What you ought to know about the different tests for your heart

The World Health Organization estimates that about 17 million people worldwide die of heart disease each year.  In the Philippines, cardiovascular disease accounts for approximately half of all deaths in the country.  The Philippine National Statistics Office in 2009 revealed that on average, nearly 300 Filipinos die of heart disease every day.  That’s equivalent to one jumbo jet crashing daily and killing all its passengers!

Most Filipinos, during their lifetimes, seek medical attention from their doctors because of concerns about the health of their heart.  Their doctors, in turn, usually prescribe various heart tests to come up with the definitive diagnosis and use them as guide to proper treatment.  During this month of February, which has been annually celebrated as Heart Month, I have decided to tackle the subject of heart tests in order to provide our readers a better understanding of these examinations.  Today’s article is the first of a two-part series on the different tests usually utilized by doctors to know more about the condition of your heart.

The tests your doctor may use to assess heart health will depend on your age and risk factors for heart disease, and whether you have any clinical signs or symptoms of heart disease, such as chest pain.  As with most medical checkups, your doctor will likely perform a physical exam and ask about your personal and family medical history before pursuing any tests.  The most important risk factors for heart disease are smoking, high blood pressure, high cholesterol, diabetes, and a family history of heart disease.  With a better picture of your overall health, your doctor will be better able to select which tests are most appropriate for you.  This two-part series will give you a closer look and a better understanding of the various tests typically used to study heart health and function.

Blood tests

Your blood offers many clues about your heart health.  Blood tests are an easy and relatively inexpensive way to look for those clues.  You are probably familiar with tests that gauge your risk of heart disease, such as routine cholesterol tests performed at annual checkups.  Results of these tests and others can help you and your doctor take preventive steps to protect your heart.

In addition to tests that profile your risk of heart disease, blood tests can also be done to follow up on a heart-related complaint — such as chest pain or fatigue — or to monitor existing heart disease.  Some of these tests your doctor may order include:

•  Troponin test.  Certain proteins from heart muscles slowly leak out into your blood if your heart has been damaged, such as during a heart attack.  If you arrive at the emergency room with signs of symptoms of a heart attack, doctors will take samples of your blood to test for the presence of these proteins.  The troponin test is one of the most commonly ordered tests because it is particularly sensitive and is a specific marker of heart muscle damage.  Levels of troponin in your body climb soon after heart damage occurs and remain elevated for up to two weeks.

• Natriuretic peptide test.  Brain natriuretic peptide, also called B-type natriuretic peptide (BNP), is a protein that your heart and blood vessels produce.  BNP helps your body eliminate fluids and sodium in the urine and relaxes your blood vessels.  High levels of BNP in your bloodstream may indicate that your body is trying to ease strain on your heart and usually suggest the presence of heart failure.

•  C-reactive protein test.  A high level of C-reactive protein (CRP) in your blood signals inflammation is present somewhere in your body.  Inflammation plays an important role in atherosclerosis, which is the buildup of fatty deposits in your coronary arteries.  While studies have shown an association between CRP levels and heart disease, a CRP test can’t tell your doctor the exact site of inflammation.

•  Lipoprotein (a).  Also known as Lp(a), it is a type of low-density lipoprotein (LDL) cholesterol.  High Lp(a) may be a sign of increased risk of heart disease, though it’s not clear how much risk.  Your Lp(a) level is determined by your genes and isn’t generally affected by lifestyle.  It may help your doctor assess the need to aggressively lower your LDL cholesterol to help lower your overall risk.

• General blood tests. Your doctor may also want to evaluate the levels of your different blood cells (complete blood count or CBC).  A low red blood cell count might indicate anemia.  Your doctor may also want to know your body’s fluid and salt balance (electrolytes) and how your organs, such as the kidneys and liver, are functioning.

