\begin{figure}
\centering
\begin{subfigure}{0.45\textwidth}
\centering
\includegraphics{figure_5_1.pdf}
\end{subfigure}
\begin{subfigure}{0.45\textwidth}
\centering
\includegraphics{figure_5_2.pdf}
\end{subfigure}
\caption{A transesophageal echocardiogram before (left) and after (right) an IV bolus injection of a transpulmonary contrast agent to confirm that the questionable mass in the left atrial appendage (LAA) was just spontaneous contrast. The IV microbubbles completely fill the LAA (right). (See Video 10; available at www.onlinejase.com.)}
\label{fig:figure_5}
\end{figure}

atrium (Table \ref{tab:table_3}). It is important that release of a Valsalva maneuver or coughing (to transiently increase right atrial pressure) occur when the saline contrast bolus arrives in the right atrium. It would be optimal for the sonographer to have $\geq$20-gauge cannula access in a good forearm or antecubital vein (preferably on the patient’s right side if the patient is lying on the left side for imaging). Optimal visualization of the interatrial septum (via either a foreshortened apical window or subxiphoid window) and use of tissue-harmonic imaging to optimize bubble detection are key features to improving the sensitivity to shunt detection.

Both right- and left-arm saline contrast injections should be used whenever a persistent left-sided superior vena cava or unroofed coronary sinus is suspected. Although femoral venous injections improve flow directed to the septum, these are too invasive for routine sonographer use in detecting a PFO.\cite{32} Sonographers should also be aware that typical intracardiac shunts (via the interatrial or interventricular septum) are usually seen within the first three beats of right atrial opacification, while pulmonary arteriovenous shunts are at least five beats after right atrial opacification. However, it is important to note that saline contrast may appear sooner with pulmonary arteriovenous shunts in high-output states, and saline contrast across a PFO may occur later than three beats if there is delayed coughing or Valsalva maneuvers. Also, false-negative saline contrast studies can occur if the interatrial septum is persistently bowed toward the right atrium during agitated saline injection, as a PFO can be held closed with the septum in this position. If there is still suspicion that a PFO exists after negative results, a repeat saline contrast injection should be performed using a blood-saline-air mixture or a more appropriately timed Valsalva or cough maneuver to ensure that the results are truly negative. Universal precautions should be adhered to with this technique to avoid blood-borne pathogen exposure. With TEE, direct visualization of the septum secundum and septum primum is recommended during saline contrast injection, to document the location and size of any right-to-left shunt. Image acquisition should be timed to begin just before the appearance of saline contrast in the right atrium and continue for at least 10 cardiac cycles after contrast appearance.

\section{VII. FUTURE CONTRAST DEVELOPMENTS FOR THE SONOGRAPHER}

This update for UCA use is designed to assist all sonographers in the optimal use of UCAs with currently available ultrasound scanner software. However, approval is being sought in the United States for other UCAs, such as SonoVue, which has been approved for several years in Europe. This agent will have unique features that may require updates, should it be approved. SonoVue is a lipid-encapsulated sulfur hexafluoride–containing microbubble that also is administered as an infusion or as small boluses during real-time very low MI imaging.\cite{33}

Furthermore, three-dimensional imaging is being used more for valvular disease and quantification of LV and right ventricular ejection fractions. Real-time three-dimensional echocardiography has been used to improve regional wall motion analysis during resting and stress echocardiography.\cite{34} Recent clinical studies have demonstrated a potential role for UCAs in improving LV regional wall motion and ejection fraction assessments.\cite{35,36} However, contrast use for three-dimensional acquisitions will require optimization of settings similar to what has been used for two-dimensional transducers, with greater attention to minimizing LV apical swirling. To date, real-time very low MI software is not routinely available with three-dimensional scanners. The writing group recommends that this software be implemented in all three-dimensional packages to achieve optimal LVO and perfusion assessments in all 17 segments.

With regard to automated border detection algorithms, they are not currently designed for detecting a bright cavity border with contrast, but the writing group strongly recommends that manufacturers of automated border detection software redesign their algorithms for contrast media, as this may further improve the accuracy and applicability of this software.

Use of transpulmonary contrast agents during TEE has recently been described for better delineation of a left atrial appendage thrombus and differentiating between spontaneous contrast and thrombus (Figure \ref{fig:figure_5}). Normal results on TEE when using transpulmonary contrast to exclude a thrombus before cardioversion for atrial fibrillation have been associated with a lower risk for stroke or systemic embolization.\cite{37} Modifications in TEE transducer design to include very low MI real-time sequences may further improve transpulmonary contrast use during TEE.

In the area of vascular imaging, contrast may also prove useful in improving carotid plaque visualization (especially soft plaque) and visualization of the vasa vasorum. It may also be useful for the detection of endoleaks after stent graft placement in abdominal aortic aneurysms.\cite{38} In this area, as well as in other peripheral vascular applications, the writing group recommends the development of specific indications for when they should be used, as well as imaging protocols.

\section{VIII. RECOMMENDED INITIATIVES}

The writing group recommends that consideration be given to programs and initiatives that will help sonographers improve the use of contrast in critical care settings. The beneficial effects of contrast are