Critically review the case for exercise testing and prescription in cardiac patient rehabilitation.
Exercise prescription as defined by Dr. , as the specific plan of fitness – related activities designed for a specific purpose, which is often developed by a fitness or rehabilitation specialist for the client or patient. Components of exercise prescription generally includes specific recommendations: (1) type of exercise or activity (walking, swimming, cycling) (2) specific workloads (watts, walking speed) (3) duration of activity or exercise session (4) intensity guidelines – target heart rate range (THR) and estimated rate of perceived perception (RPE) and (5) precautions regarding certain orthopedic or other concern related comments. further explains that Heart rate reserve (HRR) is defined as the maximal heart rate (HR max) observed during a symptom-limited exercise stress test minus the resting heart rate (HR rest). A percentage of the HRR range is added to the HR rest to determine a THR range to be used during exercise. This approach accounts for individual variability in the HR rest and better reflects the peak exercise oxygen consumption (VO2). Exercise intensity is generally recommended to be 60-90% of the HR max or 50-85% of the VO2 maximum (VO2 max) or HRR. For example, a patient with coronary heart disease on beta-blockade medication has an HR max of 120 beats per minute (bpm) and an HR rest of 55 bpm. The recommended THR would be calculated as follows: (1) HRR = 120 – 55 = 65 (2) THR range = [(HR max - HR rest) X (0.5 - 0.85)] + HR rest (3) THR = 65 X 70% = 46 + 55 = 101 bpm. Thus, the suggested THR range would be 96-108 bpm. The VO2 max is the maximal amount of oxygen that an individual can consume and use during exercise or physical work. This value may be measured or estimated and is expressed commonly in milliliters of oxygen per kilogram of body weight per minute (mL/kg/min).
The RPE scale is used widely in exercise science and sports medicine to monitor or prescribe levels of exercise intensity. The 95%-limits-of-agreement technique has recently been advocated as a better means of assessing within-subject (trial-to-trial) agreement. The perception of exertion is a monitoring behavior that uses all sources of information to govern actions that can benefit or preserve health and partake of adaptive pursuits. How a person feels about exertion moderates his or her response to exercise and effort. The perception of what is happening in exercise, and its concomitant effect on physiological function, must be known to further understand the nature of an exercise response. How a person feels modifies reactions to exercise stress and the mechanisms that underlie them. The Borg scale is as follows: (1) Six – No exertion at all (2) Seven to eight – Extremely light (very, very light) (3) Nine to ten – Very light (A1 warm-up / recovery) (4) Eleven – Light (A2 aerobic threshold) (5) Twelve to thirteen – Moderate (EN-1 anaerobic threshold) (6) Fourteen to fifteen – Hard (EN-2 VO2 max or 400 m swimming pace) (7) Sixteen to seventeen – Very hard (AN-1 peak lactate or lactate tolerance, 200 m swimming pace) (8) Eighteen to nineteen – Extremely hard (very, very hard [AN-2 anaerobic power, 25-50 m swimming pace]) (9) Twenty – Maximum all-out effort with absolutely nothing being held in reserve (1998).
Instructions for use as suggested by Dr.
During the exercise you are to rate your perception of exertion. Use this scale where 6 mean no exertion at all and 20 means a totally maximum effort. The 13, on the scale is somewhat heavy exercise but capable of being performed at steady state (i.e., anaerobic threshold). When at a level of 17, the effort level requires you to push yourself hard even though it is possible to continue for some time. For many people 19, is about as strenuous as exercise becomes because they often reserve a small amount of possible extra effort. Try to appraise the feeling of exertion as honestly as possible. Do not underestimate nor overestimate it. It is of no value to underestimate the level to produce an impression of being “brave” or “tough”. Your own feeling of effort and exertion is all that is of interest. Look at the scale and wordings and decide on the word that best describes your effort level and the number alternative associated with that description.
