Diagnosing cardiomyopathy and determining the best treatment plan can involve several tests to determine the extent of the disease and rule out other conditions that may be adding to your symptoms. Additional screening and counseling for the risk of sudden death may also be necessary in certain situations.
Despite the sophistication of many testing procedures and the valuable information they can provide, tests alone do not provide a diagnosis. The physician is ultimately responsible for interpreting test results, so it's vital that he or she has a good grasp of what each test can and cannot reveal about your condition. Before moving forward with a diagnostic test, especially an invasive test like heart catheterization, review with your physician how the test results will add to his or her understanding of your condition.
The physical exam and medical history are the cornerstone of the diagnosis and the treatment plan. From a doctor's perspective, the goals of the physical exam and medical history are to determine how the disease may be affecting your lifestyle and to collect data that may reveal information on the condition of the heart. During the visit, be prepared to discuss your and your family's medical history, including heart problems and sudden death in cousins, parents, aunts, uncles, and grandparents; your symptoms, including when they first appeared, how long they last, circumstances in which the symptoms occur; and any questions you have about your condition. During the physical exam, your doctor will listen to your heart and lungs and look for signs of swelling and/or tenderness.
Once this information has been obtained, follow-up testing will be recommended and may include any of the following:
- Blood tests
- Chest X-ray
- Ultra-fast CAT scan
- Echocardiogram (ECHO)
- Electrocardiogram (ECG)
- Electrophysiology Study (EP)
- Heart catheterization
- Nuclear Cardiac Stress Testing: Thallium Scans
- Magnetic Resonance Imaging
- Polysomnogram (Sleep Study)
Blood testing is routinely performed on people being evaluated for cardiomyopathy. Samples of blood are collected and used to evaluate basic function and conditions of the organs (including the heart) and rule out the possibility of other diseases causing the symptoms.
Preparing for a blood test usually requires abstaining from food and all beverages with the exception of water for nine to 12 hours prior to the blood draw. Check with your healthcare provider for detailed instructions. During the procedure, blood samples are drawn from a vein, usually from the inside of the elbow or the back of the hand using a thin, hollow needle.
Common blood tests used to diagnose and treat cardiomyopathy include:
- Complete blood cell count (CBC) measures the number of red and white blood cells, total amount of hemoglobin, fraction of blood consisting of red blood cells, and the size of the red blood cells, also known as mean corpuscular volume (MCV). The CBC is a screening test, used to diagnose many different diseases including those affecting fluid volume, anemia, blood loss, acute or chronic infection, allergies, and problems with clotting. Anemia, or a deficiency in the number of red blood cells, can affect the prognosis in a person with cardiomyopathy and studies are underway to determine if treating the anemia with iron and hormones improves survival.
- Lipid analysis may be performed to evaluate your general health and risk for coronary artery disease. Lipids are fatty substances that circulate in your bloodstream. Lipids include cholesterols and triglycerides. A lipid screen usually includes analysis of total cholesterol, low-density lipoproteins, high-density lipoprotein, triglycerides, and very low-density lipoprotein. The ratio of low-density lipoprotein cholesterol (LDL) to high-density lipoprotein cholesterol (HDL) is an indicator of the risk for developing plaque in your arteries. Ideally this ratio should be low--a low LDL coupled with a high HDL.
- Blood chemistries usually include a group of 20 chemical tests performed on blood serum, the portion of blood without cells, to assess the functions of the vital organs, in particular the kidneys, liver, and thyroid as well as the heart. In addition, coagulation studies to determine the amount of time for blood to clot, electrolyte levels, and many other parameters, depending on what the doctor finds in the physical exam and medical history, may also be analyzed.
- Cardiac enzymes including creatine phosphokinase isoenzymes, CK-MB, and lactate dehydrogenase (LDH) isoenzymes may be analyzed to identify potential damage to tissues of the body including the heart, lungs, skeletal system, or brain.
- Blood cultures may be analyzed to help identify any bacteria or other micro-organisms that may be infecting the heart.