Chest x-ray

A chest X-ray generates a picture of your heart, lungs, large blood vessels, ribs, and spine. If you go to your doctor or the emergency room with chest pain or shortness of breath, a chest  X-ray can help distinguish between a heart problem and lung problem or broken rib, for example.

A chest X-ray can reveal an enlarged heart — a sign of some forms of heart disease, such as heart failure, congenital heart disease, a heart valve problem or fluid around the heart (pericardial effusion). It can also reveal fluid buildup in or around your lungs, another sign of heart failure.

But a chest X-ray doesn’t show the inside of your heart.  If a more thorough look of your heart is needed, your doctor may request more detailed imaging test, such as an echocardiogram, a computerized tomography (CT) scan or a magnetic resonance imaging (MRI) scan of your heart.

Electrocardiogram

An electrocardiogram (ECG) is likely one of the first tests you’ll undergo when you seek help for chest pain or heart palpitations. An ECG can help your doctor detect irregularities in your heart’s electrical activity.  Each time your heart beats, an electrical signal passes from the top of your heart to the bottom of your heart.  As the signal travels, it causes your heart to contract and pump blood. 

For an ECG, a technician places electrodes on your chest to record your heart’s electrical impulses.  You may have an ECG while you are at rest or while you’re exercising (stress electrocardiogram). A stress ECG is particularly helpful if you experience symptoms during or after physical activity.

The few minutes that a standard ECG is recording may not capture heartbeat irregularity that comes and goes.  In this case, your doctor may recommend a Holter monitor, a portable device that you wear to record a continuous ECG, usually for 24 to 48 hours.

Stress tests

A stress test helps determine whether your arteries are transporting enough blood to your heart.  Some types of stress tests also measure how well your heart muscle is functioning.  The test results may help your doctor evaluate symptoms such as chest pain or shortness of breath that develops when you’re physically active.  The tests can help diagnose conditions such as coronary artery disease.

If you’ve had a heart attack, your doctor may order a stress test to check the damage to your heart and determine if you need additional treatment.  Stress tests are sometimes recommended before you begin a program of vigorous exercise, particularly if you have cardiovascular risk factors.  Stress tests are also sometimes used to evaluate heart valve problems and heart failure.  Test types include:

•  Exercise stress test.  A technician places electrodes on your chest, similar to a standard ECG, and wraps a blood pressure cuff on your arm.  You then walk on a treadmill while an ECG records how your heart rate responds to an increasing workload.  As the speed and grade of the treadmill are gradually increased and the workout becomes more demanding, your heart rate increases.  The doctor, who will be overseeing the test, and his/her assistant, will be monitoring factors such as heart rate and blood pressure.

For people who can’t walk on a treadmill, other forms of exercise, such as pedaling a stationary bicycle, are sometimes used.  Exercise stress tests are often combined with imaging tests, such as an echocardiogram or a cardiac nuclear scan, that produce pictures of the heart muscle to determine if it’s getting enough blood and how the valves are functioning.  Results from the test can help in setting up exercise limits and developing a specialized fitness program.

You can stop the test at any time if you need to, and a medical staff person will always be available if you need help or if anything unusual happens.

•  Non-exercise (pharmacological) stress test. This test is used for individuals who can’t exercise due to conditions such as arthritis.  Your doctor may also order this test if you have heart rhythm problems, which could make the results of an exercise test inconclusive.

For the test, a medication is injected into your bloodstream that stresses your heart, mimicking the effects of exercise.  The effects of the medication are observed with ECG and imaging tests of your heart.  If either test indicates that your heart was unaffected by stress, it is unlikely that you have significant problems with your coronary arteries.  If the test reveals problems, the results can help determine if you need additional tests, such as coronary angiogram, or medications to improve blood flow to your heart.

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To have a more complete understanding of the various tests for your heart, don’t miss the second part of this article which will appear on February 18.  Among the tests to be discussed are electrocardiography, coronary angiogram, cardiac nuclear CT scanning, and cardiac magnetic resonance imaging.