Clinical Exercise Testing and Interpretation PDF

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Clinical Exercise Testing and Interpretation ¨Chapter 5 ¨Introduction ¨Clinical exercise testing has been part of the differential diagnosis of patients with suspected ischemic heart disease (IHD) for more than 50 yr. ¨Although there are several indications for clinical exercise testing, most tests are likely performed as part of the diagnosis and evaluation of IHD. ¨There are several evidence-based statements from professional organizations related to the conduct and application of clinical exercise testing. ¡GXT, exercise stress test, ETT, CPX, CPET ¨Indications for a Clinical Exercise Test ¨Indications for clinical exercise testing encompass three general categories: 1- (a) diagnosis (e.g., presence of disease or abnormal physiologic response), 2- (b) prognosis (e.g., risk for an adverse event), and 3- (c) evaluation of the physiologic response to exercise pressure [BP] and peak exercise capacity).

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¡The most common diagnostic indication is the assessment of symptoms suggestive of IHD. 21. Gibbons RJ, Balady GJ, Bricker JT, et al. Committee to Update the 1997 Exercise Testing Guidelines. ACC/AHA 2002 guideline update for exercise testing: summary article. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1997 Exercise Testing Guidelines). J Am Coll Cardiol. 2002;40(8):1531–40. ¨Indications for a Clinical Exercise Test (Cont.) ¨The clinical utility of exercise testing is described in several evidencebased guideline statements aimed at specific cardiac diagnoses (Box 5.1). ¨In addition to indications listed in Box 5.1, an exercise test can be useful in the evaluation of patients who present to emergency departments with chest pain. ¨Conducting the Clinical Exercise Test ¨When administering clinical exercise tests, it is important to consider contraindications, the exercise test protocol and mode, test endpoint indicators, safety, medications, and staff and facility emergency preparedness ¨Box 5.2 ¨Conducting the Clinical Exercise Test (cont.)

¨ ¨Testing Staff ¡Over the past several decades, there has been a transition in many exercise testing laboratories from tests being administered by physicians to nonphysician allied health professionals, such as clinical exercise physiologists, nurses, physical therapists, and physician assistants. ¡According to the ACC and AHA, the nonphysician allied health care professional who administers clinical exercise tests should have cognitive skills similar to, although not as extensive as, the physician who provides the final interpretation ¨Conducting the Clinical Exercise Test (cont.) ¨Testing Mode and Protocol ¡The mode selected for the exercise test can impact the results and should be selected based on the test purpose and patient preference úTreadmill úCycle ergometer úOther exercise testing modes may be considered ¡Figure 5.1 ¨Conducting the Clinical Exercise Test (cont.) ¨Monitoring and Test Termination ¡Variables that are typically monitored during clinical exercise testing include HR; ECG; cardiac rhythm; BP; perceived exertion; and clinical signs and patient-reported symptoms suggestive of myocardial ischemia, inadequate blood perfusion, inadequate gas diffusion, and limitations in pulmonary ventilation ¡Measurement of expired gases through open circuit spirometry during a CPET and oxygen saturation of blood through pulse oximetry and/or arterial blood gases are also obtained when indicated ¨Conducting the Clinical Exercise Test (cont.) ¨Monitoring and Test Termination (Cont.) ¡The analysis of expired gas during a CPET overcomes the potential inaccuracies associated with estimating exercise capacity from peak workload (e.g., treadmill speed and grade). The direct measurement of V O  2 is the most accurate measure of exercise capacity and is a useful index of overall cardiopulmonary health ¡Exertional dyspnea ¡SpO2 ¨Termination criteria-When the goal is a symptom-limited maximal exercise test, a predetermined intensity should not be used as a reason to end the test

¨Conducting the Clinical Exercise Test (cont.) ¨Postexercise and safety ¡Each laboratory should develop standardized procedures for the postexercise recovery period (active vs. inactive and monitoring duration) with the laboratory’s medical director that considers the indication for the exercise test and the patient’s status during the test ¡Although untoward events do occur, clinical exercise testing is generally safe when performed by appropriately trained clinicians ¨Interpreting the Clinical Exercise Test ¨Multiple factors should be considered during the interpretation of exercise test data including patient symptoms, ECG responses, exercise capacity, hemodynamic responses, and the combination of multiple responses, as reflected by exercise test scores such as the Duke Treadmill Score ¨Interpreting the Clinical Exercise Test (Cont.) ¨Heart Rate Responses ¡The normal HR response to incremental exercise is to increase with increasing workloads at a rate of ~10 beats × min-1 per 1 MET ¡HRmax decreases with age and is attenuated in patients on b-adrenergic blocking agents. Several equations have been published to predict HRmax in individuals who are not taking a b-adrenergic blocking agent ¡All estimates have large interindividual variability with standard deviations of 10 beats or more ¨Interpreting the Clinical Exercise Test (Cont.) ¨Heart Rate Responses (Cont.) ¡Among patients referred for testing secondary adrenergic blocking agents, failure to achieve the presence of maximal effort is an indicator and is independently associated with increased

to IHD and in the absence of ban age-predicted HRmax >85% in of chronotropic incompetence risk of morbidity and mortality

