Exercise stress testing in the asymptomatic adult: family physician adherence to the guidelines

Rachel Holt, OMS, IV, 9301 Augsburger Rd., Bluffton, OH 45817.

E-mail address: rachelmarieholt@yahoo.com.

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OBJECTIVE: Exercise stress testing has not been recommended by the American Heart Association or the American College of Cardiology as a screening tool in the asymptomatic population because such testing has limited value in this population. It was the goal of this study to investigate family physician adherence to clinical guidelines regarding exercise stress testing of the asymptomatic adult.

METHODS: This trial surveyed osteopathic family physicians attending a continuing education con- ference. Physician identifiers were not requested or recorded. Both descriptive and inferential statistics were produced. Frequencies and percentages as well as chi-square analysis were performed with significance set at an a < 0.05.

RESULTS: A total of 181 osteopathic family physicians completed surveys. Participating physicians were more likely to order a stress test as the patient aged and as their Framingham risk increased. Universally more physicians ordered stress tests for men than women in all categories. Non-diabetic men (83% vs. 86%) and women (83% vs. 84.5%) greater than 59 years of age who planned to start an exercise program were stress tested with greater frequency than their age matched diabetic counterparts (p < 0.001, p < 0.001).

CONCLUSIONS: This study demonstrates that physician use of exercise stress testing as a screening tool for coronary heart disease is not well correlated with American Heart Association/American College of Cardiology evidence-based guidelines. The study also identified a lack of recognition of diabetes as a cardiovascular risk equivalent. Further studies are needed to delineate potential barriers to physician adherence of these guidelines.

Coronary heart disease (CHD) is the nation’s single leading cause of death, with more than 600,000 Americans dying from CHD in 2004.1 The estimated lifetime risk of CHD after age the age of 40 is 49% for men and 32% for women.2 The significant morbidity and mortality individuals have after a coronary event has prompted physicians to find screening mo- dalities that help to predict the 7.9 million myocardial infarc- tions that occur annually in the United States.1

Exercise stress testing has become an increasingly useful screening tool in patients with known or suspected CHD.3 However, the value of exercise stress testing in the asymp- tomatic patient is less clear because of a lack of randomized trials documenting its ability to improve clinical out- comes.4-7 Exercise stress testing has limited diagnostic ac- curacy and prognostic value in the asymptomatic popula- tion.7,8 This is partly a result of the low positive predictive value (<10%) of exercise stress testing in the asymptomatic population.9-11 Although current clinical guidelines do in- dicate a potential benefit in testing a subset of asymptomatic individuals with an increased number of risk factors (hypercholesterolemia, hypertension, smoking, diabetes, or family history of premature CHD), the test is likely to provide more prognostic than diagnostic significance.3 Therefore, universal testing of the asymptomatic population may fail to improve clinical outcomes, subject individuals to unnecessary invasive testing and over-treatment, and still miss individuals with significant disease.4

Currently, exercise stress testing is recommended for the purpose of screening for cardiovascular disease in limited populations. The American Heart Association (AHA), the American College of Cardiology (ACC), and the US Pre- ventive Services Task Force guidelines recommend screen- ing with exercise stress testing in the following populations: people with diabetes who are beginning an exercise pro- gram (Class IIa), patients with multiple risk factors for whom risk-reduction therapy needs to be guided (Class IIb), men >45 years old and women >55 years old who plan to start a vigorous exercise program (Class IIb), and patients at risk for CHD because of other diseases such as peripheral atherosclerosis and chronic renal failure (Class IIb).

Because of the limited value of exercise stress testing in the asymptomatic person, it has not been recom- mended for use as a screening tool in this population.4 Although these clinical guidelines have been provided by the American Heart Association (AHA), the American College of Cardiology (ACC) and the US Preventive Services Task Force, it is thought that there is a mismatch between these guidelines and clinical practice. Therefore, it was the goal of this study to investigate physician adherence to clinical guidelines regarding exercise stress testing of the asymptomatic adult.