Considering the different modes of exercise: (1) Intensity: This should range from low to moderate for healthy individuals. (2) Duration: Continuous aerobic activity for 20-60 minutes is recommended. (3) Frequency (3a) Individuals with a less than 3-MET capacity should engage in multiple short sessions each day. (3b) Individuals with a 3- to 5-MET capacity should engage in 1-2 sessions per day. (3b) Individuals a greater than 5-MET capacity should engage in 3-5 sessions per week.
ACC/AHA (American College of Cardiology / American Heart Association Task Force on Practice Guidelines) 2002, Guideline Update for Exercise Testing: The weight of evidence was ranked highest (1) if the data were derived from multiple randomized clinical trials that involved large numbers of patients and intermediate (B) if the data were derived from a limited number of randomized trials that involved small numbers of patients or from careful analyses of non – randomized studies or observational registries. A lower rank (C) was given when expert consensus was the primary basis for the recommendation. The ACC/AHA classifications II, III, and I are used to summarize indications as follow:
Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.
Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment.
Class IIa: Weight of evidence/opinion is in favor of usefulness/efficacy.
Class IIb: Usefulness/efficacy is less well established by evidence/opinion.
Class III: Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful / effective and in some cases may be harmful. The general context for the use of exercise testing is outlined in Figure 1.
Figure 1.General context of the exercise testing guidelines
Source:
Figure 2: Nomogram of the prognostic relations embodied in the treadmill score
Source: Source:
The value of exercise testing, according to . is that exercise testing has a sensitivity of 78% and a specificity of 70% in detecting coronary artery disease. Hence a negative test does not adequately rule out disease. A positive test is much more likely to be false in a young person than an older person unless there is a very good history as they are at much lower risk. Therefore testing of young, asymptomatic people is controversial. There is a suggestion that not enough women and the elderly are being tested (2001). Hence, as stated by Doctor prognostic testing can be useful. A positive test at a low workload is a poor prognostic sign and it indicates the need for urgent treatment. ’ theorem of diagnostic probability states that the predictive value of an abnormal test varies according to the probability of the disease in the population being study. Therefore, exercise testing is usually performed in patients with a moderate probability of coronary artery disease, rather than in those with a very low or high probability (2004).
protocol is very widely used and has been extensively validated. There are 7 stages of 3 minutes each so that a complete test takes 21 minutes. The level of exercise is estimated in METs. 1 MET or metabolic equivalent is the amount of energy expended at rest or 3.5ml oxygen per kilogram per minute. At rest, the average person has an oxygen consumption of 1 MET (or 3.5 ml/kg-min). MET values increase as more activity is performed. In stage 1 the patient walks at 1.7 mph (2.7 km) up a 10% incline. Energy consumption is estimated to be 4.8 METs during this stage. The speed and incline increase with each stage. The information from an ETT can be used to advise the patient on what activities and exercise levels are reasonable. An example of an MET chart is as follows:
METs
Exercise
Recreational
Occupational
Activities of DL
1.5 – 2.0
Strolling 1 – 1.5 mph, 1 mile in 40 – 60 minutes
Knitting; playing cards; sewing; watching TV
Desk work; driving auto/truck; sitting doing light assembly; typing; using hand tools; writing
Brushing hair / teeth, light housework; making bed; partial bath; polishing furniture; washing clothes
2.0 – 3.0
Walking, level 2.0 – 2.5 mph, 1 mile in 24- 30 min cycling, level outdoors – 5mph
Horseback riding (walk), light golf (power cart); playing musical instrument; shuffle board; woodworking
