WHAT IS CARDIOPULMONARY EXERCISE TEST (CPET)?

Cardiopulmonary Exercise Test (CPET) is the only non-invasive exercise stress test that assesses heart and lung function in real-time during exercise. Your heart and lungs work together to deliver oxygen to your working muscles where it is used to make energy; and to remove carbon dioxide from the body. CPET measures the amount of oxygen your body is using, the amount of carbon dioxide it is producing, your breathing pattern, and electrocardiogram (EKG) while you are riding a stationary bicycle.  


This data undergoes expert analysis in the data center where exercise capacity is quantified using MET-TEST powerful proprietary pattern recognition software, and the mechanism of patient symptoms is prioritized. 


This is a much more detailed level of insight and feedback to the ordering physicians than a traditional treadmill stress test. Besides detecting problems in the heart and lungs, serial testing with CPET is also used to monitor changes in your disease condition and response to therapeutic interventions such as exercise and medical therapy to ensure long-term health is headed in the right direction. More information on Treadmill vs. CPET

WHAT CONDITIONS CAN BE DETECTED AND MONITORED BY CPET AND NOT TRADITIONAL TREADMILL STRESS TEST?

The traditional treadmill stress test can only detect ischemic heart disease of the large blood vessels, and it is not very accurate at doing this. Not only does a CPET do a better job of detecting ischemic heart disease, it can also pick-up many other conditions that the treadmill stress test cannot.


Heart, lung, and metabolic conditions can cause shortness of breath, chest pain, fatigue and overall exercise intolerance.  CPET is the only test that can simultaneously determine which of these systems is causing the problem:

HEART

Coronary artery disease, heart failure and valve disease will impair ability to increase cardiac output with exertion and hence cause symptoms.  CPET is frequently abnormal when routing cardiac testing in the cardiologist’s office is normal.

CHRONOTROPIC INCOMPETENCE

Inability to increase heart rate appropriately during exertion.

LUNGS

Inability to ventilate air or poor circulation in the lungs can cause shortness of breath.  In many cases, CPET will reveal abnormalities in lung function when resting pulmonary function testing (PFT) are normal.

DECONDITIONING

Poor cardiovascular fitness that can be improved with exercise.

MUSCLE METABOLIC DISORDERS

Inability of the muscle cells to use oxygen from the bloodstream to produce energy for the working muscle tissues (example: mitochondria disorders, McArdle’s disease, enzyme deficiency).

EFFORT

Poor effort is easily detectable with appropriate interpretation on CPET.

WILL I GET THE SAME RESULTS FROM CPET AS I WOULD WITH TREADMILL OR NUCLEAR STRESS TEST?

No, other tests use fewer measurements and assess cardiac and lung function separately. A treadmill stress test only looks at a specific part of your ECG during exercise that can indicate heart disease. However, in many people with heart disease, this ECG abnormality never appears. Nuclear stress testing uses a radioactive chemical that is injected into the bloodstream to estimate how blood flows around the heart. Pictures are taken with a special camera before and after exercise to show any abnormalities. This can detect an abnormality in main, large (macrovascular) blood vessels around the heart; however, it does not show any abnormalities in the small (microvascular) blood vessels of the heart. Nuclear stress testing can also miss patients with blockages in multiple blood vessels, or in blood vessels not easily seen by the camera due to their position on the heart. The CPET is not an imaging test, but a physiological test. It measures how your heart, lungs, and muscles are functioning during exercise. CPET takes into account multiple physiological variables that might limit your ability to exercise. No other test exists that can measure heart, lung, and muscle function all at once.

HOW IS A CPET PERFORMED?

Unlike a traditional stress test, the CPET is performed on a stationary bicycle, which is safer than a treadmill. Many patients feel more comfortable riding the bicycle than walking on a treadmill as they are seated and can stop when needed. The following equipment will be worn during the test:

FACE MASK

This monitors the oxygen used, carbon dioxide produced, and the breathing pattern. The mask is placed over the mouth and nose. It does not restrict breathing and you will only be breathing in air from the environment.

