Emergency physicians must often manage critically ill patients whose hemodynamic status is unclear, especially early in the course of their disease. Correct and timely diagnosis of the prevailing hemodynamic process is of utmost importance, and the physical exam and vital signs alone are often unreliable.1 Moreover, congestive heart failure is extremely prevalent in the emergency department population, and more than half of patients with moderate to severe systolic dysfunction have never been diagnosed with heart failure.2
Bedside echocardiography by the emergency physician offers a rapid, noninvasive, and inexpensive method to determine the role that the patient’s systolic cardiac function may be playing in the disease process. Besides the diagnosis of heart failure, assessment of left ventricular (LV) function can help distinguish between cardiac and other etiologies of the undifferentiated hypotension or shock state. Multiple studies have demonstrated that emergency physicians with focused training in transthoracic echocardiography can accurately determine left ventricular ejection fraction (LVEF) in critically ill patients.3
In combination with other common emergency department ultrasound applications, such as evaluation of the inferior vena cava (IVC) as a marker of intravascular volume status, and evaluation of the lungs and pleura, assessment of LVEF can be a valuable tool in the management of critically ill patients.
Performing the Ultrasound
Place the patient in the supine position with the head of the bed as flat as the patient can tolerate. A low-frequency probe (3.5-5 MHz), such as a phased array or curvilinear probe, should be selected.
Obtaining the Cardiac Windows
There are four primary cardiac views or “windows” that can be used to obtain an adequate view of the left ventricle: subxiphoid four-chamber, parasternal long axis, parasternal short axis, and apical four-chamber. Of these, the parasternal views are preferred for the assessment of LVEF by most users.3
This view is perhaps the most familiar to emergency physicians as it is the view most often used in the focused assessment with sonography for trauma (FAST) exam. To obtain this view, the transducer is placed on the abdomen just inferior to the xiphoid process, held at a shallow, 15-degree angle to the surface of the abdomen, with the probe footprint angled toward the left shoulder. The probe marker is directed to the patient’s right. The depth should then be adjusted to include the posterior surface of the pericardium in the inferior portion of the image. In this view, the left ventricle is the larger, thicker-walled chamber in the right lower part of the image.
Parasternal Long Axis
In this view, the transducer is placed perpendicular to the chest wall at the third or fourth intercostal space just to the left of the sternal border, with the probe marker directed to the patient’s left hip. The left ventricle will be seen as the thick-walled, oval-shaped chamber in the left lower part of the resulting image.
Parasternal Short Axis
Once the parasternal long axis view is obtained, the short axis view can be visualized by rotating the probe 90 degrees clockwise, directing the probe marker toward the patient’s right hip. The left ventricle will appear in cross section as a thick-walled, roughly circular structure on the right side of the image. By sweeping the transducer from base to apex, several different short axis views may be obtained, including at the level of the papillary muscles, chodae tendinae, and mitral valve.
Apical Four Chamber
To obtain this view, the transducer should be placed at the apex of the heart, where the point of maximal impulse (PMI) may be felt, in the midclavicular line, fifth intercostal space or lower. The probe footprint should be angled toward the right shoulder with the probe marker directed toward the patient’s right. Some rotation or translation of the transducer may be required for all four chambers to appear in the image. The left ventricle will appear as the chamber in the upper right of the image.