Cardiac Rehabilitation and The Role of Exercise Stress Testing
Cardiopulmonary Assessment (CPA) or an Exercise Stress Test can be used to:
Indications for Stress Testing:
|Absolute Contraindications:||Relative Contraindications|
SpO2 <85% at rest
When to Terminate A Stress Test
|Chest pain suggestive of ischemia||SBP>240 or DPB >110|
|Ischemic ECG changes – >1mm STE w/o Q waves||Severe Desat – SPO2<80%|
|Complex Ectopy||Pt terminates due to fatigue/symptoms|
|2nd/3rd degree heart block||Dizziness/lightheadedness/confusion|
|Fall in systolic pressure >10mmhg from baseline + ischemic changes||Sustained VTach|
Goals of Stress testing in a Rehab Setting:
Exercise Stress Testing Protocols
Exercise Prescription – Cardiac Rehab Setting
CPA will provide information on patients: Heart rate (HR), Blood Pressure (BP), Rate of perceived Exertion (RPE), Expired Gases, Anaerobic Threshold, O2 saturation, VO2max. These can be used to create an exercise prescription based on the FITT (Frequency, Intensity, Type, Time) principles. If there is evidence of ischemic threshold/cardiac overload ensure patient is exercising at an intensity at least 10bpm below that level.
Approaches to Creating Aerobic Exercise Prescription based off CPA:
Frequency: “ACSM recommends 30 min of moderate intensity aerobic activity most days”. Frequency should be determined based on patients goals, current activity level, and medical history. Rehab programs in Toronto recommend exercise 5 days per week.
Intensity: there is a minimal level of intensity required to create a training effect. Typically we prescribe exercise between at levels of 60-80% of HR or VO2 max. This is considered “Moderate physical activity”. Intensity can be determined via:
Heart Rate Reserve of Karvonen Method
Training Heart Rate (THR) = (HRmax-HR rest) x %intensity + HRRest
HRmax = symptom limited HR or Peak HR achieved on CPA
THR = HR achieved at 60-80% of measured VO2max
Ventilatory Threshold/Anaerobic threshold
Work rate at which oxygen consumption exceeds circulatory systems ability to sustain aerobic metabolism. Typically coincides with a non-linear increase in minute ventilation or VCO2 relative to VO2. At a physiological level aerobic metabolism is no longer sufficient to meet the metabolic demands of the tissue and anaerobic metabolism begins taking over energy production. This coincides with an elevation in blood lactate levels. Determining the HR/RPE/VO2/pace at which this occurs during the CPA can allow you to prescribe a training heart rate that is not above this threshold.
Target Vo2 = (60 to 80%)(VO2max-Vo2rest) + VO2rest
Heart rate that reflect this target VO2 can be used as the training heart rates for exercise prescription.
ACSM Guidelines recommend training between RPE of 11-16 on Borg Scale (6-20). This is considered sufficient to cause adaptations. Use of patients RPE on exercise test can allow you to prescribe training loads for the patient. An important limiting factor is patients may under or over-report their RPE which can result in inadequate or dangerous training parameters.
20-60 minutes of continuous or non-continuous aerobic activity is recommended by the ACSM. It is important to consider the patients medical history, experience, and type of exercise.
Type of exercise should be based on patients medical history and preference. Classically rehab programs use walking or jogging. However, other acceptable modalities include: cycling, swimming, elliptical . These may be used based on a patients pre-existing conditions or preference. Ensuring patients are engaging in safe modality is imperative (e.g. appropriate temperature of pool, lifeguard, patients familiarity with equipment).
E.g. Aerobic Prescription for Rehab Patient
64M w/ hx of CAD, HTN, PCI x 2. Enrolls in Cardiac Rehab program. On Initial CPA he achieves an HR max of 162BPM, with a resting HR of 62.
Karnoven method THR60% = (162-62) X 0.60 + 62 = 122 THR = 122-142BPM
THR80%= (162-62) x 0.80 + 62 = 142
I: HR 122-142BPM
T: Indoor Walking on track
T: 20 minutes (5 min warm up, 10 min walking at THR, 5 min cool down)
High Performance and Cardiopulmonary Assessment:
The use of a cardiopulmonary assessment for high performance athletes is unlikely to detect abnormal pathology. Typically it is used to measure and track aerobic fitness via the VO2max and Anaerobic Threshold. These parameters can be used on initial intake of an athlete to determine their baseline. The values obtained at baseline can then be used to create training parameters to improve an athletes fitness based on their chosen sport. Alternatively, these tests can be used to track an athletes response to a training cycle. This information can be used by Certfied Exercise Physiologists, Strength & Conditioning Coaches, and the head coach to create training cycles to target specific a weakness.
Below are various modalities to test a athletes Aerobic Fitness:
Author: Dr. Sumeet Gill (May 14, 2020 PRND)
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