Exercise Electrocardiographic Testing

Michael A. Jolly

I. INTRODUCTION

A. Exercise electrocardiographic testing is a field in flux. In the past decade, it has become clear that ST-segment changes during exercise have low sensitivity and specificity in the evaluation of coronary artery disease (CAD) and are poor predictors of risk. This may be partially due to the fact that stable obstructive plaques, which typically result in exercise-mediated ischemia, are less relevant to myocardial infarction (MI) and sudden cardiac death than unstable nonobstructive plaques. Although the bulk of obstructive CAD screening has now shifted towards various stress imaging modalities, many of the physiologic parameters measured during exercise have emerged as powerful prognostic indicators. As such, the main uses of exercise electrocardiographic testing should be evaluation of prognosis and as a gateway to other imaging modalities. Stand-alone testing for CAD diagnosis is reserved for patients with intermediate risk for CAD and should be ordered with a careful understanding of the limitations of the test for this purpose.

1. The advantages of exercise electrocardiographic testing are its ability to assess a variety of prognostic markers, most importantly functional capacity, which is a powerful predictor of mortality, widespread availability, safety, ease of administration, and relatively low cost. The assessment of functional capacity may be particularly advantageous in patients with valvular heart disease and congenital heart disease whereupon recognition of functional limitation is often difficult to ascertain by history alone.

2. Disadvantages. As a screening test for CAD in persons without symptoms, exercise electrocardiography is generally not helpful or indicated. It has a low sensitivity and specificity, which can be improved with careful selection of the patient population undergoing testing.

B. Submaximal exercise electrocardiographic testing (i.e., testing at submaximal heart rate, discussed later) is a useful assessment before hospital discharge for patients who have had MI. The advantages are as follows:

1. It assists in setting safe levels of exercise (exercise prescription) and reassuring patients and families.

2. It is beneficial in optimization of medical therapy, in triage for intensity of follow-up testing and care, and in recognition of exercise-induced ischemia and arrhythmias.

3. For patients with uncomplicated MI who have received reperfusion therapy, submaximal exercise testing may be safely performed as early as 3 days after MI, with maximal exercise testing 3 to 6 weeks later.

II. INDICATIONS.

The indications for exercise electrocardiographic testing are divided on the basis of the degree of likelihood of disease or severity of diagnosed disease, use in valvular heart disease, and use in congenital heart disease (Table 47.1).

