BETA BLOCKERS AND CARDIAC IMAGING

If you have high blood pressure, your doctor might prescribe a type of medication called Beta blockers. These medications block the effects of the hormone epinephrine (adrenaline), causing your heart to beat more slowly and with less force. Beta blockers help lower blood pressure and widen veins and arteries to improve blood flow.

Your doctor might also send you for a type of cardiac imaging called stress testing to see how your heart functions while under stress – such as watching how it performs during exercise. During an exercise stress test, your heart’s electrical activity and your blood pressure are measured while you exercise on a treadmill. This can help measure your fitness level and show how well your blood flows through the arteries that supply the heart.

It’s important to note that if you are on beta blockers and have been booked for exercise stress testing, you will need to stop certain medications 48 hours before your exam, and during the day of your exam. This applies to both types of stress testing – an exercise stress test and myocardial perfusion imaging (MPI).

Your doctor will advise you about which heart drugs will need to be stopped prior to exercise stress testing. You will also need to let your medical imaging provider know what medications you are on.

WHAT IS STRESS TESTING?

As your body works harder, it requires more oxygen which causes the heart to pump more blood and increases your heart rate and blood pressure. By monitoring and recording these changes this stress testing can indicate if parts of the heart have inadequate blood supply, which could indicate the presence of coronary artery disease.

There are two main types of stress testing performed at Mayfair Diagnostics. An exercise stress test, and myocardial perfusion imaging (MPI). An MPI is an exercise stress test that involves an injection of a radioactive isotope, which travels to the heart muscle. The radioactive material (radiopharmaceutical) is injected intravenously at rest and at stress (during exercise) and imaged with a gamma camera. For more information about this exam, read What is Myocardial Perfusion Imaging?

WHY WOULD YOUR DOCTOR RECOMMEND A STRESS TEST?

An exercise stress test is commonly used to analyze heart rhythms and check blood flow. Issues with heart rhythms and blood flow can be the cause of chest pain, shortness of breath, and reduced exercise capacity, as well multiple other symptoms. This test can help diagnose:

• Arrythmia – an irregular heart beat where the heart can beat too fast, too slow, or irregularly.
• Coronary artery disease – where there is a decreased delivery of blood, oxygen, and nutrients to the heart due to reduced blood flow.

An exercise stress test can also check your heart before surgery.

WHAT HAPPENS DURING A STRESS TEST?

To prepare for your exam, you will need to stop beta and calcium channel blockers 48 hours before your exam and avoid caffeine 24 hours before your exam. Four hours prior to your appointment, do not take anything by mouth – no smoking/vaping or use of Nitro spray, and don’t eat/drink/chew gum or tobacco.

During stress testing, a technologist and an internal medicine physician will be monitoring you. A technologist will place 10 electrodes (adhesive patches) on your chest – they are attached to the electrocardiogram (ECG) machine, which charts your heart’s electrical activity during the test. The sites where the electrodes are placed will be cleaned with alcohol and shaved if necessary. A mild abrasive material may also be rubbed on the area prior to placing the electrodes. This helps ensure a good quality ECG recording.

Before you start exercising, the technologist will perform a resting ECG, measure your resting heart rate, and take your blood pressure. You will then be asked to begin walking slowly in place on the treadmill. The speed and incline of the treadmill is gradually increased during 5-15 minutes of exercise. Most of the test occurs at a walking pace, with some light jogging.

At regular intervals, the technologist will ask you how you are feeling, particularly if you feel chest, arm, or jaw pain or discomfort, shortness of breath, dizzy, lightheaded, or if you have any other unusual symptoms. We will stop the test if you become too tired, experience chest pain, or when we have gathered enough information.

After the exercise portion is over, you will need to sit and relax. We will continue to monitor your ECG, heart rate, and blood pressure as they return to normal. You are then free to leave.

WHAT HAPPENS AFTER MY TEST?

Your results will be reviewed by the internal medicine physician and your health care practitioner will receive a comprehensive report within a few days of your exam. Your doctor will then be able to review your results with you, along with the results of any other tests, and determine the next steps in your health care treatment plan.

There are several possible outcomes of a stress test:

• Normal – you likely don’t require further testing.
• Normal with symptoms – if you continue to have symptoms or your symptoms get worse, your doctor may order other testing.
• Abnormal – information from the test may be used to develop a treatment plan or order additional tests.

HOW DO I GET CARDIAC IMAGING?

To determine what type of imaging is appropriate for you, you will need to discuss your symptoms and medical history with your health care practitioner, who would then provide you with a requisition for cardiac imaging, if recommended. Your requisition, and any lab work and resting ECG, are sent to Mayfair for triaging. Our cardiac team will then be in touch to coordinate booking and explain how to prepare for your exam.

Please visit cardiac imaging services, for more information about what happens during these exams and how to prepare. All cardiac exams are performed at our Mayfair Place clinic.

REFERENCES

Cleveland Clinic Staff (2022) “Exercise Stress Test.” my.clevelandclinic.org. Accessed January 23, 2024.

Healthwise Staff (2022) “Beta-Blockers.” Myhealth.alberta.ca. Accessed January 23, 2024.

Mayo Clinic Staff (2023) “Beta blockers.” www.mayoclinic.org. Accessed January 23, 2024.

Mayo Clinic Staff (2022) “Stress test.” www.mayoclinic.org. Accessed January 23, 2024.

Penn Medicine (2022) “What is a stress test?”  www.pennmedicine.org. Accessed January 23, 2024.

University of Ottawa Heart Institute (2023) “Treadmill Exercise Stress Test.” www.ottawaheart.ca. Accessed January 23, 2024.