How is the probability of myocardial ischemia determined prior to a nuclear myocardial scan?

Updated: Aug 07, 2019
  • Author: Thomas F Heston, MD, FAAFP, FASNC, FACNM; Chief Editor: Eugene C Lin, MD  more...
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Answer

The value of nuclear myocardial scanning is its predictive accuracy. Most notable is the fact that normal findings are predictive of a benign outcome: normal scan results are associated with an annual rate of severe cardiac events (myocardial infarction or cardiac death) of less than 1%. By contrast, the value of positive scan findings is dependent on the pretest probability of disease. Because the accuracy of any test that is not 100% sensitive and 100% accurate depends on pretest probability, determining this probability is important for increasing the test’s clinical value.

In their landmark CAD risk analysis article, Diamond and Forrester described the relationship between clinical symptoms and angiographically significant CAD. [25] The authors described 3 types of chest pain: nonanginal, atypical, and typical. The benefit of their categorization is the ease of its use and its powerful risk stratification. Disease is categorized on the basis of 3 symptoms, which are assessed with these questions: (1) Is the pain retrosternal? (2) Is the pain precipitated by stress? (3) Is the pain relieved by rest or nitroglycerin? Patients who answer yes to all 3 questions are determined to have typical chest pain. Patients who answer yes to 2 of the questions have atypical chest pain, and patients who answer yes to only 1 question have nonanginal chest pain.

Diamond and Forrester’s findings showed a large difference in the rates of angiographically significant CAD according to chest pain category. For example, a man in his 30s with nonanginal chest pain has a relatively low risk of CAD (approximately 5%); however, if the pain is typical, the risk is higher (70%) (see the image below).

The risk of coronary artery disease (CAD) can quic The risk of coronary artery disease (CAD) can quickly be stratified by determining whether the patient's pain is nonanginal, atypical, or typical. For men in their 30s with nonanginal chest pain, the pretest probability of disease is approximately 5%; however, men in their 30s with typical chest pain have a 70% likelihood of disease (a 14-fold increase).

Although the absolute values are different for women, the same principle applies. Women with nonanginal chest pain have a lower risk of CAD than women with typical chest pain. For instance, a woman in her 50s with nonanginal chest pain has a relatively low risk of CAD (10%), whereas a woman in her 50s with anginal chest pain has a higher risk (80%) (see the image below).

In women, the risk of CAD can quickly be stratifie In women, the risk of CAD can quickly be stratified on the basis of the type of chest pain. For example, a woman in her 50s with nonanginal chest pain has a pretest probability of disease of approximately 10%, whereas a woman in her 50s with typical chest pain has a pretest likelihood of approximately 80%; this rate is an 8-fold increase.

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