Bicycle Ergometry
Most bicycle test are performed sitting upright, but supine bicycle test have become more popular.
Treadmill Test
The use of treadmill presents a number of advantages because it is possible to adjust the speed and grade of walking to the agility of the subject.
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| Correct Posture During Treadmill Exercise |
Bruce Protocol
It is the most commonly used protocol. Patients start out at 1.7 mph on a 10 per cent grade and progress to their maximum capacity at 3 minute intervals (as the haemodynamic changes stabilises at 3 minutes).
It is the most commonly used protocol. Patients start out at 1.7 mph on a 10 per cent grade and progress to their maximum capacity at 3 minute intervals (as the haemodynamic changes stabilises at 3 minutes).
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| Bruce Protocol |
The above stages can be extended upto the 7th stage, but seldom achieved in Indian patients.
Modified Bruce Protocol
It is useful for a less fit person. There are two 3minute warm up stages at 1.7 mph and 0 per cent grade and 1.7 mph and 5 per cent grade.
Modified Bruce Protocol
It is useful for a less fit person. There are two 3minute warm up stages at 1.7 mph and 0 per cent grade and 1.7 mph and 5 per cent grade.
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| Various Exercise Protocols |
Exercise Intensity
The Scandinavian committee on Electrocardiogram classification recommended target heart rates of approximately 85 per cent of the maximum. Sheffield and associates 18 found the maximum predicted heart rate to be 198 (0.14 x age) for conditioned men and 205 (0.41 x age) for non conditioned men.
Skin Prepartation
The quality of recording depends greatly on good electrode contact. The discovery of this simple fact has more to do with the good quality of exercise records. Men who are very hirsute may need to be shaved.
Lead (Electrode Position) and Attachments
The 12 lead Mason – Likar system with electrodes is used. The plastic adhesive electrodes has self contained electrode jelly in the cap and need only to be stuck on and attached to the lead wire. A few minutes delay between application and exercise allows for better contact and therefore, less battery effect at the skin contact point. This minimizes the baseline wandering. It is very important the right and left arm electrode be placed laterally rather than in the mid clavicular line as is sometimes done.
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| Likar System with Electrodes |
Exercise
The treadmill is elevated to a 10 per cent grade, then started at 1.7 mph and the patient is asked to step on. Some treadmills start out very slowly. At the end of 3 minutes of exercise an ECG and blood pressure are recorded.
Handrail Support
Many patients who are weak, fearful or shot of breath find it essential to hold tightly to the handrail while walking. If accurate aerobic information is to be obtained handrail support is not recommended or to hold handrail loosely. On the other hand, it is better to get some information than to get none at all. The heart rate and pulse pressure product are good estimates of the magnitude of coronary flow and aerobic capacity as well as the time on the protocol.
The physician should talk intermittently to the patients while they are being tested, reassuring them as to their progress and asking how they feel. When it is time to increase the speed of the treadmill, patients are notified and asked if they can go faster for short time.
Stress Laboratory Equipment
The stress lab must have the following equipment:
1) A mercury Blood Pressure apparatus.
2) A Bed so that the patients ECG can be recorded in the recovery period in supine position.
3) A trolley with resuscitative equipment – Laryngoscope, Endotracheal tube, Ambu Bag.
4) Important injections – Atropine, Dopamine, Noradrenaline, Xylocard.
5) Defibrillator.
Monitoring
The oscilloscope is under constant observation by both the technician and the physician doing the test. At the end of each three minutes, the blood pressure and ECG are recorded and the heart rate is noted on the worksheet. Ventricular premature contraction or other arrhythmias are noted on the worksheet, recorded in the strip chart. If ST depression is noted on the monitor or on the recorder the patient is frequently questioned as to the presence of pain or tightness in the chest.
Exercise Duration
Most of the subjects reach their peak predicted heart rate response within 8 to 10 minutes. For selected cases in which the subjects are well conditioned athletes, exercise duration can be increased to a total time of 12 to 15 minutes.
Termination of the Test
Test should be terminated when:
1) PVCS develop in pairs or with increasing frequency or when ventricular tachycardia develops (runs of four or more PVCS).
2) Atrial tachycardia or atrial fibrillation supervenes.
3) There is onset of heart block – either 2nd or 3rd degree A-V block.
4) Angina pain is progressive (grade 3 pain, if grade 4 is the most severe in the patients experience).
5) ST-segment depression has become severe, i.e. 3 to 4mm or more in vigorous asymptomatic subjects. If the patient is known to have severe CAD or angina at low workloads of if the patient is known to have severe CAD or angina at low work loads or if the patient has ST-segment depression at rest, exercise should be terminated with only minor increases in ST-segment depression over the baseline tracing. One should also terminate exercise when ST-segment depression exceeds 2mm if the onset of ischaemia is at low work loads.
6) The heart rate or systolic blood pressure drops progressively with continuing exercise.
7) The patient is unable to continue because of dyspnoea, fatigue or feelings of faintness.
8) Musculoskeletal pain becomes severe, such as might occur with arthritis or claudication.