In a chest X-ray, electromagnetic energy is used to create images of the internal organs and tissues, including bones. A chest X-ray can show the size, shape, and position of the heart and can detect changes in the lungs related to any heart abnormalities. Chest X-rays are a routine part of any evaluation for cardiomyopathy.
Getting a chest X-ray doesn't hurt. Before the test, you will need to remove all clothing and jewelry from the waist up. During the X-ray, you will likely be asked to stand against the plate containing the X-ray film and roll your shoulders forward while holding your arms at your sides so they do not interfere with the picture. The radiologist or technician will ask you to take a deep breath and hold it as the X-ray picture is taken. Holding your breath fills your lungs with air and helps your heart and lungs show up more clearly on the film.
Although a chest X-ray exposes you to a small amount of radiation, it is less than that experienced in daily living, and the benefits of the image greatly outweigh the slight increase in cancer risk posed by the radiation exposure. However, women who have any chance of being pregnant when the X-ray is taken should tell their doctors, so that special precautions can be taken to minimize the developing fetus's exposure to radiation.
Computed tomography is a specialized imaging technique that uses X-rays collected from many different angles around the body to generate detailed cross-sectional images as well as three-dimensional images of the body's internal structures and organs, including the heart. Ultra-fast CT scans use X-rays collected at very short intervals for a more detailed evaluation of the heart in motion.
The procedure is painless and requires the patient to lie as still as possible on a table that is guided into a machine that resembles an enormous doughnut. The machine, called a gantry, directs small doses of electromagnetic radiation toward the body from various angles. Because different tissues of the body absorb varying amounts of radiation, a computer can analyze the radiation transmitted through the body to reconstruct the images of the internal structures and organs.
Sometimes a contrast medium is injected into a vein during a CT scan to help depict blood flow through the vessels and structures of the heart. If a contrast medium is to be used, patients typically will need to fast for a few hours before the procedure. The contrast medium may, on occasion, cause an allergic reaction, most commonly hives or itchiness. In people with asthma, the allergic reaction may manifest as an asthma attack. In very rare instances, a patient may experience swelling in the throat or other areas of the body. If you experience hives, itchiness, or swelling in your throat during or after your CT scan, immediately tell the technician or doctor.
Chest and abdominal CT scans involve exposure to a dose of radiation that typically exceeds the average background dose of radiation we experience in daily living. For most patients, however, the benefits far outweigh the minor risks associated with exposure to this level of radiation. However, pregnant women may prefer to postpone getting a CT scan until after they've given birth or choose alternative testing procedures. Individuals with pacemakers or internal cardioverter defibrillators who have been advised to avoid MRIs can safely have a CT scan.
Echocardiography uses sound waves to create an image of the heart in motion. Echos are an extremely useful tool for evaluating cardiomyopathy and are used to:
- Measure the dimensions and shape of the heart
- Measure the pumping and relaxing functions of the heart
- Measure pressure gradients in the valves and vessels in and around the heart
- Evaluate the degree of obstruction, if any, within the heart
- Visualize blood flow and valve leakage
- Evaluate the condition of the valves
- Identify abnormal blood flow patterns
Echocardiography relies on the same sound wave-based technology used in prenatal sonograms and depth finders on boats. A small device that looks like a microphone, called a transducer or probe, directs ultrasound waves into the chest. The sound waves, which are inaudible to the human ear, travel into the chest and "bounce back" to a receiver, called an echocardiograph. The returning sound waves are analyzed by a computer to generate images that can be viewed on a video screen.
The information collected by the echocardiograph can be displayed three different ways:
The M-mode echocardiogram looks nothing like a heart. This abstract image is used to measure the size of various structures in the heart and the exact thickness of the heart muscle.
The 2-D echocardiogram provides snapshots of how well all the parts of the heart are working. These two-dimensional images cut through the heart, analogous to slices from a loaf of bread.
