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7: TRANSTHORACIC ECHOCARDIOGRAPHY: IMAGE ACQUISITION

Jose Cardenas-Garcia; Paul H. Mayo

Introduction

Transthoracic echocardiography (TTE) has major application in the intensive care unit (ICU). Proficiency in TTE allows the intensivist to determine the diagnosis of cardiopulmonary failure, develop management strategies, and follow the results of therapeutic interventions with serial examinations. By definition, critical care echocardiography (CCE) is performed by the intensivist in the ICU. The clinician personally acquires and interprets the image at the bedside and uses the information to immediately guide management. It follows that the intensivist must have a high level of skill in image acquisition that requires knowledge of ultrasound physics, machine controls, and transducer manipulation. This chapter reviews important elements of image acquisition with emphasis on transducer manipulation. The reader is referred to Chapters 2 and 3 for a comprehensive discussion of physics and machine controls.

Basic and Advanced CCE

Proficiency in CCE can be separated into basic and advanced levels. Basic CCE is performed as a goal-directed examination using a limited number of views (see Chapter 6 and Table 7-1). It is designed to answer specific clinical questions at the bedside. Proficiency in advanced CCE requires a high level of skill in all aspects of image interpretation and acquisition. Advanced CCE allows a comprehensive evaluation of cardiac anatomy and function using two-dimensional (2D) imaging and Doppler echocardiography. Both basic and advanced CCE require skill in image acquisition.

Table 7-1Views of the Basic Critical Care Echocardiography Exam
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Table 7-1 Views of the Basic Critical Care Echocardiography Exam
image image
View Transducer Placement Transducer Index Mark
Parasternal long axis Left 3rd, 4th, or 5th intercostal space adjacent to sternum Pointing to the patient’s right shoulder
Parasternal short axis From long-axis view rotate transducer 90 degrees clockwise Pointing toward patient’s left shoulder
Apical four chamber Anatomic apex of the left ventricle Pointing to 3 to 4 o’clock position
Subcostal four chamber Just below the xiphoid process Pointing to 3 to 4 o’clock position
Inferior vena cava From subcostal four-chamber view, rotate transducer counter clockwise Pointing to 12 o’clock position followed by angulation of the tomographic plane to the right

Figures reproduced with permission from Ma et al: Ma and Mateer’s Emergency Ultrasound, 3rd ed. McGraw-Hill 2014.

Technical Issues

The performance of TTE has challenges that relate to the fact that the heart is surrounded by lung and ribs, both of which block ultrasound transmission. Since ribs block ultrasound, cardiac transducers are designed with a small footprint to scan through the rib interspace. During scanning, left arm abduction may increase the size of the interspace. Aerated lung also blocks ultrasound, so that placing the patient in the left lateral decubitus position may be helpful. In this position, the heart is moved from behind the sternum and the left lung moves laterally, thus exposing more of the heart ...

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