Approach to Cardiac Disease Diagnosis-4

Approach to Cardiac Disease Diagnosis
CURRENT Diagnosis & Treatment in Cardiology

Approach to Cardiac Disease Diagnosis

Michael H. Crawford, MD

Physical Findings (cont'd)

B. DIAGNOSTIC STUDIES

1. Electrocardiography—Electrocardiography (ECG) is perhaps the least expensive of all cardiac diagnostic tests, providing considerable value for the money. Modern electrocardiogram-reading computers do an excellent job of measuring the various intervals between waveforms and calculating the heart rate and the left ventricular axis. These programs fall considerably short, however, when it comes to diagnosing complex ECG patterns and rhythm disturbances, and the test results must be read by a physician skilled at ECG interpretation.
Analysis of cardiac rhythm is perhaps the ECG's most widely used feature; it is used to clarify the mechanism of an irregular heart rhythm detected on physical examination or that of an extremely rapid or slow rhythm. The ECG is also used to monitor cardiac rate and rhythm; Holter monitoring and other continuous-ECG monitoring devices allow assessment of cardiac rate and rhythm on an ambulatory basis. ECG radio telemetry is also often used on hospital wards and between ambulances and emergency rooms to assess and monitor rhythm disturbances. There are two types of ambulatory ECG recorders: continuous recorders that record all heart beats over 24 or more hours and intermittent recorders that can be attached to the patient for weeks for months and then activated to provide brief recordings of infrequent events. In addition to analysis of cardiac rhythm, ambulatory ECG recordings can be used to detect ST-wave transients indicative of myocardial ischemia and certain electrophysiologic parameters of diagnostic and prognostic value. The most common use of ambulatory ECG monitoring is the evaluation of symptoms such as syncope, near-syncope, or palpitation for which there is no obvious cause and cardiac rhythm disturbances are suspected.
The ECG is an important tool for rapidly assessing metabolic and toxic disorders of the heart. Characteristic changes in the ST-T waves indicate imbalances of potassium and calcium. Drugs such as procainamide and the tricyclic antidepressants have characteristic effects on the QT and QRS intervals at toxic levels. Such observations on the ECG can be life-saving in emergency situations with comatose patients or cardiac arrest victims.
Chamber enlargement can be assessed through the characteristic changes of left or right ventricular and atrial enlargement. Occasionally, isolated signs of left atrial enlargement on the ECG may be the only diagnostic clue to mitral stenosis. Evidence of chamber enlargement on the ECG usually signifies an advanced stage of disease with a poorer prognosis than that of patients with the same disease but no discernible enlargement.
The ECG is an important tool in managing acute myocardial infarction. In patients with chest pain that is compatible with myocardial ischemia, the characteristic ST-T-wave elevations that do not resolve with nitroglycerin (and are unlikely to be the result of an old infarction) become the basis for thrombolytic therapy or primary angioplasty. Rapid resolution of the ECG changes of myocardial infarction after reperfusion therapy has prognostic value and identifies patients with reperfused coronary arteries.
Evidence of conduction abnormalities may help explain the mechanism of bradyarrhythmias and the likelihood of the need for a pacemaker. Conduction abnormalities may also aid in determining the cause of heart disease. For example, right bundle branch block and left anterior fascicular block are often seen in Chagas' cardiomyopathy, and left-axis deviation occurs in patients with a primum atrial septal defect.
A newer form of electrocardiography is the signal-averaged, or high-resolution, electrocardiogram. This device markedly accentuates the QRS complex so that low-amplitude afterpotentials, which correlate with a propensity toward ventricular arrhythmias and sudden death, can be detected. The signal-averaged ECG permits a more accurate measurement of QRS duration, which also has prognostic significance of established value in the stratification of risk of developing sustained ventricular arrhythmias in postmyocardial infarction patients, patients with coronary artery disease and unexplained syncope, and patients with nonischemic cardiomyopathy.
2. Echocardiography—Another frequently ordered cardiac diagnostic test, echocardiography is based on the use of ultrasound directed at the heart to create images of cardiac anatomy and display them in real time on a television screen or oscilloscope. Two-dimensional echocardiography is usually accomplished by placing an ultrasound transducer in various positions on the anterior chest and obtaining cross-sectional images of the heart and great vessels in a variety of standard planes. In general, two-dimensional echocardiography is excellent for detecting any anatomic abnormality of the heart and great vessels. In addition, because the heart is seen in real time, this modality can assess the function of cardiac chambers and valves throughout the cardiac cycle.
Transesophageal echocardiography (TEE) involves the placement of smaller ultrasound probes on a gastroscopic device for placement in the esophagus behind the heart; it produces much higher resolution images of posterior cardiac structures. TEE has made it possible to detect left atrial thrombi, small mitral valve vegetations, and thoracic aortic dissection with a high degree of accuracy.
The older analog echocardiographic display referred to as M-mode, motion-mode, or time-motion mode, is currently used for its high axial and temporal resolution. It is superior to two-dimensional echocardiography for measuring the size of structures in its axial direction, and its 1/1000-s sampling rate allows for the resolution of complex cardiac motion patterns. Its many disadvantages, including poor lateral resolution and the inability to distinguish whole heart motion from the motion of individual cardiac structures, have relegated it to a supporting role.
