Despite its overwhelming popularity and favorable influence on perioperative clinical decision making and outcome, the transesophageal echocardiographic (TEE) approach to a comprehensive echocardiographic examination may be limited by impaired imaging of the distal ascending aorta and aortic arch, difficulty in advancing the probe within the esophagus in some patients, and contraindications for probe placement in those with gastroesophageal pathology. Furthermore, TEE may be rarely associated with perioperative morbidity from oropharyngeal and gastroesophageal injury.1,2 In recognition of these potential limitations, the Society of Cardiovascular Anesthesiologists (SCA), American Society of Anesthesiologists (ASA), and American Society of Echocardiography (ASE) currently recommend that advanced intraoperative ultrasonographers also become familiar with epicardial echocardiography and epiaortic ultrasound in addition to TEE.3,4 The ASE and SCA have subsequently published guidelines specifically focused on acquisition techniques and indications for both epicardial echocardiography and epiaortic ultrasonography.5,6 Thus, while TEE remains the most frequently used intraoperative tool for imaging cardiac and intrathoracic vascular structures, it is imperative for an experienced intraoperative ultrasonogapher to also be familiar with other imaging modalities including epicardial echocardiographic and epiaortic ultrasound techniques in order to conduct a comprehensive perioperative echocardiographic examination.
Epicardial and epiaortic imaging are performed by placing the ultrasound transducer on the surface of the heart or aorta, respectively, to acquire two-dimensional (2D), and color-flow and spectral Doppler images in multiple planes. Due to the proximity of the probe to the heart, these techniques typically use higher frequency probes (5 to 12 MHz). Epicardial and epiaortic imaging require adherence to strict sterile technique while manipulating the probe within the operative field. Consequently, these images may only be obtained by an operator who is wearing a sterile gown and gloves. The probe is placed in a sterile sheath along with sterile acoustic gel or saline in order to optimize acoustic transmission. Warm sterile saline can be poured into the mediastinal cavity to further enhance acoustic transmission from the probe to the cardiac or aortic surface. Additional manipulation of depth, transmit focus, gain, and transducer frequency may be required to optimize the image.
The ASE/SCA guidelines currently recommend that the following seven epicardial echocardiographic imaging planes be obtained to perform a comprehensive 2D and Doppler echocardiographic evaluation.5 However, the guidelines also recognize that individual patient characteristics, anatomic variations, or time constraints may limit the ability to obtain every component of the recommended comprehensive epicardial echocardiographic examination. Furthermore, modification of the recommended views may be required to obtain a more detailed interrogation of specific anatomy or pathology.
The ultrasound transducer is placed on the aortic root above the aortic valve (AV) annulus, with the ultrasound beam directed towards the AV in a short-axis (SAX) orientation to obtain the epicardial AV SAX view (Figure 20–1). Appropriate transducer alignment requires up to 30° of clockwise rotation with the orientation marker (indentation) on the transducer directed toward the patient’s left.
Figure 20-1.
Epicardial aortic valve short-axis view. When the orientation marker (indentation) on the transducer is pointed towards the patient’s left, the right coronary cusp (R) will be at the top of the monitor screen, the left coronary cusp (L) is on the bottom left, and the noncoronary cusp (N) is on the right side of the screen adjacent to the interatrial septum.
The epicardial aortic valve long-axis (LAX) view is obtained from the epicardial AV SAX view by positioning the probe upward along the right-side surface of the aortic root with the orientation marker slightly rotated clockwise and directed toward the patient’s left. The ultrasound beam is directed posteriorly to visualize the left ventricular outflow tract (LVOT) and AV (Figure 20–2).
Figure 20-2.
Epicardial aortic valve long-axis view. This view is optimal for measuring left ventricular outflow tract (LVOT), aortic annulus, and sinotubular junction diameters. Long-axis orientation permits continuous-wave and pulsed-wave Doppler ultrasound beam assessment of pressure gradients across the aortic valve (AV) and LVOT. Similarly, color-flow Doppler interrogation of the AV can be utilized to grade the degree of aortic insufficiency. (AO, proximal ascending aorta.)
The epicardial left ventricular (LV) basal SAX view is obtained from the epicardial AV SAX position by moving the probe towards the apex along the right ventricle (RV) with the transducer orientation marker again directed towards the patient’s left (Figure 20–3). In this view, the RV is on top in the near field, while the LV is below in the far field of the ultrasound beam sector. The mitral valve (MV) is visualized including both leaflets forming the classic “fish mouth” appearance, with the anterior leaflet on the top of the screen and the posterior leaflet underneath. The anterolateral commissure lies on the right, and the posteromedial commissure on the left of the screen.
Figure 20-3.
Epicardial left ventricle basal short-axis view. The epicardial left ventricle (LV) basal short-axis (SAX) view can be used to evaluate the mitral valve annulus and both anterior (AL) and posterior (PL) leaflets. Color-flow Doppler can also be used to determine the origin of mitral regurgitation jets and obtain an estimate of the regurgitant orifice area. Finally, basal LV regional wall motion can be assessed utilizing the same LV wall orientation as seen in the epicardial left ventricle mid SAX. (ALC, anterolateral commissure; PMC, posteromedial commissure; RV, right ventricle.)
Angulating the probe inferiorly and to the left from the epicardial LV basal SAX view in an apical direction along the RV myocardial surface allows visualization of the RV and LV in SAX at the level of the papillary muscles (Figure 20–4). When the transducer orientation marker faces the patient’s left, the anterolateral papillary muscle will be on the right side of the display and the posteriomedial papillary muscle will be on the left side. The septal wall of the LV is displayed on the left followed by the anterior, lateral, and inferior walls, respectively, in a clockwise rotation. The RV can be evaluated similarly by moving the transducer further towards the patient’s right.
