Left ventricular opacification at rest and during stress

Left ventricular remodeling after acute myocardial infarction: the influence of viability and revascularization - an echocardiographic substudy of the VIAMI-trial

BACKGROUND

Viability seems to be important in preventing ventricular remodeling after acute myocardial infarction (AMI). We investigated the influence of viability, as demonstrated with low-dose dobutamine echocardiography, and the role of early revascularization on the process of left ventricular (LV) remodeling after AMI.

METHODS

We retrospectively investigated 224 patients who were initially included in the viability-guided angioplasty after acute myocardial infarction-trial (VIAMI-trial). Patients in the VIAMI-trial did not undergo a primary or rescue percutaneous coronary intervention and were stable in the early in-hospital phase. Patients underwent viability testing within 72 hours after AMI. Patients with viability were randomized to an invasive strategy or an ischemia-guided strategy. Follow-up echocardiography was performed at a mean of 205 days. In this echocardiographic substudy, patients were divided into three new groups: group 1, viable and revascularized before follow-up echocardiogram; group 2, viable, but medically treated; and group 3, non-viable patients.

RESULTS

Group 1 showed preservation of LV volume indices. The ejection fraction (EF) increased significantly from 54.0% to 57.5% (P = 0.047). Group 2 showed a significant increase in LV volume indices with no improvement in EF (53.3% versus 53.0%, P = 0.86). Group 3 showed a significant increase in LV volume indices, with a decrease in EF from 53.5% to 49.1% (P = 0.043). Multivariate logistic regression analysis indicated the number of viable segments and revascularization during follow-up as independent predictors for EF improvement, especially in patients with lower EF at baseline.

CONCLUSION

Viability early after AMI is associated with improvement in LV function after revascularization. When viable myocardium is not revascularized, the LV tends to remodel with increased LV volumes, without improvement of EF. Absence of viability results in ventricular dilatation and deterioration of EF, irrespective of revascularization status.

TRIAL REGISTRATION

NCT00149591 (assigned: 6 September 2005).

Clinical application and laboratory protocols for performing contrast echocardiography

Technically difficult echocardiographic studies with suboptimal images remain a significant challenge in clinical practice despite advances in imaging technologies over the past decades. Use of microbubble ultrasound contrast for left ventricular opacification and enhancement of endocardial border detection during rest or stress echocardiography has become an essential component of the operation of the modern echocardiography laboratory. Contrast echocardiography has been demonstrated to improve diagnostic accuracy and confidence across a range of indications including quantitative assessment of left ventricular systolic function, wall motion analysis, and left ventricular structural abnormalities. Enhancement of Doppler signals and myocardial contrast echocardiography for perfusion remain off-label uses. Implementation of a contrast protocol is feasible for most laboratories and both physicians and sonographers will require training in contrast specific imaging techniques for optimal use. Previous concerns regarding the safety of contrast agents have since been addressed by more recent data supporting its excellent safety profile and overall cost-effectiveness.

Contrast echocardiography in Australian clinical practice

BACKGROUND

The second-generation contrast agent Definity (a perflutren microsphere) became available in Australia in mid-2007. We describe the introduction of contrast echocardiography into a high-volume quaternary teaching hospital, performing over 16,000 echocardiograms per year. Workflow protocols were developed for patient selection, contrast administration, and image acquisition and analysis.

METHODS

Data were prospectively collected for all contrast cases. Endocardial definition scores were derived by three independent observers before and after contrast administration, and statistically compared.

RESULTS

161 patients received contrast in the first 12 months of the contrast program. There was statistically significant improvement in endocardial definition scores after contrast administration (p=0.0001), and reduction in inter-observer variability of wall motion assessment. A number of clinically significant findings (pseudoaneurysm, non-compaction, thrombus) were detected on contrast echo that were not apparent on standard 2D imaging. Adverse events were rare (0.6%) with no life-threatening events.

CONCLUSIONS

The introduction of a second-generation contrast agent into clinical workflow in a hospital echocardiography department resulted in a statistically significant improvement in endocardial definition, and safely provided diagnostic imaging in cases which were otherwise non-diagnostic. Inter-observer variability was reduced, and diagnostic yield increased. These results reflect previously published data, and indicate that contrast echocardiography is feasible in Australian clinical practice.

Left ventricular volume measurement with echocardiography: a comparison of left ventricular opacification, three-dimensional echocardiography, or both with magnetic resonance imaging

AIMS

Both contrast enhanced (CE) two-dimensional echocardiography (2DE) and three-dimensional echocardiography (3DE) have been proposed as techniques to improve the accuracy of left ventricular (LV) volume measurements. We sought to examine the accuracy of non-contrast (NC) and CE-2DE and 3DE for calculation of LV volumes and ejection fraction (EF), relative to cardiac magnetic resonance imaging (MRI).

