Source: www.westland-clinic.com
An Introduction
Stripped down to bare terms, an exercise stress test is a procedure where the patient is subjected to an exercise ranging from jogging to cycling depending on the machines available with wires connected to their chest as they participate in the activity recording the electrical activities of their heart as they jog or cycle through the varying phases that the doctor wishes to analyze.
As the electrical data is computed into the monitor manned by a cardiac technician and a doctor, they would start to look for signs no matter how subtle as to the changes of the electrical recordings of your heart. Stressing the heart with varying forms of exercises would identify findings that may suggest an occlusion to your coronary blood vessels.
Preparation
A consent form would usually be produced for your perusal immediately after counseling has been provided as to the methodology of the exercise stress test, its indication and what to expect.
Your doctor or the nurse would advise you to bring along a pair of sports shoes alongside sports attire to fit in with the ease of moving during the jogging. Wear light to ease the process of the exercise or wear what you would normally wear if you were going out for a morning walk or an evening jog. The most important thing is to ensure comfortable footwear so that you do not slip and fall while going on the treadmill.
Take a light breakfast before you come for the procedure, as you wouldn’t want to jog with a full stomach. Most patients who do take a heavy meal would complain of nausea and some would even progress to vomiting thus aborting the test altogether.
Based on the author’s experience, the best mode of preparing for the exercise stress test is to start by doing some form of light jogging or brisk walking by yourself prior to attempting the procedure. A brisk walk slowly upgrading to a slow jog three to four sessions a week each lasting anywhere between 30-40 minutes is the recommended regime that I would often tell my patients to do.
Indications
Here are some of the indications:-
- Chest pain on exertion or at rest – be it vague (atypical) or typical
- Chest discomfort
- Palpitations
- Lightheadedness presumed to be due to cardiac-related cause
- Reassessment or restratification (post heart operation or stenting)
Contraindications
Exercise stress tests are not suitable when there is:
- A recent heart attack
- Uncontrolled palpitations with documented electrical rhythm abnormalities
- Uncontrolled heart failure
- Uncontrolled high blood pressure
- Severe hardening and narrowing of your heart valves (aortic stenosis)
- Blood clots within the major blood vessels of the heart and lungs
- An acute inflammation (injury) towards the layers of the heart (myocarditis/pericarditis)
The Procedure
An exercise stress test machine in Hospital Keningau. Note the treadmill that has the capability to shift speed and incline and is connected to a monitor that traces the patient’s electrical activity of the heart. A printer is connected to the monitor to print out the varying stages of the exercise stress test for the doctor’s perusal and interpretation.
The Phases and Stages of an Exercise Stress Test based on the Bruce Protocol
The resting stage or pretest – often lasts anywhere between 4-6 minutes, it records the baseline electrical pattern of your heart, the heart rate and any baseline abnormalities.
- Stage 1 – a 10% incline with 2.75 km/h speed lasting for 3 minutes
- Stage 2 – a 12% incline with 4.00 km/h speed lasting for 3 minutes
- Stage 3 – a 14% incline with 5.47 km/h speed lasting for 3 minutes
- Stage 4 – a 16% incline with 6.70 km/h speed lasting for 3 minutes
Recovery stage – flat incline with progressive slowing of the treadmill until it stops, patients are given an option to stand for a while or move about around the machine before sitting down – this stage typically lasts around 4-6 minutes.
Certain centers allow the test to be increased up till Stage 5 or 6 but these aren’t generally done unless it is purely for a functional assessment and in most cases should a patient be able to reach Stage 4 without any significant problem, higher stages are irrelevant.
Each stage of the stress test would entail an automatic recording of your blood pressure and heart rate, which is vital for the cardiac technician or the doctor to consider stopping the test prematurely if you develop breathing difficulties, chest discomfort or pain, light-headedness or giddiness.
Results and Interpretation
There are often three major results that you would expect.
Positive stress test – which means there is substantial evidence to show that there is an occlusion or blockage in your coronary blood vessel. However, one is unable to tell for certain how many blood vessels are blocked or the extent of the blockages there is based on the recording strips available.
Negative stress test – which means you are given a clean bill of health with regards to your coronary blood vessel.
Inconclusive stress test – the doctors are unable to report adequately the results of the test perhaps due to the fact that not enough stages are achieved by the patient or that the heart rate did not achieve the targeted and desired response. The failure of achieving the targeted heart rate often means that the stress test imposed is submaximal.
Post Test Expectations
Should your stress test be reported as negative, and depending on the risk factor that you have with regards to other medical conditions, your doctor may order another test in the near future to reassess your heart again. However if the test is inconclusive, a consult with a senior doctor would often be done and in such a case should the condition deemed necessary, a repeat test would often be scheduled in a few days or weeks time. In other cases, another diagnostic modality would be offered where the patient need not be required to jog. Such circumstances are ideal for patients who have osteoarthritis of the knees or are not used to strenuous activities.
A positive stress test is often the major concern. Often more than not, the doctor would provide a more detailed counseling and in this manner, an invasive approach of investigating and confirming the presence and extent of your blood vessel blockages. Further intervention could then be done in the form of bypass operation or blood vessel stenting depending on the findings of coronary angiography.
Should any doubt arise, the author advises a consult with your general practitioner or your family physician to clear up the confusion.
Dr. Chiam Keng Hoong is an internal medicine physician and a MRCP holder. He currently works in Sabah.
[This article belongs to The Malaysian Medical Gazette. Any republication (online or offline) without written permission from The Malaysian Medical Gazette is prohibited.]