Bartending; crane operation; standing doing light or medium assembly; TV / auto / car repair; working heavy lever
Cooking; driving car; ironing; riding lawn mower; scrubbing floor; walls, cars; widows; showing; sweeping; tub bath
3.0 – 4.0
Walking 3.0 – 4.0 mph, 1 mile in 15 – 20 min cycling, outdoors 5.5mph
Billiards; bowling; canoeing; croquet; fly fishing; golf (pulling cart); shopping; volleyball (non – competitive)
Baling hay; driving heavy truck; heavy machine assembly; janitorial work; light welding; operating large levers; plastering; plumbing; stocking shelves
Cleaning windows; climbing stairs (slowly); General House work; kneeling; light work; pack/unpacking; power lawn mowing (light); sexual intercourse; stocking shelves; vacuuming
4.0 – 5.0
Walking 3.5 – 4.0 mph, 1 mile in cycling, 8mph calisthenics swimming (20 yd/min)
Ballet; dancing; gardening (how? Weeding, digging); golf (carrying clubs); table tennis; tennis (doubles); volleyball
Building interior of house; carrying trays / dishes; farm work (sporadic); house painting, lifting, carrying objects (20 – 40 lb); light carpentry; mechanic work
Raking leaves; shoveling light loads
5.0 – 6.0
Walking 4.0 – 4.5mph 1 mile in 13 – 15 minutes, biking in 10 mph
Canoeing (4m/hr); gardening (digging); skating (ice / roller); social / baseball (non- game); stream fishing
Handyman work (moving, shoveling); heavy carpentry; putting in sidewalk
Raking leaves; shoveling light loads
6.0 – 7.0
Walking/jogging,
4.0-5.0 mph
1 mile in 12-13 min
Biking, 11 mph
Swimming (breaststroke)
Backpacking (light); Badminton; Hiking; Hunting; Horseback riding (trot), Skiing (cross country 2.5 mph); Skiing (light downhill); quare dancing; Tennis (singles)
Exterior home building; Lifting, carrying objects (45-64 lb); Shoveling (10/min, 9 lb); Splitting wood
Lawn mowing (push mower); Snow shoveling (light snow)
7.0 – 8.0
Walking, 5 mph
1 mile in 12 min
Biking (outdoors) 12 mph
Swimming (backstroke), 40 yd/min
Badminton (competitive); Basketball (non-game); Canoeing (5 mph); golf (carrying bag); Horseback (gallop); Skiing (downhill, vigorous)
Ascending stairs with 17 lb load; Lifting, carrying (65-84 lb); Moving heavy furniture; Sawing
8.0 – 9.0
Jog/run 5.5 mph
Biking (outdoors) 13 mph
Swimming (breaststroke) 40 yd/min
Rowing machine; Rope jumping (60-80 skips/min)
Basketball (non-game); Handball/squash/racquetball; Mountain climbing; Soccer (non-team); Touch football; Tour skiing
Lifting, carrying (85-100 lb); Moving heavy furniture (moving van work); Shoveling (14 lb scoops, 10 scoops / min); Using heavy tools
9.0-10.0
Jog/run, 6 mph
1 mile in 10 min
Football (competitive); sledding / tobogganing
Heavy labor; Lumberjack; Shoveling (16 lb scoops)
Ascending stairs carrying 54 lb
11.0+
Run 7 mph (11.5 METs)
8 mph (13.5 METs)
Competitive sports: Basketball, Handball, Racquet, Rowing
Figure 3: MET chart
Source: (2006)
Patients who are candidates for exercise testing may have stable symptoms of chest pain, may be stabilized by medical therapy after symptoms of unstable chest pain, or may be post-myocardial infarction or postrevascularization patients. Patients who are unable to exercise or who have uninterpretable ECGs because of pre-excitation, electronically paced rhythm, left bundle-branch block, or ST depression greater than 1 mm require imaging studies and are beyond the scope of these guidelines. Imaging studies are considered in other ACC/AHA guidelines (5,348-350). Although some studies suggest an even lower training threshold than the one used in the particular study (i.e., < 70% maximal heart rate), especially in extremely deconditioned subjects, if individuals can regularly attain a training intensity of at least 70% maximal heart rate via brisk walking, it is likely that they will achieve improved aerobic fitness. These findings may be especially relevant for the inactive patient in whom the subjective discomfort of vigorous physical training may serve as a deterrent to long-term compliance with exercise therapy (2002). The ability of exercise training as told by (2000) is to reduce morbidity and mortality rates hasn’t been well established for elderly patients, but limited data suggest some benefit (Table 1).