9) The patient looks vasoconstricted, i.e. pale and clammy.
10) Extreme elevations in systolic and diastolic blood pressures.
11) The patient has reached or exceeded that predicted maximum pulse rate.
12) The physician is in doubt. It takes experience to determine how far to push a sick patients.
Blood Pressure Measurements
During Exercise With the onset of exercise, the resistance to blood flow through contracting muscles decreases significantly and results in a fall in the peripheral vascular resistance. When the patient begins ton exercise, the normal BP response is a gradual elevation of systolic pressure with increasing workloads and essentially no significant change in diastolic pressure. Near peak workload, the systolic BP levels off and often declines, only to rise again within 1 or 2 minutes after exercise is terminated. As the patient recovers, the pressure returns to control levels.
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| Blood Pressure Response During Exercise |
Hypertensive Response
Hypertension at rest has long been known to be a risk factor for the development of coronary artery disease (CAD). Significant elevation of BP during exercise higher than the expected normal response has been recognized as adding an additional metabolic burden.
Hypertension at rest has long been known to be a risk factor for the development of coronary artery disease (CAD). Significant elevation of BP during exercise higher than the expected normal response has been recognized as adding an additional metabolic burden.
BP Response with Age As patients grow older, although the cardiac output with exercise increase at about the same ratio as in younger subjects, the peripheral resistance is greater so that the systolic pressure is higher.The normal maximal systolic pressure in older subjects is higher as age progress, it suggests that cardiac function is good and that cardiac output can increase.BP Response in Patients with Resting Hypertension Exercise BP in most hypertensive patients increases at the same rate as it does in normal individuals, but starting from a higher baseline, the maximum systolic blood pressure is higher.Others not only have a steep rise during exercise, but the pressure continues to climb for several minutes after exercise and stays high during the recovery.
Effect of Left Ventricular Hypertrophy on Myocardial Function The increase in coronary flow has been termed flow reserve and its magnitude is important in providing adequate perfusion to the working myocardium when hypertrophy due to hypertension has occurred, the capacity to increase flow to adequately meet the demands of this hypertrophied muscle is often markedly reduced. Thus patient with hypertension may have ST depression and angina during exercise testing, even when they have normal epicardial coronary arteries.
Hypertensive Response in CAD Patients
An exercise rise in systolic blood pressure (over 200 mm Hg) has been used as a reason to terminate exercise in some centers. Sheps and coworkers found that when diastolic pressure increased with exercise, it identified a subset of patients with a higher probability of coronary artery disease.
Hypotensive Response
Systolic hypotension during exercise occurs under a number of circumstances that must be clearly identified in orders to assess its significance.
Late in Exercise
Many normal persons as well as those with cardiac pathology extend exercise beyond their aerobic threshold. At this point which is usually around 60 per cent or more of their maximum capacity, they have a more rapid increase in heart rate and ventilation and the systolic blood pressure levels off and then begins to fall because of increasing acidosis. When exercise is stopped, this decrease will rapidly abate and the systolic pressure will rebound to a point considerably greater than that recorded at the end of exercise.
Early in Exercise
Anxious patients occasionally will have a sudden rise in blood pressure for a minute or two and then drop to 10 or 20 mm even as the exercise progresses followed by a gradual increase again.This can be differentiated from a more serious decrease in cardiac output, by the vigor of the patient, then respiratory rate and the absence of signs of ischaemia.
Recovery Blood Pressure
The rate of the systolic blood pressure drop during recovery is usually fairly rapid after maximum exercise, although a rebound with a temporary rise about one minute after exercise termination is common.
Conclusions
Careful observation of blood pressure during exercise can yield important information not only about the peripheral resistance, but also the contractile state of the left ventricle. A heart that can function well when ejecting against a very high resistance (BP over 200 mmHg) is usually well perfused, as well as free from fibrosis.
When we observe a fall in pressure, despite continuiing exercise early in the test, poor perfusion or inadequate function for other reasons is almost certainly the case. Thus, careful monitoring of blood pressure at each increment of workload and during recovery, is an essential part of stress testing.
Recovery Period
At the instant exercise is discontinued, the ECG recorded is turned on and left running for a few seconds while the blood pressure is recorded and the patient lies down. The evaluation of the ST- segments and other ECG changes in the first few seconds is often very important occasionally a more stable baseline can be obtained by asking the patient to hold his or her breath for a few seconds. Blood pressure is often low at the period just after the exercise, only to rise temporarily again about one minute later. This drop in blood pressure may be due to the temporary inadequacy in cardiac pumping capacity in relation to metabolic demand, or it may be due to the vasodilatation associated with increasing the lactic acid concentrations at peak stress. The blood pressure and ECG are then recorded at 1 minute intervals for 6 minutes while the patient is supine.
It is common for the ECG pattern to be equivocal immediately after exercise. If this is so, elevating the patients legs will increase the venous return at a time when the ventricular compliance is most likely to be reduced and the peripheral resistance is still elevated. This may result in an increased left ventricular end diastolic pressure (LVEDP) and a resistant increase in ST-segment depression. The decrease in heart rate from that maximally achieved to 1 minute into recovery should be noted. Late ST-segment depression and T-wave inversion should also be noted as well as the absence or presence of arrhythmias. Patients should be monitored until the ECG has returned to baseline.
