Coronary arteriography demonstrates radiographically the anatomy of the coronary arteries. It provides direct documentation of the anatomic extent and distribution of obstruction of those arteries. This is a better technique because it provides anatomical evidence for a diagnosis of coronary artery disease. During the test it is also possible to visualize the contracting heart to measure cardiac output and to evaluate, thereby, ventricular function.

The electrocardiogram (ECG) exercise test produces a graphic tracing of the electric current produced by the polarization and depolarization of the heart muscle. It is a multistage, progressive, continuous test that measures cardiac current while the subject is at rest and is performing different levels of exercise. Variations from normal can be helpful in the diagnosis of ischemia, of exercise-induced arrhythmias and in the assessment of cardiac performance in certain clinical circumstances. It is an improved technique over the Master Two-Step procedure which it re-
placed because the amount of exertion can be specifically quantified and the ECG monitoring during and after exercise provides greater specificity and sensitivity in the diagnosis of ischemia.

The MUGA is a radionuclide imaging procedure otherwise known as multigated blood pool ventriculograph using, most commonly, technetium-99 sodium pertechnetate (99m/tc) as the tracer. The use of this technique at rest and after exercise provides for an evaluation of myocardial function and wall motion abnormalities indicative of ischemic heart disease. Left ventricular dysfunction and ejection fraction can be estimated from the test. When done at rest and after exercise, detection of exercise-induced wall motion abnormalities and/or a fall or failure of rise of ejection fraction is highly suggestive of severe heart disease. It is an improved technique because, without invasive cardiac catheterization, some gross estimate of cardiac dysfunction can be made by this test if there is a fall or failure to rise of ejection fraction, or exercise-induced dyskinesia, or akinesia of the left ventricular wall.

The thallium perfusion scan measures the perfusion of blood through the myocardium. The radionuclide thallium-201 is employed as the tracer. Resting and exercise radionuclide images are compared to detect fixed lesions present during rest and exercise and transient perfusion defects indicative of ischemia induced by exercise. As such, this is a better technique for diagnosis of ischemia and of old myocardial infarctions. Assessments of cardiac function can be made when this technique is performed in conjunction with an ECG exercise test.

This test records ultrasound waves reflected by heart structures. It is used to assess the motion and dimensions of heart chambers, wall, and valves; but its reliability is far greater for left than right-sided heart structures (and only limited views of these structures are visualized at any one time). This technique is especially helpful in evaluating the mitral valve, the aortic valve, the thickness of the ventricular wall, and the presence or absence of fluid in the pericardial space. It is a better technique because it is noninvasive and may provide diagnostic evidence that would otherwise be unavailable.

The Holter monitor produces continuous electrocardiographic tracings over extended periods of time so that ambulatory monitoring of patients is possible. The electrocardiograms can be correlated with the individual's activities and symptoms. Variations from normal are useful in the assessment of cardiac arrhythmias and of exertional or stress-induced ischemia. The fact that ECG tracings are produced over a long time period makes this an improved diagnostic technique for detection of arrhythmias and ischemia.

Venous plethysmography records changes in volume of a limb after inflation and deflation of a cuff applied to the limb. The technique is useful in the noninvasive determination of the presence of deep vein thrombosis. In many situations this is a better technique because it can be diagnostic for deep vein thrombosis without resorting to a venogram, an uncomfortable procedure and one that is sometimes associated with noxious side effects (such as an allergic reaction or new thrombosis). In the absence of venographic results, this technique provides a better basis for diagnosis than clinical observations alone.

Doppler ultrasonography is based on the shift in ultrasound frequency that arises if an ultrasound beam is transmitted to and reflected from moving blood cells. The frequency of shift is proportional to the velocity of the blood flow. The Doppler ultrasound is used to determine systolic arterial pressures. This is applicable particularly in the distal lower extremities where the blood pressure cannot be measured accurately by the regular cuff method. Measurements of segmental pressures at various levels of the lower extremities help to distinguish between aorto-iliac, femoropopliteal, or combined disease. Doppler ultrasound can measure the ankle to brachial artery pressure index at rest and after exercise. This is an improved technique because it allows a quantitative, noninvasive determination of the severity of peripheral arterial disease. The estimate of severity is especially useful if this technique is repeated after the patient exercises.

Caroid Phonoangiography (CPA) is used to record and evaluate alterations in the sound emanating from the carotid artery. It is a technical extension of auscultation and is used to assess the possibility of carotid obstruction. Although it can be used alone, its primary value is as an adjunct to hemodynamically based studies such as oculoplethysmography (OPG). It is an improved technique because it provides noninvasive evidence for the diagnosis of narrowing of the carotid artery.

This test, like the M mode echocardiography (item E above), records ultrasound waves reflected by heart structures. It allows visualization over time of the cardiac structures and the great vessels (aorta and pulmonary artery). It displays the anatomic relationships of these structures as well as their movement during the cardiac cycle. It is better because it is noninvasive and, as such, may provide evidence which would otherwise be unavailable for detection of cardiac dysfunction.

Doppler echocardiography records changing velocity of ultrasound waves generated by variations in blood flow in the heart and in the great vessels. It is used in the assessment of intracardiac and extracardiac shunts, valve flow, and cardiac output. It permits measurements of valvular gradients, quantitates valvular stenosis, and regurgitation and, in so doing, aids in estimating cardiac output. It is an improved technique because it provides data previously obtainable only by catheterization of the heart or blood vessels, eliminating the need for catheterization in many patients.

Electrophysiologic testing requires cardiac catheterization and the placement of electrode catheters within selected portions of the heart. The application of an electrical current is used to assess the propensity of the patient to develop selected cardiac arrhythmias and of the value of various drugs in preventing these arrhythmias. It is a better technique because it may document severe, nonresponsive ventricular arrhythmias.