Discover the ESC Textbook of Cardiovascular Imaging 2nd edition
standardized data acquisition in transthoracic echocardiography 9 Fig. 1.8 Display of a standardized M-mode sweep (a). The correct transducer position is documented by the M-mode sweep by a horizontal line between the ventral border of the anteroseptal septum and the ventral border of the aortic root (dotted line). Short-axis views are defined by the accurate cross-section through the left ventricular attachment of the papillary muscles (b), through the papillary muscles (c), through the chord heads as well as the chord strands (d), through the mitral valve (e), through the inter-atrial septum and the left ventricular outflow tract (f), through the aortic valve (g), the aortic root and the proximal ascending aorta (h), as well as by a nearly longitudinal plane through the pulmonary trunk and the bifurcation of the pulmonary arteries (i). The red arrows show the position of the respective short-axis view in a M-mode sweep. Additional comments in the text. heads, as well as the chord strands ( Fig. 1.8d), through the mitral valve ( Fig. 1.8e), through the inter-atrial septum and the left ventricular outflow tract ( Fig. 1.8f), through the aortic valve ( Fig.1.8g), the aortic root and the proximal ascending aorta ( Fig. 1.8h), as well as by a nearly longitudinal plane through the pulmonary trunk and the bifurcation of the pulmonary arteries ( Fig. 1.8i). The acquisition of a correct M-mode sweep is performed within 6–12 cardiac cycles using the cursor in the centre line of all parasternal short-axis views by scanning through the left ventricle over the long axis of the left ventricle by tilting the transducer starting from the shortaxis view between the papillary muscles up to the cranial shortaxis view of the centrally intersected aortic valve and ascending aorta ( Fig. 1.8a). By deriving M-modes and M-mode sweeps in the short axis, it can always be checked whether the left heart is sliced exactly in its centre line or only a secant view of the left ventricle is documented. This fact favours the acquisition of M-modes using short-axis views instead of a long-axis view. The correct transducer position is documented in the M-mode sweep by a horizontal line between the border of the ventral septum and the border of the ventral ascending aorta. The alternative to document the correct transducer position in the long-axis view simultaneously to the short-axis views is only possible by biplane scanning. The problem of isolated short-axis views is the fact that the transducer position is too much lateral or caudal, which causes an oval conformation of the ventricular wall at the level of the left ventricle. The consequence for measurements of left ventricular dimensions and wall thicknesses is that the left ventricular cavity is measured too large and the ventricular wall is measured too thick ( Fig. 1.9). For training aspects and to document manual skills of targetoriented scanning, the correct acquisition of the M-mode sweep should be integrated into the educational process like a driver’s license for echocardiography. For clinical practice the correct M-mode sweep represents a characteristic profile of the individual human heart. According to European recommendations, however, it is not mandatory to acquire the M-mode sweep. The standard documentation includes only parasternal short-axis views at the midpapillary level, at the mitral valve level and at the aortic level. In all parasternal short-axis views the centre of the left ventricle or the aortic valve should be in the middle of the scanning sector. Near the transducer the parasternal short-axis view at the mid- papillary level ( Fig. 1.10a–d) shows the free right ventricular wall, the right ventricular cavity, all mid-segments of the left ventricular wall (near the transducer: anteroseptal—0°;
10 chapter 1 conventional echocardiography—basic principles Fig. 1.9 Illustration of potential errors of measurements for left ventricular dimensions and wall thicknesses due to non-standardization. If the parasternal transducer position is too caudal and/or too lateral, the aortic root drops down on the right side of the sector. This induces too large dimensions of the left ventricular cavity and of the wall thickness (left side—differences are displayed by the white arrows). Measurements using long-axis views can be performed using secant-like sectional planes which induce too small dimensions of the left ventricular cavity and too large dimensions of the wall thickness (right side—differences are displayed by the white arrows). Additional comments in the text. Fig. 1.10 The standardized parasternal short-axis view at the mid-papillary level. Additional comments in the text.