Stress Echocardiography

Treadlift Workout

Treadmill Cardio Workouts

Get Instant Access

Stress echocardiography is based on the identification of regional wall motion abnormalities, which occur as a result of an increase in oxygen demand without a matched increased in oxygen supply in the presence of a coronary stenosis. The test has gained increasing acceptance with the introduction of digital echocardiography, harmonic imaging, and the use of contrast agents, all of which have incrementally contributed to increased image quality, reproducibility, and accuracy. However, the performance and interpretation of stress echocardiography require intensive skills. Therefore, accuracy may vary significantly among echocardiographic laboratories in clinical practice. Recent studies suggest that real-time three-dimensional (3D) echocardiography facilitates faster data acquisition and better image segmentation, and therefore may lead to improved diagnostic accuracy.3

Most commonly, regional wall motion is assessed from parasternal long, parasternal short, and apical images, using a 17-segment model of the left ventricle (LV).4 Each segment is described as normal, hypo-kinetic, akinetic, or dyskinetic, and the results of the individual segments are averaged to calculate a global wall motion score. Recent studies suggest that new quantitative indices of regional contractility, such as strain imaging, are useful in identifying stress-induced ischemia and/or viable myocardium in dysfunctional segments.5

Stress echocardiography is used to establish the diagnosis, determine prognosis, or evaluate the need for revascularization in patients with known or suspected CAD. The test may also be used to evaluate patients with cardiomyopathy or valvular heart disease. The diagnosis of CAD is based on detection of either resting or stress-induced regional wall motion abnormalities (Figs. 3-1 through 3-3). A resting regional wall motion abnormality implies in most cases a prior myocardial infarction. A stress-induced regional wall motion abnormality implies, in most cases, ischemia caused by obstructive CAD.

Figure 3-2. Abnormal stress echocardiography response in a patient with severe multivessel coronary artery disease. Images obtained at end-diastole (ED) and end-systole (ES) at rest and immediately after exercise stress from the parasternal long axis (LAX) and short axis (SAX) windows. Notice the ES dilatation of the left ventricular cavity size.

Figure 3-2. Abnormal stress echocardiography response in a patient with severe multivessel coronary artery disease. Images obtained at end-diastole (ED) and end-systole (ES) at rest and immediately after exercise stress from the parasternal long axis (LAX) and short axis (SAX) windows. Notice the ES dilatation of the left ventricular cavity size.

Figure 3-3. Abnormal stress echocardiography response in a patient with severe stenosis of the middle left anterior descending coronary artery. Images obtained at end-diastole (ED) and end-systole (ES) at rest and immediately after exercise stress from the apical four-chamber (AP4) and two-chamber (AP2) windows. Notice the relative ES dilatation of the left ventricular apical segments (arrows).

Figure 3-3. Abnormal stress echocardiography response in a patient with severe stenosis of the middle left anterior descending coronary artery. Images obtained at end-diastole (ED) and end-systole (ES) at rest and immediately after exercise stress from the apical four-chamber (AP4) and two-chamber (AP2) windows. Notice the relative ES dilatation of the left ventricular apical segments (arrows).

Exercise Echocardiography

Exercise stress testing may be performed with treadmill, supine or prone bicycle, or even arm ergometry. Treadmill stress echocardiography is by far the most commonly used modality in the United States. With treadmill exercise, only pre-exercise and post-exercise images are obtained, both with the patient in the supine lateral position. Post-exercise images need to be obtained within 1 minute after termination of exercise. Any delay may result in resolution of regional wall motion abnormalities, reducing the sensitivity of the test for moderate, single-vessel disease. Bicycle ergometry allows the operator to obtain images while the patient is still exercising, so, in theory, it is capable of detecting milder, transient wall motion abnormalities caused by ischemia. Either treadmill or bicycle ergometry allows evaluation of important functional data such as exercise capacity, blood pressure response, and hemodynamic responses to exercise, including assessment of cardiac output and pulmonary pressures, as well as ECG ST analysis. The final interpretation of the test takes into account all of these variables.

Several studies have reported sensitivities ranging from 71% to 97% and specificities ranging from 64% to more than 90%. The differences in results often relate to the use of different thresholds to define wall motion abnormalities. If hypokinesis or akinesis is defined as a threshold, sensitivity tends to be lower and specificity higher. On the other hand, if tardoki-nesis (delayed contraction or postsystolic shortening) or lack of hyperkinesis is used as a threshold, sensitivity is higher and specificity tends to be lower. Accuracy parameters also vary according to whether coronary stenosis is defined at a 50% or 70% stenosis

Follow-up (years)

Figure 3-4. Mortality rates of patients according to the total extent of wall motion abnormalities (summed stress score, expressed as vessel territories) at peak stress (N = 5375 patients). (From Marwick TH, Case C, Vasey C, et al: Prediction of mortality by exercise echocardiography: A strategy for combination with the Duke treadmill score. Circulation 2001;29:2566-2571.)

Follow-up (years)

Figure 3-4. Mortality rates of patients according to the total extent of wall motion abnormalities (summed stress score, expressed as vessel territories) at peak stress (N = 5375 patients). (From Marwick TH, Case C, Vasey C, et al: Prediction of mortality by exercise echocardiography: A strategy for combination with the Duke treadmill score. Circulation 2001;29:2566-2571.)

threshold. The sensitivity of exercise echocardiography is lower for the detection of single-vessel disease, particularly that involving the circumflex coronary artery. In patients with multivessel disease, ischemia often is detected only in the territory supplied by the most stenotic vessel, especially if the test is discontinued at submaximal workload.

Resting or exercise-induced wall motion abnormalities may occur in the presence of cardiomyopa-thy, microvascular disease, severe hypertension (increased afterload), or valvular disease and are often the cause of false-positive interpretations.

Several stress echocardiographic variables have been shown to provide important prognostic value in patients with known or suspected CAD (Fig. 3-4). A low exercise wall motion score index or a fall in exercise ejection fraction is highly predictive of increase risk for adverse cardiac events. This prognostic decision point is similar to that of a radionuclide perfusion defect size of more than 15%. Echocardiographic variables have incremental independent prognostic utility over other variables such as the Duke Treadmill Score.6 The rate of cardiac events in individuals with a normal exercise echocardiogram has been reported in several studies to be less than 1% per year.

Was this article helpful?

0 0
How To Keep Your Treadmill Running

How To Keep Your Treadmill Running

Buying a treadmill is hard enough. Choosing the best out of many treadmills in the market is nigh impossible. But once youve got the treadmill youve always wanted, are your worries truly over? Well, they certainly are, but only if you maintain your treadmill properly.

Get My Free Ebook


Post a comment