Natural language processing for identification of hypertrophic cardiomyopathy patients from cardiac magnetic resonance reports.

BACKGROUND: Cardiac magnetic resonance (CMR) imaging is important for diagnosis and risk stratification of hypertrophic cardiomyopathy (HCM) patients. However, collection of information from large numbers of CMR reports by manual review is time-consuming, error-prone and costly. Natural language processing (NLP) is an artificial intelligence method for automated extraction of information from narrative text including text in CMR reports in electronic health records (EHR). Our objective was to assess whether NLP can accurately extract diagnosis of HCM from CMR reports. METHODS: An NLP system with two tiers was developed for information extraction from narrative text in CMR reports; the first tier extracted information regarding HCM diagnosis while the second extracted categorical and numeric concepts for HCM classification. We randomly allocated 200 HCM patients with CMR reports from 2004 to 2018 into training (100 patients with 185 CMR reports) and testing sets (100 patients with 206 reports). RESULTS: NLP algorithms demonstrated very high performance compared to manual annotation. The algorithm to extract HCM diagnosis had accuracy of 0.99. The accuracy for categorical concepts included HCM morphologic subtype 0.99, systolic anterior motion of the mitral valve 0.96, mitral regurgitation 0.93, left ventricular (LV) obstruction 0.94, location of obstruction 0.92, apical pouch 0.98, LV delayed enhancement 0.93, left atrial enlargement 0.99 and right atrial enlargement 0.98. Accuracy for numeric concepts included maximal LV wall thickness 0.96, LV mass 0.99, LV mass index 0.98, LV ejection fraction 0.98 and right ventricular ejection fraction 0.99. CONCLUSIONS: NLP identified and classified HCM from CMR narrative text reports with very high performance.

TURBINE-MRE: A 3D hybrid radial-Cartesian EPI acquisition for MR elastography.

PURPOSE: To develop a novel magnetic resonance elastography (MRE) acquisition using a hybrid radial EPI readout scheme (TURBINE), and to demonstrate its feasibility to obtain wave images and stiffness maps in a phantom and in vivo brain. METHOD: The proposed 3D TURBINE-MRE is based on a spoiled gradient-echo MRE sequence with the EPI readout radially rotating about the phase-encoding axis to sample a full 3D k-space. A polyvinyl chloride phantom and 6 volunteers were scanned on a compact 3T GE scanner with a 32-channel head coil at 80 Hz and 60 Hz external vibration, respectively. For comparison, a standard 2D, multislice, spin-echo (SE) EPI-MRE acquisition was also performed with the same motion encoding and resolution. The TURBINE-MRE images were off-line reconstructed with iterative SENSE algorithm. The regional ROI analysis was performed on the 6 volunteers, and the median stiffness values were compared between SE-EPI-MRE and TURBINE-MRE. RESULTS: The 3D wave-field images and the generated stiffness maps were comparable between TURBINE-MRE and standard SE-EPI-MRE for the phantom and the volunteers. The Bland-Altman plot showed no significant difference in the median regional stiffness values between the two methods. The stiffness measured with the 2 methods had a strong linear relationship with a Pearson correlation coefficient of 0.943. CONCLUSION: We demonstrated the feasibility of the new TURBINE-MRE sequence for acquiring the desired 3D wave-field data and stiffness maps in a phantom and in-vivo brains. This pilot study encourages further exploration of TURBINE-MRE for functional MRE, free-breathing abdominal MRE, and cardiac MRE applications.

An under-recognized phenomenon: Myocardial volume change during the cardiac cycle.

BACKGROUND: Myocardial volume is assumed to be constant over the cardiac cycle in the echocardiographic models used by professional guidelines, despite evidence that suggests otherwise. The aim of this paper is to use literature-derived myocardial strain values from healthy patients to determine if myocardial volume changes during the cardiac cycle. METHODS: A systematic review for studies with longitudinal, radial, and circumferential strain from echocardiography in healthy volunteers ultimately yielded 16 studies, corresponding to 2917 patients. Myocardial volume in systole (MVs) and diastole (MVd) was used to calculate MVs/MVd for each study by applying this published strain data to three models: the standard ellipsoid geometric model, a thin-apex geometric model, and a strain-volume ratio. RESULTS: MVs/MVd<1 in 14 of the 16 studies, when computed using these three models. A sensitivity analysis of the two geometric models was performed by varying the dimensions of the ellipsoid and calculating MVs/MVd. This demonstrated little variability in MVs/MVd, suggesting that strain values were the primary determinant of MVs/MVd rather than the geometric model used. Another sensitivity analysis using the 97.5th percentile of each orthogonal strain demonstrated that even with extreme values, in the largest two studies of healthy populations, the calculated MVs/MVd was <1. CONCLUSIONS: Healthy human myocardium appears to decrease in volume during systole. This is seen in MRI studies and is clinically relevant, but this study demonstrates that this characteristic was also present but unrecognized in the existing echocardiography literature.

Cardiac MR elastography using reduced-FOV, single-shot, spin-echo EPI.

PURPOSE: To implement a reduced field of view (rFOV) technique for cardiac MR elastography (MRE) and to demonstrate the improvement in image quality of both magnitude images and post-processed MRE stiffness maps compared to the conventional full field of view (full-FOV) acquisition. METHODS: With Institutional Review Board approval, 17 healthy volunteers underwent both full-FOV and rFOV cardiac MRE scans using 140-Hz vibrations. Two cardiac radiologists blindly compared the magnitude images and stiffness maps and graded the images based on several image quality attributes using a 5-point ordinal scale. Fisher's combined probability test was performed to assess the overall evaluation. The octahedral shear strain-based signal-to-noise ratio (OSS-SNR) and median stiffness over the left ventricular myocardium were also compared. RESULTS: One volunteer was excluded because of an inconsistent imaging resolution during the exam. In the remaining 16 volunteers (9 males, 7 females), the rFOV scans outperformed the full-FOV scans in terms of subjective image quality and ghosting artifacts in the magnitude images and stiffness maps, as well as the overall preference. The quantitative measurements showed that rFOV had significantly higher OSS-SNR (median: 1.4 [95% confidence interval (CI): 1.2-1.5] vs. 2.1 [95% CI: 1.8-2.4]), P < 0.05) compared to full-FOV. Although no significant change was found in the median myocardial stiffness between the 2 scans, we observed a decrease in the stiffness variation within the myocardium from 2.1 kPa (95% CI: [1.9, 2.3]) to 1.9 kPa (95% CI: [1.7, 2.0]) for full-FOV and rFOV, respectively (P < 0.05) in a subgroup of 7 subjects with ghosting present in the myocardium. CONCLUSION: This pilot volunteer study demonstrated that rFOV cardiac MRE has the capability to reduce ghosting and to improve image quality in both MRE magnitude images and stiffness maps. Magn Reson Med 80:231-238, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Regional assessment of in vivo myocardial stiffness using 3D magnetic resonance elastography in a porcine model of myocardial infarction.

PURPOSE: The stiffness of a myocardial infarct affects the left ventricular pump function and remodeling. Magnetic resonance elastography (MRE) is a noninvasive imaging technique for measuring soft-tissue stiffness in vivo. The purpose of this study was to investigate the feasibility of assessing in vivo regional myocardial stiffness with high-frequency 3D cardiac MRE in a porcine model of myocardial infarction, and compare the results with ex vivo uniaxial tensile testing. METHODS: Myocardial infarct was induced in a porcine model by embolizing the left circumflex artery. Fourteen days postinfarction, MRE imaging was performed in diastole using an echocardiogram-gated spin-echo echo-planar-imaging sequence with 140-Hz vibrations and 3D MRE processing. The MRE stiffness and tensile modulus from uniaxial testing were compared between the remote and infarcted myocardium. RESULTS: Myocardial infarcts showed increased in vivo MRE stiffness compared with remote myocardium (4.6 ± 0.7 kPa versus 3.0 ± 0.6 kPa, P = 0.02) within the same pig. Ex vivo uniaxial mechanical testing confirmed the in vivo MRE results, showing that myocardial infarcts were stiffer than remote myocardium (650 ± 80 kPa versus 110 ± 20 kPa, P = 0.01). CONCLUSIONS: These results demonstrate the feasibility of assessing in vivo regional myocardial stiffness with high-frequency 3D cardiac MRE. Magn Reson Med 79:361-369, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Quantitative 3D magnetic resonance elastography: Comparison with dynamic mechanical analysis.

PURPOSE: Magnetic resonance elastography (MRE) is a rapidly growing noninvasive imaging technique for measuring tissue mechanical properties in vivo. Previous studies have compared two-dimensional MRE measurements with material properties from dynamic mechanical analysis (DMA) devices that were limited in frequency range. Advanced DMA technology now allows broad frequency range testing, and three-dimensional (3D) MRE is increasingly common. The purpose of this study was to compare 3D MRE stiffness measurements with those of DMA over a wide range of frequencies and shear stiffnesses. METHODS: 3D MRE and DMA were performed on eight different polyvinyl chloride samples over 20-205 Hz with stiffness between 3 and 23 kPa. Driving frequencies were chosen to create 1.1, 2.2, 3.3, 4.4, 5.5, and 6.6 effective wavelengths across the diameter of the cylindrical phantoms. Wave images were analyzed using direct inversion and local frequency estimation algorithm with the curl operator and compared with DMA measurements at each corresponding frequency. Samples with sufficient spatial resolution and with an octahedral shear strain signal-to-noise ratio > 3 were compared. RESULTS: Consistency between the two techniques was measured with the intraclass correlation coefficient (ICC) and was excellent with an overall ICC of 0.99. CONCLUSIONS: 3D MRE and DMA showed excellent consistency over a wide range of frequencies and stiffnesses. Magn Reson Med 77:1184-1192, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

In vivo, high-frequency three-dimensional cardiac MR elastography: Feasibility in normal volunteers.

PURPOSE: Noninvasive stiffness imaging techniques (elastography) can image myocardial tissue biomechanics in vivo. For cardiac MR elastography (MRE) techniques, the optimal vibration frequency for in vivo experiments is unknown. Furthermore, the accuracy of cardiac MRE has never been evaluated in a geometrically accurate phantom. Therefore, the purpose of this study was to determine the necessary driving frequency to obtain accurate three-dimensional (3D) cardiac MRE stiffness estimates in a geometrically accurate diastolic cardiac phantom and to determine the optimal vibration frequency that can be introduced in healthy volunteers. METHODS: The 3D cardiac MRE was performed on eight healthy volunteers using 80 Hz, 100 Hz, 140 Hz, 180 Hz, and 220 Hz vibration frequencies. These frequencies were tested in a geometrically accurate diastolic heart phantom and compared with dynamic mechanical analysis (DMA). RESULTS: The 3D Cardiac MRE was shown to be feasible in volunteers at frequencies as high as 180 Hz. MRE and DMA agreed within 5% at frequencies greater than 180 Hz in the cardiac phantom. However, octahedral shear strain signal to noise ratios and myocardial coverage was shown to be highest at a frequency of 140 Hz across all subjects. CONCLUSION: This study motivates future evaluation of high-frequency 3D MRE in patient populations. Magn Reson Med 77:351-360, 2017. © 2016 Wiley Periodicals, Inc.

Cardiac MR elastography for quantitative assessment of elevated myocardial stiffness in cardiac amyloidosis.

PURPOSE: To evaluate if cardiac magnetic resonance elastography (MRE) can measure increased stiffness in patients with cardiac amyloidosis. Myocardial tissue stiffness plays an important role in cardiac function. A noninvasive quantitative imaging technique capable of measuring myocardial stiffness could aid in disease diagnosis, therapy monitoring, and disease prognostic strategies. We recently developed a high-frequency cardiac MRE technique capable of making noninvasive stiffness measurements. MATERIALS AND METHODS: In all, 16 volunteers and 22 patients with cardiac amyloidosis were enrolled in this study after Institutional Review Board approval and obtaining formal written consent. All subjects were imaged head-first in the supine position in a 1.5T closed-bore MR imager. 3D MRE was performed using 5 mm isotropic resolution oblique short-axis slices and a vibration frequency of 140 Hz to obtain global quantitative in vivo left ventricular stiffness measurements. The median stiffness was compared between the two cohorts. An octahedral shear strain signal-to-noise ratio (OSS-SNR) threshold of 1.17 was used to exclude exams with insufficient motion amplitude. RESULTS: Five volunteers and six patients had to be excluded from the study because they fell below the 1.17 OSS-SNR threshold. The myocardial stiffness of cardiac amyloid patients (median: 11.4 kPa, min: 9.2, max: 15.7) was significantly higher (P = 0.0008) than normal controls (median: 8.2 kPa, min: 7.2, max: 11.8). CONCLUSION: This study demonstrates the feasibility of 3D high-frequency cardiac MRE as a contrast-agent-free diagnostic imaging technique for cardiac amyloidosis. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1361-1367.

Evaluation of liver stiffness with magnetic resonance elastography in patients with constrictive pericarditis: Preliminary findings.

PURPOSE: To evaluate with magnetic resonance elastography (MRE) whether patients with constrictive pericarditis (CP) have increased hepatic stiffness. CP results in reduced pericardial compliance, ventricular interdependence, and right heart failure. Patients with untreated CP may develop liver fibrosis and ultimately cirrhosis due to chronic venous congestion. Chronic venous congestion ± fibrosis may lead to increased liver stiffness. MATERIALS AND METHODS: Prospectively, patients with suspected CP underwent 2D transthoracic echocardiography, cardiac MRI, and liver MRE. An automated method was used to draw regions of interest (ROIs) on the stiffness maps to calculate the mean liver stiffness in kilopascals (kPa). A t-test with α = 0.05 was performed between stiffness values of patients with positive and negative CP findings based on previously published echocardiography criteria. RESULTS: Nineteen patients met inclusion criteria with a mean ± standard deviation (SD) age of 51 ± 16 years. Nine patients (47%) had CP. Mean liver stiffness trended higher in patients with CP compared to those without CP (4.04 kPa vs. 2.46; P = 0.045). Liver stiffness correlated with MRI septal bounce (P = 0.04), inferior vena cava size (P = 0.003), echo abnormal septal motion (P = 0.04), and echo mitral inflow variation >25% (P = 0.02). Only MRI septal bounce predicted CP by echocardiography (P < 0.001). CONCLUSION: CP was associated with increased liver stiffness. The increased stiffness is most likely secondary to chronic hepatic venous congestion and/or fibrosis. MRE may be useful for noninvasive liver stiffness assessment in CP. J. Magn. Reson. Imaging 2016;44:81-88.

A history of preeclampsia is associated with a risk for coronary artery calcification 3 decades later.

BACKGROUND: A history of preeclampsia is an independent risk factor for cardiac events and stroke. Changes in vasculature structure that contribute to these associations are not well understood. OBJECTIVE: The aim of this study was to quantify coronary artery calcification (CAC), a known risk factor for cardiac events, in a prospective cohort of women with and without histories of preeclampsia. STUDY DESIGN: Women without prior cardiovascular events (40 with and 40 without histories of preeclampsia, matched for parity and age at index birth) were recruited from a large population-based cohort of women who were residents of Olmsted County, Minnesota, and who delivered from 1976 through 1982. Computed tomography was performed to measure CAC in Agatston units. All pregnancy histories and covariates were confirmed by review of the medical records. Current clinical variables were assessed at the time of imaging. Differences between women with and without histories of preeclampsia were examined using χ(2) tests and tests; CAC, in particular, was compared as a categorical and ordinal variable, with a χ(2) test and with Wilcoxon 2-sample tests and ordinal logistic regression, as appropriate. RESULTS: Mean age (SD) at imaging was 59.5 (±4.6) years. Systolic and diastolic blood pressures, hyperlipidemia, and current diabetes status did not differ between women with and without histories of preeclampsia. However, the frequencies of having a current clinical diagnosis of hypertension (60% vs 20%, P < .001) and higher body mass index in kg/m(2) (expressed as median [25th-75th percentile], 29.8 [25.9-33.7] vs 25.3 [23.1-32.0], P = .023) were both greater in the women with histories of preeclampsia compared to those without. The frequency of a CAC score >50 Agatston units was also greater in the preeclampsia group (23% vs 0%, P = .001). Compared to women without preeclampsia, the odds of having a higher CAC score was 3.54 (confidence interval [CI], 1.39-9.02) times greater in women with prior preeclampsia without adjustment, and 2.61 (CI, 0.95-7.14) times greater after adjustment for current hypertension. After adjustment for body mass index alone, the odds of having a higher CAC based on a history of preeclampsia remained significant at 3.20 (CI, 1.21-8.49). CONCLUSION: In this first prospective cohort study with confirmation of preeclampsia by medical record review, a history of preeclampsia is associated with an increased risk of CAC >30 years after affected pregnancies, even after controlling individually for traditional risk factors. A history of preeclampsia should be considered in risk assessment when initiating primary prevention strategies to reduce cardiovascular disease in women. Among women with histories of preeclampsia, the presence of CAC may be able to identify those at a particularly high cardiovascular risk, and should be the subject of future studies.

Imaging Findings of Congestive Hepatopathy.

Congestive hepatopathy (CH) refers to hepatic abnormalities that result from passive hepatic venous congestion. Prolonged exposure to elevated hepatic venous pressure may lead to liver fibrosis and cirrhosis. Liver dysfunction and corresponding clinical signs and symptoms typically manifest late in the disease process. Recognition of CH at imaging is critical because advanced liver fibrosis may develop before the condition is suspected clinically. Characteristic findings of CH on conventional images include dilatation of the inferior vena cava and hepatic veins; retrograde hepatic venous opacification during the early bolus phase of intravenous contrast material injection; and a predominantly peripheral heterogeneous pattern of hepatic enhancement due to stagnant blood flow. Extensive fibrosis can be seen in chronic or severe cases. Hyperenhancing regenerative nodules that may retain hepatobiliary contrast agents are often present. Magnetic resonance (MR) elastography can show elevated liver stiffness and may be useful in evaluation of fibrosis in CH because it can be incorporated easily into routine cardiac MR imaging. Preliminary experience with MR elastography suggests its future use in initial evaluation of patients suspected of having CH, for monitoring of disease, and for assessment after therapy. To facilitate appropriate workup and treatment, radiologists should be familiar with findings suggestive of CH at radiography, ultrasonography, computed tomography, MR imaging, and MR elastography. In addition, knowledge of underlying pathophysiology, comparative histologic abnormalities, and extrahepatic manifestations is useful to avoid diagnostic pitfalls and suggest appropriate additional diagnostic testing. (©)RSNA, 2016.

Sex Differences in Aging-related Myocardial Stiffening Quantitatively Measured with MR Elastography.

Purpose To investigate the feasibility of using quantitative MR elastography (MRE) to characterize the influence of aging and sex on left ventricular (LV) shear stiffness. Materials and Methods In this prospective study, LV myocardial shear stiffness was measured in 109 healthy volunteers (age range: 18-84 years; mean age, 40 years ± 18 [SD]; 57 women, 52 men) enrolled between November 2018 and September 2019, using a 5-minute MRE acquisition added to a clinical MRI protocol. Linear regression models were used to estimate the association of cardiac MRI and MRE characteristics with age and sex; models were also fit to assess potential age-sex interaction. Results Myocardial shear stiffness significantly increased with age in female (age slope = 0.03 kPa/year ± 0.01, P = .009) but not male (age slope = 0.008 kPa/year ± 0.009, P = .38) volunteers. LV ejection fraction (LVEF) increased significantly with age in female volunteers (0.23% ± 0.08 per year, P = .005). LV end-systolic volume (LVESV) decreased with age in female volunteers (-0.20 mL/m2 ± 0.07, P = .003). MRI parameters, including T1, strain, and LV mass, did not demonstrate this interaction (P > .05). Myocardial shear stiffness was not significantly correlated with LVEF, LV stroke volume, body mass index, or any MRI strain metrics (P > .05) but showed significant correlations with LV end-diastolic volume/body surface area (BSA) (slope = -3 kPa/mL/m2 ± 1, P = .004, r2 = 0.08) and LVESV/BSA (-1.6 kPa/mL/m2 ± 0.5, P = .003, r2 = 0.08). Conclusion This study demonstrates that female, but not male, individuals experience disproportionate LV stiffening with natural aging, and these changes can be noninvasively measured with MRE. Keywords: Cardiac, Elastography, Biological Effects, Experimental Investigations, Sexual Dimorphisms, MR Elastography, Myocardial Shear Stiffness, Quantitative Stiffness Imaging, Aging Heart, Myocardial Biomechanics, Cardiac MRE Supplemental material is available for this article. Published under a CC BY 4.0 license.

Hepatic and splenic stiffness augmentation assessed with MR elastography in an in vivo porcine portal hypertension model.

PURPOSE: To investigate the influence of portal pressure on the shear stiffness of the liver and spleen in a well-controlled in vivo porcine model with magnetic resonance elastography (MRE). A significant correlation between portal pressure and tissue stiffness could be used to noninvasively assess increased portal venous pressure (portal hypertension), which is a frequent clinical condition caused by cirrhosis of the liver and is responsible for the development of many lethal complications. MATERIALS AND METHODS: During multiple intraarterial infusions of Dextran-40 in three adult domestic pigs in vivo, 3D abdominal MRE was performed with left ventricle and portal catheters measuring blood pressure simultaneously. Least-squares linear regressions were used to analyze the relationship between tissue stiffness and portal pressure. RESULTS: Liver and spleen stiffness have a dynamic component that increases significantly following an increase in portal or left ventricular pressure. Correlation coefficients with the linear regressions between stiffness and pressure exceeded 0.8 in most cases. CONCLUSION: The observed stiffness-pressure relationship of the liver and spleen could provide a promising noninvasive method for assessing portal pressure. Using MRE to study the tissue mechanics associated with portal pressure may provide new insights into the natural history and pathophysiology of hepatic diseases and may have significant diagnostic value in the future.

Quadricuspid aortic valve with ruptured sinus of Valsalva.

We present a case of a 24-year-old woman who was diagnosed with quadricuspid aortic valve with ruptured sinus of Valsalva. Quadricuspid aortic valve is a rare congenital cardiac anomaly. The recognition of quadricuspid aortic valve has clinical significance as it causes aortic valve dysfunction, and is often associated with other congenital cardiac abnormalities. We showed the important role of multimodality imaging in diagnosing a quadricuspid aortic valve associated with ruptured sinus of Valsalva.

Acute Myocardial Infarction Caused by Spontaneous Coronary Artery Dissection of the First Septal Perforator.

Spontaneous coronary artery dissection of the septal arteries is rare and may be overlooked on coronary angiogram. Additionally, dedicated intracoronary imaging may not be feasible due to artery size. Cardiac magnetic resonance imaging has an emerging role in diagnosis, which is critical because management changes significantly if spontaneous coronary artery dissection is diagnosed. (Level of Difficulty: Beginner.).

MR elastography of the in vivo abdominal aorta: a feasibility study for comparing aortic stiffness between hypertensives and normotensives.

PURPOSE: To demonstrate feasibility of using MR elastography (MRE) to identify hypertensive changes in the abdominal aorta when compared with normotensives based on the stiffness measurements. MATERIALS AND METHODS: MRE was performed on eight volunteers (four normotensives and four hypertensives) to measure the effective stiffness of the abdominal aorta. MRE wave images are directionally filtered and phase gradient analysis was performed to determine the stiffness of the aorta. Student's t-test was performed to determine significant difference in stiffness measurements between normotensives and hypertensives. RESULTS: The normotensive group demonstrated a mean abdominal aortic stiffness of 3.7 ± 0.8 kPa, while the controlled-hypertensive demonstrated a mean abdominal aortic stiffness of 9.3 ± 1.9 kPa. MRE effective stiffness of abdominal aorta in hypertensives was significantly greater than that of normotensives with p = 0.02. CONCLUSION: Feasibility of in vivo aortic MRE is demonstrated. Hypertensives have significantly higher aortic stiffness assessed through MRE than normotensives.

Magnetic resonance elastography as a method to estimate myocardial contractility.

PURPOSE: To determine whether increasing epinephrine infusion in an in vivo pig model is associated with an increase in end-systolic magnetic resonance elastography (MRE)-derived effective stiffness. MATERIALS AND METHODS: Finite element modeling (FEM) was performed to determine the range of myocardial wall thicknesses that could be used for analysis. Then MRE was performed on five pigs to measure the end-systolic effective stiffness with epinephrine infusion. Epinephrine was continuously infused intravenously in each pig to increase the heart rate in increments of 20%. For each such increase end-systolic effective stiffness was measured using MRE. In each pig, Student's t-test was used to compare effective end-systolic stiffness at baseline and at initial infusion of epinephrine. Least-square linear regression was performed to determine the correlation between normalized end-systolic effective stiffness and increase in heart rate with epinephrine infusion. RESULTS: FEM showed that phase gradient inversion could be performed on wall thickness ≈≥1.5 cm. In pigs, effective end-systolic stiffness significantly increased from baseline to the first infusion in all pigs (P = 0.047). A linear correlation was found between normalized effective end-systolic stiffness and percent increase in heart rate by epinephrine infusion with R(2) ranging from 0.86-0.99 in four pigs. In one of the pigs the R(2) value was 0.1. A linear correlation with R(2) = 0.58 was found between normalized effective end-systolic stiffness and percent increase in heart rate when pooling data points from all pigs. CONCLUSION: Noninvasive MRE-derived end-systolic effective myocardial stiffness may be a surrogate for myocardial contractility.

CT findings and long-term mortality after pulmonary embolism.

OBJECTIVE: The utility of CT findings in predicting long-term mortality in patients with acute pulmonary embolism (PE) is unknown. The purpose of this study is to retrospectively determine whether three CT findings--increased embolic burden, interventricular septal bowing toward the left ventricle, and right ventricle-to-left ventricle (RV/LV) diameter ratio greater than 1--are independent predictors of long-term all-cause mortality after acute PE. MATERIALS AND METHODS: A total of 1105 patients (47% female; mean age, 63 ± 16 years) with CT scans positive for PE from January 1, 1997, to December 31, 2002, were included. Scans were independently interpreted by two observers, with a third independent observer reviewing discrepant cases. CT findings and clinical information were compared with all-cause mortality using univariate and multivariate logistic regression analyses. RESULTS: The median duration of survival was 6.2 years following acute PE, with estimated 10-year survival of 37.4%. CT-derived embolic burden was associated with a very small decrease in long-term all-cause mortality in both univariate (hazard ratio [HR], 0.97; p < 0.001) and multivariate (HR, 0.97; p < 0.001) analyses. Interventricular septal bowing and RV/LV diameter ratio were not significantly associated with long-term all-cause mortality. CONCLUSION: CT findings are not predictive of decreased long-term survival after acute PE.

CT and MR imaging of the aortic valve: radiologic-pathologic correlation.

Valvular disease is estimated to account for as many as 20% of cardiac surgical procedures performed in the United States. It may be congenital in origin or secondary to another disease process. One congenital anomaly, bicuspid aortic valve, is associated with increased incidence of stenosis, regurgitation, endocarditis, and aneurysmal dilatation of the aorta. A bicuspid valve has two cusps instead of the normal three; resultant fusion or poor excursion of the valve leaflets may lead to aortic stenosis, the presence of which is signaled by dephasing jets on magnetic resonance (MR) images. Surgery is generally recommended for patients with severe stenosis who are symptomatic or who have significant ventricular dysfunction; transcatheter aortic valve implantation (TAVI) is an emerging therapeutic option for patients who are not eligible for surgical treatment. Computed tomography (CT) is an essential component of preoperative planning for TAVI; it is used to determine the aortic root dimensions, severity of peripheral vascular disease, and status of the coronary arteries. Aortic regurgitation, which is caused by incompetent closure of the aortic valve, likewise leads to the appearance of jets on MR images. The severity of regurgitation is graded on the basis of valvular morphologic parameters; qualitative assessment of dephasing jets at Doppler ultrasonography; or measurements of the regurgitant fraction, volume, and orifice area. Mild regurgitation is managed conservatively, whereas severe or symptomatic regurgitation usually leads to valve replacement surgery, especially in the presence of substantial left ventricular enlargement or dysfunction. Bacterial endocarditis, although less common than aortic stenosis and regurgitation, is associated with substantial morbidity and mortality. Electrocardiographically gated CT reliably demonstrates infectious vegetations and benign excrescences of 1 cm or more on the valve surface, allowing the assessment of any embolic complications.