Measurement of right ventricular ejection fraction by contrast echocardiography

The feasibility of contrast echocardiography in the assessment of right ventricular size and function

BACKGROUND

Right ventricle (RV) evaluation requires dedicated imaging to achieve a comprehensive functional and anatomical assessment. Right ventricular imaging could be technically difficult which results in suboptimal visibility and inconsistent assessment between observers. The aim of this study was to assess feasibility and the additive value of contrast enhancement for right ventricular evaluation.

METHODS

Eighty patients referred for clinically indicated echocardiography studies were included. Patients with irregular rhythms were excluded. Dedicated RV-focused view was attained; RV dimensions measured, and RV segment visualization and wall motion were assessed with and without contrast enhancement. Paired sample t test was used to compare continuous variables, Wilcoxon signed-rank test to compare segments visualization on enhanced versus (vs) nonenhanced images, and Cohen kappa coefficient to assess the agreement of wall motion between two observers. Reproducibility was measured by the absolute mean difference method.

RESULTS

A total of 240 total segments of 80 patients were analyzed, and 178 (74%) were visible on unenhanced while 221 (92%) on enhanced images, P < .05. Further, RV measurements on enhanced images were consistently larger on RV focused, SAX, and RVOT. Inter- and intra-observer reproducibility showed a higher reproducibility with a lower bias on enhanced images. Absolute agreement on RV segmental wall motion between two independent observers was higher on enhanced images. Percent agreement was 78% on UE vs 89% on CE.

CONCLUSION

Contrast RV imaging is feasible and improves RV segment visualization and inter-observer agreement. Compared with unenhanced images, RV measurements on contrast images are larger and more reproducible with lower bias.

Current role of contrast echocardiography in the diagnosis of cardiovascular diseases

The use of contrast echocardiography (CE) in cardiovascular medicine has grown significantly over the last 15 years. Depending on the site of injection, contrast enhancement of the right- or left-sided cardiac chambers or myocardium now can be achieved. Contrast echocardiography can improve the evaluation of patients with valvular heart disease by enhancing the Doppler signal; CE also improves detection of intracardiac or intrapulmonary shunts. In patients with coronary artery disease, enhancement of the endocardial blood-tissue boundary allows for improved visualization of endocardial wall motion, assessment of wall thickening, and calculation of ejection fraction. Contrast echocardiography promises to delineate myocardial perfusion and has the potential for quantitating coronary flow and assessing myocardial viability. These applications may add important physiologic information to the anatomic information readily available from noncontrast echocardiography. Because it can be rapidly performed at the bedside, CE may be a valuable tool for use with inpatients with acute myocardial ischemia. When CE has been used after recanalization of occluded coronary arteries, the assessment of myocardial salvage conveys information concerning reflow, stunning, and prognosis, and in the case of an angioplasty it provides immediate information regarding the success of the procedure. Contrast echocardiography can also assess myocardial areas at risk of irreversible damage and the presence or absence of collateral flow. When performed with transesophageal or epicardial echocardiography in the operating room, CE is emerging as a valuable tool in the assessment of cardioplegia distribution and graft patency as well as in the delineation of the regional supply of each graft. With the continued development of newer contrast agents and refinement of ultrasound imaging equipment, the applications of CE will continue to grow.

Impact of contrast echocardiography on diagnostic algorithms: pharmacoeconomic implications

The major goal of medicine in the era of managed care is to control escalating costs and to attain a high level of quality health care. Capitation has limited access to expensive and unnecessary testing, placing an emphasis on the prudent use of available technology. A vast armamentarium of available diagnostic screening tests are available within cardiology. Routine two-dimensional (2-D) echocardiography is a high-quality, low-cost test that provides enhanced portability and real-time test interpretation over other noninvasive test modalities. The echocardiogram may cost up to 50% less than competitive nuclear single-photon emission computed tomography (SPECT) imaging. However, on average 10% of routine and 33% of stress echocardiograms are suboptimal (disproportionately affecting obese patients and those with lung disease). Myocardial contrast echocardiography has been shown to provide enhanced endocardial border delineation and left ventricular opacification, to enhance Doppler signal, and to provide information on myocardial perfusion. In several recent phase II and III studies, the use of a contrast agent has been shown to improve the diagnostic accuracy of echocardiography substantially. Improvements in the diagnostic capabilities of echocardiography have been shown to (1) impact upon downstream repetitive testing in patients with an initially nondiagnostic echocardiogram, (2) potentially increase laboratory throughput, and (3) reduce the rate of false-positive and negative tests as a result of improved image quality. As clinical and cost-effectiveness parallel one another, the use of myocardial contrast echocardiography in selected patient cohorts will result in improved diagnostic accuracy and a cost-effective pattern of care.