Pretest Predictions
Bayesian Theorem: The predictive value of a test is related to the incidence of disease in the population. A history of typical angina in persons older than 30 is associated with at least an intermediate probability of CAD. Most accurate results are in patients with intermediate probability of CAD. A 50 years old man or 60 years old woman with a typical or probable angina has a 50 per cent probability of CAD. In low pre-test false positivity is higher. In high pre-test false negativity is higher.
Diagnostic uses: Sensitivity is 68 per cent and specificity is 77 per cent. In case of single vessel disease the sensitivity is 25 to 71 per cent and it is frequently associated with LAD followed by RCA and circumflex. In case of multivessel CAD the sensitivity is 81 per cent and the specificity is 66 per cent. In case of left main or TVD the sensitivity is 86 per cent and specificity is 53 per cent. Mostly lead V4 to V6 are specific for changes.
Hypertensive Response in CAD Patients
An exercise rise in systolic blood pressure (over 200 mm Hg) has been used as a reason to terminate exercise in some centers. Sheps and coworkers found that when diastolic pressure increased with exercise, it identified a subset of patients with a higher probability of coronary artery disease.
Hypotensive Response
Systolic hypotension during exercise occurs under a number of circumstances that must be clearly identified in orders to assess its significance.
Late in Exercise
Many normal persons as well as those with cardiac pathology extend exercise beyond their aerobic threshold. At this point which is usually around 60 per cent or more of their maximum capacity, they have a more rapid increase in heart rate and ventilation and the systolic blood pressure levels off and then begins to fall because of increasing acidosis. When exercise is stopped, this decrease will rapidly abate and the systolic pressure will rebound to a point considerably greater than that recorded at the end of exercise.
Early in Exercise
Anxious patients occasionally will have a sudden rise in blood pressure for a minute or two and then drop to 10 or 20 mm even as the exercise progresses followed by a gradual increase again.This can be differentiated from a more serious decrease in cardiac output, by the vigor of the patient, then respiratory rate and the absence of signs of ischaemia.
Recovery Blood Pressure
The rate of the systolic blood pressure drop during recovery is usually fairly rapid after maximum exercise, although a rebound with a temporary rise about one minute after exercise termination is common.
Conclusions
Careful observation of blood pressure during exercise can yield important information not only about the peripheral resistance, but also the contractile state of the left ventricle. A heart that can function well when ejecting against a very high resistance (BP over 200 mmHg) is usually well perfused, as well as free from fibrosis.
When we observe a fall in pressure, despite continuiing exercise early in the test, poor perfusion or inadequate function for other reasons is almost certainly the case. Thus, careful monitoring of blood pressure at each increment of workload and during recovery, is an essential part of stress testing.
Recovery Period
At the instant exercise is discontinued, the ECG recorded is turned on and left running for a few seconds while the blood pressure is recorded and the patient lies down. The evaluation of the ST- segments and other ECG changes in the first few seconds is often very important occasionally a more stable baseline can be obtained by asking the patient to hold his or her breath for a few seconds. Blood pressure is often low at the period just after the exercise, only to rise temporarily again about one minute later. This drop in blood pressure may be due to the temporary inadequacy in cardiac pumping capacity in relation to metabolic demand, or it may be due to the vasodilatation associated with increasing the lactic acid concentrations at peak stress. The blood pressure and ECG are then recorded at 1 minute intervals for 6 minutes while the patient is supine.
It is common for the ECG pattern to be equivocal immediately after exercise. If this is so, elevating the patients legs will increase the venous return at a time when the ventricular compliance is most likely to be reduced and the peripheral resistance is still elevated. This may result in an increased left ventricular end diastolic pressure (LVEDP) and a resistant increase in ST-segment depression. The decrease in heart rate from that maximally achieved to 1 minute into recovery should be noted. Late ST-segment depression and T-wave inversion should also be noted as well as the absence or presence of arrhythmias. Patients should be monitored until the ECG has returned to baseline.
Pretest Predictions
Bayesian Theorem: The predictive value of a test is related to the incidence of disease in the population. A history of typical angina in persons older than 30 is associated with at least an intermediate probability of CAD. Most accurate results are in patients with intermediate probability of CAD. A 50 years old man or 60 years old woman with a typical or probable angina has a 50 per cent probability of CAD. In low pre-test false positivity is higher. In high pre-test false negativity is higher.
Diagnostic uses: Sensitivity is 68 per cent and specificity is 77 per cent. In case of single vessel disease the sensitivity is 25 to 71 per cent and it is frequently associated with LAD followed by RCA and circumflex. In case of multivessel CAD the sensitivity is 81 per cent and the specificity is 66 per cent. In case of left main or TVD the sensitivity is 86 per cent and specificity is 53 per cent. Mostly lead V4 to V6 are specific for changes.
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