Q. What is ST Elevation in Leads without Q-Wave?

ST elevation in leads without Q-waves can occur in few very different situations, both of which are fairly uncommon. The first is when patients have a very high grade proximal LAD stenosis or a high graft stenosis of a large right coronary artery. The ischaemia associated with ST depression is subendocardial whereas ischaemia producing ST elevation is transmural, affecting the full thickness of the heart. It follows that full thickness ischaemia is rare during exercise even with high grade proximal stenosis.

The second cause of ST elevation is coronary spasm i.e. so severe that it completely obliterates antegrade flow through epicardial arteries. This has been termed Prinzmetals angina and is most commonly seen at rest, but very occasionally occurs with exercise. It is common for arrhythmias to accompany this process. It appears that patient with angiographically normal coronary arteries and Prinzmetal's syndrome due to spasm usually have no change during exercise. If they have CAD, with or without spasm, ST elevation as well as depression may be seen. Exercise induced ST elevation in a subject with variant angina probably indicates hemodynamically significant coronary atheroma.