Impact of ultrasound enhancing agents on clinical management

PURPOSE OF REVIEW

Ultrasound enhancing agents (UEAs), microbubbles which are composed of lipid or albumin shells containing high molecular weight gases with nonlinear acoustic properties in the ultrasound field, are important components of the diagnostic armamentarium in echocardiography. This review highlights the substantial value of UEAs in delineating endocardial border definition and influencing downstream decision-making in cardiovascular ultrasound.

RECENT FINDINGS

In this article, we review recent updates to the clinical applications of UEAs, special circumstances regarding use, the impact of use on downstream testing and cost-effectiveness, and recommended approaches for optimizing workflow in the echocardiography laboratory with UEAs.

SUMMARY

In multiple studies, UEAs have been identified as a useful tool in echocardiography, improving study accuracy and reader confidence, while reducing downstream testing and procedures and resulting in significant changes in clinical management. Despite their proven efficacy and cost-effectiveness, recent studies have suggested utilization remains low, in part due to perceived concerns and workflow issues that impair uptake. With an increasingly broader list of indications for echocardiography, UEAs will continue to play an important role in the diagnosis and management of patients with cardiovascular and noncardiovascular diseases.

Intraventricular synchronism assessment by gated-SPECT myocardial perfusion imaging in cardiac resynchronization therapy. Does cardiomyopathy type influence results?

Purpose

To analyze the evolution post-cardiac resynchronization therapy (CRT) in left ventricular non-compaction (LVNC) cardiomyopathy (CM) patients compared to other types of CM, according to clinical and functional variables, by using gated-SPECT myocardial perfusion imaging (MPI).

Methods

Ninety-three patients (60 ± 11 years, 28% women) referred for pre-CRT assessment were studied and divided into three groups: 1 (non-ischemic CM with LVNC, 11 patients), 2 (ischemic CM, 28 patients), and 3 (non-ischemic CM, 53 patients). All were studied by a ^99mTc-MIBI gated-SPECT MPI at rest pre-CRT implantation and 6 ± 1 months after, including intraventricular dyssynchrony assessment by phase analysis. Quality of life was measured by the Minnesota Living with Heart Failure Questionnaire (MLHFQ).

Results

No differences in sex, atherosclerotic risk factors other than smoking habit, and MLHFQ results were found among groups. LVNC CM patients were younger, with greater QRS width and lower left ventricular ejection fraction (LVEF) at baseline, but the differences were not significant. No significant differences were found at baseline regarding ventricular function, although end-systolic volume was slightly higher in LVNC CM patients. Mean SRS was significantly higher (p < 0.0001) in ischemic patients (14.9) versus non-ischemic ones (8.7 in group 1 and 9 in group 2). At baseline, LVNC CM patients were significantly more dyssynchronous: Their phase standard deviation (PSD) was higher (89.5° ± 14.2°) versus groups 2 (65.2° ± 23.3°) and 3 (69.7° ± 21.7°), p = 0.007. Although the quality of life significantly improved in all groups, non-ischemic patients (with or without LVNC) showed a higher LVEF increase and volumes reduction at 6 months post-CRT. Dyssynchrony reduced post-CRT in all groups. Nevertheless, those more dyssynchronous at baseline (LVNC CM) exhibited the most significant intraventricular synchronism improvement: PSD was reduced from 89.5° ± 14.2° at baseline to 63.7° ± 20.5° post-CRT (p = 0.028). Six months post-CRT, 89% of patients were responders: 11 (100%) of those with LVNC CM, 25 (86%) of those with ischemic CM, and 47 (89%) of patients with non-ischemic CM. No patient with LVNC CM had adverse events during the follow-up.

Conclusion

CRT contributes to a marked improvement in non-ischemic CM patients with non-compaction myocardium. Phase analysis in gated-SPECT MPI is a valuable tool to assess the response to CRT.

Quantitative Assessment of Inflammation in a Porcine Acute Terminal Ileitis Model: US with a Molecularly Targeted Contrast Agent

PURPOSE

To evaluate the feasibility and reproducibility of ultrasonography (US) performed with dual-selectin-targeted contrast agent microbubbles (MBs) for assessment of inflammation in a porcine acute terminal ileitis model, with histologic findings as a reference standard.

MATERIALS AND METHODS

The study had institutional Animal Care and Use Committee approval. Acute terminal ileitis was established in 19 pigs; four pigs served as control pigs. The ileum was imaged with clinical-grade dual P- and E-selectin-targeted MBs (MBSelectin) at increasing doses (0.5, 1.0, 2.5, 5.0, 10, and 20 × 10(8) MB per kilogram of body weight) and with control nontargeted MBs (MBControl). For reproducibility testing, examinations were repeated twice after the MBSelectin and MBControl injections. After imaging, scanned ileal segments were analyzed ex vivo both for inflammation grade (by using hematoxylin-eosin staining) and for expression of selectins (by using quantitative immunofluorescence analysis). Statistical analysis was performed by using the t test, intraclass correlation coefficients (ICCs), and Spearman correlation analysis.

RESULTS

Imaging signal increased linearly (P < .001) between a dose of 0.5 and a dose of 5.0 × 10(8) MB/kg and plateaued between a dose of 10 and a dose of 20 × 10(8) MB/kg. Imaging signals were reproducible (ICC = 0.70), and administration of MBSelectin in acute ileitis resulted in a significantly higher (P < .001) imaging signal compared with that in control ileum and MBControl. Ex vivo histologic grades of inflammation correlated well with in vivo US signal (ρ = 0.79), and expression levels of both P-selectin (37.4% ± 14.7 [standard deviation] of vessels positive; P < .001) and E-selectin (31.2% ± 25.7) in vessels in the bowel wall of segments with ileitis were higher than in control ileum (5.1% ± 3.7 for P-selectin and 4.8% ± 2.3 for E-selectin).

CONCLUSION

Quantitative measurements of inflammation obtained by using dual-selectin-targeted US are reproducible and correlate well with the extent of inflammation at histologic examination in a porcine acute ileitis model as a next step toward clinical translation.

Left ventricular non-compaction and its cardiac and neurologic implications

Left ventricular non-compaction, also known as left ventricular hypertrabeculation (LVHT), is a morphological abnormality of the left ventricular myocardium, characterised by a meshwork of myocardial strings, interlacing, and orderless in arrangement. LVHT is most frequently located in the apex and the lateral wall and may occur with or without other congenital or acquired cardiac abnormalities. LVHT is believed to be congenital in the majority of the cases but may develop during life in single cases (acquired LVHT). Congenital LVHT is believed to result from defective late-stage embryonic development of the myocardial architecture. The pathogenesis of acquired LVHT remains speculative. LVHT is most frequently found on transthoracic echocardiography and cardiac MRI but may be visualised also with other imaging techniques. In the majority of the cases, LVHT is associated with hereditary cardiac, neuromuscular, non-cardiac/non-muscle disease, or chromosomal aberrations. In the majority of the cases, LVHT is complicated by ventricular arrhythmias, systolic dysfunction, cardiac embolism, or sudden cardiac death. LVHT per se does not require a specific treatment. Only in case of complications, such as ventricular arrhythmias, cardioembolism, or systolic dysfunction, adequate therapy is indicated. Though initially assessed as poor, the prognosis of LVHT has meanwhile improved, most likely due to the increased awareness for the abnormality and the timely administration of adequate therapy.

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.