ELECTROCARDIOGRAPHY

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ELECTROCARDIOGRAPHY Electrocardiography measures the electrical activity of the heart and assumes the mechanical action follows. The ECG is the single most important screening tool for the diagnosis of coronary heart disease. It is the single criterion for positive and negative exercise testing.
	ECG can provide information on Rhythm Ischemia Infarct Size Location Electrolyte Imbalance Pericarditis

The placement for the limb leads for a standard resting 12 lead electrocardiogram are illustrated on the left hand figure. The placement during exercise are illustrated on the right hand figure. This is called the Mason-Likar system. ECGs during exercise are therefore different than standard resting 12 lead. Supine and standing 12 leads are analyzed prior to exercise to rule out recent infarctions and/or recent changes in ECG as contraindications for exercise.

Each of the 12 leads takes an electrical picture of a different aspect of the heart. Some leads use two electrodes whereas other use all 12.

The ECG is observed continuously throughout the exercise test and during recovery. It is more prudent to look at leads that represent the left ventricle right ventricle inferior heart than to look at all leads that reflect the left ventricle.

Elements of ExRx	Contraindications	Risk Stratification	Pulmonary Functions	Graded Exercise Testing Interpretation
Blood Chemistries	Body Composition	ECG	top

EXERCISE TESTING When exercise testing is used in the clinical setting the testing is often called Stress Testing. Whereas exercise testing used for exercise prescription is often called Graded Exercise Testing or GXT. The purpose of the stress testing is to find disease whereas the purpose of the GXT is to evaluate functional capacity and to prescribe exercise. To compare characteristics of stress testing to GXT, see the table below. GXT Stress Testing Medications Tested on medications because the client will be exercising on medications Tested off medications because the purpose is to find disease and medications often hide disease. Progression Moderate to simulate exercise progressions Rapid to offer more stress and uncover disease Recovery Active recovery to simulate recoveries following an exercise session. Supine recoveries are often used in stress testing because the venous return from the supine position provides more "stress" for the heart. More stress uncovers more disease In the health and fitness setting exercise testing includes strength and flexibility testing. For the most part, exercise testing in the clinical setting is limited to cardiovascular function. Strength and flexibility testing are utilized in the clinical setting when the patient exhibits co morbidities in neuromuscular or musculoskeletal diseases.
	Most supervised tests are continuous with increasing intensity each stage. Other types of tests include: Single stage Intermittent Ramp Modes of testing include: Treadmill (walk or run) Cycle ergometer Arm Crank Step Testing Timed Walk/Run
The most simple exercise testing would be a single stage step test. Whereas the most complex would be a graded exercise test to maximal capacity with the measurement of VO2max. The most common exercise test recommended for the health and fitness setting is a graded submaximal cycle ergometer test. The most common test performed in the clinical setting are graded submaximal treadmill tests. When submaximal tests are used, the test must end beyond the intensity prescribed for the client/patient .

An important decision about test protocols is, "should the test be maximal or submaximal?" Most tests in the clinical setting are submaximal with the end point being 85% of heart rate max. However, according to the work of Cumming and colleagues, 50% of the individuals who exhibited a positive electrocardiographic response to maximal graded exercise testing would have been missed had the test terminated at 80% of heart rate max (British Heart Journal 34:919, 1972). Had these individuals been tested to 80% heart rate max, yet prescribed exercise intensity above the 80%, they may have been in danger of an adverse event during exercise. If you choose to perform a submaximal GXT, you need to realize that you may have missed vital information.
Variables measured during exercise testing are summarized below. Variable measured at rest and in recovery have an asterisks: Variable Protocol for Measurement Work rate Beginning/ending of each stage Rated Perceived Exertion End of each stage Heart rate* End of each stage Blood Pressure* End of each stage Whenever ECG changes are found Symptoms* Continuously Angina/Dyspnea whenever presented ECG* Continuously VO2 End of test The first five are the most important in a health & fitness setting.

Elements of ExRx	Contraindications	Risk Stratification	Pulmonary Functions	Graded Exercise Testing Interpretation
Blood Chemistries	Body Composition	ECG	top

