Maximizing Image Quality
Because of the complex shape and motion of the heart, the number of structures to be identified, and patient factors such as body habitus, adequate cardiac views can sometimes be difficult to obtain. The following techniques can be used to improve the quality of the images obtained:
Explore This IssueACEP News: Vol 31 – No 10 – October 2012
PIMove the transducer in a coordinated and systematic fashion, using the four main types of motions: sliding side to side in the direction of the probe marker, fanning in the short axis of the transducer, twisting or rotating, and angling the probe in relation to the surface of the chest wall.
- Hold the probe as close to the footprint as possible and place the fifth digit against the chest wall for stability.
- Use an adequate amount of conducting gel.
- Optimize depth and gain settings.
- Moving the patient into a left lateral decubitus position can help bring mediastinal structures closer to the anterior chest wall.
Evaluation and Interpretation of Left Ventricular Systolic Function Many methods exist for echocardiographic assessment of LVEF, ranging from simple visual estimation to complex methods involving multiple measurements and biometric software calculations.
The fastest and most practical method for emergency physicians to estimate LVEF is a visual assessment. Typically, this assessment is separated into three categories: hyperdynamic or normal (LVEF greater than 50%), moderate dysfunction (LVEF 30%-50%), and severe dysfunction (LVEF less than 30%).4 A subjective visual assessment should be made of the degree of contraction between systole and diastole, with the heart evaluated in at least two views. All visualized walls of the ventricle should move symmetrically and vigorously toward the center of the chamber during systole, and the walls should thicken as the muscle contracts. This method is somewhat operator-dependent; however, even with only several hours of training, emergency physicians have been shown to be able to make assessments that correlate well with echocardiography performed by cardiologists. The best way to become more proficient is to practice at the bedside, especially in patients known to have normal or depressed cardiac function.