TABLE 47.1 ACC/AHA Guidelines for Exercise Testing

Exercise testing in the diagnosis of obstructive CAD
Class I^a
	Adult patients (including those with complete right bundle branch block or < 1 mm of resting ST depression) with an intermediate pretest probability of CAD on the basis of sex, age, and symptoms
Class IIa
	Patients with vasospastic angina
Class IIb
	Patients with a high pretest probability of CAD on the basis of age, symptoms, and sex
	Patients with a low pretest probability of CAD on the basis of age, symptoms, and sex
	Patients with < 1 mm of baseline ST depression and taking digoxin
	Patients with electrocardiographic criteria of left ventricular hypertrophy and < 1 mm of baseline ST depression
Class III
	Patients with baseline electrocardiographic abnormalities
		Preexcitation (Wolff-Parkinson-White) syndrome
		Electronically paced ventricular rhythm
		> 1 mm of resting ST depression
		Complete left bundle branch block
	Patients with a documented myocardial infarction or prior coronary angiographic findings of disease and an established diagnosis of CAD (ischemia and risk can be determined with testing)
Risk assessment and prognosis among patients with symptoms or a history of CAD
Class I
	Patients undergoing initial evaluation with suspected or known CAD (exceptions in class 2b), including those with complete right bundle branch block or < 1 mm of resting ST depression
	Patients with suspected or known CAD previously evaluated, now presenting with marked change in clinical status
	Low-risk unstable angina patients 8-12 h after presentation who have been free of active ischemic or heart failure symptoms
	Intermediate-risk unstable angina patients 2-3 d after presentation who have been free of active ischemic or heart failure symptoms
Class IIa
	Intermediate-risk unstable angina patients with initial cardiac markers that are normal, a repeat electrocardiographic study without significant change, cardiac markers 6-12 h after symptom onset that are normal, and no other evidence of ischemia during observation
Class IIb
	Patients with baseline electrocardiographic abnormalities
		Preexcitation (Wolff-Parkinson-White) syndrome
		Electronically paced ventricular rhythm
		1 mm or more of resting ST depression
	Complete left bundle branch block or any interventricular conduction defect with QRS duration > 120 milliseconds
	Patients with a stable clinical course who undergo periodic monitoring to guide treatment
Class III
	Patients with severe comorbidity likely to limit life expectancy and/or candidacy for revascularization
	High-risk unstable angina patients
After acute myocardial infarction
Class I
	Before discharge for prognostic assessment, activity prescription, or evaluation of medical therapy (submaximal at about 4-6 d)
	Early after discharge for prognostic assessment and cardiac rehabilitation if the predischarge exercise test was not performed (symptom limited, about 14-21 d)
	Late after discharge for prognostic assessment, activity prescription, evaluation of medical therapy, and cardiac rehabilitation if the early exercise test was submaximal (symptom limited, about 3-6 wk)
Class IIa
	After discharge for activity counseling or exercise training as part of cardiac rehabilitation of patients who have undergone coronary revascularization
Class IIb
	Patients with electrocardiographic abnormalities
		Complete left bundle branch block
		Preexcitation (Wolff-Parkinson-White) syndrome
		Left ventricular hypertrophy
		Digoxin therapy
		Electronically paced ventricular rhythm
		>1 mm of resting ST depression
	Periodic monitoring for patients who continue to participate in exercise training or cardiac rehabilitation
Class III
	Severe comorbidity likely to limit life expectancy or candidacy for revascularization
	Patients with acute myocardial infarction and uncompensated congestive heart failure, cardiac arrhythmia, or noncardiac conditions that severely limit exercise ability
	Before discharge, patients who have been selected for or have undergone cardiac catheterization (stress imaging tests are recommended)
Exercise testing for persons without symptoms or known CAD
Class I
	None
Class IIa
	Asymptomatic persons with diabetes mellitus to start vigorous exercise
Class IIb
	Persons with multiple risk factors
	Men older than 45 y and women older than 55 y without symptoms
		Who plan to start vigorous exercise (especially if sedentary)
		Who are involved in occupations in which impairment might affect public safety
		Who are at high risk for CAD because of other diseases
Class III
	Routine screening of men or women without symptoms
Exercise testing for persons with valvular heart disease
Class I
	None
Class IIa
	Patients with chronic AR and equivocal symptoms to assess functional capacity and symptomatic response
Class IIb
	Asymptomatic patients with AS may be considered to elicit exercise-induced symptoms and abnormal blood pressure responses
	In asymptomatic or symptomatic patients with chronic AR (with radionuclide angiography) for assessment of left ventricular function
Class III
	Exercise testing should not be performed in symptomatic patients with AS
Exercise testing for persons with congenital heart disease
Class I
	None
Class IIa
	Asymptomatic young adults < 30 y of age to determine exercise capability, symptoms, and blood pressure response
	Adolescent or young adult patient with AS who has a Doppler mean gradient > 30 mm Hg or a peak velocity > 50 mm Hg if the patient is interested in athletic participation or if the clinical findings and Doppler findings are disparate
	Asymptomatic young adult with a mean Doppler gradient > 40 mm Hg or a peak Doppler gradient > 64 mm Hg or when the patient anticipates athletic participation or pregnancy
	As part of the initial evaluation of adolescent and young adult patients with TR and serially every 1-3 y
	In patients with atrial septal defect with symptoms that are discrepant with clinical findings or to document changes in oxygen saturation in patients with mild or moderate PAH
	In patients with subvalvular AS testing to determine exercise capability, symptoms, ECG changes or arrhythmias, or increase in LVOT gradient is reasonable in the presence of otherwise equivocal indications for intervention
	In patients with supravalvular AS (along with other imaging modalities) testing can be useful to evaluate the adequacy of myocardial perfusion
Class IIb
	In patients with aortic coarctation, testing may be performed at intervals determined in consultation with the regional ACHD center
Class III
	Patients with atrial septal defect or patent ductus arteriosus with severe PAH
	Symptomatic patients with AS or those with repolarization abnormality on ECG or systolic dysfunction on echocardiography
^aClass 1, conditions for which there is evidence or agreement that a given procedure or treatment is useful and effective; Class 2, conditions for which there is conflicting evidence or a divergence of opinion about the usefulness or efficacy of a procedure or treatment; Class 2a, weight of evidence or opinion is in favor of usefulness and efficacy; Class 2b, usefulness or efficacy is less well established on the basis of evidence and opinion; Class 3, conditions for which there is evidence or general agreement that the procedure or treatment is not useful or effective and in some cases may be harmful. CAD, coronary artery disease; AR, aortic regurgitation; AS, aortic stenosis; TR, tricuspid regurgitation; PAH, pulmonary arterial hypertension; ECG, electrocardiogram; LVOT, left ventricular outflow tract; ACHD, adult congenital heart disease.
From Gibbons RJ, Balady GJ, Bricker JT, et al. ACC/AHA 2002 guideline update for exercise testing: a report of the American College of Cardiology/American Heart Association Task Force on practice guideline (committee on exercise testing). J Am Coll Cardiol. 2002;40:1531-1540, with permission. Adapted from Bonow RO, Carabello BA, Chatterjee K, et al. 2008 focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on practice guidelines (writing committee to develop guidelines for the management of patients with valvular heart disease). J Am Coll Cardiol. 2008;52:e1-e142 and from Warnes CA, Williams RG, Bashore TM, et al. ACC/AHA 2008 guidelines for the management of adults with congenital heart disease: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on practice guidelines (writing committee to develop guidelines for the management of adults with congenital heart disease). J Am Coll Cardiol. 2008;52:1890-1947.