Doppler ultrasound can be combined with two-dimensional imaging to investigate blood flow in the heart and great vessels. It is based on determining the change in frequency (caused by the movement of blood in the given structure) of the reflected ultrasound compared with the transmitted ultrasound, and converting this difference into flow velocity. Color-flow Doppler echocardiography is most frequently used. In this technique, frequency shifts in each pixel of a selected area of the two-dimensional image are measured and converted into a color, depending on the direction of flow, the velocity, and the presence or absence of turbulent flow. When these color images are superimposed on the two-dimensional echocardiographic image, a moving color image of blood flow in the heart is created in real time. This is extremely useful for detecting regurgitant blood flow across cardiac valves and any abnormal communications in the heart.
Because color-flow imaging cannot resolve very high velocities, another Doppler mode must be used to quantitate the exact velocity and estimate the pressure gradient of the flow when high velocities are suspected. Continuous-wave Doppler, which almost continuously sends and receives ultrasound along a beam that can be aligned through the heart, is extremely accurate at resolving very high velocities such as those encountered with valvular aortic stenosis. The disadvantage of this technique is that the source of the high velocity within the beam cannot always be determined but must be assumed, based on the anatomy through which the beam passes. When there is ambiguity about the source of the high velocity, pulsed-wave Doppler is more useful. This technique is range-gated such that specific areas along the beam (sample volumes) can be investigated. One or more sample volumes can be examined and determinations made concerning the exact location of areas of high-velocity flow.
Two-dimensional echocardiographic imaging of dynamic left ventricular cross-sectional anatomy and the superimposition of a Doppler color-flow map provide more information than the traditional left ventricular cine-angiogram can. Ventricular wall motion can be interrogated in multiple planes, and left ventricular wall thickening during systole (an important measure of myocardial viability) can be assessed. In addition to demonstrating segmental wall motion abnormalities, echocardiography can estimate left ventricular volumes and ejection fraction. In addition, valvular regurgitation can be assessed at all four valves with the accuracy of the estimated severity equivalent to contrast angiography.
Doppler echocardiography has now largely replaced cardiac catheterization for deriving hemodynamics to estimate the severity of valve stenosis. Recorded Doppler velocities across a valve can be converted to pressure gradients by use of the simplified Bernoulli equation (pressure gradient = 4 × velocity2). Cardiac output can be measured by Doppler from the velocity recorded at cardiac anatomic sites of known size visualized on the two-dimensional echocardiographic image. Cardiac output and pressure gradient data can be used to calculate the stenotic valve area with remarkable accuracy. A complete echocardiographic examination including two-dimensional and M-mode anatomic and functional visualization, and color-, pulsed-, and continuous-wave Doppler examination of blood flow provides a considerable amount of information about cardiac structure and function. A full discussion of the usefulness of this technique is beyond the scope of this chapter, but individual uses of echocardiography will be discussed in later chapters.
Unfortunately, echocardiography is not without its technical difficulties and pitfalls. Like any noninvasive technique, it is not 100% accurate. Furthermore, it is impossible to obtain high-quality images or Doppler signals in as many as 5% of patients—especially those with emphysema, chest wall deformities, and obesity. Although TEE has made the examination of such patients easier, it does not solve all the problems of echocardiography. Despite these limitations, the technique is so powerful that it has moved out of the noninvasive laboratory and is now frequently being used in the operating room, the emergency room, and even the cardiac catheterization laboratory, to help guide procedures without the use of fluoroscopy.
3. Nuclear cardiac imaging—Nuclear cardiac imaging involves the injection of tracer amounts of radioactive elements attached to larger molecules or to the patient's own blood cells. The tracer-labeled blood is concentrated in certain areas of the heart, and a gamma ray detection camera is used to detect the radioactive emissions and form an image of the deployment of the tracer in the particular area. The single-crystal gamma camera produces planar images of the heart, depending on the relationship of the camera to the body. Multiple-head gamma cameras, which rotate around the patient, can produce single-photon emission computed tomography, displaying the cardiac anatomy in slices, each about 1-cm thick.
a. Myocardial perfusion imaging—The most common tracers used for imaging regional myocardial blood-flow distribution are thallium-201 and the technetium-99m-based agents, sestamibi and teboroxime. Thallium-201, a potassium analog that is efficiently extracted from the bloodstream by viable myocardial cells, is concentrated in the myocardium in areas of adequate blood flow and living myocardial cells. Thallium perfusion images show defects (a lower tracer concentration) in areas where blood flow is relatively reduced and in areas of damaged myocardial cells. If the damage is from frank necrosis or scar tissue formation, very little thallium will be taken up; ischemic cells may take up thallium more slowly or incompletely, producing relative defects in the image.