INTERPRETATION OF EXERCISE TESTING All the variables measured during the GXT need to be interpreted. In that interpretation, a conclusion (positive or negative) for the test needs to be made. PHYSICAL WORK CAPACITY - (PWC) is the outcome variable for any GXT. It is a measure of the cardiorespiratory endurance. It gives an indication about the types of activities that the client/patient will be able to perform. The most direct measure of physical work capacity is VO2max or VO2peak as it should be called in the clinical setting. If expired gases were not collected during the test, the VO2peak can be estimated from the ACSM metabolic equations. Metabolic equations for estimated physical work capacity from the final workrate of a GXT Mode Equation Treadmill Walking VO2 (ml/ min kg) =[ 0.1(speed)] +[ 1.8(speed)(grade)] +[ 3.5 (ml/min kg)] Treadmill Running VO2 (ml/ min kg) =[ 0.2(speed) ]+[ 0.9(speed)(grade)] +[ 3.5 (ml/ min kg)] Leg Ergometry VO2 (ml/ min kg) = [1.8(workrate)/Mass] + 7.0 (ml/ min kg) or VO2 (ml/ min kg) = (10.8)(Watts)(Mass)] + 7.0 (ml/ min kg) Arm Ergometry VO2 (ml/ min kg) = [3(workrate)/Mass] + 3.5 (ml/ min kg) or VO2 (ml/ min kg) = (18)(Watts)(Mass)] + 3.5 (ml/ min kg) Stepping VO2 (ml/ min kg) =[ 0.2(rate)]+[1.33(1.8)(height)(rate)] +[ 3.5 (ml/ min kg)] Speed = m/min Grade = fraction of 100 (i.e. 10% grade = 0.10) Workrate = kpm/min Mass = body weight in kg Rate = steps/min Height = height of step in meters 1 kg = 2.2 pounds 1 mph = 26.8 m/min Watts = (kgm/min)/ 6 Ending workrate provides a measure of physical work capacity if VO2max is not measured. In any case, the ending work (estimated or measured) is compared to predicted. Formulas to predict physical work capacity or VO2 max (ml/min kg) Category Young Adults (<35 years old) Middle-Aged Adults (>35 years old) Men Women Men Women Sedentary = 49.8 - 0.36(age) The women’s formulas are 80% of the men’s =57.8 – 0.445(age) 42.3 - 0.356 (age) Moderately Active = 55.7 - 0.36 (age) Active = 63.0 - 0.36 (age) =69.7 - 0.621 (age) =42.9 – 0.312 (age) Conclusions are: Higher than predicted for age and physical activity Within limits of predicted for age and physical activity Below predicted for age and physical activity HEART RATE - The heart rate may be the single best indicator of heart work. Heart rate has a normal response to graded exercise. The athlete often exhibits an increases of 4-8/min for each increase in MET; whereas sedentary adults increase 8-12/min for each MET increase. Obesity can exhibit as high as 18/min per MET increase. As the workrate increases, the heart rate should also. Medications such as Beta Blockers blunt the heart rate response. It is not unusual to find a maximal heart rate of 125/min for a person on beta blockers who should have a predicted HRmax around 150 per minute. If the client/patient is not on beta blockade medication, however, the heart rate response is abnormal. Anxiety HR response would increase rapidly, then exhibit a normal heart rate where it becomes normal. Similarly, the maximal heart rate should be within predicted. HRmax = 220-age (+ 12/min) A conclusion should be documented regarding the heart rate response as well as the maximal achieved.. RATED PERCIEVED EXERTION- RPE is often not interpreted, but used for exercise prescription to help the client/patient guide exercise intensity. BLOOD PRESSURE - BP is probably the variable measured during the test that provides the best information on exercise tolerance. In the clinical setting Systolic Blood Pressure represents cardiac output and Diastolic Blood Pressure represents vascular resistance to blood flow. Systolic blood pressure should increase progressively through graded exercise because cardiac output should increase for each increase in workrate. Diastolic blood pressure should stay the same or decrease because resistance to blood flow should not increase during scenarios of increased blood flow. The mean systolic blood pressure response to graded exercise is: 7.5 mm Hg/MET Hypertensive response is >12 mm Hg/MET Hypotensive response is <5 mm Hg/MET The hypotensive systolic blood response means the cardiac output is not increasing with the workrate. The heart is failing to adjust to the workrate. Several factors could contribute to the hypotensive response: ECG rhythm abnormalities ECG ischemic responses A drop in systolic blood pressure is an indication to terminate the test early. A drop in systolic blood pressure with an increase in diastolic pressure is immediate termination. Putting the HR and BP response on the same graph, SBP is most often greater than HR. However, it is not unusual in young women to find HR greater than SBP. In the Beta blockade response, both HR and SBP will be significantly lower. The SBP response to anxiety is similar to the HR response. ECG - The ECG is the single criterion used to determine whether the test is positive or negative. Although, often symptoms, blood pressure, and physical work capacity is also used in the determination of positive/negative testing. The ST segment of the ECG is the part of the ECG that is used in this evaluation. ST segment depression indicates an area of the heart is ischemic. Ischemia means low blood flow. Low blood flow occurs when the blood flow cannot match the work demand for it. Atherosclerotic lesions are the primary cause of ischemia during exercise testing. ST segment >1 mm of horizontal depression, for at least 0.80 seconds following the J-point in three consecutive complexes; and is the clinical definition of ischemia and a positive stress test. If an exercise ECG does not exhibit ST segment depression it is a negative test. In other cases, an abnormal blood pressure response in the absence of a positive ECG may have medical follow-up. ST segment elevation indicates an area of injury. This means a heart attack is happening. An exercise test should be terminated immediately if this exhibits during testing. If this exhibits before testing, testing should be cancelled and the patient should go to the ER. SYMPTOMS - Symptoms important during exercise testing include: Muscle or skeletal Shortness of Breath or Dyspnea Light handedness Dizziness Ischemic symptoms Angina or chest discomfort Shortness of breath Excessive Sweating Pallor Color of skin Other Symptoms often accompany ischemia. The classic symptom is angina, a chest discomfort. Other signs of ischemia, in the absence of angina, include shortness of breath, excessive sweating and/or pallor. These symptoms will often be accompanied by a drop in blood pressure; although can occur without a drop. Angina can be a discomfort anywhere above the waist. It is not a sharp pain. It is pressure, heaviness, or burning. It is typically in the chest and radiates to the left arm. But it can be in the jaw or back. It is relieved by rest or nitroglycerine. Angina and dyspnea are measured on specific scales. Angina Scale Dyspnea Scale 1    Light, Barely noticeable 2    Moderate, bothersome 3     Severe, very uncomfortable 4     Most severe pain ever experienced 1    Mild, noticeable to patient, but not tester 2    Mild, some difficulty, noticeable to tester 3     Moderate difficulty, but can continue 4     Severe difficulty, cannot continue Dyspnea is more often measured in pulmonary patients.

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