People who are at high risk for cardiac disease or present with symptoms such as shortness of breath and chest pain may be advised to undergo tests to look for the blockage of major cardiac blood vessels. These tests will help determine the presence of fatty plaques within the blood vessel and the extent of risk they pose for a heart attack.
There are many tests for the purpose and the ideal test for one individual may not be so for another. The cardiologist decides with the informed consent of the patient.
Tests for blocked arteries:
Treadmill stress test
- Initially, evaluation begins with non-invasive tests such as the treadmill stress test. This test is ordered when there are cardiac symptoms such as chest pain. The treadmill test involves walking on the treadmill at a brisk pace with a mild inclination while connected to the leads of an electrocardiogram and a blood pressure monitor. This gives an idea of the functioning of the heart when under stress. This test measures the heart rate, blood pressure and electric activity of the heart during and after exercise.
- Stress echocardiography is usually advised in cases of suspected heart failure, heart valve malfunction, or to assess damage after a heart attack. This evaluates the pumping and functioning of the valves of the heart. The device placed on the chest sends ultrasound waves which are reflected by the heart and its valves producing a moving image of the beating heart and valves.
Nuclear stress test
- This test is advised when cardiac symptoms are present. It is recommended to assess blood flow to the heart and also in patients with a history of previous heart attacks. A radioactive dye is injected into the bloodstream at rest and after exercise. When viewed through a camera, blocks and narrowings of the blood vessels causing compromised blood flow to the heart can be seen. It also helps to see scarred areas due to a prior heart attack.
Cardiac computed tomography (CT) Angiography
- This test can be done when a person presents with symptoms of a heart attack. Computed tomography (CT) allows visualization of plaques within blood vessels as well as the severity of the narrowing of cardiac arteries. This helps determine the extent of compromise of cardiac function and the ideal treatment options.
- A negative CT angiography would mean an extremely low risk of a heart attack and almost no significant cardiac pathology.
Cardiac Magnetic Resonance Imaging (MRI) stress test
- MRIs are expensive and usually done after a cardiac arrest to assess the damage, or to evaluate cardiomyopathies, which are disorders due to dysfunction of the cardiac muscles and could be due to various reasons. Magnetic Resonance Imaging helps pick up rare disorders, the presence of cardiac tumours and cardiac muscle dysfunctions. The person is made to lie within a machine at rest as well as after being given medication to increase blood flow to the heart. This helps to identify areas of scarring as well as how different regions of the heart contract.
- While an Electrocardiogram tells you the area of the heart that has impaired blood flow and is not contracting properly after exercise, nuclear studies and the Magnetic Resonance Imaging (MRI) can reveal which portions of the heart are receiving low blood flow indicating a blocked artery.
- Most people have a certain degree of blockage in major arteries with ageing due to a process known as atherosclerosis. Whether this narrowing is affecting the blood supply to the cardiac muscles is determined by these tests for blocked arteries.
What does a positive stress test mean?
A positive stress test means an artery may have one or more fatty plaques within its lumen that are significant enough to cause compromised blood supply to the heart muscles.
The gold standard for the confirmation of the same is done by angiogram, which is an invasive test done by cardiac catheterisation. A non-invasive alternative is the Computed Tomography angiogram which allows visualisation of the blocks.
What should you know before you undergo a test for blocked arteries?
- Why you should undergo the test. Understand that the doctor suspects that a heart attack is about to happen or has already occurred. This may be because of your symptoms such as chest pain or the feeling of chest tightness.
- Alternative tests that you can undergo: It is your right to make an informed decision after consulting the treating cardiologist.
- How the test results will affect your treatment.
- Preparation before you take the test. You may be advised to stop taking certain medications such as blood thinners or aspirin before the test.
How is the risk of a heart attack determined?
Despite multiple tests, sometimes it is not possible to exactly determine the risk associated with a detected blocked artery. When a larger region of the heart shows reduced blood supply, there is a reason for concern. Sometimes a small block can rupture, which has a grave prognosis. However, there is no way to know which plaque is more prone to rupture.
Reviewed by Dr. Sreenivasa B Consultant – Cardiology – Adult | Davangere – SS Narayana Heart Centre