Echocardiographic assessment of myocardial function and mechanics during veno-venous extracorporeal membrane oxygenation.

BACKGROUND: Transthoracic echocardiography (TTE) plays a fundamental role in the management of patients supported with extra-corporeal membrane oxygenation (ECMO). In light of fluctuating clinical states, serial monitoring of cardiac function is required. Formal quantification of ventricular parameters and myocardial mechanics offer benefit over qualitative assessment. The aim of this research was to compare unenhanced (UE) versus contrast-enhanced (CE) quantification of myocardial function and mechanics during ECMO in a validated ovine model. METHODS: Twenty-four sheep were commenced on peripheral veno-venous ECMO. Acute smoke-induced lung injury was induced in 21 sheep (3 controls). CE-TTE with Definity using Cadence Pulse Sequencing was performed. Two readers performed image analysis with TomTec Arena. End diastolic area (EDA, cm2), end systolic area (ESA, cm2), fractional area change (FAC, %), endocardial global circumferential strain (EGCS, %), myocardial global circumferential strain (MGCS, %), endocardial rotation (ER, degrees) and global radial strain (GRD, %) were evaluated for UE-TTE and CE-TTE. RESULTS: Full data sets are available in 22 sheep (92%). Mean CE EDA and ESA were significantly larger than in unenhanced images. Mean FAC was almost identical between the two techniques. There was no significant difference between UE and CE EGCS, MGCS and ER. There was significant difference in GRS between imaging techniques. Unenhanced inter-observer variability was from 0.48-0.70 but significantly improved to 0.71-0.89 for contrast imaging in all echocardiographic parameters. CONCLUSION: Semi-automated methods of myocardial function and mechanics using CE-TTE during ECMO was feasible and similar to UE-TTE for all parameters except ventricular areas and global radial strain. Addition of contrast significantly decreased inter-observer variability of all measurements.

Radiation Exposure of Operators Performing Transesophageal Echocardiography During Percutaneous Structural Cardiac Interventions.

BACKGROUND: Transesophageal echocardiography operators (TEEOP) provide critical imaging support for percutaneous structural cardiac intervention procedures. They stand close to the patient and the associated scattered radiation. OBJECTIVES: This study sought to investigate TEEOP radiation dose during percutaneous structural cardiac intervention. METHODS: Key personnel (TEEOP, anesthetist, primary operator [OP1], and secondary operator) wore instantly downloadable personal dosimeters during procedures requiring TEE support. TEEOP effective dose (E) and E per unit Kerma area product (E/KAP) were calculated. E/KAP was compared with C-arm projections. Additional shielding for TEEOP was implemented, and doses were measured for a further 50 procedures. Multivariate linear regression was performed to investigate independent predictors of radiation dose reduction. RESULTS: In the initial 98 procedures, median TEEOP E was 2.62 µSv (interquartile range [IQR]: 0.95 to 4.76 µSv), similar to OP1 E: 1.91 µSv (IQR: 0.48 to 3.81 µSv) (p = 0.101), but significantly higher than secondary operator E: 0.48 µSv (IQR: 0.00 to 1.91 µSv) (p < 0.001) and anesthetist E: 0.48 µSv (IQR: 0.00 to 1.43 µSv) (p < 0.001). Procedures using predominantly right anterior oblique (RAO) and steep RAO projections were associated with high TEEOP E/KAP (p = 0.041). In a further 50 procedures, with additional TEEOP shielding, TEEOP E was reduced by 82% (2.62 µSv [IQR: 0.95 to 4.76] to 0.48 µSv [IQR: 0.00 to 1.43 µSv] [p < 0.001]). Multivariate regression demonstrated shielding, procedure type, and KAP as independent predictors of TEEOP dose. CONCLUSION: TEE operators are exposed to a radiation dose that is at least as high as that of OP1 during percutaneous cardiac intervention. Doses were higher with procedures using predominantly RAO projections. Radiation doses can be significantly reduced with the use of an additional ceiling-suspended lead shield.

Contrast microsphere enhancement of the tricuspid regurgitant spectral Doppler signal - Is it still necessary with contemporary scanners?