¡The rate of decline in HR following exercise provides independent information related to prognosis ¨Interpreting the Clinical Exercise Test (Cont.) ¨Blood Pressure Response ¡The normal systolic blood pressure (SBP) response to exercise is to increase with increasing workloads at a rate of ~10 mm Hg per 1 MET. There is normally no change or a slight decrease in diastolic blood pressure (DBP) during an exercise test úSpecific SBP responses: Hypertensive response Hypotensive Response

Blunted Response Postexercise response ¨Interpreting the Clinical Exercise Test (Cont.) ¨ Rate Pressure Product ¡Rate-pressure product (also known as double product) is calculated by multiplying the values for HR and SBP that occur at the same time during rest or exercise. Rate-pressure product is a surrogate for myocardial oxygen uptake úThere is a linear relationship between myocardial oxygen uptake and both coronary blood flow and exercise intensity úThe normal range for peak rate-pressure product is 25,000–40,000 mm Hg × beats × min -1 ¨Interpreting the Clinical Exercise Test (Cont.) ¨Electrocardiogram ¨The normal response of the ECG during exercise includes the following: ¨P-wave: increased magnitude among inferior leads ¨PR segment: shortens and slopes downward among inferior leads ¨QRS: Duration decreases, septal Q-waves increase among lateral leads, R waves decrease, and S waves increase among inferior leads. ¨Interpreting the Clinical Exercise Test (Cont.) ¨Electrocardiogram ¨The normal response of the ECG during exercise includes the following (Cont.): ¨J point (J junction): depresses below isoelectric line with upsloping ST segments that reach the isoelectric line within 80 ms ¨T-wave: decreases amplitude in early exercise, returns to preexercise amplitude at higher exercise intensities, and may exceed preexercise amplitude in recovery ¨QT interval: Absolute QT interval decreases. The QT interval corrected for HR increases with early exercise and then decreases at higher HRs. ¨Interpreting the Clinical Exercise Test (Cont.) ¨Electrocardiogram ¨The normal response of the ECG during exercise includes the following (Cont.): ¡ST-segment changes (i.e., depression and elevation) are widely accepted criteria for myocardial ischemia and injury. The interpretation of ST segments may be affected by the resting ECG configuration and the presence of digitalis therapy ¨Interpreting the Clinical Exercise Test (Cont.)

¨ Electrocardiogram ¨Abnormal response of the ST segment during exercise includes the following: ¡To be clinically meaningful, ST-segment depression or elevation should be present in at least three consecutive cardiac cycles within the same lead. The level of the ST segment should be compared relative to the end of the PR segment. Automated computer-averaged complexes should be visually confirmed. ¡Horizontal or downsloping ST-segment depression > 1 mm (0.1 mV) at 80 ms after the J point is a strong indicator of myocardial ischemia. ¨Interpreting the Clinical Exercise Test (Cont.) ¨Electrocardiogram ¨Abnormal response of the ST segment during exercise includes the following (Cont.): ¡Clinically significant ST-segment depression that occurs during postexercise recovery is an indicator of myocardial ischemia. ¡ST-segment depression at a low workload or low rate-pressure product is associated with worse prognosis and increased likelihood for multivessel disease. ¡When ST-segment depression is present in the upright resting ECG, only additional ST-segment depression during exercise is considered for ischemia. ¨Interpreting the Clinical Exercise Test (Cont.) ¨Electrocardiogram ¨Abnormal response of the ST segment during exercise includes the following (Cont.): ¡When ST-segment elevation is present in the upright resting ECG, only STsegment depression below the isoelectric line during exercise is considered for ischemia. ¡Upsloping ST-segment depression > 2 mm (0.2 mV) at 80 ms after the J point may represent myocardial ischemia, especially in the presence of angina. However, this response has a low positive predictive value; it is often categorized as equivocal. ¨Interpreting the Clinical Exercise Test (Cont.) ¨Electrocardiogram ¨Abnormal response of the ST segment during exercise includes the following (Cont.): ¡Among patients after myocardial infarction (MI), exercise-induced ST-segment elevation (> 1 mm or > 0.1 mV for 60 ms) in leads with Q waves is an abnormal response and may represent reversible ischemia or wall motion abnormalities. ¡Among patients without prior MI, exercise-induced ST-segment elevation most often represents transient combined endocardial and subepicardial ischemia but may also be due to acute coronary spasm.

