Stress Echocardiography

Stress echocardiography, both pharmacologic and physiological, is an established noninvasive diagnostic method of detecting coronary artery disease. It also has a role in the assessment of patients with chest pain, the assessment of cardiovascular risk before noncardiac surgery, the assessment of patients after a myocardial infarction, the detection of viability in dysfunctional myocardium, and the prediction of functional recovery. The prognostic value of stress echocardiography is emerging. In this article, we discuss the methodology, diagnostic accuracy, and various clinical applications of stress echocardiography. We also review its limitations and compared it with other noninvasive methods of assessing patients with coronary artery disease.     

Stress fractures

Stress fractures are being increasingly reported as a common cause of morbidity in both healthy populations and those withunderlying diseases involving abnormal bone. An insight into the types and pathogenesis of stress fractures is necessary to considering the diagnosis, management and prevention of such conditions. The classification, aetiology and aspects of management are discussed.     

Stress fractures

Stress fractures are common over-use injuries which include fatigue and insufficiency fractures. Athletes, soldiers and osteoporotic patients are some of the individuals at high risk for the development of this injury. Owing to the low sensitivity of plain radiography at the onset of symptoms the diagnosis of this entity may be easily overlooked. Occasionally, some of these fractures, such as tibial fracture in children and fractures in the clavicle and pelvic ring, can be misdiagnosed as tumoral or infectious processes; moreover, although most stress fractures are uncomplicated and can be managed by rest and restriction from precipitating activity, a subset of these fractures can present a high risk for progression to complete fracture or non-union problems. All of this indicates that the various types of stress fracture, owing to their different clinical characteristics and evolution, should be commented on in detail. In this chapter different types of stress fracture are described with special reference to their localization, clinical characteristics, evolution and treatment.     

Stress echocardiography

Within the last decade of this millennium, stress echocardiography has been established for the diagnosis and follow-up of coronary artery disease. The basis is the technical development of the echo machines: first, the improved echocardiographic resolution and, second, the digital image storage of a whole cineloop, which may be interpreted frame-by-frame in an ECG synchronized manner for several exercise levels simultaneously. Myocardial ischemia can be detected much earlier by regional contraction abnormalities of the left ventricular myocardium than in conventional ECG exercise tolerance testing explaining the higher sensitivities. Furthermore, the extent and localization, including the correlation with the stenotic coronary anatomy, is possible. The usage of pharmacological stress agents (dobutamine, arbutamine, dipyridamole, adenosine) or electrical stimulating methods (transesophageal, intracardial) allow the examination of patients unable to exercise in similar accuracy.     

Stress echocardiography

Stress echocardiography has become an accepted noninvasive method for the diagnosis of coronary artery disease. Stress echocardiography is more sensitive than exercise electrocardiography and as sensitive and specific as radionuclide perfusion studies for detecting coronary artery disease. Pharmacologic stress echocardiography using dobutamine also has excellent diagnostic accuracy for patients who are unable to exercise. Dobutamine stress echocardiography can provide prognostic data to determine perioperative cardiac risks in patients who are undergoing vascular surgery.     

Stress echocardiography

Stress echocardiography is the combination of 2D echocardiography with a physical, pharmacological or electrical stress. The diagnostic end point for the detection of myocardial ischemia is the induction of a transient worsening in regional function during stress. Stress echocardiography provides similar diagnostic and prognostic accuracy as ra-dionuclide stress perfusion imaging, but at a substantially lower cost, without environmental impact, and with no biohazards for the patient and the physician. Among different stresses of comparable diagnostic and prognostic accuracy, semisupine exercise is the most used, dobutamine the best test for viability, and dipyridamole the safest and simplest pharmacological stress. The additional clinical benefit of myocardial contrast echo-cardiography, tissue Doppler imaging and real time 3-D echocardiography has been inconsistent and disappointing, whereas the potential of adding coronary flow reserve evaluation of left anterior descending coronary artery by transthoracic Doppler echocardiography adds another important dimension to stress echocardiography. In spite of its dependence upon operator's training, stress echocardiography is today the best possible imaging choice to achieve the still elusive target of sustainable cardiac imaging in the field of noninvasive diagnosis of coronary artery disease.     

Bicycle Stress Echocardiography

Bicycle stress echocardiography involves the recording and interpretation of two-dimensional echocardiographic information before, during, and after bicycle exercise. The exercise test can be performed in the supine or upright posture. While there are important physiological differences between these two positions, they appear to provide similar diagnostic information on the presence or absence of coronary artery disease. A major advantage of bicycle stress echocardiography compared to treadmill exercise is the ability to image at peak exercise, rather than relying solely on pre- and postexercise imaging. This contributes to the greater sensitivity of the test for the detection of ischemia. The recent application of digital processing techniques may also improve sensitivity by permitting side-by-side comparison of rest and stress images. In summary, bicycle stress echocardiography is a useful tool in the management of patients with known or suspected coronary artery disease. It is a versatile and accurate technique, which competes favorably with other imaging modalities and provides information on regional and global left ventricular function.     

Stress during internship

Mood changes of interns during the internship year were studied using the Profile of Mood States (POMS), a standardized adjective checklist. All 35 interns in the University of California, Irvine-Long Beach Medical Program completed the POMS at internship orientation and at five other times during the year. Of the six mood factors measured by the POMS, four changed significantly during the testing period. Anger-hostility scores were higher (p<0.01) in December than at orientation and remained so throughout the year. Tension-anxiety scores were higher (p<0.01) and fatigue-inertia scores were lower (p<0.01) at orientation than at any other time during the year. Vigor-activity scores were higher (p<0.01) at orientation than at the end of the year. Depression-dejection and confusion-biwilderment scores did not change significantly during the study period. Recognition of these mood changes is helpful for drawing the attention of house staff and faculty members to emotional stresses of training, and for identifying issues for discussion in intern support groups. Received from the Division of General Internal Medicine and Primary Care, VA Medical Center, Long Beach, California, and the University of California, Irvine, California. Supported in part by a grant (5-D28 PE-19162) from the US Public Health Service.     

Post-Traumatic Stress Disorder

No abstract available for this article.     

Stress and metabolism

Obesity, lipid disorders, type 2 diabetes, high blood pressure and coronary heart disease are frequently encountered in wealthy populations. All these disorders frequently occur as clusters, constituting the metabolic syndrome. It is currently admitted that insulin resistance plays a central role in the pathogenesis of this syndrome. Stress responses include activation of the sympathetic nervous system and stimulation of epinephrine and cortisol release. These hormones may over the long term reduce insulin sensitivity. Cortisol may also favour the development of central obesity. In healthy individuals, mental stress increases heart rate, but simultaneously decreases vascular resistance in skeletal muscle. This results in a moderate increase in blood pressure, and an acute increase in insulin-mediated glucose disposal. In obese patients, mental stress elicits responses which differ widely from those of healthy individuals. While mental stress enhances catecholamine-mediated energy expenditure in obese patients to the same extent as in lean subjects, it fails to decrease systemic vascular resistance due to endothelial dysfunction. This leads to enhanced blood pressure responses and the absence of stimulation of glucose disposal in obese subjects during mental stress. It can be hypothesized that repeated professional or social stress may activate the sympathoadrenal system, resulting in high cortisol levels, stimulation of the sympathetic nervous system, and epinephrine secretion. All these factors may eventually lead to the development of central obesity and insulin resistance. Furthermore, the blood pressure responses to mental stress may be enhanced in insulin-resistant individuals, favouring the development of vascular complications.