Cardiac Stress Test is done to know if there is reduced blood supply to the heart muscles.
This happens if there is blockage in the arteries of the heart muscle and those arteries, known as coronary arteries. If coronary arteries have narrowed, the blood supply is reduced. Such patients will be comfortable at rest. Hence, a regular ECG, which is done when a patient is lying down, is at rest, will not show any irregularity. However, in the stress test we introduce an exercise which increases the heart rate, consequently, the blood requirement of the heart muscles. However, as the demand increases the blood supply does not increase, due to the blockage in the artery, we witness change in the ECG which was not highlighted in the regular ECG.
Hence, this test is an exercise ECG, in which we record the ECG while doing the exercise. We take a serial ECG & blood pressure every 3 minutes and the cardiologist sees the changes in the electrocardiogram. After each interval the treadmill slope & speed is increased.The ECG is recorded till the target heart rate is reached.
Depending on these changes the doctor identifies if the stress test is normal(Negative) or abnormal (Positive). If the test is positive, it implies that the patient has a block in the coronary artery. Following which the patient has to undergo a final diagnostic test called angiography. All patients cannot undergo angiography as it is an invasive test and also expensive. Hence, a simple test which can be done on an OPD basis is a cardiac stress test.
This test is performed under the supervision of a certified cardiologist and trained sister.
Precautions one has to take before a Cardiac Stress Test
To do the stress test it is mandatory that the patient should be able to walk. IF the patient cannot walk sufficiently the stress test cannot be performed.
Certain drugs have to be stopped 48 hours. before the procedure. Especially drugs which slow the heart rate.
When is Stress test adviced?
Depending on the symptoms or if there are any changes in the ECG, or is the heart doctor suspects a bloackage in the coronary artery, the doctormight advise Stress test to ischemic heart disease.
Who should undergo Stress test?
When patient has a partial bloackage, chest pain or angina lasting for 5 mins.
Patient has chest pain after walking.
Patient has problem breathing after walking or exertion.
Who should not do ECG?
Patient with heart failure and certain abnormal ECG or if the patients BP is very high we have to postpone the Stress Test.
How long does the stress test take?
The time for completing this test depends on the patients capacity. When the maximum heart rate or target heart rate of a patient is reached the doctor stops the test or if the patient having any symptoms or complain the test is stopped. A full stress test generally takes about 21 minutes. However, most patients walk for about 9-12 minutes. While patients with sedentary lifestyle they fatigue in 7-8 minutes.
How is the target heart rate calculated?
The target heart rate is calculated by the formula: 220- (Age of patient)
When does the doctor stop the test?
The test is stopped if the patient complains of giddiness, severe chest pain or severe breathlessness, blackout.
The doctor might also stop the Stress test if there is any change in the cardiogram or if the patient reached the target heart rate.