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CHAPTER SIX

CHAPTER SIX. 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

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CHAPTER SIX

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  1. CHAPTER SIX • 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

  2. INTERPRETING THE DATA • 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

  3. WHAT DETERMINES MAXIMAL EFFORT? • 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)

  4. HR and BP RESPONSE • 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

  5. ABNORMAL BP RESPONES • SBP greater than 250 mmHg is criteria for test termination • DBP greater than 114 mmHg (115 mmHg in book) is criteria for test termination

  6. MORE • 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

  7. ECG WAVEFORMS • Test 2 – You’ll need to know PQRST and be able to determine HR from an ECG strip

  8. DIAGNOSTIC VALUE OF EXERCISE TESTING • To detect for CAD • Sensitivity • Specificity • Prevalence • Predictive value--positive and negative

  9. SENSITIVITY • 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

  10. SENSITIVITY • Test sensitivity is decreased by failure to reach maximum stress, meds, and poor ECG monitoring • Using the correct precordial leads increase sensitivity

  11. SPECIFICITY • 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%

  12. PREDICTIVE VALUE • 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

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