The most common ECG dilemmas one encounters is to differentiate between the ST segment depression and T wave inversion due to LVH from that of primary ischemia.
Very often , the entity is misdiagnosed . The implication can be serious , and adding further complexity is exercise stress testing is alos prone for errors in these group of patients as false negative or positive results are very common due to basline ST/T changes.So it needs a CAG to confirm or rule out CAD in many .
Still the clinical acumen with the help of ECG can help us to a great extent !
A rough and approximate way to identify primary ischemia is given below.
Though these humble ECG features may not be specific to diagnose CAD . One need to remember even a normal coronary angiogram is not synonymous with normal coronary arteries !
Read this blog on limitations of CAG .