Which Cardiac Stress Test, and Why

Fourth in a Series

There are so many choices, you have so little time. You are taking your recertification exam, and you’re asked whether you want an exercise stress test, as opposed to a dobutamine stress, and, if so, whether you want to choose from a menu of imaging choices the likes of thallium or echo. Or maybe you should skip that option altogether and go straight to cardiac catheterization.

Well, there is method to the “madness” surrounding cardiac stress tests. Let’s establish a few fundamental rules for making wise choices and getting successful results:

• The level of evaluation-that is, the test selected (or whether any test is indicated)-is directly correlated with the pretest probability of ischemic heart disease. For example, if a validated instrument is applied (such as the Diamond-Forrester estimate of pretest probabilities), who would be more likely to have underlying coronary disease, a 45-year-old man with atypical chest pain or a 45-year-old woman with similar, atypical symptoms? Pretest probabilities would be 46% and 13%, respectively! For an order of magnitude, the probability for a 70-year-old man with chest pain would be about 70%.

To provide an example, a 68-year-old man presents with central, retrosternal chest pain on exercise that is better with rest. From choices such as exercise ECG, coronary angiography, exercise echocardiography, and exercise thallium imaging-or nothing-what is the correct answer?

The correct answer is coronary angiography. This patient’s pretest probability is high, so rob the bank where the money is: when probability is high, obtain maximum information with catheterization to define the site, severity, and extent of coronary disease.

• The choice of an optimal stress test also depends on whether underlying cardiac disease is present. Taking pretest probability another step, adding cardiac disease, let’s choose a correct answer.

What should you do with a 48-year-old man who has both left ventricular hypertrophy (LVH) and atypical chest pain?

How about an exercise ECG because the patient is not as likely to have coronary disease as the 68-year-old man discussed above? Because his pretest probability is about 46%, not 70%, cardiac catheterization is not indicated. But, exercise ECGs may be nondiagnostic in patients who have LVH. A stress thallium study also would be limited by LVH. So, exercise echo, more specific in the setting of chest pain plus LVH, would be the best answer.

• There are occasions where “discretion is the better part of valor.” Considering a 28-year-old woman with hypertension and diabetes mellitus who has chest pain, both at rest and with exercise, which test is best? Now we go back to our first rule-what is the pretest probability of coronary disease in this patient? It is only about 4%. This time the answer would be no stress testing.

If you are recertifying in a primary care field, you are not going to be asked to read thallium images or echoes with stress. You are going to be asked to demonstrate an understanding of whether the likelihood of having coronary disease is substantial for a person who has chest pain. You also need to consider accompanying findings, like LVH, that interfere with certain tests for ischemia.

This also means that physical exam findings like ventricular enlargement will help you get the answer right.

References:

1. Stoller JK, Nielsen C, Buccola J, Brateanu A. The Cleveland Clinic Intensive Review of Internal Medicine. 6th ed. Philadelphia: Wolters Kluwer; 2014: 350-352.