Methods

This study included a survey (see Appendix) of family physicians attending either the Ohio University College of Osteopathic Medicine (OU-COM) Annual CME Confer- ence or the American College of Osteopathic Family Phy- sicians (ACOFP) Annual Convention and Exhibition. Ap- proval for the study was obtained from the St. Vincent Mercy Medical Center Institutional Review Board (IRB) and the Ohio University IRB. Investigators were granted permission to complete the study during the conventions. Physicians were solicited at the continuing medical educa- tion (CME) conferences to fill out a short survey. A cover letter was provided to participants, and return of a com- pleted survey to a designated drop box at the CME confer- ence implied consent. Only physicians who designated themselves as family physicians or family medicine resi- dents were included in the study. Physician identifiers were not requested or recorded. All data was entered into an Excel database by key and entry format.

Results were analyzed using SPSS version 16.0 (SPSS Inc., Chicago, IL); both descriptive and inferential statistics were produced. Frequencies and percentages, as well as chi-square analysis, was performed, with significance set at a < 0.05. Reliability of the survey instrument, Cronbach’s alpha, was found to be 0.95.

Results

A total of 200 physicians completed surveys. At the ACOFP Annual Convention and Exhibition, 141 surveys were com‌pleted representing 21.8% of physicians in attendance (647 total physicians were in attendance). All 141 surveys met inclusion criteria and were included in the study. Fifty-nine surveys were returned at the OU-COM Annual CME Confer- ence, representing 21.7% of physicians in attendance (240 = total physicians in attendance). Forty of the 59 surveys met inclusion criteria for the study. Residents represented 9.4% of all survey responders, 38.1% were physicians practicing for 0 to 10 years, 22.1% were physicians practicing 11 to 20 years, 21.5% were physicians practicing 21 to 30 years, and 8.3% were physicians practicing 21 to 40 years.

Frequencies for use of stress testing as a screening test for CHD in the asymptomatic adult male, female, and spe- cial populations are found in Tables 1, 2, and 3, respec- tively. In general, physicians were more likely to order a cardiac stress test as the patient age and perceived Framing- ham risk increased. Universally, more physicians would order cardiac stress testing in men than women across all ages, regardless of Framingham risk.

Nondiabetic men older than 59 years who planned to start an exercise program were stress tested with greater frequency than their age-matched diabetic counterparts (p < 0.001). Non- diabetic women older than 59 years who planned to start an exercise program were also stress tested with greater frequency than their age-matched diabetic counterparts (p < 0.001).

More than 50% of people above the age of 40 who requested a stress test had their request granted. In fact, the likelihood of ordering the test approximated the percentage that is recommended in the high Framingham risk group. In addition, physicians were more likely to order stress tests with peripheral vascular disease than chronic renal disease across all age categories.

Seventy-five percent of physicians indicated their medi- cal management of cardiovascular risk factors was altered if an asymptomatic individual with a negative test result was shown to have poor exercise capacity, poor heart rate re- serve, or poor heart rate recovery.

Of the asymptomatic patients who would not receive an exercise stress test, 31.6% of family physicians would order a carotid ultrasound for the purpose of CHD screening, 40.8% would order an ankle brachial index (ABI), 3.9% a plasminogen activator inhibitor-1 level, 21.2% a coronary calcium score, 29.6% lipoprotein a level, 41.4% LDL size stratification, and 40.1% a homocysteine level.

Conclusions

This study demonstrates that physicians’ use of exercise stress testing as a screening tool for CHD is not well correlated with AHA/ACC evidence-based guidelines.

