M mode lecture

Editor's Notes

• #12: RESOLUTION Resolution is the ability to distinguish between two objects in close proximity. It has at least two components: spatial and temporal Spatial resolution is defined as the smallest distance that two targets must be separated by for the system to distinguish between them. It, too, has two components: Axial resolution refers to the ability to differentiate two structures lying along the axis of the ultrasound beam (i.e., one behind the other), and lateral resolution refers to the ability to distinguish two reflectors that lie side by side relative to the beam . 9. • A third component of resolution is called contrast resolution. Contrast resolution refers to the ability to distinguish and to display different shades of gray within the image. This is important both for the accurate identification of borders and for the ability to display texture or detail within the tissues. 10. • Temporal resolution, or frame rate, refers to the ability of the system to accurately track moving targets over time. It is dependent on the amount of time required to complete a scan, which in turn is related to the speed of ultrasound and the depth of the image as well as the number of lines of information within the image. Generally, the greater the number of frames per unit of time, the smoother and more aesthetically pleasing the realtime image. Factors that reduce frame rate, such as increasing depth of field, will diminish temporal resolution. This is particularly important for structures with relatively high velocity, such as valves. Temporal resolution is the main reason that M-mode echocardiography is still a useful clinical tool
• #13: Standard views are often categorized as ‘‘long axis’’ or ‘‘short axis’’,11 and these are described in Table 1. General optimization techniques in two- dimensional (2D) imaging have been outlined previously for children.11 Several technical factors can influence the accuracy of spatial measure- ments: (1) axial resolution parallel to the ultrasound beam is superior to lateral resolution perpendicular to the beam, so views allowing for linear axial measurements are better than those for which only lateral mea- surements are available (parasternal views are better than apical views for the aortic annulus); (2) lateral resolution degrades with increasing distance secondary to beam spread, so the transducer should be posi- tioned as close as possible to a structure when only a lateral measure- ment is available; and (3) for large image depths, the ultrasound resolution often exceeds the pixel resolution of the image display, so de- creasing the image depth or magnifying the region of interest can often alleviate the limitations of the monitor resolution.
• #19: With m-mode echocardiography, the strength of the reflecting echo structure is demonstrated by the brightness of the image on the ultrasound screen. Time is represented in milliseconds; with respect to the cardiac cycle (systole and diastole), it is displayed on the horizontal axis. Distance of the reflecting cardiac structure is displayed on the vertical axis. EDV, End diastolic volume; IVS, interventricular septum; LV, left ventricle; PSAX, parasternal short axis; PW, posterior wall; RV, right ventricle.
• #20: With m-mode echocardiography, the strength of the reflecting echo structure is demonstrated by the brightness of the image on the ultrasound screen. Time is represented in milliseconds; with respect to the cardiac cycle (systole and diastole), it is displayed on the horizontal axis. Distance of the reflecting cardiac structure is displayed on the vertical axis. EDV, End diastolic volume; IVS, interventricular septum; LV, left ventricle; PSAX, parasternal short axis; PW, posterior wall; RV, right ventricle. Courtesy of Bernard E. Bulwer, MD, FASE.
• #23: This figure illustrates the most common m-mode measurements obtained from the parasternal long-axis view, including measurements of the aortic root, cusp separation of the aortic valve leaflets, mitral valve opening and closure, and left ventricular measurements including internal dimensions in diastole and systole and septal and posterior wall thickness in end-diastole. Courtesy of Bernard E. Bulwer, MD, FASE.
• #33: Quantitative assessment of each structure should be performed in multiple views, and orthogonal planes should be used for noncircular structures such as the atrioventricular (AV) valves. Early reports based on M-mode echocardiography recommended measurements from the leading edge of the near-field reflector to the leading edge of the far-field reflector,12 and normative data for the proximal aorta in adults have involved leading edge–to–leading edge measurements.13 However, current guidelines for chamber, annular, and vessel quanti- fication involve measurements of intraluminal dimensions from one inner edge to the opposite inner edge.14 In addition, published pediat- ric normative databases based on 2D echocardiography have used in- ner edge–to–inner edge measurements of vessel diameters.15-17 There are two important caveats with these measurements: vascular diameters should be perpendicular to the long axis of the vessel, and valvar and vascular diameters should be measured at the moment of maximum expansion. In other words, the inferior vena cava (IVC) diameter should be measured during exhalation, the mitral valve (MV) and tricuspid valve (TV) annular diameters in diastole, and the aortic valve (AoV) and pulmonary valve (PV) annular diameters as well as arterial diameters in systole. These recommendations are based on hemodynamic considerations, correspond to the methodologies used in published pediatric normative databases,15-17 and often differ from the quantification approach used in adults.1,13
• #34: M-mode echocardiography from a parasternal short-axis view showing the left ventricular cavity over the cardiac cycle (see ECG tracing) during systole and diastole. Abbreviations: IVS, interventricular septum; LV, left ventricle; LVEDD, left ventricle end-diastolic dimension; LVESD, left ventricle end-systolic dimension; LVPW, left ventricle posterior wall.
