You make an appointment to see your Primary Care Physician (PCP) for a feeling of mild pressure in your chest which you have noticed recently. Your doctor performs an electrocardiogram (ECG) which you are told is normal, but she still wants you to have more testing. Your question is: “Do I need to be worried?” When it comes to testing for heart disease, there seems to be an endless array of heart tests to which a patient with symptoms can be subjected. In this article, we will address testing for patients WITH symptoms and how these tests differ from one another.
Primary Care Physicians, Primary Care Providers, and cardiologists frequently encounter patients with symptoms which may be related to their heart. These symptoms include chest pain, chest pressure, shortness of breath, left arm pain or numbness, jaw pain, and upper back pain. When confronted with such symptoms, the medical provider’s number one priority is to make sure the symptom is not a signal of underlying heart disease; more specifically, of plaque (composed of cholesterol and inflammatory cells) clogging the blood vessels that carry oxygenated blood to the heart muscle. Heart related symptoms usually occur only when such a blood vessel is more than 60-70% “clogged.”
The first step your doctor usually performs is an ECG, which is a simple evaluation of the heart structure and function based on the electrical activity of the heart picked up by 12 sticker “leads” placed on the skin. It is indeed a rather “crude” screening test: an ECG which is abnormal does not necessarily signify a problem with the heart, nor does a normal ECG eliminate the possibility of a heart problem. Nevertheless, it is simple to perform and a “first-step” tool to help your doctor increase or decrease his or her suspicion that your symptom is or is not related to your heart.
At the other end of the spectrum, the most definitive test for clogged arteries is a cardiac catheterization. In this procedure, dye is injected into the arteries of the heart via a small tube inserted through an artery in the groin or wrist. This is the definitive, or “gold standard”, procedure for determining if a patient’s symptom is indeed caused by a blockage in a heart artery. However, this test is invasive and therefore carries the risk associated with invasive procedure and the dye used in the test can cause kidney problems for patients who are at risk for kidney disease. Moreover, in New York State, it must be performed in the hospital, and thus it is inconvenient and expensive. For these reasons, cardiac catheterization is reserved for patients whose symptoms and medical history make it highly likely that they have a blocked artery.
That brings us to the array of tests which fall between the simple ECG and the invasive cardiac catheterization. As a cardiologist, I divide the remaining tests into two major categories: tests designed to give information on the presence of abnormal blood flow to the heart muscle, and tests designed to display the arteries of the heart themselves in order to reveal the presence or absence of “clogging”.
Testing used to examine for abnormal blood flow to the heart muscle involves some form of stress testing. The most basic of these tests is a “regular” exercise stress test in which a patient is placed on a treadmill while attached to an ECG machine. The treadmill increases in speed and incline every 3 minutes, and evidence of lack of blood flow (presumably from a blocked artery) is suspected based on changes in the ECG during exercise or development of symptoms during exercise. The benefit of this type of test is that it is fairly simple to perform; however, it does require that a patient be able to exercise and that his or her ECG is normal prior to the test.
A more sensitive and specific way to perform stress testing is to combine the stress test with pictures of the heart. One way to obtain these pictures is to use ultrasound immediately after the stress test in order to assess the movement of the heart (abnormal movement is indicative of a blockage in an artery). This type of testing is known as a “Stress Echocardiogram”; its benefits are that it is easy to perform, adds important information to a stress test, and does not involve any radiation. The drawback, however, is that it still requires that a patient to be able to exercise. It also does not perform well with heavier patients where the extra weight interferes with the ability to obtain good images of the heart using ultrasound.
The second type of stress testing in which pictures are taken to assess for blood flow is nuclear stress testing. In a nuclear stress test, a patient performs an exercise stress test, but at the peak of the exercise, the patient is injected with a tiny amount of radioactive “dye”. This dye then flows to the heart muscle through the arteries supplying the heart with blood. Pictures of the heart are then obtained showing where and how much of the dye has made it to the heart muscle. Areas where there is little or no radioactivity can be assumed to be supplied by a blood vessel which is clogged.
Nuclear stress tests can also be performed WITHOUT exercise by using a medication to “stress” the patient. (An important misconception made by patients is that the “stress medication” is actually stressing the body in the way that exercise does with increased heart rate and blood pressure. In reality, these medications just cause dilatation of the blood vessels of the heart and are not truly a “stress” on the body, yet the accuracy of the test is the same as if the patient had exercised.) The benefits of nuclear stress testing are both that it adds important information to stress tests and also that it is easy to perform in patients who cannot exercise. The drawbacks are that it does involve a small dose of radiation and it takes several hours of time to complete the test.
A more advanced form of nuclear stress testing is called a Positron Emission Test (PET) scan. In a PET scan, the patient is given a medication to “stress” them and a different type of radioactive “dye” is used to assess blood flow. PET scans use LESS radiation than traditional nuclear stress tests but create better images due to the type of radioactive dye and camera utilized. A PET scan is rather fast and the test usually takes less than 1 hour to complete. The PET scan performs particularly well with obese patients because of the quality of the images from the advanced camera and type of radioactive dye. The drawback of PET scans is that they are more expensive than a traditional nuclear stress test and do involve radiation (though less than traditional nuclear stress testing).
The other type of test used to evaluate for blockage is a test which looks at the arteries themselves to directly assess the degree of blockage. The “gold standard” cardiac catheterization does this, but so does a non-invasive, advanced CT scan known as a Coronary CT Angiogram (Coronary CTA). In this type of test, dye is injected through an IV during a CT scan to display the arteries and degree of blockage. This type of test is best suited for a patient who has symptoms which could potentially be cardiac in origin, but the suspicion for actual coronary disease as a cause of the symptoms is still low. The benefits of the CT angiogram are that it is fast, easy to perform, does not involve any exercise, and displays if there is ANY coronary artery disease (not just if there are “clogged” arteries as stress tests do). The drawbacks are that it does involve use of CT scan dye (which can injure the kidneys in patients with abnormal kidney function) and it also involves a small dose of radiation.
In the end, there are a multitude of different tests which can be ordered by your doctor to determine if your symptoms are truly due to a blocked artery in the heart. From a patient perspective, the nuances of the tests can be confusing and each type of test has both positive and negative aspects. The role of your doctor is to choose the “right test for the right patient”, which is the test which helps answer the question: “Do I need to be worried?”
Written by: Dr. Lance E. Sullenberger, Co-Medical Director of the Cardiovascular CT Scanning Suite at Capital Cardiology Associates
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