A stress test, also known as an exercise stress test or graded exercise tolerance test, measures the efficiency of the heart during a dynamic exercise stress period on a motor-driven treadmill or ergometer. It is valuable for diagnosing ischemic heart disease and investigating physiologic mechanisms underlying cardiac symptoms such as angina, dysrhythmias, inordinate blood pressure elevations, and functionally incompetent heart valves. Exercise testing can also measure functional capacity for work, sports, or participation in rehabilitation programs, and it can be a predictor of potential response to medical or surgical treatment. Additionally, upper limits of physiologically responsive pacemakers can be evaluated.

Systolic blood pressure normally increases with exercise, and diastolic pressure normally remains essentially unchanged. Stress exercise testing takes place under controlled conditions that include low temperatures (20 °C) and low humidity.

There are many different types of stress tests. Most include the following steps:

1. Place recording electrodes on the patient's chest (see description of ECG) and attach to a monitor. Place a blood pressure recording device appropriately.

2. As the patient walks on a motor-driven treadmill, or pedals an ergometer if walking is not possible, computerized ECG and heart monitoring devices record performance. The patient walks at progressively greater speeds and higher levels of elevation to increase both heart rate and workload.

3. Record the initial or resting ECG, heart rate, and blood pressure. Ask the patient to report any symptoms such as chest pain or shortness of breath experienced during the test. Normal persons are symptom free at submaximal efforts; however, at peak or maximal efforts, symptoms expected in normal persons include exhaustion, fatigue, and, sometimes, nausea or dizziness.

4. Have the patient undergo stress testing in stages. Each stage consists of a predetermined treadmill speed (in miles or kilometers per hour) and a treadmill grade elevation (in percentage grade or degrees).

5. Monitor the ECG, heart rate, and blood pressure continually for abnormalities and any unusual symptoms such as intolerable dyspnea, chest pain, or severe cramping (claudication) in the legs.

6. Record vital signs, together with other abnormalities and complaints, at 1- to 3-minute intervals for 6-8 minutes posttest as the patient rests. The test is terminated if ECG abnormalities, fatigue, weakness, abnormal blood pressure changes, or other intolerable symptoms occur during the test.

7. The common criteria for terminating a test include the following:

   1. Achieving maximum possible performance

   2. Emerging signs or symptoms that indicate an existing disease process

   3. Recording a predetermined end point, such as 85% of age-related maximal heart rate, arbitrary workload (one that raises heart rate to 150 beats/minute), or diagnostic ECG change

8. Total examination time is about 30 minutes; however, ask the patient to plan to be in the laboratory for 1-1.5 hours.

9. Follow guidelines in Chapter 1 for safe, effective, informed intratest care.

Abnormal responses to exercise testing include the following:

1. Alterations in blood pressure, such as:

   1. Failure of systolic pressure to rise

   2. Progressive fall in systolic pressure

   3. Elevation of diastolic blood pressure

2. Alterations in heart rate, such as:

   1. Tachycardia above that which is predetermined

   2. Brachycardia

3. Changes in ECG, such as:

   1. Depression or elevation of ST segments caused by ischemia

   2. Dysrhythmias, VT, multifocal premature ventricular contractions, atrial tachycardia, second- or third-degree AV block

   3. Pacemaker failure to perform within set rate limits

4. Ventricular or supraventricular ectopics are considered abnormal responses not necessarily ischemic in origin.

5. Ischemic ST-segment depression >0.2 mm or elevation >1.0 mm is the most common abnormality. Men aged 40-59 years who develop ST depression during exercise that is not present at rest have five times the risk for overt coronary heart disease compared with men without this ST depression.

6. Unusual symptoms such as:

   1. Anginal pain

   2. Severe breathlessness

   3. Faintness, dizziness, lightheadedness, confusion

   4. Claudication, leg pain

7. Unusual signs such as:

   1. Cyanosis, pallor, skin mottling

   2. Cold sweats, piloerection

   3. Ataxia, glassy stare

   4. Gallop heart sounds

   5. Valvular regurgitation

Pretest Patient Care

1. Explain test purpose and procedure. Tell the patient that no food, coffee, or cigarettes are allowed for 2 hours before testing, although water may be taken.

2. Ensure that a legal consent form is signed by the patient or patient's designee.

3. Ask the patient to wear flat walking shoes or tennis shoes (no slippers). Men should wear gym shorts or light, loose-fitting trousers. Women should wear a bra, a short-sleeved blouse that buttons in front, and slacks, shorts, or pajama pants (no one-piece undergarments, pantyhose, or slips).

4. Explain which medications should be withheld or discontinued before testing. Dosages of beta-adrenergic blocking agents (e.g., propranolol) should be reduced or tapered gradually. The healthcare provider should write orders regarding management of the patient's drug regimen well before the test.

5. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Common causes of false-positive exercise ECG responses include the following:

1. Left ventricular hypertrophy

2. Digitalis toxicity

3. ST-segment abnormality

4. Hypertension

5. Valvular heart disease

6. Left bundle branch block

7. Anemia

8. Hypoxia

9. Vasoregulatory asthenia

10. Lown-Ganong-Levine syndrome

11. Panic or anxiety attack

12. Wolff-Parkinson-White syndrome

Normal

• Negative when the patient does not exhibit significant symptoms, arrhythmias, or other ECG abnormalities at 85% of maximum heart rate predicted for age and gender