• #41: M-mode echocardiography obtained from a patient (left image) with normal left ventricular systolic function (FS = 34% and EF = 65%) and in a patient (right image) with dilated cardiomyopathy with severe left ventricular systolic dysfunction (FS = 8% and EF = 16%), LVEDD with green arrow and LVESD with blue arrow. Abbreviations: EF, ejection fraction; FS, fractional shortening; LVEDD, left ventricle end-diastolic dimension; LVESD, left ventricle end-systolic dimension.
• #44: In congenital heart disease, hypokinesia and dyskinesia of the interventricular septum occur in the presence of RV volume loading (e.g., large atrial septal defect). This can cause paradoxical septal motion with the septum moving away from the inferolateral wall during systole (Fig. 13.7). Paradoxical septal motion can also be present in the immediate postoperative (post bypass) period and in the presence of left bundle branch block where maximal systolic motion of the inferolateral wall and septum do not occur simultaneously.
• #45: In congenital heart disease, hypokinesia and dyskinesia of the interventricular septum occur in the presence of RV volume loading (e.g., large atrial septal defect). This can cause paradoxical septal motion with the septum moving away from the inferolateral wall during systole (Fig. 13.7). Paradoxical septal motion can also P.344 be present in the immediate postoperative (post bypass) period and in the presence of left bundle branch block where maximal systolic motion of the inferolateral wall and septum do not occur simultaneously.
• #57: Torn chordae amvl sec to bac endocarditis
• #68: Normal m-mode examination of the aortic root, aortic valve cusps, and left atrium. Measurements are obtained in the parasternal long-axis imaging plane. Note the holosystolic opening of the aortic valve cusps. By convention, m-mode measurements are made leading edge to leading edge, which differs from two-dimensional measurements. The m-mode cursor is placed perpendicular to the aortic valve leaflets. Ao, Aorta; AoR, aortic root; AV, aortic valve; Cusp, aortic leaflet separation; LA, left atrium; Root, aortic root.
• #70: M-mode examination of a bicuspid aortic valve obtained from the parasternal long-axis view. Note that in this case the closing of the valve is asymmetric (arrow) . If present, this may be an important clue in establishing the diagnosis of bicuspid aortic valve. In some situations, bicuspid aortic valves may open symmetrically. ant, Anterior; pos, posterior.
• #74: Figure 6 (A) Example of aortic regurgitation (AR) jet impinging on the anterior mitral valve leaflet with a reverse doming of the anterior mitral valve leaflet; (B) M-mode recording showing the fluttering motion of the anterior mitral leaflet in a patient with severe AR.
• #79: Normal m-mode examination of the pulmonic valve obtained from the parasternal short-axis view. This recording may also be obtained from the parasternal right ventricular outflow view and the main pulmonary artery and bifurcation view. Note the holosystolic opening of the cusps, similar to the aortic valve. Often, m-mode of the pulmonic valve only transects the right posterior leaflet. In this example, both the anterior and right posterior leaflets are transected. The m-mode letter designations for the pulmonic valve are as follows: (a), atrial contraction; (b), onset of ventricular systole; (c), ventricular ejection; (d), during ventricular ejection; (e), end of ventricular ejection.
• #86: Normal m-mode examination of the tricuspid valve obtained from the right ventricular inflow view. Usually only the anterior leaflet of the tricuspid valve is transected. RA, Right atrium; RV, right ventricle; TV, tricuspid valve. The m-mode letter designations for the tricuspid valve are as follows: (D), onset of diastole; (E), maximal opening of the leaflet; (F), most posterior position of the leaflet; (E–F slope), closing motion of the leaflet; (A), leaflet reopening with atrial contraction; (C), leaflet closure following ventricular systole. 
• #95:  collapse lasting more than 1/3 of systole is almost 100% sensitive and specific for tamponade. 
• #99: As we inhale, intrapleural pressure drops; there is a decrease in intrathoracic pressure that promotes venous inflow into the chest increasing right heart filling. However, this does not equate to an increased filling of the left heart during inspiration. This is because, as one inhales, the lungs expand and pull radial traction on the pulmonary vasculature increasing its capacitance, momentarily sequestering blood in the chest, and dropping blood flow to the left heart, decreasing pre-load and consequently cardiac output. The opposite occurs during expiration, thus systolic pressure normally decreases during inspiration and increases during expiration. 
• #106: During normal inspiration, both intrapleural and intrapericardial pressure fall in tandem to roughly the same degree, and this pressure drop is transmitted to the cardiac chambers. In constrictive pericarditis, the thickened pericardium will prevent the normal decrease in pressure from reaching the ventricles; thus, the normal drop in filling pressures will be blunted by the thick pericardium. This is important because in the pulmonary veins (which are extrapericardial), the pressure drop will be greater than left ventricular diastolic pressure drop (intrapericardial), and the gradient for left ventricular filling will be decreased, resulting in decreased left ventricular filling. The opposite occurs during expiration.
• #108: M-mode echocardiography shows the characteristic findings of septal bouncing ("double components"; arrow) with an increased pericardial thickness (arrowhead)
• #122: VP in a patient with DCM with flow propagation velocity <45 cm/s: impaired relaxation