BACKGROUND: Accurate evaluation of the tricuspid regurgitant (TR) spectral Doppler signal is important during transthoracic echocardiographic (TTE) evaluation for pulmonary hypertension (PHT). Contrast enhancement improves Doppler backscatter. However, its incremental benefit with contemporary scanners is less well established. The aim of this study was to assess whether the TR spectral Doppler signal using contemporary scanners was improved using a second generation contrast agent, Definity® (CE), compared to unenhanced TTE (UE). METHODS: Analysis of patients who underwent UE then CE TR interrogation was performed. TR signal was evaluated by an experienced reader and graded 1 (clear-high level of confidence of interpretation and complete spectral Doppler envelope), 2 (suboptimal with medium-low level of confidence of interpretation and incomplete envelope), 3 (poor-absent and no measurable spectral Doppler signal). Maximal TR velocity (TRV) was defined as peak velocity that could be clearly identified. An inexperienced sonographer read 30 randomly selected studies. RESULTS: 176 TTE were performed in 173 patients (mean age 57 ± 14.8 years). Wilcoxon signed rank test demonstrated significant improvement (p < 0.0001) in TR spectral Doppler signal quality with CE TTE. Mean score CE TTE vs. TTE = 2.32 ± 0.85 vs. 2.56 ± 0.75 respectively (p < 0.0001). Mean maximal TRV CE TTE vs. UE TTE = 2.61 ± 0.44 m/s vs. 2.54 ± 0.49 m/s respectively (p < 0.0001). The inexperienced reader had a greater improvement in scoring CE TTE signals vs. UE TTE (p < 0.0001). CONCLUSION: In the era of contemporary scanners, CE improved the ability to detect and measure TRV, except in those with clear unenhanced TR spectral Doppler signals or greater than mild tricuspid regurgitation.

Usefulness of Mitral Valve Prosthetic or Bioprosthetic Time Velocity Index Ratio to Detect Prosthetic or Bioprosthetic Mitral Valve Dysfunction.

This study aimed to investigate the utility of transthoracic echocardiographic (TTE) Doppler-derived parameters in detection of mitral prosthetic dysfunction and to define optimal cut-off values for identification of such dysfunction by valve type. In total, 971 TTE studies (647 mechanical prostheses; 324 bioprostheses) were compared with transesophageal echocardiography for evaluation of mitral prosthesis function. Among all prostheses, mitral valve prosthesis (MVP) ratio (ratio of time velocity integral of MVP to that of left ventricular outflow tract; odds ratio [OR] 10.34, 95% confidence interval [95% CI] 6.43 to 16.61, p<0.001), E velocity (OR 3.23, 95% CI 1.61 to 6.47, p<0.001), and mean gradient (OR 1.13, 95% CI 1.02 to 1.25, p=0.02) provided good discrimination of clinically normal and clinically abnormal prostheses. Optimal cut-off values by receiver operating characteristic analysis for differentiating clinically normal and abnormal prostheses varied by prosthesis type. Combining MVP ratio and E velocity improved specificity (92%) and positive predictive value (65%) compared with either parameter alone, with minimal decline in negative predictive value (92%). Pressure halftime (OR 0.99, 95% CI 0.98 to 1.00, p=0.04) did not differentiate between clinically normal and clinically abnormal prostheses but was useful in discriminating obstructed from normal and regurgitant prostheses. In conclusion, cut-off values for TTE-derived Doppler parameters of MVP function were specific to prosthesis type and carried high sensitivity and specificity for identifying prosthetic valve dysfunction. MVP ratio was the best predictor of prosthetic dysfunction and, combined with E velocity, provided a useful parameter for determining likelihood of dysfunction and need for further assessment.

Intervendor consistency and reproducibility of left ventricular 2D global and regional strain with two different high-end ultrasound systems.