¨Interpreting the Clinical Exercise Test (Cont.) ¨Electrocardiogram ¨Abnormal response of the ST segment during exercise includes the following (Cont.): ¡Repolarization changes (ST-segment depression or T-wave inversion) that normalize with exercise may represent exercise-induced myocardial ischemia but is considered a normal response in young subjects with early repolarization on the resting ECG. ¨In general, dysrhythmias that increase in frequency or complexity with progressive exercise intensity and are associated with ischemia or with hemodynamic instability are more likely to cause a poor outcome than isolated dysrhythmias ¨Interpreting the Clinical Exercise Test (Cont.) ¨Symptoms ¡Symptoms that are consistent with myocardial ischemia (e.g., angina, dyspnea) or hemodynamic instability (e.g., light-headedness) should be noted and correlated with ECG, HR, and BP abnormalities (when present). ¨Interpreting the Clinical Exercise Test (Cont.) ¨Exercise Capacity ¡Evaluating exercise capacity is an important aspect of exercise testing úA high exercise capacity is indicative of a high peak Q and therefore suggests the absence of serious limitations of left ventricular function úA significant issue relative to exercise capacity is the imprecision of estimating exercise capacity from exercise time or peak workload. The standard error in estimating exercise capacity from various published prediction equations is at least ± 1MET ¨Interpreting the Clinical Exercise Test (Cont.) ¨Cardiopulmonary Exercise Testing ¡A major advantage of measuring gas exchange during exercise is a more accurate measurement of exercise capacity ¡CPET data may be particularly useful in defining prognosis and defining the timing of cardiac transplantation and other advanced therapies in patients with heart failure ¡CPET is also helpful in the differential diagnosis of patients with suspected cardiovascular and respiratory diseases ¨Interpreting the Clinical Exercise Test (Cont.) ¨Maximal versus Peak Cardiorespiratory Stress ¡When an exercise test is performed as part of the evaluation of IHD, patients should be encouraged to exercise to their maximal level of exertion or until a

clinical indication to stop the test is observed ¡Various criteria have been used to confirm that a maximal effort has been elicited during a GXT: úA plateau in V O  2peak úFailure of HR to increase with increases in workload úA post exercise venous lactate concertation > 8.0 mmol × L-1 úRPE at peak exercise > 17 (6-20 scale) or >7 (0-10 scale) úA peak RER > 1.10 ¨Diagnostic Value of Exercise Testing for the Detection of Ischemic Heart Disease ¨The diagnostic value of the clinical exercise test for the detection of IHD is influenced by the principles of conditional probability ¨The factors that determine the diagnostic value of exercise testing (and other diagnostic tests) are the sensitivity and specificity of the test procedure and prevalence of IHD in the population tested ¨Diagnostic Value of Exercise Testing for the Detection of Ischemic Heart Disease (Cont.) ¨Sensitivity, Specificity and Predictive Value ¡Sensitivity refers to the ability to positively identify patients who truly have IHD ¡Specificity refers to the ability to correctly identify patients who do not have IHD. ¡The predictive value of clinical exercise testing is a measure of how accurately a test result (positive or negative) correctly identifies the presence or absence of IHD in patients and is calculated from sensitivity and specificity úTP and FN ¡ ¨Diagnostic Value of Exercise Testing for the Detection of Ischemic Heart Disease (Cont.) ¨Clinical Exercise Test Data and Prognosis ¨First introduced in 1991 when the Duke Treadmill Score was published, the implementation of various exercise test scores that combine information derived during the exercise test into a single prognostic estimate has gained popularity. ¨The most widely accepted and used of these prognostic scores is the Duke Treadmill Score or the related Duke Treadmill Nomogram. ¨Clinical Exercise Tests with Imaging ¨When the resting ECG is abnormal, exercise testing may be coupled with other

techniques designed to either augment the information provided by the ECG or to replace the ECG when resting abnormalities (Box 5.5) make evaluation of changes during exercise impossible ¨Radioistopes such as

201

thallium and

199

mtechnetium sestamibi (Cardiolite)

¨Field Walking Test ¨Non–laboratory-based clinical exercise tests are also frequently used in patients with chronic disease. These are generally classified as field or hallway walking tests and are typically considered submaximal ¨Similar to maximal exercise tests, field walking tests are used to evaluate exercise capacity, estimate prognosis, and evaluate response to treatment ¡6MWT, incremental and endurance shuttle walk tests ¨...