The Doppler echocardiogram helps doctors evaluate the blood flow paths through the heart. The "whoosh" sound heard during the procedure is the echocardiograph's interpretation of blood flowing past the heart's various structures.
No preparation is needed for the standard transthoracic echocardiogram, which usually takes one to two hours to complete. Electrodes are attached to the chest to monitor the heart's electrical activity during the test. A technician applies a watery gel to the chest and then slides the transducer across the chest to scan the heart from various angles. In some cases, a contrasting agent or dye is injected into a vein to improve the images from the echo. Most patients say that the procedure is painless, although some report slight discomfort from the pressure of the transducer on the chest.
Other types of echocardiograms that may be used to evaluate cardiomyopathy include:
Transesophageal echocardiogram. For more detailed information about the heart valves and possible blood clots in the heart, a transesophageal echocardiogram or TEE may be necessary. In this procedure, the transducer is mounted on the tip of a half-inch-diameter, flexible tube that is inserted through the patient's mouth down into the esophagus, the passageway that runs from the throat to the stomach. The advantage of the transesophageal echocardiogram is that it provides a more detailed image of the heart valves and blood flow because the esophagus is close to the heart.
Patients are asked to fast for at least eight hours before the test; ask your physician about taking medications. This procedure does not interfere with breathing, and patients are given a numbing medication and a mild sedative to make them more comfortable. Most patients rest comfortably during the procedure, which usually lasts between 15 and 20 minutes. Some individuals experience a minor sore throat following this procedure.
Stress Echocardiogram. A stress echocardiogram is done under conditions that increase the workload on the heart to determine its pumping capacity and efficiency and to evaluate any blockages of the coronary arteries. Patients undergoing a stress echo are asked to fast for three hours before the exam, wear comfortable clothing, and take medications as usual unless otherwise instructed.
The stress echo starts by obtaining images of the heart at rest. Then, depending on the type of stress echocardiogram being performed, the technician will take additional images after the workload of the heart has been increased. For an exercise stress test, patients walk on a treadmill or pedal a stationary bicycle to reach their peak exercise level. For patients who are unable to exercise, a medication is injected to simulate the effects of exercise on the heart, usually dobutamine. Dobutamine causes the heart rate to gradually increase. After receiving the drug, some people experience a slight flushing in the cheeks, a tingling scalp, and the uncomfortable feeling that their heart is beating faster and harder. Alternatively, the medication atropine may be used, but it has potentially serious side effects for people with undiagnosed glaucoma.
Although echocardiography uses ultrasound, which poses no known risk to the body, a stress test is not completely risk free. On rare occasions, a heart problem can occur during a stress test. To detect any problems that may arise, blood pressure and the heart's electrical activity are monitored continuously throughout the test. The technicians administering the test are trained to treat potential complications.
An electrocardiogram is a recording of the electrical activity of the heart. The timing and duration of each electrical phase of the heartbeat is recorded in the ECG tracing. The ECG can provide clues to potential thickening of the heart muscle, structural abnormalities, evidence of heart attacks, heart rhythm abnormalities, inadequate blood and oxygen supply to the heart muscle, or enlargement of the heart's chambers--and at no risk to the patient and relatively little cost. In most cases, if the ECG indicates an abnormality, additional testing may be needed to confirm a diagnosis.
In an ECG, the electrical activity of the heart is recorded by electrodes that are temporarily attached to the skin with sticky pads. The electrodes transmit the heart's electrical impulses to a device that records these impulses as wave-shaped lines, called a tracing, on a scrolling paper or a monitor. Different sections of the waves represent the various areas of the heart and can impart a lot of information. The main components of the ECG tracing are:
- The P wave, representing currents in the atria
- The QRS complex, representing currents in the ventricles
- The T wave, representing the electrical recovery period of the ventricles
An ECG can reveal the strength and duration of the electrical impulses in the heart. It also can show a deviation in the electrical firing sequence of the heart, which normally starts in the atria and proceeds to the ventricles.