Myocardial perfusion problems are separated from nonviable myocardium by the fact that thallium eventually washes out of the myocardial cells and back into the circulation. If a defect detected on initial thallium imaging disappears over a period of 3–24 h, the area is presumably viable. A persistent defect suggests a myocardial scar. In addition to detecting viable myocardium and assessing the extent of new and old myocardial infarctions, thallium-201 imaging can also be used to detect myocardial ischemia during stress testing (see item 5. Stress Testing) as well as marked enlargement of the heart or dysfunction. The major problem with thallium imaging is photon attenuation because of chest wall structures, which can give an artifactual appearance of defects in the myocardium.
The technetium-99m-based agents take advantage of the shorter half-life of technetium (6 h; thallium 201's is 73 h); this allows for use of a larger dose, which results in higher energy emissions and higher quality images. Technetium-99m's higher energy emissions scatter less and are attenuated less by chest wall structures, reducing the number of artifacts. Because sestamibi undergoes considerably less washout after the initial myocardial uptake than thallium does, the evaluation of perfusion versus tissue damage requires two separate injections. Teboroxime, on the other hand, undergoes rapid washout after its initial accumulation in the myocardium, and imaging must be completed within 8 min after injection. It is used to detect rapid changes in the patient's status caused by dynamic changes in coronary patency that are produced by progression of the disease or the effects of treatment.
In addition to detecting perfusion deficits, myocardial imaging with the single-photon emission computed tomography (SPECT) system allows for a three-dimensional reconstruction of the heart, which can be displayed in any projection on a monitor screen. Such images can be formed at intervals during the cardiac cycle to create an image of the beating heart, which can be used to detect wall motion abnormalities and derive left ventricular volumes and ejection fraction. Matching wall motion abnormalities with perfusion defects provides additional confirmation that the perfusion defects visualized are true and not artifacts of photon attenuation. Also, extensive perfusion defects and wall motion abnormalities should be accompanied by decreases in ejection fraction.
b. Radionuclide angiography—Radionuclide angiography is based on visualizing radioactive tracers in the cavities of the heart over time. Radionuclide angiography is usually done with a single gamma camera in a single plane, and only one view of the heart is obtained. The most common technique is to record the amount of radioactivity received by the gamma camera over time and plot it. Although volume estimates by radionuclide angiography are not as accurate as those obtained by other methods, the ejection fraction is quite accurate. Wall motion can be assessed in the one plane imaged, but the technique is not as sensitive as other imaging modalities for detecting wall motion abnormalities.
Of the two basic techniques for performing radionuclide angiography, the oldest is the first-transit technique. This requires injecting a bolus of technetium-99m and observing its movement through the venous system into the right heart, pulmonary circulation, and finally to the left heart and the aorta. Because the sampling rate is relatively short in relation to the ECG R-R interval, it is possible to sample at least one cardiac cycle in each chamber of the heart. By determining the change in radioactivity over time, it is possible to measure the stroke volume or ejection fraction for each ventricle or chamber. The more popular radionuclide angiographic technique is multiple-gated acquisition (MUGA), or equilibrium-gated blood pool, radionuclide angiography. In this approach, technetium-99m is used to label the patient's own red blood cells, which remain within the vascular space, allowing imaging studies to be acquired for several hours. Imaging acquisition is synchronized with the R wave of the ECG, so that the lower amounts of radioactivity generated from this equilibrium technique can be accumulated from beat to beat. Once enough counts are collected in each phase of the cardiac cycle, the camera computer generates a composite cardiac cycle, with the final time/activity curve and imaging representing a composite of approximately 200 heart beats. MUGA is well suited for exercise stress testing because one injection of isotope can be used for both the resting and the exercise studies. Because many heart beats must be collected, imaging during exercise must be done during steady-state periods, when no marked fluctuations are present in heart rate. One limitation of the technique is that sudden beat-to-beat changes in left ventricular performance are obscured by the averaging technique. Because ischemic heart disease often results in such changes, the exercise MUGA has lost favor as a technique for detecting ischemic heart disease, since its sensitivity is not as high as other techniques. Currently, the major use of MUGA is to assess left ventricular performance (ejection fraction), especially in patients with technically inadequate echocardiograms.
4. Other cardiac imaging
a. Plain-film chest radiography—Plain-film chest radiography is used infrequently now for evaluating cardiac structural abnormalities because of the superiority of echocardiography in this regard. The chest x-ray film, however, has no equal for assessing pulmonary anatomy and is very useful for evaluating pulmonary venous congestion and hypoperfusion or hyperperfusion. In addition, abnormalities of the thoracic skeleton are found in certain cardiac disorders and radiographic corroboration may help with the diagnosis. Detection of intracardiac calcium deposits by the x-ray film or fluoroscopy is of some value in finding coronary artery, valvular, or pericardial disease.
