Cardiac Rehabilitation, Stress Testing and Exercise Prescription

Cardiac Rehabilitation and The Role of Exercise Stress Testing 

Cardiopulmonary Assessment (CPA) or an Exercise Stress Test can be used to: 

• Assess extent and probability of coronary artery disease 
• Determine patient functional capacity at baseline (Predicted VO2max, Anerobic threshold) 
• Monitor progress or response of patient to an exercise program 

Indications for Stress Testing: 

• Symptoms suggestive of ischemia 
• Acute chest pain in patients who do not have ACS 
• Recent ACS treated w/ coronary angiograph or revascularization 

• Or prior coronary revascularization  

• Known CAD with worsening symptoms 
• Valvular heart disease  
• Arrythmias (Atrial fibrillation, AV Blocks, Bradycardias) 
• Newly diagnosed HF or cardiomyopathy 

Absolute Contraindications:

Relative Contraindications

Acute MI  Unstable Angina not treated w/ medical therapy  Uncontrolled arrythmias causing symptoms or hemodynamic instability  Symptomatic Aortic stenosis  Uncontrolled heart failure  Acute Pulmonary Embolism   Severe pulmonary hypertension  Acute myocarditis, pericarditis, or endocarditis  Acute aortic dissection  High Grade AV blocks  Severe hypertension (SBP > 200 or DBP > 110 or both)  Inability to exercise  Thrombosis of lower extremities  Uncontrolled Asthma  SpO2 <85% at rest

Left Main Coronary stenosis or equivalent  Moderate stenotic valvular disease  Tachyarrhythmias/bradyarrhythmias  Hypertrophic cardiomyopathy  Pulmonary Hypertension  Advanced or complicated pregnancy  Electrolyte imbalances  Inability to exercise due to orthopedic impairment

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: 

• Improve long-term survival for patients after a cardiac hospitalization (up to 50% long-term mortality reduction) 
• Create exercise program to aid in: 

• Increase exercise capacity à improved functional capacity 

• Reduction of hospital admission  
• Improve cardiac symptoms 
• Improve psychological effects of disease burden on patient  
• Stabilize or reverse progression of atherosclerosis 
• Alter natural history of CAD 

• Decrease risk of sudden death or reinfarction 

Exercise Stress Testing Protocols 

• Classically Treadmill or stationary cycle ergometer 

• Hand ergometer can also be used for those with conditions that do not allow them to perform treadmill/stationary cycle ergometer 
• Graded exercise test where the velocity or grade is be increased in a sequential manner until patient reaches defined end points (see above “when to terminate a test”) 

• Standard Bruce Protocol 

• Most often used protocol due to it being well validated and ability to measure exercise capacity in metabolic equivalents (METs).  
• 3 minutes per stage 
• 7 Stages (initial stage 1.7mph, Grade 10%) 

• Modified Bruce Protocol 

• Modification for patients with poor exercise capacity via addiction of 2 warm-up stages 
• 3 minutes per stage 
• 9 Stages (initial stage 1.7 MPH, Grade 0) 

• Naughton Protocol 

• More gradual increase in exertion with shorter stages 

• Allows for diagnostic results in older & deconditioned patients 
• 2 minutes per stage 
• 7 stages (initial stage 1.0 MPH, Grade 0) 

• Other protocols have been developed and may vary by institution. Should use the same protocol for any subsequent retests for a patient unless there is a contraindication to do so (change in illness, injury, mobility).  

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: 

1. Heart Rate Reserve (Karvonen) 

1. % of max 

1. Ischemic threshold 

1. Arrythmia threshold 

1. Device threshold (ICD) 

1. Percent VO2max 

1. Ventilatory Threshold via expired gas analysis 

1. BP response  

1. Rate of Perceived exertion  

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 

Percent VO2max
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.  

VO2 Reserve 

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.  

RPE 

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.  

Timing
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
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
F: 3x/week 
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: 

1. Direct Maximal Aerobic Power or VO2max test: measure respiratory gases while subject performs a graded maximal exercise test – typically on treadmill or stationary cycle  

1. Wingate Anaerobic Test: maximal test of anaerobic system. Measures peak power and rate of power decrement.  

1. Indirect VO2Max test: predicted VO2max based on heart rate and formulas to predict a athletes VO2max, respiratory gases are not used and these can be performed with minimal equipment 

1. Canadian Aerobic Fitness Tests  

1. Leger 20m shuttle run 

1. Bruce Maximal treadmill test 

1. Astrand-Ryhming Submaximal cycle ergometer 

1. WHO Submaximal cycle ergometer  

Author: Dr. Sumeet Gill (May 14, 2020 PRND) 

References: 

Alter, David & Oh, Paul & Chong, A.. (2009). Relationship between cardiac rehabilitation and survival after acute cardiac hospitalization within a universal health care system. European journal of cardiovascular prevention and rehabilitation : official journal of the European Society of Cardiology, Working Groups on Epidemiology & Prevention and Cardiac Rehabilitation and Exercise Physiology. 16. 102-13. 10.1097/HJR.0b013e328325d662. 

Albouaini, K., Egred, M., Alahmar, A., & Wright, D. J. (2007). Cardiopulmonary exercise testing and its application. Postgraduate medical journal, 83(985), 675–682. https://doi.org/10.1136/hrt.2007.121558 

Arena, R, Myers, J, Guazzi, M. “The clinical and research applications of aerobic capacity and ventilatory efficiency in heart failure: an evidence-based review”. Heart Fail Rev. vol. 13. 2008. pp. 245-69. 

Bacon, A. P., Carter, R. E., Ogle, E. A., & Joyner, M. J. (2013). VO2max trainability and high intensity interval training in humans: a meta-analysis. PloS one, 8(9), e73182. https://doi.org/10.1371/journal.pone.0073182 

Garner KK, Pomeroy W, Arnold JJ. Exercise Stress Testing: Indications and Common Questions. Am Fam Physician. 2017 Sep 1;96(5):293-299. PubMed PMID:28925651. 

 

Grant, John & JOSEPH, AMY & Campagna, Philip. (1999). The Prediction of Vo2max: A Comparison of 7 Indirect Tests of Aerobic Power. The Journal of Strength & Conditioning Research. 13. 10.1519/00124278-199911000-00008. 

Tessler J, Bordoni B. Cardiac Rehabilitation. [Updated 2020 Mar 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537196/