Intervention
Reduces Mortality
Reduces Morbidity
Control of diabetes mellitus
Yes
Yes
Control of obesity
Not clear
Not clear
Dyslipidemia therapy
Yes
Yes
Exercise
Yes*
Not clear
Hypertension therapy
Yes
Yes
Psychosocial interventions
Not clear
Not clear
Smoking cessation
Yes
Yes
Table 1: Impact of Interventions on All – Cause Mortality and Cardiovascular Morbidity in Elderly Patients
Source: (2005)
In the , which enrolled men with known CHD (mean age, 63 years), light to moderate physical activity in the form of regular walking, frequent recreational activities (e.g., gardening), or once-weekly sporting activities (e.g., jogging, swimming), was associated with a significant reduction in all-cause mortality at five years of follow-up. More vigorous types of activities did not show a statistically significant reduction in that same endpoint (2000). A Cochrane review of men and women of all ages with previous MI, revascularization or angina found that exercise-only cardiac rehabilitation reduced all cause mortality by 27%, cardiac death by 31% and a combined end point of mortality, non fatal myocardial infarction and revascularization by 19% (2000).
Prior to initiating an exercise program for the post-rehab client, the trainer will need to obtain a health history form, a signed informed consent, a physician’s referral / release for exercise and, if possible, a copy of the client’s rehab records. The physician’s referral/release form should indicate the trainer’s credentials and state that no medical monitoring (e.g., blood pressure, ECG, pulse oximetry, etc.) will be performed. The physician should be asked to provide a training intensity if age-predicted target heart rate range is not appropriate. A request for exercise precautions should also be included (2001).
For most patients, clinical risk stratification based on history, examination and resting ECG combined with a functional capacity test such as a shuttle walking test or a six minute walking test will be sufficient. The test was supervised by a physical therapist and was performed,if indicated by the physician, using telemetry monitoring. Subjectswere asked to walk at their own maximal pace along a 35-m long,flat, and straight hospital corridor. No encouragement was offered.The test was symptom limited, so patients were allowed to stopif signs or symptoms of significant distress occurred (severedyspnea, dizziness, angina, skeletal muscle pain), though they were instructed to resume walking as soon as possible. The distance covered during the test was recorded in meters. The 6MWT has become one of the most popularclinical exercise tests for evaluating functional capacity. It is a practical, simple, and inexpensive test, and does not require any exercise equipment or advanced training for technicians (2004). The shuttle walking test (cited in SIGN Publication No. 57) is a low cost low tech alternative to exercise testing that informs the rehabilitation team on a suitable exercise programme and appropriate training heart rate, and allows assessment of progress during cardiac rehabilitation without the need for cardiac technicians, physicians or expensive equipment (2005). The shuttle walking test protocol is given in Box 1.
Shuttle Walking Test
Equipment required
Calibrated cassette player and shuttle walk test tape. Two marker cones and non slippery, flat walking surface at least 10 meters in length. Heart rate monitor with record facility and adjustable upper alarm limits.
Protocol
Each subject should be screened by a member of the cardiac rehabilitation team for any exclusion criteria before proceeding. Place two cones exactly 9 meters apart, thus allowing the subjects to walk 10 meters when they go round the cone at the end of each shuttle. Subjects then listen to the instructions on the audio cassette. These should be repeated verbally to ensure that they understand what is expected during the test. Subjects walk around the 10 meter course aiming to be turning at the first marker cone when the first audio signal is given, and turning at the second cone at the next audio signal. Subjects should be accompanied around the first level of the test to help them keep pace with the audio signals. Thereafter the operator stands mid way between the two marker cones offering advice on completion of a level: ‘Walk a bit faster now if you can’. Progression to the next level of difficulty is indicated by a triple bleep which lets the subject know that an increase in walking speed is required. The full test comprises 12 levels each of one minute duration with walking speeds that rise incrementally from 1.2 miles per hour (1.9 km per hour) to 5.3 miles per hour (8.5 km per hour). The test is completed at 12 minutes or if one of the termination criteria is met.