Nondiabetic men and women older than 59 years who planned to start an exercise program were stress tested with greater frequency than their age-matched diabetic counterparts. People with diabetes and people of increasing age have a higher risk for cardiovascular disease and, therefore, should be stress tested more frequently than lower-risk populations. Risk of cardiac events in asymptomatic patients with diabetes is estimated to be equal to patients with CHD but no history of diabetes.12-14 In addition, people beginning an exercise pro- gram are at risk for cardiac events if they have undetected coronary heart disease, and high-risk individuals should there- fore be tested before beginning exercise.15 Evidence-based literature more strongly supports the use of exercise stress testing in persons with diabetes who plan to start an exercise program than in their age-matched controls.3,4 Vigilance in ruling out the potential for harm for diabetic women who plan to begin exercise is particularly important because they have a five-fold increased risk for CHD.16 Furthermore, more physi- cians would order a stress test in asymptomatic men than women despite the fact that women are much more likely to have atypical symptoms of angina.17 Perhaps most concerning is the fact that the individuals at greatest risk for CHD (patients with documented peripheral atherosclerosis, renal failure, and diabetes) were tested with similar frequencies as patients with significantly less predicted risk. The higher the patient’s pretest probability for inducible myocardial ischemia, the more mean- ingful a positive result will be (i.e., the result is less likely to be a false positive).8 These principles, which are laid out in Bayes’ theorem, aid physicians when ordering tests. If a stress test is ordered for a patient with a low pretest probability, the validity of a positive test result could be questioned. Further- more, if the stress test is ordered for the purpose of screening for cardiovascular disease, a positive result may lead to further invasive testing. In a low prevalence population, the patient’s result is likely to be a false positive and the provider is sub- jecting the patient to unnecessary invasive testing.

Although our study was focused primarily on physician use of exercise stress testing as a means for screening for CHD, the physicians were also asked about their use of the test as a prognostic indicator. Seventy-five percent of physicians indi- cated their medical management of cardiovascular risk factors was altered if an asymptomatic individual with a negative test result was shown to have poor exercise capacity, poor heart rate reserve, or poor heart rate recovery, which are all associ- ated with increased risk of death and higher rates of major cardiac events, even after accounting for standard risk fac- tors.4,7 However, there is no evidence that gaining this knowl- edge improves outcomes or that more intensive risk factor modification produces clinical benefit.4‌

The major limitation to this study is the fact that it is a survey based on physicians’ own perception and self-report- ing of their practice as opposed to a chart review of what physicians actually practice. Although physicians perceive that they would order a stress test on an individual who meets certain criteria, their actual clinical use of stress testing may be different. Another limitation of the study is that all physicians surveyed were pursuing CME. It is pos- sible that physicians attending CME conferences have dif- ferent clinical decision-making process for stress testing in asymptomatic adults than physicians who would not be inclined to attend these conferences. In addition, 9.4% of surveys were completed by family medicine residents. With their limited clinical experience, the resident responses could have been different from those of practicing physi- cians. In this study, statistical analysis failed to demonstrate any statistically significant differences or relationships. De- mographic data on practice location of physicians was not ascertained in the study and therefore could limit the gen- eralizability of the study. However, because the majority of surveys were collected at a national CME conference, one could conclude that a wide range of practice locations were represented by the surveys. Lastly, it is possible that phy- sicians may order stress tests differently if they provide stress testing as a service in their office. However, our study failed to ask physicians this important question as part of the survey.

‌In summary, survey results demonstrate that family physi- cian use of exercise stress testing in the asymptomatic patient does not adhere to current evidence-based guidelines. Further studies are needed to delineate potential barriers to physician adherence of AHA/ACC guidelines to determine whether there is a knowledge, adoption, or implementation deficit.

Acknowledgments

Special thanks to Grace Brannan, PhD, for her help with statistical analysis. This study was supported in part by a grant from The Centers for Osteopathic Research and Education.

References

1. American Heart Assocation. Heart disease and stroke statistics—2007 update. American Heart Assoc 1-41, 2007.

2. Lloyd-Jones DM, Jarson MG, Beiser A, et al. Lifetime risk of devel- oping coronary heart disease. Lancet 353:89-92, 1999.