The actual ECG reading takes only 30 to 60 seconds. The test requires no preparation on the part of the patient. Usually, 12 to 15 electrodes are attached to various parts of the body, including one on each arm and each leg and six across the chest. The remaining electrodes are attached at other sites in the chest, neck, and back. After the leads are attached, the readings are recorded. There is no discomfort associated with this test.
Other types of ECG used in the evaluation of cardiomyopathy include:
Continuous or Ambulatory ECG. A Holter monitor is a portable ECG device that makes a continuous, or ambulatory, recording of the heart's electrical activity during a patient's daily routine. Usually worn for 24 to 72 hours, the Holter monitor, which is the size of a small paperback novel or smaller, can detect intermittent heart rhythm irregularities.
Event monitor. For irregular heartbeats that occur sporadically, a small, portable ECG device is used to record the electrical activity of the heart. Ranging from the size of a small paperback novel down to a thin deck of cards, it can be clipped to the clothing and is equipped with electrodes that are readily attached to the chest with sticky pads when the patient experiences the symptoms of an irregular heart rhythm. When the symptoms develop, a push of a button begins the ECG recording. The events can be recorded or transmitted across telephone lines.
Exercise ECG. Also known as a stress test, this procedure assesses how well your heart is working. It can detect coronary circulatory problems and abnormalities related to insufficient blood and oxygen supply to the heart muscle. Rhythm abnormalities triggered by exercise may also be detected and used to identify exercise limits and develop an individual fitness program.
Minor preparations are required for an exercise test, usually involving diet restrictions. The exercise ECG is performed with the individual on a treadmill or stationary bike, so wear comfortable clothing and athletic shoes. The exercise portion of the test usually lasts five to 15 minutes, with the entire test lasting 30 to 40 minutes. The exertion level will increase gradually at regular intervals until the peak exertion level, as determined by the healthcare team, is met. Shortness of breath and sweating are normal, but be sure to tell the healthcare team if you experience chest pain, severe shortness of breath, dizziness, or leg cramps. The ECG readings are recorded continuously before, during, and after exercise. Changes in blood pressure and exercise capacity are also recorded.
Oxygen consumption may also be measured to determine how well the heart and lungs are working together. This involves wearing a nose clip that forces you to breathe through your mouth and a special mouthpiece that measures the amount of oxygen you breathe during exercise.
An exercise ECG carries a small risk because it involves increasing the workload of the heart. The chances of suffering heart problems during the test are remote, however. For instance, just 48 out of 10,000 people taking an exercise ECG experience a serious heart rhythm problem; 3.5 in 10,000 experience a heart attack. Moreover, the healthcare professionals administering the test are trained to diagnose and treat these kinds of complications appropriately and quickly.
Electrophysiology studies use electrodes attached directly to the heart to collect detailed information in people with heart rhythm disorders caused by cardiomyopathy. These studies produce very precise maps of the pathways that electrical impulses travel in the heart. The results can be difficult to interpret and must be evaluated in light of all other medical information. Unlike an ECG, an electrophysiology study is an invasive procedure requiring heart catheterization.
Electrophysiology studies may take as long as four hours. Once the catheter is put in place, the physician stimulates the heart with tiny electrical impulses that cannot be felt. However, the impulses may trigger the arrhythmia that is causing your symptoms. This allows the physician to see where the arrhythmias are occurring and the mechanisms of the heart that may be causing the irregular heartbeat. During the study the physician can also evaluate the effectiveness of treatment alternatives for your particular arrhythmia, including medications and pacing devices.
As with other catheterization procedures, electrophysiology studies carry risk. In general, less than one of every 100 people undergoing an electrophysiology study experiences a complication. These include bleeding, bruising, blood clots, and infection. There also is a small risk of a stroke or a tear in the lining of a blood vessel during catheterization. In addition, there is a risk of developing a severely abnormal heart rhythm, including ventricular fibrillation. The physician team is trained and prepared for handling this emergency.
Heart catheterization can be used to both diagnose and treat heart problems. Diagnostic testing for cardiomyopathy using heart catheterization includes the following.
