Cardiovascular disease is the leading cause of death in both men and women.¹ Nearly 2,400 Americans die of cardiovascular disease every day, an average of one death every 37 seconds.¹ CVD — which includes congestive heart failure, coronary heart disease (MI, angina pectoris), hypertension and stroke — caused 35.2% of deaths (or 1 of every 2.8) in the United States in 2005.¹ More lives are lost each year to CVD than to accidents, cancer, chronic lower respiratory diseases, and diabetes mellitus combined.¹

Accurate and swift diagnosis of CVD is crucial for improved patient outcomes. Patient care in many settings may include cardiac procedures as part of patient evaluation. Healthcare practitioners should understand a variety of cardiac tests and the rationale behind them to reduce patients’ anxiety about procedures and improve patient adherence. This module focuses on noninvasive cardiac procedures with an emphasis on patient preparation and care.

Electrocardiograms

An electrocardiogram (ECG) is a test that records the electrical activity of the heart and is considered the first step in the evaluation of chest pain.² Resting ECG is indicated in all patients with suspected CVD.³ Symptoms that indicate the need for an ECG include chest pain, dizziness and syncope. Patient preparation includes instructing the patient to remove necklaces and watches. In addition, a woman should remove her bra. All these may interfere with the ECG machine’s reading the electrical activity. Explain to patients that a technician or healthcare practitioner will place small electrodes (self-sticking plastic patches) on their arms and legs and across their chest. Occasionally, if a patient has used lotion or if the skin is oily, electrodes may not adhere well. An alcohol wipe can be used to cleanse the area. Allow the area to air dry before placing electrodes. If men have excessive chest hair, a small area can be shaved for improved electrode adherence. The electrodes are then connected to leads, or wires attached to the ECG machine.

Patients are asked to lie still while the tracing is made. The test is performed in minutes. An ECG evaluates heart rate and rhythm and can distinguish between a recent myocardial infarction, myocardial ischemia, and/or heart muscle damage from a previous MI. An ECG is also useful in detecting an irregular conduction disorder (dysrhythmia), cardiac chamber enlargement, electrolyte imbalances, and electrical pacemaker function. Among noninvasive tests, the ECG is the most versatile and provides the most information at the lowest cost.³

Echocardiograms

An echocardiogram uses high-frequency sound waves, called ultrasound, to provide images of intracardiac structures and ventricular function along with a detailed image of blood flow. An ECG is recorded simultaneously.³ To perform an echocardiogram test, a technician places a handheld ultrasound probe, also called a transducer, against the chest wall to take images of the heart. Although the procedure is relatively painless, the patient may feel pressure when the probe is pressed against the chest. The test usually takes 30 to 45 minutes, and no special preparation is required. Tell patients they may hear a whooshing sound, timed with their heartbeat. This is the blood movement near the transducer. An ECG will record electrical activity in coordination with the blood flow of the heart. This information will help the healthcare provider interpret any abnormal findings. An echocardiogram provides information about the heart chamber size, wall motion or strength of the heart muscle (also referred to as ejection fraction or EF), valve movements and their integrity, and structural changes in and around the heart. The test does not give information about the arteries of the heart, but it can note changes in the overall function of the muscle wall, which may suggest an alteration in myocardial blood flow.⁴ The echocardiogram can be useful in evaluating pulmonary artery pressure, intracardiac shunts, intracardiac masses, and pericardial effusions.⁴ The test is recorded on videotape or digital image and is read by a cardiologist. Occasionally, obesity, the position of the ribs, or emphysema may limit transmission of the ultrasound and produce suboptimal images.

