Cardiac Stress Test

The function and blood flow through the heart can be assessed with an echocardiogram. When an echocardiogram is performed after exercise, it can detect areas of decreased wall motion from cardiac ischemia and tell if a person is suffering from heart failure. An echocardiogram can also detect If there is an abnormal amount of fluid around the heart.

Echocardiograms are more routinely used in the diagnosis and management of patients with coronary artery disease. It can detect the shape and size of the heart, the pumping capacity of the heart, and the location of various wall-motion abnormalities. Things like the cardiac output, diastolic function, and ejection fraction are also assessed. Hypertrophic cardiomyopathy, dilated cardiomyopathy, and valvular changes are assessible with an echocardiogram. It is completely non-invasive.

Doppler echocardiography can detect the flow of blood through the heart, using color Doppler or spectral Doppler devices. Leakage or stenosis of valves can be seen as the flow is being assessed. Tissue motion is done by “tissue Doppler echocardiography”. IV contrast is used during “contrast echocardiography”. The usual echocardiography technique is transthoracic, which uses probes/transducers placed on the chest.

A transesophageal echocardiogram is done with a transducer placed in the esophagus. This allows for imaging of the posterior aspect of the heart, and can be done when a more precise image of the heart is needed or when obtaining an external image may be difficult. Stress echocardiography measures the images of the heart prior to exercise and after exercise, looking for wall motion abnormalities after exercise that aren’t absent before exercise. It is not invasive and does not assess the patency of the coronary arteries.

Three-dimensional echocardiography and four-dimensional echocardiography (using the movement of the heart as the fourth dimension) allows for the management and assessment of any pathology in the heart (especially cardiomyopathy and valvular disease). It takes computer technology and constructs a 3D image of the structures of the heart and is used during the placement of catheter-delivered valvular devices and various intraoperative assessments.

Contrast-enhanced echocardiography can use IV contrast dye made of tiny bubbles that circulate during the test and which acts as a reflective surface for the ultrasound image. It is a good test for the evaluation of the global and regional wall motion function of the heart. It is the best test to evaluate LV thrombi and ventricular wall thickness. It can be used for the assessment of blood perfusion through the myocardial tissues (which might be abnormal in coronary artery disease).

A cardiac stress test is the best noninvasive way to determine whether a person has significant heart disease. It can detect arrhythmias that occur during physical activity and if the heart suffers from any kind of strain on the muscles during activity. Other names for this test include the “treadmill test”, the graded exercise test, the exercise electrocardiogram, or the stress EKG. In some cases, it can be combined with an echocardiogram performed immediately after exercise, and is an accurate way to detect early heart disease.

Figure 5 depicts a typical cardiac stress test:

Figure 5

If a patient cannot exercise for physical reasons, a dobutamine or adenosine stress test can be done. The patient is hooked up to a cardiac monitoring device that measures the electrical activity of the heart. They are given intravenous adenosine or dobutamine—both of which stimulate the heart rate and mimic the effects of exercise on the heart. The blood pressure, heart rate, and ECG readings are measured to see if the elevated heart rate brings on ischemic changes in the heart muscle or a dangerous cardiac arrhythmia.

A nuclear stress test is another way of detecting ischemic areas in the heart. The patient is injected with a radioactive uptake substance that is utilized by the heart muscle as part of heart muscle cell metabolism. Pictures of the radioactive uptake are taken of the heart at rest and again after exercising, looking for areas of decreased uptake after exercise. Areas of the heart muscle that are underperfused can be seen on the nuclear scan of the heart. Medications can also be used to elevate the heart rate among individual who can’t exercise. The cardiac stress test can compare the function of the coronary circulation before exercise and after maximal physical exertion, detecting abnormal blood flow to the rapidly beating heart. It is a good noninvasive way of screening for ischemic heart disease and assessing a patient’s heart function and prognosis after a heart attack. Heart simulation through exercise on a treadmill, pedaling a stationary bicycle, or turning a crank with their arms. Medications can also be used to mimic the effect of exercise. The test increases the heart rate gradually up to a heart rate near the patient’s maximal heart rate. Sometimes an echocardiogram or a nuclear test can be combined with an exercise test.

In a stress echocardiogram, the stress test is combined with a before-and-after echocardiogram so wall motion differences between the resting and the exercise state can be determined. The test can also be done with dobutamine in patients who are unable to exercise. Obstructive coronary artery disease can also be assessed with this technique.

The cardiac stress test is considered the first-line test to detect coronary artery disease in patients at a medium risk for CAD, including those with a family history of CAD, diabetes, hyperlipidemia,