Coronary angiogram. Also known as an arteriogram, a coronary angiogram is a valuable tool for evaluating the degree of obstruction in the blood flow path in the heart. The test uses a contrast medium to create highly detailed X-ray pictures of the structures inside the heart, particularly the ventricles and arteries.
Oxygen levels. Oxygen levels from different parts of the heart can be measured using cardiac cath and used to identify abnormal blood patterns within the heart.
Heart pressures. Pressure measurements within different parts of the heart are used to evaluate blood flow patterns in the heart. These measurements are critical to determining how much fluid buildup is present, and which part of the heart (e.g. left or right side) is causing the most problems.
Biopsy. Tissue samples, or biopsies, of heart muscle can be collected for microscopic evaluation in the laboratory to identify diseases of the heart muscle itself, like hypertrophic or restrictive cardiomyopathy.
Because cardiac cath involves inserting a thin tube into a vein or artery that ultimately is guided into the heart, this procedure is performed in a hospital. The exact length of the stay depends upon the type of procedure being performed and the medical condition of the individual. An otherwise healthy person having a minor procedure may have the procedure done as an outpatient. In other cases, a hospital stay of two to three days may be necessary. The cardiologist will provide specific guidance about preparing for the procedure, including instructions on fasting, medication use, and showering prior to arriving at the hospital.
Although the catheterization itself takes only about 30 minutes, the preparations take two to three hours. These include drawing a blood sample, obtaining an ECG if one has not been done recently, and discussing the details of the procedure. The insertion site is then prepared by shaving the hair from a small area in the groin or the inside of an elbow. An intravenous line is inserted to administer fluids and medications as needed during the procedure. At this time, a mild sedative may be administered to help the patient relax. Also, the patient is hooked up to monitoring equipment, including ECG electrodes and a blood pressure cuff.
Catheterization is done in a specialized suite that is similar to an operating room but equipped with an X-ray machine. In adults, heart catheterization is done under a local anesthetic with the patient remaining awake throughout the procedure. Typically, the procedure starts with the physician inserting a needle into a small artery of the groin. A sequence of wires and tubes are snaked through the insertion site, up through the artery, into the heart. However, sometimes an artery in the arm is used for catheterization.
Once the catheter is accurately positioned in an area of interest, the cardiologist will perform various tests and procedures. A biopsy may be collected for microscopic evaluation of the heart muscle fibers. Often, blood oxygen levels and blood pressure readings are measured; the cardiologist may also inject a contrast agent through the catheter to make the heart chambers or blood vessels visible in X-ray images. This often causes patients to feel suddenly warm or flushed for about 30 seconds. Once the physician has all the information needed, the catheter is removed and the insertion site is stitched or bandaged. Thanks to the sedating medications and painkillers administered to the injection site, patients undergoing this procedure generally don't experience much pain or discomfort.
After the catheter has been removed, the patient will be taken to a recovery room for 30 to 60 minutes before being moved to a hospital room. Usually, activity can gradually resume after a period of approximately six hours, but patients should not drive the day of the procedure.
The most common complication is bruising at the site where the catheter was inserted. Other less frequent complications include infection of the insertion site, irritation of the nerve fibers causing a tingling feeling (this typically is temporary), and bulges or even blockage of the artery at the insertion site.
Much more rare are complications such as irregular heart rhythms, stroke, and even cardiac arrest. The overall risk of developing one these more serious complications is between 1 in 100 and 1 in 1,000 for all people undergoing catheterizations. An individual's risk depends upon his or her overall health, the actual tests being performed, and the skill of the cardiologist. Critically ill people who undergo heart catheterization on an emergency basis are at highest risk for serious complications; the risk is typically lower for an otherwise healthy person having a scheduled catheterization.
Occasionally, patients with dilated or restrictive cardiomyopathy may have a nuclear cardiac stress test to evaluate how well the heart muscle is being supplied with blood and how well the ventricles or chambers are working. This information is used to determine the best way to treat their symptoms.
