certain indications, like coronary arterial disease, or the evaluation of the hemodynamic significance of certain valvar lesions, studying the heart during stress provides extra information, which might help subsequent treatment Pharmacologic stress and exercise echocardiography are the two common stressors used to evaluate the hemodynamic and myocardial responses Exercise can be performed after a baseline echocardiography on a treadmill or on a bicycle, and immediately after peak exercise the echocardiographic study is repeated with the patient in a supine position Alternatively, exercise echocardiography can be performed on a supine bicycle, which allows continuous imaging during the test This implies that the cardiac response can be assessed at different stages of exercise and images can be recorded at peak exercise instead of during the recovery phase Typical pharmacologic stress includes the administration of dobutamine, or vasodilators such as adenosine or dipyridamole In children, the most common indications for a stress test are the detection of vasculopathy after transplantation, or problems with the coronary arteries after operations such as the arterial switch procedure or the Ross operation In younger children, dobutamine stress echocardiography requires sedation or general anesthesia related to the discomfort induced by high-dose dobutamine Quantitative Echocardiography A full morphologic evaluation includes measurement of cardiac structures (valve sizes, ventricular dimensions, great artery dimensions) A full echocardiographic study should also provide information on hemodynamics, (pressures and flows), valvar function (stenosis and regurgitation), and ventricular systolic and diastolic function Quantification of Echocardiographic Dimensions Measurement of the size of cardiac structures and great vessels is essential for the diagnosis and treatment of congenital cardiac disease One of the challenges facing the pediatric echocardiographer is the fact that cardiovascular structures grow along with body size To be able to compare measurements, methods need to be developed to normalize cardiac dimensions for growth As essential as normalization of the measurements for growth is the standardization of cardiac measurements The American Association for Echocardiography has published recommendations for standardization of echocardiographic measurements.9 So, when using normative data, it is important to perform the measurement exactly the same way as the initial data were obtained The best way to normalize measurements in children is to use z-scores.10 The z-score of a variable corresponds to the position of an observed case relative to the mean of the distribution in the population expressed in standard deviations The z-scores are derived from a large number of normal observations within populations in which the mean and standard deviation are derived as a function of the body surface area Representing a measurement as a z-score immediately provides the information how the measurement is positioned relative for the mean of the population A z-score of −4 for the annulus of the mitral valve is four standard deviations below the mean for the normal population The z-scores can be derived from published normograms or formulas.11,12 The problem is that for different cardiac structures different z-scores have been developed with sometimes significant differences between the published z-scores Ideally, each laboratory performing pediatric echocardiography should be able to establish its own z-scores for use as a reference A project supported by the Pediatric Heart Network in North America is establishing “universal z-scores” by collecting a very large normal dataset This should hopefully further standardize the use of zscores and provide normal data for clinical use In the meantime, apart from reporting z-scores, providing a normal range for body size can help to determine how abnormal a certain measurement is compared with a normal control population Although the pediatric quantification guidelines recommend the use of twodimensional echocardiography for measuring ventricular dimensions, the Mmode technique is still commonly used in pediatric echocardiographic laboratories The high frame rate allows accurate recording of events that occur rapidly, such as mural motion, change in cavity size, and motion of leaflets (Fig 19.42) Measurements can be made at precise times within the cardiac cycle For this reason, an M-mode recording should always be accompanied by an electrocardiogram End-diastolic measurements are typically made at the onset of the QRS complex, whereas maximal mural excursion is often used for the definition of end-systole, which usually corresponds to the end of the T wave M-mode measurements can be made in the parasternal short-axis at the level of the leaflets of the mitral valve Cross-sectional imaging should be used to align the M-mode cursor so as to avoid oblique cuts The M-mode measurements are then used to calculate fractional shortening on the basis of left ventricular end- diastolic dimension minus left ventricular end-systolic dimension divided by the left ventricular end-diastolic dimension It can also be used to calculate the index of left ventricular mass Left atrial and ascending aortic dimensions are measured with the M line at the level of the leaflets of the aortic valve in parasternal long- or short-axis sections (see Fig 19.42) Left ventricular ejection fraction can be assessed by calculating ejection fraction based on biplane Simpson or on the area-length method Right ventricular systolic function quantification is based on combining different measurements including tricuspid annular systolic planar excursion, fractional area change, and tissue Doppler measurements and myocardial strain measurements Three-dimensional echocardiography allows quantification of left and right ventricular volumes and ejection fraction as discussed in subsequent sections FIG 19.42 M-mode tracing recorded perpendicular to the major axis of the left ventricle just distal to the mitral valve This image is used to calculate left ventricular dimensions and fractional shortening Quantification of Flow and Identification of Patterns of Flow Normal Doppler Examination Doppler measures the velocities of blood pools, providing both quantitative and qualitative information When making such measurements, it is important to ... Ideally, each laboratory performing pediatric echocardiography should be able to establish its own z-scores for use as a reference A project supported by the Pediatric Heart Network in North America is establishing “universal z-scores” by collecting a... Although the pediatric quantification guidelines recommend the use of twodimensional echocardiography for measuring ventricular dimensions, the Mmode technique is still commonly used in pediatric echocardiographic