Stressechocardiography is a highly accurate noninvasive method which is used
1) To demonstrate the presence of coronary disease and identify patients who will benefit from invasive diagnostic procedure-coronary angiography
2) To identify patients with known coronary artery disease who will benefit from the “opening up” of the coronary artery (in many cases selected on the basis of investigation medical treatment is as good as or if not better than opening the arteries)
3) To guide interventional treatment - -angioplasty - by identifying a "culprit" lesion –a lesion in the coronary artery which causes lack of blood supply to the cardiac muscle
4) To identify patients who could be at risk from cardiac events during planned non cardiac surgery
5) For patients in heart failure to assess the possibility of recovery of the heart muscle
6) For patients with disease of the cardiac valves when resting echocardiography does not give enough information
7) For patients with pulmonary hypertension to assess the level of increased pressure in the lungs on exercise
Stress Echocardiography utilizes the ability of ultrasound to detect movement (motion) of different parts of the cardiac muscle with ultrasound. Movements of the cardiac muscle are significantly affected by a lack of blood supply and this can be visualized as lack of movement to different degrees. This coupled with the knowledge of the supply of different parts of the cardiac muscle by different coronary arteries gives an accurate functional assessment of the coronary artery supply of cardiac muscle
In addition, during Stress Echo it is possible to assess the state of the valves as well as the intracardiac pressures at rest and on exertion.
Stress Echocardiography could be of different varieties depending on the type of Stress used:
a. Treadmill(or Bicycle) Stress Echo,
b. Pharmacological (mainly Dobutamine) Stress Echo
c.Pacing Stress Echo (when a patient has an implanted pacemaker it is used to increase the heart rate).
Stress Echocardiography as any ultrasound investigation is absolutely devoid of any radiationexposure.
Myocardial Perfusion Imaging (MPI)
Myocardial perfusion imaging has been long used for the detection of coronary artery disease and the assessment of its severity. Recent developments have led to the possibility of assessment of the left ventricular function by MPI. All nuclear cardiology studies depend on injection into the patient of an isotope and distribution of the isotope in myocardium. This isotope will then emit photons that can be detected by camera. MPI could be exercise or pharmacological depending of the type of Stress used. MPI usually utilizes 2 day protocols which are quite time consuming. Accuracy of Stress Echocardiography and Myocardial Perfusion Stress Tests for the detection and assessment of Coronary Artery Disease are comparable. At the same time it should be noted that the rate of false positive results in women with MPI is usually higher. A major drawback of MPI is the amount of radiation involved which ishigh with 201-thallium and in the middle range with 99m-Tc-sestamibi and 99m-Tc-tetrofosmin.