Hepatopulmonary syndrome in patients with hypoxic hepatitis

BACKGROUND & AIMS

The hepatopulmonary syndrome (HPS) is defined as the triad of liver disease, arterial deoxygenation, and widespread pulmonary vasodilatation. Hypoxic hepatitis, also known as ischemic hepatitis, is the leading cause of acute liver impairment in hospitals. It is unknown whether HPS occurs in hypoxic hepatitis. We assessed the prevalence and clinical consequences of HPS in patients with hypoxic hepatitis.

METHODS

Forty-four patients with hypoxic hepatitis were screened prospectively for HPS using established criteria: (1) presence of hepatic disease, (2) increased alveolar-arterial difference for the partial pressure of oxygen greater than the age-related threshold, and (3) intrapulmonary vasodilatation detected via contrast-enhanced echocardiography. Sixty-two critically ill patients with different cardiopulmonary diseases but without hepatic disease were screened for prevalence of intrapulmonary vasodilatation as a control group.

RESULTS

Criteria of HPS were fulfilled in 18 patients with hypoxic hepatitis. HPS-positive patients had a significantly decreased partial pressure of arterial oxygen (P = .001) and partial pressure of arterial oxygen/fraction of inspired oxygen ratio (P = .034) at the time of diagnosis of HPS, a significant decreased area under the curve of the partial pressure of arterial oxygen/fraction of inspired oxygen ratio during the first 48 hours after diagnosis of hypoxic hepatitis (P = .009), and a significantly increased peak serum aspartate transaminase level (P = .028), compared with patients without HPS. Complete resolution of intrapulmonary vasodilatation was observed during follow-up evaluation. Contrast-enhanced echocardiography was negative for intrapulmonary vasodilatation in all 62 control patients.

CONCLUSIONS

Intrapulmonary vasodilatation indicating HPS frequently occurs in patients with hypoxic hepatitis. It is reversible after normalization of the hepatic dysfunction. Clinicians should consider intrapulmonary vasodilatation and HPS in patients with hypoxic hepatitis.

[Assessment of right ventricular function using contrast echocardiography in patients with myocardial infarction]

OBJECTIVE

To evaluate right ventricular size, motility, and ejection fraction (RVEF) by contrast echocardiography.

METHODS

We studied consecutive patients admitted to the coronary intensive care unit with acute inferior myocardial infarction, without prior infarction and with or without right ventricle involvement, according to accepted electrocardiographic findings. Polygelin, 3.5% solution, was used for contrast echocardiography. The reference standard was equilibrium radionuclide angiography.

RESULTS

We studied 44 patients using contrast echocardiography, average patient age 60.8 +/- 10.6 years, 38 men and 6 women. Abnormal right ventricular size (more than 25 mm) yielded a sensitivity of 79%, specificity of 87%, positive and negative predictive values of 92 and 68%, respectively, and a likelihood ratio of 6. Abnormal right ventricular motility had a sensitivity of 70%, specificity of 94%, positive and negative predictive values of 95 and 67%, respectively, and a likelihood ratio of 11.6. Right ventricular ejection fraction < 30% with contrast echocardiography had a sensitivity of 69%, specificity of 97%, positive and negative predictive values of 90 and 88% respectively, and a likelihood ratio of 6.9.

CONCLUSION

In patients with acute inferior myocardial infarction, contrast echocardiography with the area-length method is a valid and reproducible technique for evaluating right ventricular ejection fraction, which is easy to perform and can be done at the patient's bedside.

