Contrast Echocardiography for Right-Sided Heart Conditions

Abstract

Contrast echocardiography is recognized to be a safe, effective technique for evaluating the endocardial border and left ventricular function in patients who have suboptimal noncontrast echocardiograms. However, its use in diagnosing right-heart conditions is less well established. Herein, we report our experience with the use of contrast echocardiography for diagnosing 3 distinct right-sided heart conditions (hypokinesis of the right ventricular free wall, severe tricuspid regurgitation, and cardiac tamponade) in patients who had suboptimal echocardiograms. Further studies should be done to validate the use of contrast echocardiography for diagnosing right-heart conditions.

Contrast echocardiography (CE) is a safe, effective technique for evaluating the endocardial border and left ventricular function in patients with sub-optimal noncontrast echocardiograms.^1,2 It is also a sensitive means of diagnosing coronary artery disease by detecting wall-motion abnormalities during stress echocardiography^3–5 Although CE is well validated for use in these settings, it is less well established for the study of right-sided heart conditions. A few investigators have suggested that CE be used for diagnosing tricuspid regurgitation (TR) or measuring right ventricular (RV) volumes using Simpson's formula,⁶ but it is not widely used for these purposes. In this article, we report the cases of 3 patients that illustrate our experience with the use of CE for diagnosing 3 distinct right-sided heart conditions in patients who had suboptimal echocardiograms. We also review the medical literature on the use of contrast agents in the diagnosis of right-sided heart conditions.

Case Reports

Patient 1: Evaluation of Right Ventricular Function

A 47-year-old man presented with chest pain, shortness of breath, and left-leg swelling of 3 days' duration. His symptoms had all developed after a recent hunting trip. One year earlier, he had experienced deep vein thrombosis in his left arm, for which he had completed a 4-month course of warfarin therapy. During the current admission, duplex ultrasonography showed extensive deep vein thrombosis that involved the femoral, popliteal, tibial, and peroneal veins. A ventilation/perfusion scan showed multiple segmental and subsegmental areas of decreased perfusion that were highly consistent with pulmonary embolism. Computed tomography of the chest, performed in accordance with pulmonary embolism protocol,⁷ showed a large “saddle” thrombus that involved the central portion of the left and right pulmonary arteries, without marked dilation of the right ventricle. A 2-dimensional (2D) echocardiogram with Doppler imaging showed a small left ventricle with normal function and systolic pulmonary artery pressure of 40 to 45 mmHg. However, RV dimensions and function were difficult to evaluate because of poor endocardial definition (Fig. 1A). Contrast echocardiography, using perflutren lipid microspheres (Definity,® Bristol-Myers Squibb Medical Imaging, Inc.; Billerica, Mass), was better able to evaluate these variables in order to rule out RV compromise by a massive pulmonary embolism. Contrast echocardiography showed a moderately enlarged RV with severely depressed systolic function. Moreover, McConnell's sign was positive, which indicated hypokinesis of the RV free wall with sparing of the RV apex (Fig. 1B). This sign has a 77% sensitivity and 94% specificity for diagnosing acute pulmonary embolism, with a positive predictive value of 71% and a negative predictive value of 96%.⁸ Because of his severe RV compromise, the patient was given thrombolytic a gents, and an inferior vena cava filter was implanted. In this case, studies such as computed tomography or noncontrast echocardiography were not able to adequately diagnose RV compromise. Contrast echocardiography aided us in making a therapeutic decision by clearly showing RV compromise.

Fig 1 Patient 1. A) Two-dimensional Doppler flow echocardiography (4-chamber view) provides poor visualization of the right ventricle. B) Contrast echocardiogram shows McConnell's sign. Arrow points to sparing of the right ventricular apex.

Real-time motion images are available at texasheart.org/journal

Patient 2: Diagnosis of Severe Tricuspid Regurgitation

A 59-year-old woman with known arrythmogenic RV dysplasia underwent 2D echocardiography with Doppler imaging to evaluate her eligibility for a cardiac transplant. The echocardiogram showed a severely dilated RV and right atrium and severely depressed RV systolic function. Spontaneous echocardiographic contrast was noted in the RV. Color and spectral Doppler techniques were indeterminate for TR severity. The TR velocity, by a well-placed interrogating beam, showed a well-defined but unusually low peak flow velocity at <0.3 m/sec; and color Doppler seemed to indicate almost laminar transannular flow (Fig. 2A). Other features of the examination suggested severe TR (markedly paradoxical ventricular septal motion with severe RV and tricuspid valve annular dilatation). We performed a right ventricular CE study (Definity) to rule out suspected RV thrombus that could be missed due to heavy RV spontaneous echocardiographic contrast (“smoke”). In an incidental but apparently diagnostic finding, subcostal views with CE showed dramatic, pulsatile systolic flow reversal into the hepatic veins and hepatic vasculature (Fig. 2B). Similar findings by use of intravenous saline contrast have previously been reported to be a specific sign of severe TR.⁹ The very low TR jet velocity on surface Doppler echocardiography may then be explained by a very large tricuspid valve regurgitant orifice and low cardiac output. The severe TR was not effectively labeled by either color or spectral Doppler, likely due to a small regurgitant volume (the consequence of a low-output state) despite a probable high regurgitant fraction. Although it was not acquired with contrast, the color or spectral Doppler signal would not, we think, have been greatly enhanced by contrast, due to the very low velocity of the regurgitant flow. This case is interesting, because the usual signs of severe TR were not evident on color or spectral Doppler. While other methods may suffice in diagnosing severe TR, CE may support the diagnosis of severe TR in low-output states, as was shown in this patient.