AIMS: We aimed to assess intervendor agreement of global (GLS) and regional longitudinal strain by vendor-specific software after EACVI/ASE Industry Task Force Standardization Initiatives for Deformation Imaging. METHODS AND RESULTS: Fifty-five patients underwent prospective dataset acquisitions on the same day by the same operator using two commercially available cardiac ultrasound systems (GE Vivid E9 and Philips iE33). GLS and regional peak longitudinal strain were analyzed offline using corresponding vendor-specific software (EchoPAC BT13 and QLAB version 10.3). Absolute mean GLS measurements were similar between the two vendors (GE -17.5 ± 5.2% vs. Philips -18.9 ± 5.1%, P = 0.15). There was excellent intervendor correlation of GLS by the same observer [r = 0.94, P < 0.0001; bias -1.3%, 95% CI limits of agreement (LOA) -4.8 to 2.2%). Intervendor comparison for regional longitudinal strain by coronary artery territories distribution were: LAD: r = 0.85, P < 0.0001; bias 0.5%, LOA -5.3 to 6.4%; RCA: r = 0.88, P < 0.0001; bias -2.4%, LOA -8.6 to 3.7%; LCX: r = 0.76, P < 0.0001; bias -5.3%, LOA -10.6 to 2.0%. Intervendor comparison for regional longitudinal strain by LV levels were: basal: r = 0.86, P < 0.0001; bias -3.6%, LOA -9.9 to 2.0%; mid: r = 0.90, P < 0.0001; bias -2.6%, LOA -7.8 to 2.6%; apical: r = 0.74; P < 0.0001; bias -1.3%, LOA -9.4 to 6.8%. CONCLUSIONS: Intervendor agreement in GLS and regional strain measurements have significantly improved after the EACVI/ASE Task Force Strain Standardization Initiatives. However, significant wide LOA still exist, especially for regional strain measurements, which remains relevant when considering vendor-specific software for serial measurements.

ePLAR - The echocardiographic Pulmonary to Left Atrial Ratio - A novel non-invasive parameter to differentiate pre-capillary and post-capillary pulmonary hypertension.

BACKGROUND: Right heart catheterisation is the gold-standard for differentiating pre-capillary pulmonary hypertension (high mean pulmonary artery pressure, normal pulmonary wedge pressure) from post-capillary physiology (elevated pulmonary wedge pressure). The new non-invasive parameter, ePLAR (echocardiographic Pulmonary to Left Atrial Ratio) is calculated from the maximum tricuspid regurgitation continuous wave Doppler velocity (m/s) divided by the transmitral E-wave:septal mitral annular Doppler Tissue Imaging e'-wave ratio (TRVmax/E:e'). METHODS: Pulmonary hypertension patients (mean pulmonary artery pressure>25mmHg, n=133, 66 male, average 65.0±16.8years) were classified by right heart catheterisation as pre-capillary or post-capillary [subdivided into isolated post-capillary (diastolic pulmonary gradient <7mmHg) or combined pre- and post-capillary cases]. The ePLAR values of these groups were compared to each other and to a population sample of 16,356 population reference echocardiograms. RESULTS: ePLAR values for the normal reference population of 16,356 echocardiograms (age 56±16.6years) were 0.30±0.09m/s. Pre-capillary pulmonary hypertension patients (n=35, 26 male, PAPsys 63.9±16.6mmHg, PAPdiast 24.1±7.3mmHg, PAPmean 37.9±9.4mmHg, PCWP 10.6±2.7mmHg) had significantly higher ePLAR values than post-capillary cases (n=98, 40 male, PAPsys 59.9±17.6mmHg, PAPdiast 25.0±7.4mmHg, PAPmean 38.1±9.8mmHg, PCWP 23.5±6.4mmHg)-ePLAR 0.44±0.22m/s vs 0.20±0.11m/s (p<0.001). ePLAR values were significantly lower in isolated post-capillary pulmonary hypertension than in combined pre- and post-capillary cases (0.18±0.08m/s vs 0.28±0.18m/s, p<0.001). CONCLUSIONS: ePLAR is a simple echocardiographic parameter which can accurately differentiate the smaller subset of patients with pre-capillary pulmonary hypertension from the more common post-capillary aetiology. The use of this easily obtained echocardiographic parameter has the potential to enhance non-invasive triage of patients for specific pulmonary vasodilator therapy.