III. CONTRAINDICATIONS.

Contraindications to exercise testing are divided into absolute

and relative categories (Table 47.2).

IV. LIMITATIONS OF EXERCISE ELECTROCARDIOGRAPHIC TESTING.

Before ordering an exercise electrocardiography test, the physician should have an understanding of Bayes’ theorem and the limitations of the test.

A. Bayes’ theorem states that the probability of a positive test result is affected by the likelihood (i.e., conditional probability) of a positive test result among the population that has undergone the test (i.e., pretest probability). The higher the probability that a disease is present in a given individual before a test is ordered, the higher is the probability that a positive test result is a true-positive test result. Pretest probability is determined on the basis of symptoms, age, sex, and risk factors and can be divided into very low, low, intermediate, and high (Table 47.3).

B. Sensitivity and specificity. The likelihood that an abnormal electrocardiographic finding indicates CAD is much higher for an older person with multiple risk factors than for a young person with no risk factors. Sensitivity and specificity vary with the population being tested.

1. Exercise electrocardiographic testing is best used in the evaluation of a patient at intermediate risk with an atypical history or a patient at low risk with a typical history.

2. For the general population, the sensitivity is 68% and the specificity is 70%. Values are lower for persons at low risk.

3. Exercise electrocardiographic testing has a higher sensitivity and specificity for persons at high risk. For most of these patients, however, invasive testing is preferred for a more definitive diagnosis and possible intervention. Excluding patients with left ventricular hypertrophy or resting ST depression and those taking digoxin also improves sensitivity and specificity.

TABLE 47.2 Contraindications to Exercise Testing

Absolute contraindications

Acute myocardial infarction (within 2 d)

High-risk unstable angina

Uncontrolled cardiac arrhythmias causing symptoms or hemodynamic compromise

Symptomatic, severe aortic stenosis

Uncontrolled symptomatic heart failure

Acute pulmonary embolus or pulmonary infarction

Suspected or known dissecting aneurysm

Active or suspected myocarditis, pericarditis, or endocarditis

Acute noncardiac disorder that may affect exercise performance or be aggravated by exercise (e.g., infection, renal failure, or thyrotoxicosis)

Considerable emotional distress (psychosis)

Relative contraindications

Left main coronary stenosis or its equivalent

Moderate stenotic valvular heart disease

Resting diastolic blood pressure > 110 mm Hg or resting systolic blood pressure > 200 mm Hg

Electrolyte abnormalities (e.g., hypokalemia and hypomagnesemia)

Fixed-rate pacemaker

High-degree atrioventricular block

Frequent or complex ventricular ectopy

Ventricular aneurysm

Uncontrolled metabolic disease (e.g., diabetes, thyrotoxicosis, and myxedema)