METHODS AND RESULTS

We studied 50 patients (46 men, age 63 +/- 10 year) with past myocardial infarction who underwent echocardiographic assessment of LV volume and function. All patients sequentially underwent NC-2DE followed by NC-3DE. CE-2DE and CE-3DE were acquired during contrast infusion. Resting echocardiographic image quality was evaluated on the basis of NC-2DE. The mean LV end-diastolic volume (LVEDV) of the group by MRI was 207 +/- 79 mL and was underestimated by 2DE (125 +/- 54 mL, P = 0.005), and less by CE-2DE (172 +/- 58 mL, P = 0.02) or 3DE (177 +/- 64 mL, P = 0.08), but EDV was comparable by CE-3DE (196 +/- 69 mL, P = 0.16). Limits of agreement with MRI were similar for NC-3DE and CE-2DE, with the best results for CE-3D. Results were similar for calculation of LVESV. Patients were categorized into groups of EF (< or =35, 35-50, >50%) by MRI. NC-2DE demonstrated a 68% agreement (kappa 0.45, P = 0.001), CE-2DE a 62% agreement (kappa 0.20, P = 136), NC-3DE a 74% agreement (kappa 0.39, P = 0.005) and CE-3DE an 80% agreement (kappa 0.56, P < 0.001).

CONCLUSION

CE-2DE is analogous to NC-3DE in accurate categorization of LV function. However, CE-3DE is feasible and superior to other NC- and CE-techniques in patients with previous infarction.

Improved Visualization of Aortic Intima-media Thickening with the Use of Perflutren Lipid Microspheres

BACKGROUND

Transesophageal echocardiography (TEE) has been used to diagnose atherosclerotic disease for patients who present with systemic embolic events. The primary aim of this study was to assess the supplemental value of echocardiographic contrast to standard TEE in identifying the aortic intima-medial thickness.

METHODS

An aorta phantom was used to validate the accuracy of border delineation with and without contrast during TEE imaging. In all, 44 patients underwent TEE imaging of the thoracic aorta with a subsequent administration of a 0.3-mL bolus of perflutren lipid microspheres (Definity). Precontrast and postcontrast images were analyzed semiquantitatively for border delineation and quantitatively for intima-medial thickness and cross-sectional area.

RESULTS

Wall thickness in the aortic phantom model with contrast was smaller, more accurate, and more reproducible to the true measurement. The clinical studies reflected similar results with average contrast intima-medial thickness measured at 0.15 +/- 0.08 cm and noncontrast at 0.18 +/- 0.08 cm (P < .01). The lateral wall showed the greatest improvement with a score of 1.23 increasing to an average of 1.82 (P < .001) with contrast. The medial, anterior, and posterior walls improved to an average 1.98, 1.39, and 2.0, respectively (P = .01).

CONCLUSIONS

Contrast agents provide better aortic intima-media enhancement during TEE.

Instantaneous quantitative video intensity heterogeneity: evaluation with low mechanical index contrast echocardiography

BACKGROUND

Instantaneous video intensity of myocardium has been poorly characterized. Myocardial video intensity is usually displayed in the fitted curve from the exponential equation, y = a(1 - e (-bt)). However, information from the fitted curve will be as accurate as the original video intensity data from the perfusion image. Therefore, we sought to characterize the intramyocardial instantaneous video intensity from low mechanical index (MI) contrast echo imaging for variation.

METHOD

Low-MI imaging using a nonlinear cancellation technique was performed on 10 subjects with normal myocardium. Quantitative video intensity was analyzed in five segments in the epicardium and subendocardium, as well as in systole and diastole.

RESULTS

Video intensity varied between the epicardium and endocardium in each of the region that was analyzed, with the greatest variation in the inferior region (P < 0.0001). Diastolic and systolic differences were also present.

CONCLUSION

Instantaneous video intensity is heterogeneous within the myocardium. Differences can result from attenuation, myocardial fiber structure, and even isotropic effects of the contrast agent, and should be taken into account when data are fitted into an exponential function.

Usefulness of contrast echocardiography in arrhythmogenic right ventricular dysplasia

Arrhythmogenic right ventricular (RV) dysplasia or cardiomyopathy is a familiar heart muscle disease, characterized by progressive fibrofatty replacement of RV myocardium. Echocardiography can be used to evaluate the wide spectrum of abnormalities that range from a normal RV to severe RV dilation, with localized aneurysms. In the context of a positive family history, even minimal RV abnormalities represent a disease expression. This suggests the need for a careful echocardiographic investigation focusing in subtle structural changes. However, echocardiography may be limited by poor endocardial visualization in several patients. Contrast echocardiography may improve endocardial border delineation in these cases and, thus, the ability to assess arrhythmogenic RV dysplasia or cardiomyopathy at the initial stages of the disease.