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C HAPTER 1 9 / Exercise Testing 425
and increases in work are individualized, permitting test duration logically, 52 it is affected by age, gender, health, type of exercise,
to be targeted. Because there are no stages per se, the numbers of body position, blood volume, and environment. Of these factors,
errors associated with predicting exercise capacity alluded to pre- age is the most important. There is an inverse relationship be-
viously are lessened. 4,8,25 tween maximal heart rate and age, with correlation coefficients
typically in the order of 0.40. However, the scatter around the
Submaximal Testing regression line is quite large, with standard deviations ranging
In general, maximal, symptom-limited tests are not considered from 10 to 15 beats/min (Fig. 19-3). Thus, age-predicted “target”
appropriate until 1 month after MI or surgery. Thus, submaximal maximal heart rate is a limited measurement for clinical purposes
exercise testing has an important role clinically for predischarge, and should not be used as an endpoint for exercise testing. 4,8,17,50
post-MI, or postbypass surgery evaluations. Submaximal tests
have been shown to be important in risk stratification 44–46 for Blood Pressure
making appropriate activity recommendations, for recognizing
the need for modification of the medical regimen, or for further Assessment of systolic and diastolic blood pressure at rest and dur-
interventions in patients who have sustained a cardiac event. A ing the exercise test is important for patient safety and can provide
submaximal, predischarge test appears to be as predictive for fu- important diagnostic and prognostic information. Properly
ture events as a symptom-limited test among patients less than trained personnel can obtain accurate and reliable blood pressures
1 month after MI. Submaximal testing is also appropriate for pa- using noninvasive auscultatory techniques, and guidelines have
tients with a high probability of serious arrhythmias. The testing been developed for this purpose. 53,54 Blood pressure should be
endpoints for submaximal testing have traditionally been arbitrary measured at rest before the test in the supine and standing posi-
but should always be based on clinical judgment. A heart rate tions. Blood pressure at rest, when measured before an exercise
limit of 140 beats/min and an MET level of 7 are often used for test, may be elevated compared with normal resting conditions
patients younger than 40 years, and limits of 130 beats/min and because of pretest anxiety. Uncontrolled hypertension is a relative
an MET level of 5 are often used for patients older than 40 years. contraindication to exercise testing. 4,8 However, if blood pressure
For those using -blockers, a Borg perceived exertion level in the is elevated because of anxiety, it is not uncommon or of concern
range of 7 to 8 (1 to 10 scale) or 15 to 16 (6 to 20 scale) are con- to observe a slight decrease in blood pressure during the initial
servative endpoints. The initial onset of symptoms, including fa- stage of an exercise test when the workloads are light.
tigue, shortness of breath, or angina, is also indication to stop the The increase in systolic blood pressure during exercise reflects
test. A low-level protocol should be used, that is, one that uses no the inotropic reserve of the left ventricle. Systolic and diastolic
more than 1-MET increments per stage. The Naughton proto- blood pressure should be assessed during the last minute of each ex-
col 39,47 is commonly used for submaximal testing. Ramp testing ercise stage and more frequently if hypotensive or hypertensive re-
is also ideal for this purpose because the ramp rate (such as 5 sponses are observed. Normally, systolic blood pressure increases in
METs achieved over a 10-minute duration) can be individualized parallel with an increase in work rate, and it is not uncommon in
depending on the patient tested. 25 healthy people to exceed 200 mm Hg. In general, a value above 250
mm Hg is an indication to terminate the exercise test. 4,8 Diastolic
pressure normally stays the same or increases slightly during exer-
cise. The fifth Korotkov sound, however, can be frequently heard all
INTERPRETATION OF EXERCISE the way to zero in a young, healthy person. A diastolic blood pres-
TEST RESPONSES sure exceeding 115 mm Hg is an indication to terminate the exer-
cise test. 4,8 A decrease in systolic blood pressure with progressive ex-
The important exercise test responses that should be monitored ercise suggests that cardiac output is unable to increase in
and recorded are heart rate, blood pressure, electrocardiographic accordance with the work rate and is usually a reflection of severe is-
changes, exercise capacity, and subjective responses, including chemia. If systolic blood pressure appears to decrease, it should be
chest discomfort, undue fatigue, shortness of breath, leg pain, and remeasured immediately, and if the decrease is confirmed, the test
rating of perceived exertion. Each of these responses should be de- should be terminated. The clinical consequences of abnormal blood
scribed in a comprehensive test report. Useful programs have been pressure responses to exercise range from modest 45,55 to severe, in
developed that automatically summarize the test responses and ap- which decreases in systolic blood pressure have been associated with
56
57
ply published regression equations that report pretest and posttest ventricular fibrillation in the laboratory. Dubach et al. have ob-
risks of coronary disease, and some provide mortality estimates. 48 served that systolic blood pressure must drop below the standing
An example of one such report is presented in Display 19-2. resting value to be prognostically valuable, whereas others have sug-
gested that more modest decreases, in the order of 10 to 20 mm Hg,
Heart Rate are associated with severe ischemia, left ventricular impairment, a
high incidence of future cardiac events, or all three. 58,59
Heart rate increases linearly with oxygen uptake during exercise.
Of the two major components of cardiac output, heart rate and Exercise Capacity
stroke volume, heart rate is responsible for most of the increase in
cardiac output during exercise, particularly at higher levels. Thus, Exercise capacity can be an extremely important test response to
maximal heart rate achieved is a major determinant of exercise ca- document because it has important implications concerning the
pacity. 17,49,50 The inability to appropriately increase heart rate efficacy of current therapies, the assessment of disability, and
during exercise (chronotropic incompetence) has been associated risk stratification. A patient’s exercise capacity says a great deal
with the presence of heart disease and a worse prognosis. 49–51 about overall cardiovascular health. The most accurate method
Although maximal heart rate has been difficult to explain physio- of measuring exercise capacity is with the use of ventilatory gas