Fig. 2A Patient 2. Top: Two-dimensional echocardiogram with color Doppler image of the right ventricular inflow tract shows only mild tricuspid regurgitation (arrow). Bottom: Apical 4-chamber view (upper panel) with color Doppler shows almost trans annular flow. Spectral Doppler (lower panel) indicates low velocity of tricuspid regurgitation jet.

RA = right atrium; RV = right ventricle

Real-time motion images are available at texasheart.org/journal

Fig. 2B Patient 2. Contrast echocardiography with Definity® microspheres shows reversal of contrast material in the hepatic vein.

RA = right atrium; RV = right ventricle

Real-time motion images are available at texasheart.org/journal

Patient 3: Diagnosis of Cardiac Tamponade

A 75-year-old man underwent emergent coronary artery bypass surgery at our hospital after he presented with an acute myocardial infarction. During surgery, he was also found to have an aortic root dissection, so he under-went aortic root and aortic valve replacement in addition to coronary artery bypass surgery. Postoperatively, his condition remained hemodynamically unstable with unexplained hypotension. A 2D echocardiographic examination was performed to evaluate his left ventricular function and to rule out cardiac tamponade. In this critically ill, intubated patient, standard surface imaging was inadequate for evaluating pericardial effusion and RV size and function (Fig. 3A). Intravenous Definity was given in the hope of making an expedient diagnosis and avoiding transesophageal echocardiography. Contrast echocardiography markedly improved visualization of the RV. Moreover, CE showed a large pericardial hematoma that compressed the right atrium and RV and displayed the physiologic characteristics of tamponade (Fig. 3B). The patient was emergently taken to the operating room for evacuation of the hematoma, without the additional delay that would have been needed for trans-esophageal echocardiographic confirmation.

Fig. 3 Patient 3. A) Two-dimensional echocardiography (subcostal view) shows poor visualization of the right ventricle. Arrow indicates hematoma; arrowhead points to right ventricular free wall. B) Contrast echocardiogram in the same view shows collapse of the right ventricle.

Real-time motion images are available at texasheart.org/journal

Discussion

The development of echocardiographic contrast media has improved left ventricular endocardial definition in a variety of clinical circumstances.^4,10,11 Contrast echocardiography with inotropic agents such as dobutamine is also an extremely sensitive tool for diagnosing coronary artery disease by detecting subtle changes in wall motion with inotropic stimulation.^3,5,12 Moreover, studies are ongoing to evaluate the use of microbubbles for delivering targeted therapy to the myocardium. Other investigators have used contrast media to better distinguish the pericardial space from the RV space during pericardiocentesis.¹³

Two-dimensional echocardiography with color and spectral Doppler imaging is an extremely useful tool for studying RV anatomy and function. However, a major shortcoming of echocardiography is its frequent inability to acquire enough diagnostic information, especially in patients who are obese, have chronic obstructive pulmonary disease, are intubated, or have otherwise poor echocardiographic imaging windows. In these patients, CE can potentially improve visualization of right-sided cardiac structures, much as it does on the left side of the heart.

Concerning Patient 2 (severe TR): Previous studies of CE for right-sided heart lesions predate the development of new contrast media such as Definity and perflutren protein-type A microspheres (Optison®, Molecular Biosystems, Inc., part of Alliance Pharmaceutical Corp.; San Diego, Calif).¹⁴ Studies of agitated saline and indocyanine green as echocardiographic contrast media have given conflicting evidence regarding their usefulness, compared with that of color and spectral Doppler methods. Most of these studies have been done to determine the usefulness of an intravascular contrast agent for diagnosing TR. When Lieppe and coworkers⁹ used normal saline and indocyanine dye in a comparison of CE diagnosis of TR with clinical and angiographic diagnosis, they found CE to be 100% specific. Later, Meltzer and associates¹⁵ used 5% dextrose in saline (with 100% carbon dioxide) as the contrast medium in comparing CE diagnosis of TR with clinical and angiographic diagnosis in 62 patients. These researchers found that M-mode examination through the inferior vena cava was a sensitive and specific method for diagnosing TR. Curtius and colleagues¹⁶ compared contrast and Doppler echocardiography with RV angiography in 68 patients. The sensitivity and specificity, respectively, were 82% and 100% for CE and 91% and 86% for Doppler methods. Brown and Anderson¹⁷ reported that the contrast agent may appear in the inferior vena cava and hepatic veins in many subjects in whom TR is unlikely on clinical grounds. However, these investigators did not compare CE with either color Doppler echocardiography or RV angiography.

Generally, agitated saline has been the preferred medium for enhancing the visualization of right-sided cardiac structures and intracardiac structures. However, under certain conditions, such as diagnosis of TR, the use of agitated saline has not been convincingly shown to be better than color or spectral Doppler (see above). In all 3 cases described here, echocardiographic contrast media were used primarily to enhance endocardial definition for the purpose of evaluating left ventricular function. Incidentally, in all 3 cases, administration of these media enhanced the visualization of right-sided conditions. Agitated saline was not administered in these cases. To our knowledge, no existing studies compare agitated saline with the newer media in the diagnosis of these conditions.

We have shown how CE may be used to delineate right-sided cardiac abnormalities involving 3 distinct clinical settings. In our patients, either the RV was exceedingly large (patients 1 and 2) or exceedingly small (patient 3); and this may have contributed to the ability of CE to delineate RV endocardium and provide additional clinically useful information. We believe that in certain clinical circumstances, such as those that we have presented above, CE can be of substantial clinical usefulness. Further studies are needed to evaluate the sensitivity and specificity of CE in comparison with noncontrast echocardiography for diagnosing RV conditions.