Termination criteria
o Any anginal symptoms or feeling too breathless to continue.
o Feeling dizzy or faint.
o Leg pain limiting further exercise.
Achieved level of perceived exertion >=15 (Borg Scale)
Achieved heart rate >=85% predicted (detected by audible upper alarm limit). Failure to meet the speed requirements of the test – subject more than half a meter from the cone when the bleep sounds.
Following the test
Subjects should continue to walk slowly around the course a further four times to avoid any syncopal attacks associated with abrupt cessation of exercise. Subjects are then seated and asked to confirm their limiting symptom. Record total distance walked heart rate and perceived exertion for each level completed, peak heart rate and reason for test termination. If subjects have fully recovered after 10 minutes then no further action is required. If they report continuing breathlessness or angina then a further rest period should follow during which they may receive sublingual nitrates, have an ECG or be seen by a doctor as appropriate.
Box 1.Shuttle Walking Test
Source: (2005)
Cardiac rehabilitation (.) today targets people with ischaemic heart disease, congestive heart failure and people with a high risk of developing ischaemic heart disease. The short-term goals of cardiac rehabilitation are to stabilize heart disease, to limit the physical and mental effects of heart disease, to improve the functioning of the people with heart disease and to improve their quality of life. The long-term goals are to reduce patients’ long-term risk of heart disease, to stop the progression of heart disease and to reduce morbidity and mortality. According to current evidence, these goals can best be realized through comprehensive cardiac rehabilitation programmes based on exercise training, patient education, lifestyle intervention, risk factor management and clinical assessment, psychosocial support and optimizing the pharmaceutical treatment of symptoms. Pharmaceutical treatment comprises an important part of overall rehabilitation (2003).
Efforts to prevent heart disease can be divided into primary, secondary and tertiary prevention. Primary prevention means preventing disease from arising at all. Secondary prevention means identifying patients at high risk of developing ischaemic heart disease and identifying symptoms and disease at early stages to reduce the course of disease and contribute to improving the prognosis. Tertiary prevention means preventing remission of disease and preventing chronic conditions, including reduced functioning as a result of disease (2003).
In summary, the finding of this particular study suggest that physicians and allied health professionals can prescribe brisk walking on a flat surface to their cardiac patients with confidence that this intensity will achieve cardiorespiratory and health benefits. Furthermore, these results serve to discount the lingering notion that cardiac patients need to participate in vigorous exercise such as jogging or running in order to benefit from an exercise training program. Phase II cardiac rehabilitation programs are associated with improvements in exercise tolerance, coronary risk factors, and psychosocial well-being. Nevertheless, previous reports have generally evaluated the global effectiveness of these programs (i.e., on all subjects, collectively), which may serve to camouflage or attenuate the impact of these interventions on specific patient subsets. In one particular study, the researchers investigated the effectiveness of a contemporary, exercise-based cardiac rehabilitation program that included a cardiovascular risk-reduction intervention, using a computerized database on 117 patients (average age, 66.5 years; 68% men; 96% white) who completed pre-phase II and post-phase II evaluations (2002). As pointed out by, ( 2004) cardiac rehabilitation begin with a patient assessment that helps us develop an individualized, goal-directed treatment plan with short-term and long-term objectives for reducing cardiovascular risk and improving quality of life. Ideally, patients should be referred to cardiac rehabilitation within 1 month of a coronary event, but they can begin the program (12 to 36 sessions, depending on individual need) for up to 1 year after an event. Therefore, there are short term and long term goals that will benefit the patient in a short term basis and long term basis depending on the program that was intended for the patient and the extent of the disease. also added, physicians have an obligation to strongly recommend cardiac rehabilitation and reinforce that message in follow-up visits. More patients would comply with the recommendation if the message — that cardiac rehabilitation increases survival and improves quality of life — were strongly emphasized (2004).
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