Quantification of perflutren microsphere contrast destruction during transit through an ex vivo extracorporeal membrane oxygenation circuit.

BACKGROUND: Echocardiography is a key investigation in the management of patients on extracorporeal membrane oxygenation (ECMO). However, echocardiographic images are often non-diagnostic in this patient population. Contrast-enhanced echocardiography may overcome many of these limitations but contrast microspheres are hydrodynamically labile structures prone to destruction from shear forces and turbulent flow, which may exist within an ECMO circuit. This study sought to evaluate microsphere destruction (utilising signal intensity as a marker of contrast concentration) during transit through an ECMO circuit. METHODS: Activated Definity® contrast was diluted to 50 ml with normal saline and infused into a crystalloid primed ex vivo ECMO with a Quadrox oxygenator at 150 ml/h. Imaging was performed on pre- and post-pump head/oxygenator sections of the circuit using a Philips iE33 scanner and S5-1 transducer. Five-millimetre regions of interest were placed in the centre of the ultrasound field. Average signal intensity (decibels) was calculated at speeds of 1000, 2000, 3000 and 4000 rpm and then repeated with an infusion rate of 300 ml/h. The oxygenator was then spliced out of the circuit and the measures repeated. RESULTS: There was a significant reduction in contrast concentration during passage through the ECMO circuit at all speeds (with higher pump head speeds resulting in greater microsphere destruction). In a circuit with an oxygenator, relative decrease in signal intensity was 21.4 versus 5.2 % without an oxygenator. There was significant destruction of contrast microspheres during passage through the ECMO circuit at all pump head speeds. An oxygenator contributed to microsphere destruction at a significantly greater level than the pump head alone. There was no significant difference in mean signal intensity reduction in the circuit between an infusion of 150 or 300 ml/h (3.5 ± 3.2 versus 3.6 ± 2.5 dB, respectively, p = 0.79). CONCLUSIONS: Flow of contrast through an ECMO circuit results in significant destruction of microspheres. Circuits with an oxygenator result in significantly greater levels of contrast destruction than by the pump head alone. Clinicians should be cognisant of the relationship between ECMO circuit configurations, pump head speed and contrast destruction when performing a contrast-enhanced echocardiogram in patients supported with ECMO.

Accuracy of quantitative echocardiographic measures of right ventricular function as compared to cardiovascular magnetic resonance.

BACKGROUND: Many echocardiographic parameters have been proposed to evaluate right ventricular (RV) systolic function. We comprehensively assessed a wide range of quantitative echocardiographic parameters in a single cohort compared with same-day cardiovascular magnetic resonance (CMR). METHODS AND RESULTS: 92 subjects were examined prospectively: Group 1 consisted of 46 healthy controls (21 males, 33.4 ± 11.4 years), Group 2 consisted of 46 patients (20 males, 38.5 ± 18.9 years) undergoing RV functional assessment by CMR (1.5 T). Echocardiography was performed on the same day as CMR; fractional area change (RVFAC), myocardial performance index via spectral Doppler (RVMPI), RVMPI via Doppler tissue imaging (RVMPI-DTI), peak systolic myocardial velocity by DTI (RVSm), tricuspid annular plane systolic excursion (TAPSE), speckle tracking strain, and three dimensional right ventricular ejection fraction (3DE-RV). Linear regression, Bland-Altman and receiver-operator-characteristic (ROC) analyses were performed. At ROC analysis, the most predictive echocardiographic methods were; RVFAC (AUC = 0.892), RVMPI (AUC 0.785), TAPSE (AUC 0.849) and 3DE-RV (AUC 0.909). 3DE-RV appeared the most accurate compared to CMR, although underestimated true RV volumes. CONCLUSION: As compared to CMR; 3DE-RV, RVFAC, TAPSE and RVMPI were the most reliable predictors of RV function. These parameters can be recommended for clinical use.

Quantitation of mitral regurgitation after percutaneous MitraClip repair: comparison of Doppler echocardiography and cardiac magnetic resonance imaging.