In that case, the healthcare provider may order a transesophageal echocardiogram instead of a standard echocardiogram. During a TEE, a transducer is placed directly in the esophagus, allowing a much clearer image of the heart, particularly the left atrium and thoracic aorta, as the images are obtained from the posterior view of the heart, which may not be seen as well by a standard echocardiogram. Patients are placed on their left side for a TEE. The throat is sprayed with an anesthetic, and intravenous sedation is typically given. The transducer is much smaller than the echocardiogram equipment and is positioned at the end of a flexible tube (similar to the tube used during endoscopy). When the patient begins to swallow the tube, the procedure begins. The transducer at the end of the tube is positioned in the esophagus, directly behind the heart. By rotating and moving the tip of the transducer, the healthcare provider can examine the heart from several angles. The heart rate, blood pressure and oxygen saturation are monitored during and immediately after the procedure in accordance with the agency’s protocol for conscious sedation. Oxygen is given, and suction should always be available. This procedure can be scheduled in the patient’s room (if monitoring capabilities are available) the GI lab or the cardiac cath lab. A TEE is also frequently performed for patients in atrial fibrillation before cardioversion to be sure no clots are present within the heart, specifically the left atrium. Cardioversion delivers an electric shock synchronized with the intrinsic activity of the heart in an attempt to restore sinus rhythm. Patient preparation for a TEE includes nothing by mouth after midnight the night before the procedure, information about drug allergies and previous reactions to conscious sedation, and removal of dentures.

Exercise Testing

Exercise is a common physiological stress that can produce cardiac abnormalities or symptoms that may not be apparent at rest. An exercise test, sometimes called a treadmill test, provides information on how well the heart handles work. The test is relatively safe although a small risk of fatal cardiac arrhythmia exists.⁵ Exercise stress tests are safe and most patients prefer them. However, avoid exercise in patients within two days of acute MI or with high-risk unstable angina, those with unstable cardiac arrhythmias or hemodynamic compromise, those with symptomatic severe aortic stenosis or decompensated heart failure; those with acute myocarditis or pericarditis; and those with life-threatening noncardiac conditions, such as acute pulmonary embolus or pulmonary infarction.²

As the body works harder during the exercise test, it requires more oxygen, so the heart must pump more blood by increasing the heart rate. The test can detect ischemic changes because of a reduction in the blood supply from the coronary arteries that feed the heart muscle. Essentially, an evaluation of supply (coronary artery blood flow) and demand (increased heart rate) is made. An ECG recording during exercise can illustrate changes in pattern that may indicate acute or chronic ischemia to the heart muscle. Elevation in the ST segment may indicate acute ischemia. If acute ischemia is noted, the test should be stopped and the patient placed in a position of rest. The ST segment of the ECG is the time of rest and repolarization for the ventricles of the heart. When electrical repolarization is delayed, as a result of ischemia or injury, the ECG tracing will show an elevation in this segment.⁶

Patient instructions include telling the patient to wear comfortable clothes and shoes for the procedure and to have nothing to eat or drink for four hours before the test. Patients should not consume caffeinated drinks 24 hours before the day of the test. Taking medication the day of the procedure is at the discretion of the healthcare provider, especially with respect to beta-blockers or other rate-controlling medication, as it may be difficult to achieve an elevation in heart rate which is required for diagnostic decision making.

In the standard exercise stress test, the patient exercises by walking on a treadmill for three-minute intervals with increasing speed and incline while being monitored. The patient is connected to a 12-lead ECG that will record the heart rhythm continuously. Blood pressure is monitored at frequent intervals. Oxygen saturation may be monitored if the patient complains of shortness of breath during the test. Looking down at the treadmill may produce dizziness, so it is best that patients focus on a point in front of them. A health professional or proctor proficient in 12-lead ECG interpretation will be present during the test, and the patient should alert him or her immediately of chest pain or heaviness, unusual shortness of breath or other symptoms not ordinarily part of exercising. Successful completion of the test is achieved when the patient achieves 85% of age-predicted maximal heart rate.⁷ The duration of exercise (exercise capacity) is a strong prognostic indicator in patients with coronary artery disease.6

The exercise is stopped when the desired level of exercise is obtained, an abnormality of the heart is detected by changes in the ECG, or the patient is unable to continue because he or she develops symptoms (chest pain, fatigue, etc.).⁶ The test may also be terminated at the request of the patient.

