The Impact of Vendor-Specific Ultrasound Beam-Forming and Processing Techniques on the Visualization of In Vitro Experimental "Scar": Implications for Myocardial Scar Imaging Using Two-Dimensional and Three-Dimensional Echocardiography

BACKGROUND

Myocardial scar appears brighter compared with normal myocardium on echocardiography because of differences in tissue characteristics. The aim of this study was to test how different ultrasound pulse characteristics affect the brightness contrast (i.e., contrast ratio [CR]) between tissues of different acoustic properties, as well as the accuracy of assessing tissue volume.

METHODS

An experimental in vitro "scar" model was created using overheated and raw pieces of commercially available bovine muscle. Two-dimensional and three-dimensional ultrasound scanning of the model was performed using combinations of ultrasound pulse characteristics: ultrasound frequency, harmonics, pulse amplitude, steady pulse (SP) emission, power modulation (PM), and pulse inversion modalities.

RESULTS

On both two-dimensional and three-dimensional imaging, the CR between the "scar" and its adjacent tissue was higher when PM was used. PM, as well as SP ultrasound imaging, provided good "scar" volume quantification. When tested on 10 "scars" of different size and shape, PM resulted in lower bias (-9.7 vs 54.2 mm³) and narrower limits of agreement (-168.6 to 149.2 mm³ vs -296.0 to 404.4 mm³, P = .03). The interobserver variability for "scar" volume was better with PM (intraclass correlation coefficient = 0.901 vs 0.815). Two-dimensional and three-dimensional echocardiography with PM and SP was performed on 15 individuals with myocardial scar secondary to infarction. The CR was higher on PM imaging. Using cardiac magnetic resonance as a reference, quantification of myocardial scar volume showed better agreement when PM was used (bias, -645 mm³; limits of agreement, -3,158 to 1,868 mm³) as opposed to SP (bias, -1,138 mm³; limits of agreement, -5,510 to 3,233 mm³).

CONCLUSIONS

The PM modality increased the CR between tissues with different acoustic properties in an experimental in vitro "scar" model while allowing accurate quantification of "scar" volume. By applying the in vitro findings to humans, PM resulted in higher CR between scarred and healthy myocardium, providing better scar volume quantification than SP compared with cardiac magnetic resonance.

Sex differences in transaortic flow rate and association with all-cause mortality in patients with severe aortic stenosis

AIMS

It is not known whether transaortic flow rate (FR) in aortic stenosis (AS) differs between men and women, and whether the commonly used cut-off of 200 mL/s is prognostic in females. We aimed to explore sex differences in the determinants of FR, and determine the best sex-specific cut-offs for prediction of all-cause mortality.

METHODS AND RESULTS

Between 2010 and 2017, a total of 1564 symptomatic patients (mean age 76 ± 13 years, 51% men) with severe AS were prospectively included. Mean follow-up was 35 ± 22 months. The prevalence of cardiovascular disease was significantly higher in men than women (63% vs. 42%, P < 0.001). Men had higher left ventricular mass and lower left ventricular ejection fraction compared to women (both P < 0.001). Men were more likely to undergo an aortic valve intervention (AVI) (54% vs. 45%, P = 0.001), while the death rates were similar (42.0% in men and 40.6% in women, P = 0.580). A total of 779 (49.8%) patients underwent an AVI in which 145 (18.6%) died. In a multivariate Cox regression analysis, each 10 mL/s decrease in FR was associated with a 7% increase in hazard ratio (HR) for all-cause mortality (HR 1.07; 95% CI 1.03-1.11, P < 0.001). The best cut-off value of FR for prediction of all-cause mortality was 179 mL/s in women and 209 mL/s in men.

CONCLUSION

Transaortic FR was lower in women than men. In the group undergoing AVI, lower FR was associated with increased risk of all-cause mortality, and the optimal cut-off for prediction of all-cause mortality was lower in women than men.

Determinants of outcome in patients with heart failure with reduced ejection fraction & secondary mitral regurgitation

BACKGROUND

The outcome of secondary mitral regurgitation (MR) in patients with heart failure is poor. Survival is related to the severity of MR. We sought to investigate the effect of left ventricular contractility, the ratio of left ventricular end-diastolic volume (LVEDV) to effective orifice area (EROA) and the ratio of regurgitant volume (RVol) to stroke volume (SV) on cardiovascular survival.

METHODS

188 patients with a left ventricular ejection fraction (LVEF) < 50% and secondary MR were included. Groups were divided into tertiles. The Kaplan Meier method and log rank test were used to identify differences in survival between groups. Cox regression was used to identify independent predictors of cardiac mortality.

RESULTS

Median follow-up was 30.4 months. Patients with a more abnormal global longitudinal strain (GLS) had lower survival, p = 0.001. There was no difference in survival between patients with an LVEF <30%, 30%-40% and >40%, p = 0.27. Patients with a higher RVol/SV ratio had lower survival than those with a lower ratio, p < 0.0001. Patients with a lower LVEDV/EROA ratio had worse survival than those with a higher ratio, p < 0.0001. Independent predictors of cardiovascular mortality were GLS (<5.6%) hazard ratio (HR) 2.7, the ratio of RVol/SV (>1.38) HR 4.96 and the ratio of LVDEV to EROA (<263) HR 4.49.

CONCLUSION

The main determinants of cardiovascular mortality in patients with secondary MR and heart failure are more abnormal GLS, lower LVEDV/EROA ratio and higher RVol/SV ratio. These may help risk stratify patients to help determine the optimal management strategy.