ELECTROCARDIOGRAM (EKG)

Ten stickers will be placed on your chest with monitoring wires attached. This is used to monitor your heart rate and rhythm.

BLOOD PRESSURE CUFF

Your blood pressure will be taken multiple times during the test. The cuff wraps around the upper part of your arm and tightens to measure your blood pressure.

Before exercise begins, you will be asked to perform two lung tests. The results of these tests will be compared to your breathing during exercise. Your technician will then fit the required equipment to you and help you get on the bicycle. While you are resting on the bicycle, your technician will explain the testing procedure in greater detail. 


At the end of the rest period, you will be asked to begin pedaling lightly for a few minutes, to warm up. The resistance on the bicycle will then slowly become harder and harder as if you were going up a hill that keeps gently getting steeper and steeper. The test will continue until you are giving your maximum effort and can no longer continue.


To get the most accurate results for your doctor, it is important that you give your best effort for as long as you possibly can. If you do not give a maximum effort, your test may be “indeterminate” and your doctor will not have the most accurate information to help you. The exercise work load will be adjusted on an individual basis to enable each person give his or her best effort. Your technician will keep encouraging you to continue to get your best effort until he or she sees that you cannot continue. However, if your technician notices that you are experiencing certain symptoms the test will be immediately stopped. After the test is over, your technician will ask you to pedal slowly and gently to cool down while he or she continues monitoring your vital signs.


The actual time it takes to perform the test, from the time you get on the bike, through the exercise portion and recovery will be between 15 and 25 minutes. However, you will only be asked to exercise at a hard intensity for about 3 to 4 minutes.


For best results:

  • Give your best effort and exercise for as long and hard as possible
  • Keep your legs moving at the same speed for the entire test, even when it is difficult
  • Avoid speaking during the test unless you have discomfort or pain
  • Let the technician know if you have discomfort or pain at any point during the test

HOW OFTEN SHOULD I HAVE A CPET?

With progression of coronary disease, peak cardiac function (Peak VO2) will deteriorate, so serial CPET testing serves as a key tool to help monitor changes in cardiac health over time. Improvements can be seen within six months of implementing lifestyle and medical therapies, but at the very minimum, patients with an abnormal CPET should have one done annually to follow the course of their disease and confirm response to therapeutic interventions.



Patients started on beta-blocker medication may need to repeat their test in one month to determine the most effective dosage for optimizing cardiac function (since this will vary among individuals).

The goal in every person is to increase Peak VO2 from baseline by 10% or more per test until the underlying cardiac dysfunction pattern is completely normalized (as seen in the case study HERE).


The evolving role of cardiopulmonary exercise testing in ischemic heart disease.

Purpose of review 

Cardiopulmonary exercise testing (CPET) is the gold standard for directly assessing cardiorespiratory fitness (CRF) and has a relatively new and evolving role in evaluating atherosclerotic heart disease, particularly in detecting cardiac dysfunction caused by ischemic heart disease. The purpose of this review is to assess the current literature on the link between cardiovascular (CV) risk factors, cardiac dysfunction and CRF assessed by CPET.


Recent findings 

We summarize the basics of exercise physiology and the key determinants of CRF. Prognostically, several studies have been published relating directly measured CRF by CPET and outcomes allowing for more precise risk assessment. Diagnostically, this review describes in detail what is considered healthy and abnormal cardiac function assessed by CPET. New studies demonstrate that cardiac dysfunction on CPET is a common finding in asymptomatic individuals and is associated with CV risk factors and lower CRF. This review covers how key CPET parameters change as individuals transition from the asymptomatic to the symptomatic stage with progressively decreasing CRF. Finally, a supplement with case studies with long-term longitudinal data demonstrating how CPET can be used in daily clinical decision making is presented.


Summary 

In summary, CPET is a powerful tool to provide individualized CV risk assessment, monitor the effectiveness of therapeutic interventions, and provide meaningful feedback to help patients guide their path to improve CRF when routinely used in the outpatient setting.


For more information, click on the Link:  Current Opinion in Cardiology, Dated: August 22, 2023.
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