Stress echocardiography with exercise or pharmacologic stress is used to assess for left ventricular systolic or diastolic dysfunction, valvular heart disease, and the extent of infarction and stress-induced ischemia.⁸ Exercise stress can be done with a treadmill or stationary bicycle. Pharmacologic stress is achieved with dobutamine for those patients unable to exercise. Transient wall motion abnormality evident via echocardiography is a marker for coronary artery disease.³

Nuclear Scans

In conjunction with an exercise test, the healthcare provider may order a nuclear scan, a noninvasive means of detecting the presence and significance of coronary artery disease. This test may be particularly helpful for decision making among patients with baseline ECG abnormalities or patients with a history of coronary artery disease or previous coronary revascularization.⁷

During the exercise stress test, the patient is given a small, harmless amount of a radioactive substance (isotope), such as thallium or sestamibi, through an IV line when the predicted maximum heart rate is achieved.⁶ Exercise continues for one minute after the isotope has been injected to ensure prompt circulation to the heart. The patient is transported to the nuclear medicine department, where images are taken and, in the case of thallium, repeated up to three hours later to view how much of the isotope remains. Sestamibi, having a longer half life, can remain in the cardiac muscle for a longer time. Imaging may be finished later in the day or the next day. Once in the body, the radioactive substance emits rays that can be picked up by a special (gamma) camera. The rays allow the camera to produce clear pictures of the heart muscle on a video monitor. These pictures illustrate whether the blood supply is adequate to the heart muscle. Slow or reduced blood flow may indicate a blockage in one or more of the arteries feeding the heart. Areas of decreased blood flow and nonviable myocardium have decreased isotope uptake and show up as fixed (present at rest as well as with exercise) or reversible (stress induced) defects on the initial images.

As with an exercise stress test, the patient cannot eat or drink four hours before the procedure. Eating increases the blood flow to the stomach and may interfere with the pictures of the heart. Fasting reduces the incidence of nausea caused by strenuous exercise. Instruct the patient to avoid caffeine for 24 hours before the procedure because caffeine may erroneously increase the heart rate and blood pressure and may interact with medications given during the test. The patient should be informed that each imaging session takes about 30 minutes and that there is a three-hour wait between sessions. A light snack between sessions may be allowed. As with treadmill testing, the healthcare provider will indicate whether medications are to be taken or held the day of the procedure. A nuclear medicine healthcare provider reviews the tests, and the results are generally available in one or two days.

The major limitation with nuclear scans is the high percentage of false positive test results, especially in women and patients who are obese.^5,6 Breast or diaphragmatic attenuation (a loss in the strength of the imaging signal because of interference) can reduce the accuracy of the nuclear study.

Pharmacological Stress Tests

Patients who cannot exercise because of severe peripheral vascular disease, orthopedic disability or pulmonary disease may receive a pharmacologic agent (dobutamine, dipyridamole or adenosine) via IV to increase the heart rate and blood pressure, thus imitating the effects of exercise.⁶ During the infusion of the drug, patients will feel their heart rate increasing and the heart working harder, causing an unsettling feeling of anxiety. A flushed feeling or nausea is not unusual. These sensations pass quickly once the medication infusion has been terminated, and they are not harmful. When the infusion is discontinued, the heart rate and blood pressure return to pretest levels, typically within 5 to 10 minutes. The patient may be asked to do light exercise, such as leg lifts, to help reach the target (85% of age-predicted maximal) heart rate. An ECG is recorded continuously throughout the procedure, and BP is checked every three minutes. This medication can be used in conjunction with echocardiography or nuclear scanning, which increases the diagnostic accuracy of the test.⁶

Potential adverse effects associated with dobutamine include reflex tachycardia, which may require control with a rate-lowering medication if it persists and causes hemodynamic compromise. Adenosine and dipyridamole are bronchoconstrictors and therefore contraindicated for patients with a history of asthma or COPD. Potential adverse effects associated with these medications include hypotension, flushing, chest pain, headache, nausea, dyspnea or AV block. Because of the short half life of adenosine, adverse effects usually abate when the infusion is terminated.