OBJECTIVE: Percutaneous valve intervention for severe mitral regurgitation (MR) using the MitraClip is a novel technology. Quantitative assessment of residual MR by transthoracic echocardiography (TTE) is challenging, with multiple eccentric jets and artifact from the clips. Cardiovascular magnetic resonance (CMR) is the reference standard for left and right ventricular volumetric assessment. CMR phase-contrast flow imaging has superior reproducibility for quantitation of MR compared to echocardiography. The objective of this study was to establish the feasibility and reproducibility of CMR in quantitating residual MR after MitraClip insertion in a prospective study. METHODS: Twenty-five patients underwent successful MitraClip insertion. Nine were excluded due to non-magnetic resonance imaging (MRI) compatible implants or arrhythmia, leaving 16 who underwent a comprehensive CMR examination at 1.5 T (Siemens Aera) with multiplanar steady state free precession (SSFP) cine imaging (cine CMR), and phase-contrast flow acquisitions (flow CMR) at the mitral annulus atrial to the MitraClip, and the proximal aorta. Same-day echocardiography was performed with two-dimensional (2D) visualization and Doppler. CMR and echocardiographic data were independently and blindly analyzed by expert readers. Inter-rater comparison was made by concordance correlation coefficient (CCC) with 95% confidence intervals (CIs), and Bland-Altman (BA) methods. RESULTS: Mean age was 79 years, and mean LVEF was 44%±11% by CMR and 54%±16% by echocardiography. Inter-observer reproducibility of echocardiographic visual categorical grading by expert readers was poor, with a CCC of 0.475 (-0.7, 0.74). Echocardiographic Doppler regurgitant fraction reproducibility was modest (CCC 0.59, 0.15-0.84; BA mean difference -3.7%, -38% to 31%). CMR regurgitant fraction reproducibility was excellent (CCC 0.95, 0.86-0.98; BA mean difference -2.4%, -11.9 to 7.0), with a lower mean difference and narrower limits of agreement compared to echocardiography. Categorical severity grading by CMR using published ranges had good inter-observer agreement (CCC 0.86, 0.62-0.95). CONCLUSIONS: CMR performs very well in the quantitation of MR after MitraClip insertion, with excellent reproducibility compared to echocardiographic methods. CMR is a useful technique for the comprehensive evaluation of residual regurgitation in patients after MitraClip. Technical limitations exist for both techniques, and quantitation remains a challenge in some patients.

The Feasibility and Clinical Utility of Microsphere Contrast-enhanced Transthoracic Echocardiography in Adult Congenital Heart Disease.

BACKGROUND: Transthoracic echocardiography (TTE) plays a key role in adult congenital heart disease (ACHD). However, a significant number of studies are nondiagnostic due to poor image quality. Enhancement of the blood pool-tissue interface with contrast-enhanced TTE (CE-TTE) can improve image quality in suboptimal studies. The aim of this analysis was to evaluate feasibility and clinical utility of CE-TTE in the assessment of patients with ACHD. METHODS: A retrospective analysis of all CE-TTE performed in ACHD patients at our institution from August 2007 to May 2014 was performed. Endocardial definition scores (EDS) for each segment in the right and left ventricles were graded pre- and postcontrast imaging, as 1 = good, 2 = suboptimal, 3 = not seen. The endocardial border definition score index (EBDSI) was also calculated pre- and postcontrast imaging. RESULTS: Twenty patients with ACHD had 24 CE. Summation data for all ventricular EDS for unenhanced TTE vs. CE-TTE imaging was: EDS 1 = 136 vs. 314, EDS 2 = 119 vs. 72, EDS 3 = 162 vs. 31, respectively. Wilcoxon matched-pairs rank-signed test showed a significant ranking difference (improvement) pre- and postcontrast for the combined ventricular data (P < .0001) and the individual left and right ventricular data (all P < .0001). The EBDSI for combined ventricular data using CE-TTE was significantly lower than for noncontrast imaging (1.23 ± 0.49 vs. 2.06 ± 0.62, P < .0001). There was one minor contrast adverse reaction. CONCLUSIONS: CE-TTE resulted in significantly improved right and left ventricular endocardial definition and improved EDBSI. CE-TTE should be viewed as an additional imaging technique that is available to help assess patients with ACHD, especially those with nondiagnostic images.

