Contrast echocardiography in cardiac masses

Key points

• Newer echocardiographic techniques may provide incremental information to help characterize cardiac masses.

• Myocardial contrast echocardiography allows an improved definition of intracavity structures and an assessment of vascularity.

• The difference in the perfusion of cardiac masses may help distinguish between vascular tumors and nonvascular tumors or thrombi.

• Contrast agents improve the opacification of the cardiac cavities and the delineation of the endocardial borders in addition to helping perfusion evaluation.

Contrast echocardiography is based on the intravenous injection of microbubbles that act as blood flow tracers and increase ultrasound signals. Contrast agents enhance the opacification of the cardiac cavities and the delineation of the endocardial borders in addition to helping perfusion evaluation. Contrast echocardiography has recently been used to evaluate cardiac masses and shown to be valuable in the diagnosis of the different types of cardiac masses ( Table 10.1 ).

Transthoracic echocardiography remains a versatile and globally the most common cardiac diagnostic imaging modality. Nonetheless, there is still a need to improve image resolution when acoustic windows are limited and endocardial definition suboptimal, which may result in potentially missed or incorrect diagnoses and consequential adverse outcomes. Microbubble ultrasound contrast is now regarded as an essential tool in the day-to-day practice of the clinical echocardiography laboratory to overcome some of these limitations. The contemporary approved and appropriate indications for the use of ultrasound contrast agents include left ventricular opacification and improvement of endocardial border detection . Currently, the validity of this method for the differential diagnosis of cardiac masses is argued based on their vascular pattern analysis. Intracardiac masses can be a normal variant of cardiac structures such as false chordae, accessory papillary muscles, or prominent trabeculations or can be pathological such as thrombi, vegetations, and tumors. Any suspicious cardiac mass, when not evident on baseline images, can be confirmed or refuted after the injection of the intravenous contrast for a better delineation of the structures. As is the case with unenhanced echocardiography, off-axis images and longer loop acquisitions may be required to identify and characterize intracardiac thrombi or masses with the general understanding that benign tumors have lower vascularization, thrombi are avascular, and malignant tumors are highly irrigated.

Despite advances in other imaging modalities, echocardiography remains the initial tool for diagnosis and risk stratification in patients predisposed to developing cardiac thrombi. The use of ultrasound-enhancing agents facilitates left ventricular thrombus detection by providing opacification within the cardiac chambers so that the filling defect of an intracardiac thrombus can be demonstrated. Ultrasound-enhancing agents can increase the sensitivity for the detection of left ventricular thrombi, improve the negative predictive value, and increase the certainty that a thrombus is truly absent when it is not visualized on echocardiography. It is recommended that nontraditional “off-axis” views be obtained in order to visualize the entire apex while imaging with ultrasound-enhancing agents. While delayed enhancement cardiac magnetic resonance (CMR) has the highest sensitivity and specificity for the detection of left ventricular thrombi, performing echocardiography with an ultrasound-enhancing agent is a more clinically feasible initial test. Nevertheless, CMR should be considered when echocardiography with ultrasound-enhancing agents fails to detect an intracardiac thrombus but clinical suspicion persists ( Figs. 10.2 and 10.3 ).

By differentiating malignant/highly vascular tumors from benign tumors and thrombi, echocardiographic contrast perfusion imaging may aid in the early identification and appropriate treatment of cardiac masses. A complete lack of enhancement, signaling thrombi, would be an indication for anticoagulation with a follow-up imaging study to evaluate resolution and could prevent unnecessary cardiac surgery. A further application is the detection and evaluation of malignant or highly vascular tumors or metastases within the myocardium that do not protrude into cardiac cavities. The objective hyperenhancement of an area of the myocardium may raise the suspicion of intramyocardial tumor infiltration ( Fig. 10.4 ).

Most malignant tumors have abnormal neovascularization with high blood supplies, which explains why these tumors present an enhancement of the mass by the contrast agent. Myxomas have poor blood supplies, with partial enhancement by the contrast agent. Finally, thrombi are avascular, with no enhancement. Thus, regardless of the experience of the physician, contrast echocardiography is highly reproducible and confers an accurate diagnosis with a simple and fast injection of the contrast agent, which permits heart opacification ( Fig. 10.5 ).