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Clinical Echocardiography

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  1. Introduction to echocardiography and ultraound imaging
    12 Chapters
  2. Principles of hemodynamics
    5 Chapters
  3. The echocardiographic examination
    3 Chapters
  4. Left ventricular systolic function and contractility
    11 Chapters
  5. Left ventricular diastolic function
    3 Chapters
  6. Cardiomyopathies
    5 Chapters
  7. Valvular heart disease
    8 Chapters
  8. Miscellaneous conditions
    5 Chapters
  9. Pericardial disease
    2 Chapters

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  • Elspeth
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  • Hakan Ozerol
  • KIHYUN LEE
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    Standardized myocardial segmentation for echocardiography and cardiac imaging

    Cardiovascular imaging modalities have developed rapidly in the past few decades. The repertoire of available methods includes echocardiography, cardiovascular magnetic resonance (CMR), cardiac computed tomography (CT), single-photon emission computed tomography (SPECT), positron emission computed tomography (PET) and coronary angiography. These modalities aim to image the myocardium, assess wall motions and myocardial perfusion. However, due to varying strengths, limitations and clinical applications of these modalities, the definitions of cardiac planes, ventricular segments, and coronary arterial territories evolved differently. This resulted in difficulties when comparing examinations in clinical practice and research. Therefore, the American Heart Association (AHA) and the European Society for Cardiology (ESC) have established a standardization for ventricular segmentation, nomenclature and assignment of coronary arterial territory (Cerqueira et al).

    The purpose of standardizing ventricular segmentation, arterial territories and nomenclature is to develop consistency across examinations. This is of utmost importance when assessing myocardial structure, perfusion and wall motion.

    Cardiac planes

    All imaging modalities define, orient and display the heart using the long axis of the left ventricle and selected planes oriented at 90° angles relative to the long axis. With regards to echocardiography, this implies that the following planes are used: short axis, vertical long axis, and horizontal long axis. These three planes correspond to the parasternal short-axis view (PSAX), apical two-chamber view (A2C), and apical four-chamber view (A4C), respectively (Table 1).

    Table 1. Cardiac Planes in Echocardiography

    PlaneEchocardiographic view
    Short axisParasternal short-axis view (PSAX)
    Vertical long axisApical two-chamber view (A2C)
    Horizontal long axisApical four-chamber view (A4C)

    Segments of the left ventricle

    Based on anatomical landmarks and autopsy studies (Edwards et al), the left ventricle is divided into three equal parts along the long axis of the ventricle. This creates three circular sections of the left ventricle named basalmid-cavity, and apical. These three parts are divided into a total of 17 segments (Figure 1). Six basal segments, constituting 35% of myocardial mass; six mid-cavity segments, constituting 35% of myocardial mass and 5 apical segments, constituting 30% of myocardial mass. The 17-segment model provides the best agreement with anatomic data, as compared with other segmentation models.

    Figure 1. Standardized myocardial segmentation and nomenclature for echocardiography. The left ventricle is divided into 17 segments for 2D echocardiography. One can identify these segments in multiple views.
    Figure 1. Standardized myocardial segmentation and nomenclature for echocardiography. The left ventricle is divided into 17 segments for 2D echocardiography. One can identify these segments in multiple views.

    The basal part is divided into six segments of 60° each. The segments along the circumference are basal anteriorbasal anteroseptalbasal inferoseptalbasal inferiorbasal inferolateral, and basal anterolateral. The mid-cavity part is also divided into six 60° segments (mid anteriormid anteroseptalmid inferoseptalmid inferiormid inferolateral, and mid anterolateral). The apical part is divided into four 90° segments (apical anteriorapical septalapical inferior, and apical lateral) and the apex (Table 2).

    Table 2. The 17 segments of the left ventricle

     Basal Segments Mid-cavity Segments Apical Segments
    1.basal anterior7.mid anterior13.apical anterior
    2.basal anteroseptal8.mid anteroseptal14.apical septal
    3.basal inferoseptal9.mid inferoseptal15.apical inferior
    4.basal inferior10.mid inferior16.apical lateral
    5.basal inferolateral11.mid inferolateral17.apex
    6.basal anterolateral12.mid anterolateral  

    These 17 segments can be arranged as a polar (bull’s-eye) plot with the apex in the center, the four apical segments as the first ring, the six mid-cavity segments as the second ring, and the six basal segments as the outer ring (Figure 2).

    Figure 2. Display, on a circumferential polar plot, of the 17 myocardial segments and the recommended nomenclature for tomographic imaging of the heart.
    Figure 2. Circumferential polar plot of the 17 myocardial segments and the recommended nomenclature for tomographic imaging of the heart.

    The attachment of the right ventricular wall to the left ventricle is used to identify and separate the septum from the left ventricular anterior and inferior free walls.

    Figure 3. Assignment of the 17 myocardial segments to the territories of the left anterior descending (LAD), right coronary artery (RCA), and the left circumflex coronary artery (LCX).
    Figure 3. Assignment of the 17 myocardial segments to the territories of the left anterior descending (LAD), right coronary artery (RCA), and the left circumflex coronary artery (LCX).

    References

    Cerqueira et al: Standardized Myocardial Segmentation and Nomenclature for Tomographic Imaging of the Heart A Statement for Healthcare Professionals From the Cardiac Imaging Committee of the Council on Clinical Cardiology of the American Heart Association (2002).

    Edwards et al: Standardized nomenclature and anatomic basis for regional tomographic analysis of the heart. Mayo Clin Proc. 1981;56:479–497.

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