Right ventricular dP/dt/P(max), not dP/dt(max), noninvasively derived from tricuspid regurgitation velocity is a useful index of right ventricular contractility

BACKGROUND

Although right ventricular (RV) contractility is important in determining functional capacity, few quantification methods are clinically available. RV dP/dt(max) can be assessed by Doppler echocardiography by using tricuspid regurgitation (TR) but is not routinely used because of its dependency on a Doppler incident angle and preload. Doppler-derived dP/dt/P(max) is relatively insensitive to preload and theoretically independent of the incident angle. We investigated the clinical feasibility of this index as an RV contractility index.

METHODS

We computed RV dP/dt(max) and dP/dt/P(max) from the TR-derived RV pressure in 68 patients with dominant RV failure (13 in New York Heart Association [NYHA] class I, 33 in class II, 17 in class III, and 5 in class IV). Peak oxygen consumption (peak VO(2)) was measured in 20 patients during a maximal bicycle ergometer test.

RESULTS

dP/dt(max) did not significantly correlate with NYHA class. In contrast, dP/dt/P(max) decreased monotonically with the functional class (r = -0.49, P <.0001), and correlated with peak VO(2) (r = 0.66, P <.002).

CONCLUSION

TR-derived dP/dt/P(max), not dP/dt(max), is a clinically useful index of RV contractility, allowing researchers to account for the functional capacity.

Contrast harmonic color Doppler left ventriculography: machine-interpreted left ventricular ejection fraction compared with equilibrium-gated radionuclide ventriculography

BACKGROUND

Multi-gated acquisition (equilibrium-gated radionuclide ventriculography) (MUGA) is considered the gold standard for measuring left ventricular ejection fraction (LVEF) because it is accurate, machine interpreted, and reproducible. Echocardiographic LVEF measurements are subject to variability in image acquisition and interpretation and to the limitations of 2-dimensional (2D) versus 3-dimensional imaging.

GOAL

The shortcomings of traditional echocardiography may be addressed by combining multiplane 2D harmonic imaging, echocardiographic contrast, color Doppler ultrasonography, and digital image processing to create a new imaging modality: contrast harmonic color Doppler left ventriculography.

METHODS

We compared the accuracy of a new method for measuring LVEF that allows for machine interpretation and uses contrast-enhanced intermittent harmonic color Doppler ultrasonography (CHCD). Quantitative LVEF measurements by hand-traced harmonic 2D echocardiography, contrast-enhanced harmonic 2D echocardiography, CHCD, and machine-interpreted CHCD were compared with MUGA in 35 patients.

RESULTS

Contrast-enhanced intermittent harmonic color Doppler provided images with vivid endocardial definition in all patients, but hand-traced harmonic 2D echocardiography and contrast-enhanced harmonic 2D echocardiography had inadequate images in 9% of patients. The MUGA LVEF range was 0. 09 to 0.70. All echocardiographic methods showed excellent correlation with the MUGA LVEF (R (2) > 0.96), but the CHCD method had the best limits of agreement.

CONCLUSIONS

Contrast-enhanced intermittent harmonic color Doppler LVEF correlates with MUGA at least as well as traditional noncontrasted echocardiography, but it provides diagnostic images in a greater proportion of patients. The CHCD images have vivid endocardial delineation and can be machine interpreted.

History of echocardiographic contrast agents

Since its experimental introduction over 30 years ago, the use of cardiac ultrasound has expanded expeditiously, particularly in the last decade. The inception of managed care has fueled this expansion because ultrasound technology has the potential to enhance cost-effective diagnosis and medical care. Another important factor driving the growth of cardiac ultrasound has been the recent and rapid development of contrast echocardiography (CE). This diagnostic technique, involving the injection of a contrast agent to enhance ultrasound imaging, provides a safe, noninvasive means of directly assessing myocardial perfusion and a host of other aspects of cardiovascular health and integrity.

The emerging role of contrast agents in echocardiography

Because of an outstanding track record for diagnostic accuracy, noninvasive properties, ease of use, and relatively low expense, echocardiography has become a leading technique in the evaluation of cardiac disorders. In the three decades since echocardiography entered the ranks of standard cardiac diagnostic tools, refinements and technological advances have progressively increased its usefulness. One of the most noteworthy advancements has been the development of ultrasound contrast agents, which investigators are avidly seeking to apply to a broad spectrum of clinical settings and issues.