Chronic infectious disease (e.g., mononucleosis, hepatitis, and acquired immunodeficiency syndrome)

Neuromuscular, musculoskeletal, or rheumatoid disorders exacerbated by exercise

Advanced or complicated pregnancy

Hypertrophic cardiomyopathy and other forms of outflow tract obstruction

Mental impairment leading to inability to cooperate

Adapted from Kenney WL, Humphrey RH, Bryant CX, eds. ACSM’s Guidelines for Exercise Testing and Prescription. Baltimore, MD: Williams & Wilkins, 1995; from Fletcher GF, Fletcher GF, Blair SN, et al. Statement on exercise. Benefits and recommendations for physical activity programs for all Americans. A statement for health professionals by the Committee on Exercise and Cardiac Rehabilitation of the Council on Clinical Cardiology, American Heart Association. Circulation. 1992;86:340-344; and from Gibbons RJ, Balady GJ, Bricker JT, et al. ACC/AHA 2002 guideline update for exercise testing: a report of the American College of Cardiology/American Heart Association Task Force on practice guideline (committee on exercise testing). J Am Coll Cardiol. 2002;40:1531-1540.

C. Positive predictive value (PPV). After pretest probability and the sensitivity and specificity are known, PPV can be calculated. PPV is a measure of the likelihood that an abnormal test finding represents a true-positive result. It is highly dependent on pretest probability (i.e., prevalence of disease) in the population being tested. For example, in a population at low risk, the PPV of electrocardiographic exercise testing is only 21%, but in a population at high risk, PPV rises to 83%.

TABLE 47.3 Pretest Probability of Coronary Artery Disease according to Age, Sex, and Symptoms

Age (y)	Sex	Typical/definite angina pectoris	Atypical/probable angina pectoris	Nonanginal chest pain	Asymptomatic
30-39	Men	Intermediate	Intermediate	Low	Very low
	Women	Intermediate	Very low	Very low	Very low
40-49	Men	High	Intermediate	Intermediate	Low
	Women	Intermediate	Low	Very low	Very low
50-59	Men	High	Intermediate	Intermediate	Low
	Women	Intermediate	Intermediate	Low	Very low
60-69	Men	High	Intermediate	Intermediate	Low
	Women	High	Intermediate	Intermediate	Low
Reproduced with permission from Gibbons RJ, Balady GJ, Bricker JT, et al. ACC/AHA 2002 guideline update for exercise testing: a report of the American College of Cardiology/American Heart Association Task Force on practice guideline (committee on exercise testing). J Am Coll Cardiol. 2002;40:1531-1540.

V. PATIENT PREPARATION

A. Instructions.

Table 47.4 provides a typical list of instructions given to patients before testing.

B. Medications

1. Before diagnostic testing, cardiovascular drugs are withheld at the discretion of and under the guidance of the supervising physician. This greatly increases the sensitivity of the test.

a. β-Blockers pose a special problem. Patients taking β-blockers often do not have an adequate increase in heart rate to achieve the level of stress needed for the test. Abrupt withdrawal of β-blockers is to be discouraged because of reflex tachycardia. The best possible solution is to withdraw the β-blocker over several days before an exercise test, if the test is for diagnostic purposes. This is not always possible, however, because of time constraints or the necessity of drug therapy. In these cases, the records should reflect β-blocker use at the time of testing.

b. Digoxin may cause problems in test interpretation. To avoid a reading that cannot be used to confirm a diagnosis, digoxin should be withheld for 2 weeks before testing.

2. Patients undergoing diagnostic testing should take their other usual medications on the day of the test to reproduce more closely the conditions outside the exercise laboratory.

VI. EXERCISE PROTOCOLS.

There are advantages and disadvantages to each exercise protocol (Table 47.5). Selection depends on the patient characteristics, the equipment available, and the familiarity and comfort of the testing personnel with the protocol.

A. An optimal protocol achieves peak workload and maximizes the sensitivity and specificity of the test.

1. Workload.

An optimal protocol incorporates a gradual increase in the level of work, so that the patient’s true peak workload can be determined. If there are large increases in workload, maximum oxygen consumption (Mvo₂ max) may
fall between two levels. The test is also more comfortable for the patient if the increases in workload are not large.

TABLE 47.4 Patient Preparation

Only gold members can continue reading. Log In or Register to continue