b. Computed tomographic scanning—Computed tomography (CT) has been applied to cardiac imaging, but the image suffers because of the motion of the heart. Computed tomography has done a better job with evaluating the thoracic aorta and the pericardium, which are less mobile than the heart. Both these structures are more accurately evaluated with magnetic resonance imaging (MRI), however. Electron beam computed tomography (EB-CT) solves some of the motion problems and can be used more successfully for cardiac imaging. The major application of this newer technology to date has been the detection of small amounts of coronary artery calcium as an indicator of atherosclerosis in the coronary arterial tree. Although this technique has tremendous potential, its actual clinical utility, compared with other standard approaches is controversial.
c. Magnetic resonance imaging—Magnetic resonance imaging (MRI) probably has the most potential as a technique for evaluating cardiovascular disease. It is excellent for detecting aortic dissection and pericardial thickening and assessing left ventricular mass. Newer computer analysis techniques have solved the problem of myocardial motion and can be used to detect flow in the heart, much as color-flow Doppler is used. In addition, regional molecular disturbances can be created that place stripes of a different density in either the myocardium or the blood; these can then be followed through the cardiac cycle to determine structural deformation (eg, of the left ventricular wall) or the movement of the blood. When its full potential is reached, MRI might well compete successfully, in terms of image quality and information obtained, with Doppler echocardiography. Unfortunately, MRI studies take a long time to perform and are not readily done in sick patients who need a bedside evaluation; it is not likely to replace echocardiography in the near future.
d. Positron emission tomography—Positron emission tomography (PET) is a technique using tracers that simultaneously emit two high-energy photons. A circular array of detectors around the patient can detect these simultaneous events and accurately identify their origin in the heart. This results in improved spatial resolution, compared with single-photon emission computed tomography. It also allows for correction of tissue photon attenuation, resulting in the ability to accurately quantify radioactivity in the heart. PET scanning can be used to assess myocardial perfusion and myocardial metabolic activity separately by using different tracers coupled to different molecules. Most of the tracers developed for clinical use require a cyclotron for their generation; the cyclotron must be in close proximity to the PET imager because of the short half-life of the agents. Agents in clinical use include oxygen-15 (half-life 2 min), nitrogen-13 (half-life 10 min), carbon-11 (half-life 20 min) and fluorene-18 (half-life 110 min). These tracers can be coupled to many physiologically active molecules for assessing various functions of the myocardium. Because rubidium-82, with a half-life of 75 s, does not require a cyclotron and can be generated on-site, it is frequently used with PET scanning, especially for perfusion images. Ammonia containing nitrogen-13 and water containing oxygen-15 are also used as perfusion agents. C-11-labeled fatty acids and 18F fluorodeoxyglucose are common metabolic tracers used to assess myocardial viability, and acetate containing carbon-11 is often used to assess oxidative metabolism.
The main clinical uses of PET scanning involve the evaluation of coronary artery disease. It is used in perfusion studies at rest and during pharmacologic stress (exercise studies are less feasible). In addition to a qualitative assessment of perfusion defects, PET allows for a calculation of absolute regional myocardial blood flow or blood flow reserve. PET also assesses myocardial viability, using the metabolic tracers to detect metabolically active myocardium in areas of reduced perfusion. The presence of viability imply that returning perfusion to these areas would result in improved function of the ischemic myocardium. Although many authorities consider PET scanning the gold standard for determining myocardial viability, it has not been found to be 100% accurate. Thallium reuptake techniques and echocardiographic and MR imaging of wall-thickening characteristics have proved equally valuable for detecting myocardial viability in clinical studies.
5. Stress testing—Stress testing in various forms is most frequently applied in cases of suspected or overt ischemic heart disease (Table 1–3). Because ischemia represents an imbalance between myocardial oxygen supply and demand, exercise or pharmacologic stress increases myocardial oxygen demand and reveals an inadequate oxygen supply (hypoperfusion) in diseased coronary arteries. Stress testing can thus induce detectable ischemia in patients with no evidence of ischemia at rest. It is also used to determine cardiac reserve in patients with valvular and myocardial disease. Deterioration of left ventricular performance during exercise or other stresses suggests a diminution in cardiac reserve that would have therapeutic and prognostic implications. Although most stress test studies use some technique (Table 1–4) for directly assessing the myocardium, it is important not to forget the symptoms of angina pectoris or extreme dyspnea: light-headedness or syncope can be equally important in evaluating patients. Physical findings such as the development of pulmonary rales, ventricular gallops, murmurs, peripheral cyanosis, hypotension, excessive increases in heart rate, or inappropriate decreases in heart rate also have diagnostic and prognostic value. It is therefore important that a symptom assessment and physical examination always be done before, during, and after stress testing.