3. Gibbons RJ, Balady GJ, Bricker JT, et al. ACC/AHA 2002 guideline update for exercise testing: Summary article: A report of the American College of Cardiology/American Heart Association task force on prac- tice guidelines (committee to update the 1997 exercise testing guide- lines). Circulation 106:1883-1892, 2002.

4. Lauer M, Froelicher ES, Williams M, Kligfield P. Exercise testing in asymptomatic adults: A statement for professionals from the American Heart Association Council on Clinical Cardiology, subcommittee on exercise, cardiac rehabilitation and prevention. Circulation 112:771- 776, 2005.

5. Lee TH, Brennan TA. Direct-to-consumer marketing of high-technol- ogy screening tests. N Engl J Med 346:529-531, 2002.

6. O’Rourke RA, Brundage BH, Froelicher VF, et al. American Col- lege of Cardiology/American Heart Association expert consensus document on electron-beam computed tomography for the diagno- sis and prognosis of coronary artery disease. Circulation 102:126- 140, 2000.

7. Balady GJ, Larson MG, Vasan RS, et al. Usefulness of exercise testing in the prediction of coronary disease risk among asymptomatic persons as a function of the Framingham risk score. Circulation 110:1920- 1925, 2004.

8. Pasternak RC, Abrams J, Greenland P, et al. Task force #1: Identifi- cation of coronary heart disease risk: Is there a detection gap? J Am Coll Cardiol 41:1853-1874, 2003.

9. Bruce RA, Fisher LD, Hossack DF. Validation of exercise-enhanced risk assessment of coronary heart disease events: Longitudinal changes in incidence in Seattle community practice. J Am Coll Cardiol 5:875- 881, 1985.

10. Blumenthal RS, Becker DM, Moy RF, et al. Exercise thallium tomog- raphy predicts future clinically manifest coronary heart disease in a high-risk asymptomatic population. Circulation 93:915-923, 1996.

11. Multiple Risk Factor Intervention Trial Research Group. Exercise electrocardiogram and coronary heart disease mortality in the multiple risk factor intervention trial. Am J Cardiol 55:16-24, 1985.

12. Haffner SM, et al. Mortality from coronary heart disease in subjects with type 2 diabetes and in nondiabetic subjects with and without prior myocardial infarction. N Engl J Med 339:229-234, 1998.

13. National Cholesterol Education Program. Executive summary of the third report of the national cholesterol education program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults (adult treatment panel III). JAMA 285:2486-2497, 2001.

14. Lauer MS. Coronary artery disease in diabetes: Which (if any) test is best? Cleveland Clin J Med 72:6-9, 2005.

15. Corrado D, Migliore F, Basso C, et al. Exercise and the risk of sudden cardiac death. Herz 6:553-558, 2006.

16. Krolewski RS. Evolving natural history of coronary artery disease in diabetes mellitus. Am J Med 90:56S-61S, 1991.

17. Vitale C, Miiiceli M, Rosano GMC. Gender-specific characteristics of atherosclerosis in menopausal women: Risk factors, clinical course and strategies for prevention. Climacteric 10(Suppl 2):16-20, 2007.

‌Appendix

Exercise Stress Testing in the Asymptomatic Adult Principle Investigator: Rachel M. Holt, OMS 3

Please indicate your area of specialty (check only one):

     Cardiology

     Family Practice

     Other

Please indicate the number of years you have been practicing the above specialty (not including years in residency/fellowship)

     Currently in residency/fellowship training program

     0-10

     10-20

     20-30

     30-40

For which of the following patient groups would you order an exercise stress for the purpose of screening for CAD, check all that apply:

Is your medical management of cardiovascular risk factors altered if the negative stress test result is given with either a poor exercise capacity, poor HR reserve, or poor heart rate recovery?

         Yes               No

Which of the following CAD screening tests do you order for the asymptomatic patient you choose NOT to exercise stress test, check all that apply: