Sharon W. Kirschbaum

Accuracy and Reproducibility of Quantitation of Left Ventricular Function by Real-Time Three-Dimensional Echocardiography Versus Cardiac Magnetic Resonance

The aim of this study was to investigate the accuracy and reproducibility of the quantification of left ventricular (LV) function by real-time 3-dimensional echocardiography (RT3DE) using current state-of-the-art hardware and software. Compared with cardiac magnetic resonance (CMR), previous generations of hardware and software for RT3DE significantly underestimated LV volumes partly because of inherent factors such as limited spatial and temporal resolution. Also, RT3DE volumes were compared with short-axis CMR data, whereas a combined short-axis and long-axis analysis is known to be superior. Twenty-four subjects (mean age 51 +/- 12 years, 17 men) in sinus rhythm and with good to excellent 2-dimensional image quality underwent RT3DE and CMR within 1 day. The acquisition of RT3DE data was done with current state-of-the-art hardware and software. Two blinded experts performed off-line LV volume analysis. Global LV volumes were determined from semiautomated border detection on the basis of endocardial speckle tracking with biplane projections using QLAB version 6.0. Volumes derived by magnetic resonance imaging were quantified from combined short-axis and long-axis series. The volume-rate on RT3DE was 33 +/- 8 Hz (range 19 to 42). Excellent correlations were found (R2 > or = 0.97) between CMR and RT3DE for global LV end-diastolic volume, LV end-systolic volume, the LV ejection fraction, and LV phase volumes (24 phases/cardiac cycle). Bland-Altman analyses showed mean differences of -7.1 ml, -4.2 ml, 0.2%, and -5.8 ml and 95% limits of agreement of +/-19.7 ml, +/-8.3 ml, +/-6.2%, and +/-15.4 ml for global LV end-diastolic volume, LV end-systolic volume, the LV ejection fraction, and LV phase volumes, respectively. Interobserver variability was 5.2% for global LV end-diastolic volume, 6.4% for LV end-systolic volume, and 7.6% for the LV ejection fraction. In conclusion, in patients with good acoustic windows, RT3DE using state-of-the-art technology provides accurate and reproducible measurements of global LV volumes, LV volume changes over time, and the LV ejection fraction.

Addition of the long-axis information to short-axis contours reduces interstudy variability of left-ventricular analysis in cardiac magnetic resonance studies

Objectives:To reduce interstudy variability using long-axis information for correcting short-axis (SA) contours at basal and apical level for left-ventricular analysis by magnetic resonance imaging. Materials and Methods:A total of 20 patients with documented heart failure and 20 volunteers underwent magnetic resonance imaging examination twice for measuring endocardial end-diastolic volume, endocardial end-systolic volume, mass, and ejection fraction. The boundary of the left ventricle, the mitral valve plane, and apex were marked manually on the 2- and 4-chamber long-axis images. Automatic epicardial and endocardial contour detection was performed on the SA images using the intersection of the outlines from the long axis as starting positions. The same observer compared the interstudy variability of this method with analysis that was based on the SA images only. Results:The interstudy variability decreased when information from the long axis was included; for end-systolic volume, 9.6% versus 4.7% (P = 0.00014); for end-diastolic volume, 4.9% versus 2.5% (P = 0.0011); for mass, 7.4% versus 5.0% (P = 0.11); and for ejection fraction 12.2% versus 5.6% (P = 0.0017), respectively. Conclusions:Identification of the mitral valve plane and apex on long-axis images to limit the extent of volume at the base and the apex of the heart reduces interstudy variability for left-ventricular functional assessment.

The role of shear stress in atherosclerosis: action through gene expression and inflammation?

Atherosclerotic lesions preferentially localize near side branches or curved vessels. During the last few decades, research has been shown that low or low and oscillating shear stress is associated with plaque location. Despite ample evidence, the precise mechanism is unknown. This is mainly because of a lack of appropriate animal models. We describe two novel methods to study the hypothesis that shear stress acts through endothelial gene expression or shear stress acts through localizing of inflammation. Both literature evidence and own findings support a role for both mechanisms in atherosclerosis.

A Simplified Continuity Equation Approach to the Quantification of Stenotic Bicuspid Aortic Valves using Velocity-Encoded Cardiovascular Magnetic Resonance

OBJECTIVE We aimed to compare velocity-encoded cine cardiac magnetic resonance (CMR) with an established echocardiographic method for noninvasive measurement of aortic valve area (AVA) using the continuity equation. METHODS AND RESULTS Twenty consecutive young adults with stenotic bicuspid aortic valves were examined with CMR and transthoracic echocardiography (TTE). CMR AVA was calculated by the continuity equation, dividing stroke volume by the aortic velocity-time integral (VTIAorta), the stroke volume measured both by ventricular volume analysis and by phase contrast velocity mapping at 4 levels (1 subvalvar and 3 supravalvar). Stroke volumes measured at all levels correlated well with those from volumetric analysis. The CMR AVAs calculated using volumetric analysis and VTIAorta from jet velocity mapping correlated and agreed well with TTE AVA measurements (R2 = 0.83). When CMR AVA was calculated more rapidly using volume flow and VTIAorta both measured from the same trans-jet velocity acquisition, R2 was 0.74, with a bias and limits of agreement of 0.02 (-0.44, 0.47) cm2. CONCLUSIONS Continuity equation calculation of the AVA using CMR velocity mapping, with or without ventricular volumetric measurement, correlated and agreed well with the comparable and widely accepted TTE approach.

Combining magnetic resonance viability variables better predicts improvement of myocardial function prior to percutaneous coronary intervention

OBJECTIVE To optimize the predictive value of cardiac magnetic resonance imaging (MRI) for improvement of myocardial dysfunction prior to percutaneous coronary intervention (PCI). METHODS We performed cardiac MRI in 72 patients (male 87%, age 60 years) before and 6 months after successful PCI (43/72) or unsuccessful PCI (29/72) of a chronic total coronary occlusion (CTO). Before PCI, 5 viability parameters were evaluated: transmural extent of infarction (TEI), contractile reserve during dobutamine, end diastolic wall thickness, unenhanced rim thickness and segmental wall thickening of the unenhanced rim (SWTur). Multivariate analysis was performed and based on the regression coefficient (RC) a predictive score was constructed. Diagnostic performance to predict improvement in myocardial function for each parameter and for the viability score was determined. RESULTS The predictive value of a combination of contractile reserve, SWTur and TEI was incremental to TEI alone (AUROC 0.91 vs. 0.77; p<0.001). A viability score of ≥ 5 based on contractile reserve (RC=4), SWTur (RC=1) and TEI (RC=2) was 91% sensitive and 84% specific in predicting improvement of myocardial function. CONCLUSION Combining viability parameters results in a better prediction of improvement of dysfunctional myocardial segments after a successful PCI.

Complete Percutaneous Revascularization for Multivessel Disease in Patients With Impaired Left Ventricular Function: Pre- and Post-Procedural Evaluation by Cardiac Magnetic Resonance Imaging

OBJECTIVES The aim of this study was to investigate the effect of complete, incomplete, and unsuccessful revascularization by percutaneous coronary intervention (PCI) on left ventricular ejection fraction (EF) in patients with multivessel disease and impaired left ventricular function and assess the diagnostic accuracy of cardiac magnetic resonance imaging (MRI) for improvement in EF. BACKGROUND The effect of PCI for multivessel coronary artery disease on long-term myocardial function and the predictive value of cardiac MRI on global function are incompletely investigated. METHODS Cardiac MRI was performed in patients with multivessel disease before and 6 months after complete revascularization (n = 34) or incomplete revascularization (n = 22) or in patients without successful revascularization (n = 15). For the prediction of recovery of EF, wall thickening was quantified on cine images at rest and during 5- and 10-microg/kg/min dobutamine. The transmural extent of infarction was quantified on delayed enhancement cardiac MRI. RESULTS The EF improved significantly after complete revascularization (46 +/- 12% to 51 +/- 13%; p < 0.0001) but did not change after incomplete (49 +/- 11% to 49 +/- 10%; p = 0.88) or unsuccessful revascularization (49 +/- 13% to 47 +/- 13%; p = 0.11). Sensitivity, specificity, positive and negative predictive value for the prediction of improvement in EF of >4% after PCI were 100%, 75%, 74%, and 100%, respectively, for dobutamine-cardiac MRI and 70%, 77%, 70%, and 77%, respectively, for delayed enhancement-cardiac MRI. CONCLUSIONS Complete revascularization for multivessel coronary artery disease improves EF, whereas EF did not change in patients after incomplete or unsuccessful revascularization. Improvement in EF can be predicted by performing cardiac MRI before PCI.

Accurate automatic papillary muscle identification for quantitative left ventricle mass measurements in cardiac magnetic resonance imaging.

RATIONALE AND OBJECTIVES We sought to evaluate the automatic detection of the papillary muscle and to determine its influence on quantitative left ventricular (LV) mass assessment. MATERIALS AND METHODS Twenty-eight Yorkshire-Landrace swine and 10 volunteers underwent cardiac magnetic resonance imaging (CMR) of the left ventricle. The variability in measurements of LV papillary muscles traced automatically and manually were compared to intra- and interobserver variabilities. CMR-derived LV mass with the papillary muscle included or excluded from LV mass measurements was compared to true mass at autopsy of the Yorkshire-Landrace swine. RESULTS Automatic LV papillary muscle mass from all subjects correlated well with manually derived LV papillary muscle mass measurements (r = 0.84) with no significant bias between both measurements (mean difference +/- SD, 0.0 +/- 1.5 g; P = .98). The variability in results related to the contour detection method used was not statistically significant different compared to intra- and interobserver variabilities (P = .08 and P = .97, respectively). LV mass measurements including the papillary muscle showed significantly less underestimation (-10.6 +/- 7.1 g) with the lowest percentage variability (6%) compared to measurements excluding the papillary muscles (mean underestimation, -15.1 +/- 7.4 g percentage variability, 7%). CONCLUSION The automatic algorithm for detecting the papillary muscle was accurate with variabilities comparable to intra- and interobserver variabilities. LV mass is determined most accurately when the papillary muscles are included in the LV mass measurements. Taken together, these observations warrant the inclusion of automatic contour detection of papillary muscle mass in studies that involve the determination of LV mass.

Contractile reserve in segments with nontransmural infarction in chronic dysfunctional myocardium using low-dose dobutamine CMR

OBJECTIVES This study sought to quantify contractile reserve of chronic dysfunctional myocardium, in particular in segments with intermediate transmural extent of infarction (TEI), using low-dose dobutamine cardiac magnetic resonance (CMR) in patients with a chronic total coronary occlusion (CTO). BACKGROUND Recovery of dysfunctional segments with intermediate TEI after percutaneous coronary intervention is variable and difficult to predict, and may be related to contractility of the unenhanced rim. METHODS Fifty-one patients (mean age 60 +/- 9 years, 76% male) with a CTO underwent CMR at baseline and 35 patients underwent CMR at follow-up to quantify segmental wall thickening (SWT) at rest during 5 and 10 microg/kg/min dobutamine, and at follow-up. Delayed-enhancement CMR was performed to quantify TEI. Dysfunctional segments were stratified according to TEI, end-diastolic wall thickness (EDWT), or unenhanced rim thickness, and SWT was quantified. Segments with an intermediate TEI (25% to 75%) were further stratified according to baseline SWT of the unenhanced rim (SWT(UR)) (<45% and >45%), and SWT was quantified. For each parameter, odds ratio (OR) and diagnostic performance for the prediction of contractile reserve were calculated. RESULTS Significant contractile reserve was present in dysfunctional segments with EDWT >6 mm, unenhanced rim thickness >3 mm, or TEI of <25%; only TEI had significant relation with contractile reserve (OR: 0.98; 95% confidence interval [CI]: 0.96 to 0.99; p = 0.02). In segments with intermediate TEI (n = 58), mean SWT did not improve significantly. However, segments with SWT(UR) <45% showed contractile reserve and improved at follow-up, whereas segments with SWT(UR) >45% were unchanged. SWT(UR) had a significant relation with contractile reserve (OR: 0.98; 95% CI: 0.97 to 0.99; p = 0.02). CONCLUSIONS CMR quantification of transmurality of infarcted myocardium allows the assessment of the potential of dysfunctional segments to improve in function during dobutamine of most segments. However, in segments with intermediate TEI, measurement of baseline contractility of the epicardial rim better identifies which segments maintain contractile reserve.

Comprehensive visualization of multimodal cardiac imaging data for assessment of coronary artery disease: first clinical results of the SMARTVis tool.

PurposeIn clinical practice, both coronary anatomy and myocardial perfusion information are needed to assess coronary artery disease (CAD). The extent and severity of coronary stenoses can be determined using computed tomography coronary angiography (CTCA); the presence and amount of ischemia can be identified using myocardial perfusion imaging, such as perfusion magnetic resonance imaging (PMR). To determine which specific stenosis is associated with which ischemic region, experts use assumptions on coronary perfusion territories. Due to the high variability between patient’s coronary artery anatomies, as well as the uncertain relation between perfusion territories and supplying coronary arteries, patient-specific systems are needed.Material and methodsWe present a patient-specific visualization system, called Synchronized Multimodal heART Visualization (SMARTVis), for relating coronary stenoses and perfusion deficits derived from CTCA and PMR, respectively. The system consists of the following comprehensive components: (1) two or three-dimensional fusion of anatomical and functional information, (2) automatic detection and ranking of coronary stenoses, (3) estimation of patient-specific coronary perfusion territories.ResultsThe potential benefits of the SMARTVis tool in assessing CAD were investigated through a case-study evaluation (conventional vs. SMARTVis tool): two experts analyzed four cases of patients with suspected multivessel coronary artery disease. When using the SMARTVis tool, a more reliable estimation of the relation between perfusion deficits and stenoses led to a more accurate diagnosis, as well as a better interobserver diagnosis agreement.ConclusionThe SMARTVis comprehensive visualization system can be effectively used to assess disease status in multivessel CAD patients, offering valuable new options for the diagnosis and management of these patients.

Comparison of adenosine magnetic resonance perfusion imaging with invasive coronary flow reserve and fractional flow reserve in patients with suspected coronary artery disease

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