Stress testing is one modality used to screen for CAD. The goal is to identify a fixed obstruction to coronary blood flow (typically plaque > 50%) such as in stable angina. However, in ACS, both USA and AMI, the underlying pathophysiology is plaque rupture (typically plaque < 50%) and thrombus formation that may not have been significant enough to cause a positive stress test.
The use of a prior negative stress test to determine the disposition of ED chest pain patients is questionable. The history of present illness should dictate patient disposition. In one study 20.7% of patients presenting to the ED with a negative stress test within three years of presentation still had significant CAD defined as a positive cardiac markers, subsequent positive stress test of any type, cardiac catheterization requiring intervention, or death due to medical cardiac arrest within 30 days of ED presentation.
References
Walker J, Galuska M, Vega D. Coronary Disease in Emergency Department Chest Pain Patients With Recent Negative Stress Test. Western Journal of Emergency Medicine. September 2010; Volume XI, Num. 4