In a sense, nuclear testing is the opposite of X-rays. X-rays direct radiation into the body to create images; in a nuclear scan, the body emits the radiation from within to create the image. Trace amounts of thallium, a radioactive substance that emits gamma radiation, are injected into the bloodstream, usually through an IV in the arm. The thallium travels in the blood through the arteries and veins into the heart muscle. A special camera that detects gamma radiation is used to create images of the heart that are interpreted by nuclear medicine specialists.
Preparing for the test involves some dietary restrictions, including avoiding caffeine 24 hours before the scheduled test and wearing comfortable clothing and shoes. The test can last between two and four hours and begins with the insertion of an IV line for administering the thallium and the attaching of electrodes to the skin for monitoring the heartbeat with an electrocardiogram (ECG) machine. During the test, two sets of images are captured: one at rest and the other when the heart is stressed. Each set of images takes about 20 minutes to complete and requires the patient to lie as still as possible while the gamma camera rotates.
Thallium stress tests rely on either physical exercise using a treadmill or stationary bicycle or medication to stress the heart. Several different medications can be used to increase the workload to the heart; talk with your healthcare provider about which one is the best choice for you. The most common side effects from the medication are feeling flushed and feeling that your heart is beating faster and harder.
MRIs use strong magnetic fields and radio waves, instead of radiation, to create three-dimensional images and two-dimensional cross-sections of the heart. The images produced by MRIs are similar to X-ray images but show more detail of the soft tissues of the body.
An MRI machine has a large tube that is big enough to accommodate a patient lying down inside. Radio waves and strong magnetic fields are generated inside the shell of the tube and directed toward the body during an MRI scan. The body responds by emitting weak energy signals that are detected by the MRI machine. A computer converts these signals into three-dimensional images of the heart that can be manipulated to show any two-dimensional cross section.
Before the test, you must remove all accessories and clothing containing metal, including jewelry, metal fasteners, dentures, wigs, and hearing aids. Metal objects may interfere with the magnetic field of the MRI, affecting the quality of the image.
An MRI exam is painless and generally lasts between 30 and 60 minutes. The procedure involves lying on a table that slides into the tube. Movement can blur the images, so it is important to lie still. The space inside the tube is quite narrow, and some patients may feel claustrophobic. Often patients will be offered headphones or earplugs to help block out the loud tapping and thumping sounds made by the MRI machine and to help them relax.
Magnetic resonance angiography (MRA) is one of the newer uses of MRI. For this test, a contrast agent, similar to a dye, is injected into the arm or leg through an intravenous line. The contrast agent makes it easier to visualize the heart and blood vessels. One advantage of the MRA is that the contrast agents are less likely to cause allergic reactions than those used during computed tomography (CT or CAT scans).
There are no known risks from the magnetic fields and radio waves produced by MRI machines. However, people who have pacemakers, cardioverter defibrillators, or other metal-containing objects inside their bodies cannot get MRIs. Also, the affects of magnetic fields on fetuses are not well understood, so getting an MRI may not be advisable for pregnant women.
A polysomnogram is a painless, noninvasive study of an individual's sleep patterns. Lasting a minimum of six hours, a sleep study is used to determine if you have any respiratory-related sleep disorders such as sleep apnea, which can contribute to dilated cardiomyopathy.
The polysomnogram uses electrodes attached to your body to collect data on your general sleep behavior and physical state during the different stages of sleep as well as microphones to record noises. Body position and movement, heart and respiratory rates, eye movement, brain waves, blood oxygen levels, muscle tone, and amount of snoring are usually recorded.
A sleep study is usually performed at night in a laboratory equipped with monitoring equipment that is attached to your head, abdomen, and chest. After the technician attaches the monitoring equipment and verifies it's working properly, the lights will be turned off and you will be left alone to sleep. Perhaps surprisingly, most people are able to sleep with this equipment attached. During the study, you will be monitored continuously and always able to speak to the technician.
Last reviewed on 12/31/2008
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