Instruct the patient to withhold food and medications per the healthcare provider’s instructions, as with any exercise test. A cardiologist, healthcare practitioner or physician's assistant is present for the procedure, which usually takes 45 minutes. The patient may resume his or her usual diet and medications when the test is finished.

Tilt-Table Testing

A tilt-table test is used to diagnose neurally mediated syncope. Syncope is a transient loss of neurologic function because of a global reduction in cerebral blood flow.⁹ The result is an inability to maintain postural tone (i.e., loss of consciousness, collapse) that resolves spontaneously without medical intervention. Syncope is responsible for 1% to 6% of ED visits and 1% to 3% of hospital admissions.10 Causes of syncope range from benign to life threatening. The goal of evaluation is to determine whether the patient is at increased risk of death from life-threatening causes. Assess for underlying heart disease, Wolfe-Parkinson-White syndrome, long QT syndrome, Brugada syndrome, and ventricular tachycardia.⁷ Tilt-table testing is an inexpensive evaluation tool that many experts consider a first-line testing modality. It has been estimated that in 40% of cases the cause of syncope remains unexplained despite extensive medical evaluation.⁷ This test is particularly helpful for patients with no evidence of heart disease by history, physical exam or ECG testing.

Neurally mediated syncope (also known as vasovagal syncope, neurocardiogenic syncope, common or emotional fainting, or reflex syncope) is the most common type.⁷ Neurally mediated syncope is characterized by peripheral vasodilation and hypotension, along with bradycardia.

Instruct the patient to remain NPO for at least six hours before a tilt-table test, as many patients experience nausea during the test, secondary to low BP. Medications are held before the test, especially those that affect BP. Diabetic agents may be given along with a small meal, depending on the time of the test and at the discretion of the ordering healthcare provider. An IV infusion of normal saline is started before the test to reduce the risk of orthostatic hypotension.

Before the procedure, explain to patients that they will be placed on a table and securely strapped in place. Encourage patients to wear comfortable clothing and tennis shoes. A technician will be in constant attendance. A cardiac monitor with recording capabilities is placed along with continuous blood pressure monitoring. Rhythm strips and blood pressure recordings are taken every five minutes or as symptoms occur. The patient will remain on the table in a supine position for 20 minutes. The table then is tilted to a 70-degree angle. This change in angle is intended to induce symptoms of syncope while the patient is monitored. The patient is quickly returned to a supine position with a positive response (fainting), at his or her request, or at the end of 45 minutes. The physiologic mechanism involves an increase in vagal tone and a decrease in sympathetic tone, leading to hypotension and/or bradycardia along with syncope or pre-syncope (a feeling that syncope is imminent). This response signals a positive test, indicating that the syncope is neurally mediated.⁷ A test is also considered positive if the patient remains tachycardic but without obtainable BP. If the test is negative (i.e., if the patient doesn’t faint or experience a significant drop in BP or heart rate), an isoproterenol (Isuprel) infusion may be given at the discretion of the monitoring cardiologist. This sympathomimetic drug acts as a cardiac stimulant, increasing the heart rate, myocardial contractility, and cardiac output with the intention of provoking syncope. About 30% to 40% of patients with vasovagal-mediated or neurally mediated syncope have a true positive test without isoproterenol, and the number increases to 80% if isoproterenol is added.⁴

The number of cardiac tests ordered daily is growing at an explosive rate. Understanding the variety of cardiac tests will improve patient education, thereby reducing patient anxiety about the procedures. Adherence should improve when patients understand the rationale behind procedural preparation. Diagnosing heart disease accurately and swiftly is an important way to improve patient outcomes and reduce the morbidity and mortality of CVD.

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