Pain (angina) is the last in a sequence of features resulting from myocardial ischaemia.
As the level of exercise increases, the myocardium first shows diastolic stiffness, then progressive depression of contractility, before the onset of pain. This is why you can develop dyspnoea as a feature of painless ischaemia.
The early appearance of a perfusion defect helps explain why nuclear stress tests are such a good stratifier and why perfusion images in other modalities are keenly developed. The late appearance of systolic contraction abnormalities does mean that false positives are unusual in dobutamine and physical stress imaging.
Go to the next page for an illustration of coronary perfusion.