Cardiac Stress Test - Diagnostic Value

Diagnostic Value

The common approach for stress testing by American College of Cardiology and American Heart Association indicates the following:

• Treadmill test: sensitivity 73-90%, specificity 50-74% (Modified Bruce Protocol)
• Nuclear test: sensitivity 81%, specificity 85-95%

(Sensitivity is the percentage of sick people who are correctly identified as having the condition. Specificity indicates the percentage of healthy people who are correctly identified as not having the condition.)

The value of stress tests has always been recognized as limited in assessing heart disease such as atherosclerosis, a condition which mainly produces wall thickening and enlargement of the arteries. This is because the stress test compares the patient's coronary flow status before and after exercise and is suitable to detecting specific areas of ischemia and lumen narrowing, not a generalized arterial thickening.

According to American Heart Association data, about 65% of men and 47% of women have as their first symptom of cardiovascular disease a heart attack or sudden cardiac arrest. Stress tests, carried out shortly before these events, are not relevant to the prediction of infarction in the majority of individuals tested. Over the past two decades, better methods have been developed to identify atherosclerotic disease before it becomes symptomatic.

These detection methods have included either anatomical or physiological.

Examples of anatomical methods include

• CT coronary calcium score
• Intima-media thickness (IMT)
• Intravascular ultrasound (IVUS)

Examples of physiological methods include

• Lipoprotein analysis
• HbA1c
• Hs-CRP
• Homocysteine

The anatomic methods directly measure some aspects of the actual process of atherosclerosis itself and therefore offer the possibility of early diagnosis, but are often more expensive and may be invasive (in the case of IVUS, for example). The physiological methods are often less expensive and more secure, but are not able to quantify the current status of the disease or directly track progression.