Discover the EACVI Textbook of Echocardiography 2nd edition
Chapter 11 Stress echocardiography: introduction and pathophysiology Rosa Sicari and Raluca Dulgheru Contents Summary 90 Pathophysiology 90 References 91 Summary Stress echocardiography is the combination of two-dimensional (2D) echocardiography with a physical, pharmacological, or electrical stress. The diagnostic end point for the detection of myocardial ischaemia is the induction of a transient change in left ventricular (LV) regional function during stress. The stress echo sign indicative of myocardial ischaemia is a stress-induced worsening in LV regional function, that is, worsening of LV myocardial wall thickening in a region contracting normally at baseline. The stress echo sign of myocardial viability is a stress-induced improvement of LV regional function during low levels of stress in an abnormally contracting myocardial region at rest [1,2]. Pathophysiology A transient regional imbalance between myocardial oxygen demand and supply usually results in myocardial ischaemia, the signs and symptoms of which can be used as a diagnostic tool. Myocardial ischaemia results in a typical ‘cascade’ of events in which the various markers are hierarchically ranked in a well-defined time sequence: regional mechanical dysfunction (with reduction of movement and segmental thickening) is an early event, linearly and closely related to the reduction of subendocardial flow, and more sensitive than electrocardogram changes and the onset of chest pain. The pathophysiological concept of the ischaemic cascade is translated clinically into a gradient of sensitivity of different available clinical markers of ischaemia, with chest pain being the least and regional malperfusion the most sensitive. Regardless of the stress modality used and the morphological substrate, ischaemia tends to propagate centrifugally with respect to the ventricular cavity: it involves primarily the subendocardial layer, whereas the subepicardial layer is affected only at a later stage if the ischaemia persists (see % Videos 11.1 and 11.2). In fact, extravascular pressure is higher in the subendocardial than in the subepicardial layer; this provokes a higher metabolic demand (wall tension being among the main determinants of myocardial oxygen consumption) and an increased resistance to flow. In the absence of coronary artery disease, coronary flow reserve can be reduced in microvascular disease (e.g. in syndrome X or LV hypertrophy). In this condition, angina with ST-segment depression can occur with regional perfusion changes, typically in the absence of any regional wall motion abnormalities during stress. Wall motion abnormalities are more specific than coronary flow reserve and/or perfusion changes for the diagnosis of coronary artery disease [2,3] (see % Video 11.3).
Chapter 12 Stress echocardiography: methodology Maria João Andrade and Albert Varga Contents Summary 92 The machine 92 The echocardiographer 92 The stressors 93 General protocol 93 Exercise echocardiography 93 Dobutamine echocardiography 94 Dipyridamole echocardiography 94 Comparison of dipyridamole and dobutamine tests 94 Adenosine echocardiography 95 Pacing stress echocardiography 95 Ergonovine stress test 95 References 95 Summary Stress echocardiography is the combination of echocardiography with a physical, pharmacological, or electrical stress. The fact that different stresses have different pathophysiological and clinical targets, broadened the versatility and the suitability of stress echocardiography for evaluation of patients with various cardiovascular diseases: coronary heart disease, valvular heart diseases, cardiomyopathies, and pulmonary hypertension. Before starting a stress echocardiographic examination, at least three important requirements should be fulfilled: 1. A dedicated room large enough to accommodate all the facilities required for stress echo performance and to ensure patient privacy and comfort: echo machine and examination table, exercise stress equipment, electrocardiogram (ECG) recorder and sphygmomanometer, resuscitation apparatus and drugs, oxygen source. 2. An ultrasound system with adequate image quality and equipped with stress echocardiography software and digital acquisition with ECG triggering (second harmonic imaging is mandatory) (% Fig. 12.1). 3. An experienced echocardiographer not only full trained in transthoracic echocardiography but also prepared for both acquiring and interpreting images during stress. A physician with expertise in both echocardiography and resuscitation should be available in the immediate vicinity. The machine Despite the efforts towards the development of techniques for quantification of regional wall motion during stress echocardiography, the standard approach continues to be based on qualitative assessment before, during, and following stress. Therefore good quality images are absolutely necessary as even a small uncertainty can lead to an increase in false positive or negative results . The endocardial border delineation can be enhanced through the administration of a contrast agent (either as a slow bolus or continuous infusion) for left ventricular opacification, although these agents are not always available and require training on how to use it properly . The echocardiographer It is not reasonable to begin using stress echo without complete training in standard transthoracic echocardiography, in particular as regards appraisal of regional dyssynergies . It was shown that the interpretation of stress echocardiographic tests by an