Table 1–3. Indications for stress testing.

Table 1–4. Methods of detecting myocardial ischemia during stress testing.

Electrocardiographic monitoring is the most common cardiac evaluation technique used during stress testing; it should be part of every stress test in order to assess heart rate and detect any arrhythmias. In patients with normal resting ECGs, diagnostic ST depression of myocardial ischemia has a fairly high sensitivity and specificity for detecting coronary artery disease in symptomatic patients if adequate stress is achieved (peak heart rate at least 85% of the patient's maximum predicted rate, based on age and gender). Exercise ECG testing is an excellent low-cost screening procedure for patients with chest pain consistent with coronary artery disease, normal resting ECGs, and the ability to exercise to maximal age- and gender-related levels.
A myocardial imaging technique is usually added to the exercise evaluation in patients whose ECGs are abnormal or, for some reason, less accurate. It is also used for determining the location and extent of myocardial ischemia in patients with known coronary artery disease. Imaging techniques, in general, enhance the sensitivity and specificity of the tests but are still not perfect, with false-positives and -negatives occurring 5–10% of the time.
Which adjunctive myocardial imaging technology to choose depends on the quality of the tests, their availability and cost, and the services provided by the laboratory. If these are all equal, the decision should be based on patient characteristics. For example, echocardiography might be appropriate for a patient suspected of developing ischemia during exercise profound enough to depress segmental left ventricular performance and worsen mitral regurgitation. On the other hand, in a patient with known three-vessel coronary artery disease and recurrent angina after revascularization, perfusion scanning might be the best test to determine which coronary artery is producing the symptoms.
Choosing the appropriate form of stress is also important (Table 1–5). Exercise, the preferred stress for increasing myocardial oxygen demand, also simulates the patient's normal daily activities and is therefore highly relevant clinically. There are essentially only two reasons for not choosing exercise stress, however: the patient's inability to exercise adequately because of physical or psychologic limitations; or the chosen test cannot be performed readily with exercise (eg, PET scanning). In these situations, pharmacologic stress is appropriate.

Table 1–5. Types of stress tests.

