Nuclear Stress Tests are the Mammography of the Heart
If we are looking for a cardiac test that has characteristics similar to mammography, the nuclear stress test is much closer than CAC.
With a nuclear stress test we are using a radio tracer injected intravenously, which subsequently traverses the coronary arteries into the heart muscle. Subsequent imaging of the photons emitted by the radio tracer allows assessment of the status of blood flow down the coronary arteries.
The test is designed to identify coronary arteries with flow limiting blockages (usually >70% blocked), caused by atherosclerotic plaques. Such blockages are more likely to be causing symptoms and therefore more likely to require treatment with coronary stents or bypass surgery.
Like mammography, then, nuclear stress tests are either abnormal or normal, and when abnormal they can be falsely abnormal.
Nuclear stress tests have a very high incidence of false positives. These false positives result in invasive catheterization procedures to more directly image the arteries, and may result in inappropriate coronary stenting or bypass procedures with associated risks.
It is because of the high risk of false positives and attendant harm that in the last decade, all cardiac societies recommend against the routine use of stress testing in asymptomatic patients.
As pointed out in the Widowmaker, there is no data which suggest that stress testing improves outcomes for cardiac patients.
Stress tests by design tell us nothing about the noncritical build up of atherosclerotic plaque. You can have a normal stress test and have a huge burden of plaque in your arteries.
It is this silent build up of atherosclerosis, with sudden rupture of plaque, which results in sudden death in most cardiac patients.
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