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# ACSM’s Guidelines For Exercise Testing & Prescription PowerPoint PPT Presentation

ACSM’s Guidelines For Exercise Testing & Prescription. Chapter 6 Interpretation Of Clinical Test Data. World Health Organization :

ACSM’s Guidelines For Exercise Testing & Prescription

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### ACSM’s Guidelines For Exercise Testing & Prescription

Chapter 6

Interpretation Of Clinical Test Data

World Health Organization :

“The primary purpose of an exercise test is to determine the responses of the individual to [exercise] efforts at given levels and from this information to estimate probable performance in specific life and occupational situations.”

• Bayes Theorem states :

“The post-test probability of a patient having disease is determined by the disease probability before the test and by the probability that the test will provide a true result.”

• Bayes Theorem speaks to the issue that an exercise test must have two qualities : sensitivity and specificity.

### Sensitivity

• Sensitivity refers to the percent of patients tested who have CAD and who demonstrate a positive (abnormal) test outcome - i.e. - how often the test will identify a sick individual (~ 70%).

### Specificity

• Specificity refers to the percent of healthy people without CAD who also demonstrate a negative (normal) stress test - i.e. - how often the test is able to identify a healthy individual (~80%).

### False Negative Tests

• Failure to reach ischemic threshold

• Monitoring an insufficient # of leads

• Failure to recognize non-EKG signs & symptoms associated w/ CAD

• Technical & observer error

### False Positive Tests

• Drugs - digitalis preparations

• Wolff-Parkinson-White syndrome

• Left Bundle Branch Block

• Cardiac hypertrophy

• Hypokalemia

• Mitral valve prolapse

• Coronary spasm - Prinzmetal angina

### Predictive Value

• The predictive value of exercise testing is a measure of how accurately a test result correctly identifies the presence or absence of CAD in the test population.

• Using exercise tests to screen large numbers of asymptomatic people is of questionable value.

• Testing individuals with symptoms is a much more practical reason for an exercise test.

• Symptoms which make Bayesian senseand which increase the predictive value of an exercise test would be :

• Angina, chest discomfort/pressure

• Anginal equivalents

• Recurrent palpitations w/ exercise

• SOB w/ exertion that is unexpected

• Dizziness, syncope, vertigo, diplopia w/ ex.

### Imaging Stress Tests

• Generally speaking, echocardiogaphic studies will slightly improve the sensitivity & specificity of simple GXT’s .

• Exercise GXT’s with technetium-Tc99m sestamibi imaging or thallium chloride-201 imaging tend to improve the sensitivity and specificity of the test to ~ 85+%.

• The sensitivity and specificity of any test is improved by the number of diseased vessels.