6. Cardiac catheterization—Cardiac catheterization is now mainly used for the assessment of coronary artery anatomy by coronary angiography. In fact, the cardiac catheterization laboratory has become more of a therapeutic than a diagnostic arena. Once significant coronary artery disease is identified, a variety of catheter-based interventions can be used to alleviate the obstruction to blood flow in the coronary arteries. At one time, hemodynamic measurements (pressure, flow, oxygen consumption) were necessary to accurately diagnose and quantitate the severity of valvular heart disease and intracardiac shunts. Currently, Doppler echocardiography has taken over this role almost completely, except in the few instances when Doppler studies are inadequate or believed to be inaccurate. Catheter-based hemodynamic assessments are still useful for differentiating cardiac constriction from restriction, despite advances in Doppler echocardiography. Currently, the catheterization laboratory is also more often used as a treatment arena for valvular and congenital heart disease. Certain stenotic valvular and arterial lesions can be treated successfully with catheter-delivered balloon expansion.
Myocardial biopsy is necessary to treat patients with heart transplants and is occasionally used to diagnose selected cases of suspected acute myocarditis. For this purpose, a biotome is usually placed in the right heart and several small pieces of myocardium are removed. Although this technique is relatively safe, myocardial perforation occasionally results.
7. Electrophysiologic testing—Electrophysiologic testing uses catheter-delivered electrodes in the heart to induce rhythm disorders and detect their structural basis. Certain arrhythmia foci and structural abnormalities that facilitate rhythm disturbances can be treated by catheter-delivered radiofrequency energy (ablation) or by the placement of various electronic devices that monitor rhythm disturbances and treat them accordingly through either pacing or internally delivered defibrillation shocks. Electrophysiologic testing and treatment now dominate the management of arrhythmias; the test is more accurate than the surface ECG for diagnosing many arrhythmias and detecting their substrate, and catheter ablation and electronic devices have been more successful than pharmacologic approaches at treating arrhythmias.
8. Test selection—In the current era of escalating health-care costs, ordering multiple tests is rarely justifiable, and the physician must pick the one test that will best define the patient's problem. Unfortunately, cardiology offers multiple competing technologies that often address the same issues, but only in a different way. The following five principles should be followed when considering which test to order:



What information is desired? If the test is not reasonably likely to provide the type of information needed to help the patient's problem, it should not be done, no matter how inexpensive and easy it is to obtain. At one time, for example, routine preoperative ECGs were done prior to major noncardiac surgery to detect which patients might be at risk for cardiac events in the perioperative period. Once it was determined that the resting ECG was not good at this, the practice was discontinued, despite its low cost and ready availability.



What is the cost of the test? If two tests can provide the same information and one is much more expensive than the other, the less expensive test should be ordered. For example, to determine whether a patient's remote history of prolonged chest pain was a myocardial infarction, the physician has a choice of an ECG or one of several imaging tests, such as echocardiography, resting thallium-201 scintigraphy, and the like. Because the ECG is the least expensive test, it should be performed for this purpose in most situations.



Is the test available? Sometimes the best test for the patient is not available in the given facility. If it is available at a nearby facility and the patient can go there without undue cost, the test should be obtained. If expensive travel is required, the costs and benefits of that test versus local alternatives need to be carefully considered.



What is the level of expertise of the laboratory and the physicians who interpret the tests? For many of the high-technology imaging tests, the level of expertise considerably affects the value of the test. Myocardial perfusion imaging is a classic example of this. Some laboratories are superlative in producing tests of diagnostic accuracy. In others, the numbers of false-positives and -negatives is so high as to render the tests almost worthless. Therefore, even though a given test may be available and inexpensive and could theoretically provide essential information, if the quality of the laboratory is not good, an alternative test should be sought.



What quality of service is provided by the laboratory? Patients are customers, and they need to be satisfied. If a laboratory makes the patients wait a long time, if it is tardy in getting the results to the physicians, or if great delays occur in accomplishing the test, choose an alternative lab (assuming, of course, that alternatives are available). Poor service cannot be tolerated.
Many other situations and considerations affect the choice of tests. For example, a young patient with incapacitating angina might have a high likelihood of having single-vessel disease that would be amenable to catheter-based revascularization. It might be prudent to take this patient directly to coronary arteriography with an eye toward diagnosing and treating the patient's disease in one setting for maximum cost-effectiveness. This approach, however, presents the risk of ordering an expensive catheterization rather than a less-expensive noninvasive test if the patient does not have significant coronary disease. If an assessment of left ventricular global performance is desirable in a patient known to need coronary arteriography, the assessment could be done by left ventricular cine-angiography at the time of cardiac catheterization. This would avoid the extra expense of echocardiography if it was not otherwise indicated. Physicians are frequently solicited to use the latest emerging technologies, which often have not been proved better than the standard techniques. It is generally unwise to begin using these usually more expensive methods until clinical trials have established their efficacy and cost-effectiveness.
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