Feasibility of perflutren microsphere contrast transthoracic echocardiography in the visualization of ventricular endocardium during venovenous extracorporeal membrane oxygenation in a validated ovine model.

BACKGROUND: Transthoracic echocardiography (TTE) during extra corporeal membrane oxygenation (ECMO) is important but can be technically challenging. Contrast-specific TTE can improve imaging in suboptimal studies. These contrast microspheres are hydrodynamically labile structures. This study assessed the feasibility of contrast echocardiography (CE) during venovenous (VV) ECMO in a validated ovine model. METHOD: Twenty-four sheep were commenced on VV ECMO. Parasternal long-axis (Plax) and short-axis (Psax) views were obtained pre- and postcontrast while on VV ECMO. Endocardial definition scores (EDS) per segment were graded: 1 = good, 2 = suboptimal 3 = not seen. Endocardial border definition score index (EBDSI) was calculated for each view. Endocardial length (EL) in the Plax view for the left ventricle (LV) and right ventricle (RV) was measured. RESULTS: Summation EDS data for the LV and RV for unenhanced TTE (UE) versus CE TTE imaging: EDS 1 = 289 versus 346, EDS 2 = 38 versus 10, EDS 3 = 33 versus 4, respectively. Wilcoxon matched-pairs rank-sign tests showed a significant ranking difference (improvement) pre- and postcontrast for the LV (P < 0.0001), RV (P < 0.0001) and combined ventricular data (P < 0.0001). EBDSI for CE TTE was significantly lower than UE TTE for the LV (1.05 ± 0.17 vs. 1.22 ± 0.38, P = 0.0004) and RV (1.06 ± 0.22 vs. 1.42 ± 0.47, P = 0.0.0006) respectively. Visualized EL was significantly longer in CE versus UE for both the LV (58.6 ± 11.0 mm vs. 47.4 ± 11.7 mm, P < 0.0001) and the RV (52.3 ± 8.6 mm vs. 36.0 ± 13.1 mm, P < 0.0001), respectively. CONCLUSIONS: Despite exposure to destructive hydrodynamic forces, CE is a feasible technique in an ovine ECMO model. CE results in significantly improved EDS and increased EL.

A novel echocardiographic imaging technique, intracatheter echocardiography, to guide veno-venous extracorporeal membrane oxygenation cannulae placement in a validated ovine model.

BACKGROUND: Echocardiography plays a fundamental role in cannulae insertion and positioning for extracorporeal membrane oxygenation (ECMO). Optimal access and return cannulae orientation is required to prevent recirculation. The aim of this study was to compare a novel imaging technique, intracatheter echocardiography (iCATHe), with conventional intracardiac echocardiography (ICE) to guide placement of ECMO access and return venous cannulae. METHODS: Twenty sheep were commenced on veno-venous ECMO (VV ECMO). Access and return ECMO cannulae were positioned using an ICE-guided technique. Following the assessment of cannulae position, the ICE probe was then introduced inside the cannulae, noting location of the tip. After 24 h, the sheep were euthanized and cannulae position was determined at post mortem. The two-tailed McNemar test was used to compare iCATHe with ICE cannulae positioning. RESULTS: ICE and iCATHe imaging was possible in all 20 sheep commenced on ECMO. There was no significant difference between the two methods in assessing access cannula position (proportion correct for each 90%, incorrect 10%). However, there was a significant difference between ICE and iCATHe success rates for the return cannula (p = 0.001). Proportion correct for iCATHe and ICE was 80% and 15% respectively. iCATHe was 65% more successful (95% CI 27% to 75%) at predicting the placement of the return cannula. There were no complications related to the ICE or iCATHe imaging. CONCLUSION: iCATHe is a safe and feasible imaging technique to guide real-time VV ECMO cannulae placement and improves accuracy of return cannula positioning compared to ICE.