Transcript Chapter 6 - Academic Resources at Missouri Western

CHAPTER SIX
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Interpretation of Clinical Test Data
Posttest probability of disease is
determined by pretest probability and
the probability of the test providing a
true result
Pretest probability determined mainly
by angina but also by major risk factors
Exercise testing in the apparently
healthy not recommended
INTERPRETING THE DATA
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Purpose of the test and patient
conditions including medications and
resting ECG abnormalities
Objectives of exercise testing address :
exercise tolerance, max VO2,
hemodynamics (HR, BP), changes
associated with electrical functions of
heart and limiting signs or symptoms
WHAT DETERMINES MAXIMAL
EFFORT?
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Failure of HR to increase with increase
in exercise
Plateau in oxygen consumption--hard to
determine
Lactic acid measure of > 8 mmol
RPE > 17 ( 6-20 scale)
HR and BP RESPONSE
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Inability to appropriately increase HR
and/or delayed decrease in recovery HR
usually indicate heart disease and
impact prognosis
Drop or failure to increase SBP with
increasing exercise is abnormal
Normal postexercise SBP presents as a
progressive decline with a greater drop
during passive recovery
ABNORMAL BP RESPONES
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SBP greater than 250 mmHg is criteria
for test termination
DBP greater than 114 mmHg (115
mmHg in book) is criteria for test
termination
MORE
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RPP= SBP X HR represent myocardial
oxygen consumption--ischemia happens
at a reproducible product
Increase of DBP > 10 mmHg
questionable as to disease
Some medications make BP responses
hard to evaluate
ECG WAVEFORMS
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Test 2 – You’ll need to know PQRST and
be able to determine HR from an ECG
strip
DIAGNOSTIC VALUE OF
EXERCISE TESTING
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To detect for CAD
Sensitivity
Specificity
Prevalence
Predictive value--positive and negative
SENSITIVITY
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Refers to the percent of patients that
have disease and test positive for
disease= true positive test
A false negative test fails to identify a
patient with disease
See box 6-3 for causes leading to false
negative tests
SENSITIVITY
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Test sensitivity is decreased by failure to
reach maximum stress, meds, and poor
ECG monitoring
Using the correct precordial leads
increase sensitivity
SPECIFICITY
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The percent of patients considered normal
that present with negative tests=true
negative-see box 6-4 for causes for FP
A false positive test incorrectly identifies a
person as having disease when they do not
Sensitivity and Specificity of exercise testing
vary based on patient selection, test
protocols, and ECG criteria for CAD
Sensitivity=68% and Specificity=77%
PREDICTIVE VALUE
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Predictive value measures how
accurately a test result identifies a
person with or without disease
Predictive value is driven by disease
prevalence in the population under
study