2. When should you rule out stress testing?
Stress testing is unnecessary in asymptomatic patients. Numerous studies have documented the lack of benefit from screening asymptomatic people for CAD using exercise stress testing.5,6 The US Preventive Services Task Force gives this a Grade D recommendation—recommending against routine stress testing.7
There are also numerous contraindications, both absolute and relative (TABLE).8 Relative contraindications, which include severe hypertension, left main coronary stenosis, moderate stenotic valvular disease, electrolyte abnormalities, cardiomyopathy, serious mental or physical impairment, and atrioventricular block are conditions that are likely to interfere with test performance or reliability.
Absolute contraindications, generally related to unstable cardiopulmonary disease, pose a far more serious threat. Indeed, administering a treadmill stress test to a patient with 1 or more absolute contraindications greatly increases the risk of death associated with the test.8
Even if a patient does not have any relative or absolute contraindications, there is still some risk of moving forward with the test. There is about a 1 in 2500 risk of MI or death during, or related to, exercise stress testing.8 The greater the likelihood that a patient has CAD, the higher the risk.
There is also a risk of hospitalization after the test, usually related to persistent chest pain or arrhythmias. (I generally admit patients whose chest pain is unresponsive to 3 doses of nitroglycerine or who develop EKG changes that persist after 20 minutes at rest.) The test also raises the possibility of injury from the equipment, such as sprains or fractures caused by falling from the treadmill.
Nuclear stress testing also has a small risk of an allergic reaction to the isotope used as a tracer. The radiation dose is 8 to 9 mSV, comparable to a computed tomography (CT) scan of the chest and generally less than that of a coronary angiogram.9
TABLE
Stress testing: Absolute and relative contraindications8
| Absolute contraindications |
|---|
| Recent MI (<2 days) |
| Unstable angina |
| Uncontrolled ventricular arrhythmia |
| Uncontrolled atrial arrhythmia that compromises cardiac function |
| Symptomatic HF (uncontrolled) |
| Severe aortic stenosis (uncontrolled) |
| Dissecting aneurysm (suspected or confirmed) |
| Myocarditis (active) |
| Pulmonary or systemic embolus (recent) |
| Acute pericarditis |
| Relative contraindications* |
| Severe hypertension |
| Left main coronary stenosis |
| Moderate stenotic valvular disease |
| Electrolyte abnormalities |
| Cardiomyopathy, including hypertrophic cardiomyopathy |
| Mental or physical impairment that results in an inability to exercise adequately |
| high-degree atrioventricular block |
| HF, heart failure; MI, myocardial infarction. |
| *Relative contraindications are conditions that are likely to interfere with test performance or reliability. |
3. Does the evidence support the use of stress tests for asymptomatic patients with diabetes? Are preop stress tests advisable?
The jury is still out on both questions.
The question of asymptomatic testing for patients with diabetes mellitus, who are more likely than those without the disease to develop CAD, frequently arises. Although individuals with diabetes have higher rates of silent ischemia than the general population, however, estimates of this prevalence vary widely.10 There are no clear guidelines for evaluation of asymptomatic diabetic patients with exercise stress testing. (See “Test your skills with these 3 cases”)
The addition of nuclide imaging adds diagnostic value to the test, but it is still not clear that this should be the preferred test for patients with diabetes who have normal resting EKGs.10,11 A recent randomized controlled trial investigating screening with pharmacologic stress testing in asymptomatic patients with type 2 diabetes did not show a reduction in cardiac event rates in patients who were screened compared with those who were not screened.12
Similarly, preoperative stress testing is subject to debate.13 Many studies have been done to evaluate the utility of preoperative stress testing, with revascularization procedures done before the planned surgery when significant CAD is found. (See “Before surgery: Have you done enough to mitigate risk?” J Fam Pract. 2010;59:202-211.) And, while many demonstrate the predictive power of various parameters that stress tests measure, literature reviews show that—with the exception of patients with unstable CAD—postop event rates are about the same for patients who underwent stress testing and subsequent revascularization vs those who were treated medically instead.13,14
Test your skills with these 3 cases
CASE 1 Daniel G, a 68-year-old whom you’ve been treating for hypertension for more than 10 years, is about 25 pounds overweight. He has decided to begin an exercise regimen, and the trainer he hired to work with him at the gym has asked for medical clearance.
CASE 2 Marge H, age 73, has peripheral neuropathy and spinal stenosis. She sees a neurologist regularly, but has come to see you today to report that for the last several nights, her heart has been racing and she’s felt an uncomfortable sensation in her chest.
CASE 3 Ed W, a trim 56-year-old, has been swimming 5 days a week for years. Last week, he experienced a tightening in his chest in the middle of his swim. The pain subsided shortly after he stopped swimming, but it returned as soon as he got up to full speed again. He asks whether you think it’s a pulled muscle or angina.
Should any—or all—of these patients undergo cardiac stress testing?
CASE 1 Daniel’s case highlights the discrepancy between commonly held beliefs and medical evidence. For decades, people have been told to get a medical evaluation before starting an exercise program, and a stress test has commonly been part of that evaluation. However, numerous studies have failed to show a benefit of stress testing in asymptomatic people. The US Preventive Services Task force recommends against routine stress testing in asymptomatic people.7 And, while the american heart association/american college of cardiology guidelines suggest that stress testing in men over the age of 45 with 1 or more risk factors may occasionally yield useful information, the organizations acknowledge that this opinion is based on weak information.23
You tell Daniel that moderate exercise is unlikely to provoke a serious cardiac event and that if symptoms arise during exercise, he should report them promptly so that appropriate testing can be ordered.
CASE 2 Marge’s primary complaint sounds more like an arrhythmia than angina. however, coronary ischemia cannot be excluded; ischemia could be caused by decreased cardiac output from an arrhythmia, or it could be the cause of an arrhythmia. A holter monitor would be a good initial test for this patient, followed by stress testing to determine if angina is the cause of her symptoms. Because of marge’s peripheral neuropathy and spinal stenosis, she may be a candidate for a pharmacologic stress test.
Given that stress testing is less sensitive in women than in men, there is a widespread belief that women should not be tested with exercise stress testing alone. however, the available literature suggests that this test has appropriate predictive value for women with an intermediate CAD risk.4
CASE 3 Ed presents with typical symptoms of angina pectoris. While some noncardiac diseases—esophageal spasm, for example—can cause nearly identical symptoms, the likelihood that this patient has symptomatic CAD is high. Thus, he should undergo stress testing with nuclide imaging. This patient is physically fit and therefore can take an exercise test, which will provide information—most notably, functional capacity and the level of exertion needed to cause symptoms—that a pharmacologic stress test would not.