in reality not useful to rule out ACS prone CAD. To include it in routine master health has little meaning , if that message is conveyed to our patients. (Of course a negative TMT rules out a severely obstructive lesion , that is really be a comforting news)
Read this Editorial from Dr Prem Pais for more insights.
Final message
TMT can never rule out the presence of ACS prone lesions at any level of exercise loads/METS . Hence the 70-80 % negative predictive value , we confer to it, is clearly misplaced in terms of ACS risk.
Reference
Postamble
Less we think, more stable will be our confidence levels in treating CAD patients.
Please read this Does normal coronary angiogram mean normal coronary artery ?
