Homaa Ahmad

University of Chicago, Chicago, Illinois, United States

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Publications (14)43.76 Total impact

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    ABSTRACT: Currently, no real-time three-dimensional echocardiographic (RT3DE) indices are recommended by the official guidelines for the assessment of diastolic dysfunction (DD). We hypothesized that recent developments in RT3DE imaging technology that allow dynamic quantification of both left ventricular (LV) volume and 3D myocardial deformation, could be utilized to objectively assess DD. Transthoracic RT3DE datasets were acquired (Philips iE33, X5 transducer, frame rate 19 ± 4) in 76 subjects, including 20 normal controls (NL), 16 mild DD, 20 moderate DD and 20 severe DD (grade 1, 2 and 3, respectively, using ASE guideline). Images were analyzed using prototype software (TomTec) that performs 3D speckle tracking to generate time curves of LV volume and segmental myocardial strain. Indices of diastolic LV function were calculated: volume at 25, 50 and 75 % of filling duration (FD) in percent of end-diastolic volume (volume index, LVVi), and rapid filling volume (RFV) fraction. Temporal indices included: FD in % of RR, and rapid filling duration (RFD) in % of FD. Additionally, longitudinal, radial and circumferential strains at 25, 50 and 75 % of FD were calculated. Inter-groups differences were tested using ANOVA. LVVi and RFV fraction showed a biphasic pattern with the severity of DD characterized by an initial decrease (grade 1), a pseudo-normalization (grade 2), and then an increase above normal (grade 3). FD progressively decreased with severity of DD. RFD was significantly increased in all 3 groups compared to NL. After normalization by peak systolic values, all three strain components showed a linear pattern with the severity of DD, suggesting potential clinical usefulness. This is the first study to show that current RT3DE technology allows combined quantitative analysis of LV volume and 3D myocardial strain, which is sensitive enough to demonstrate differences in myocardial relaxation in patients with different degrees of DD.
    No preview · Article · Jun 2012 · The international journal of cardiovascular imaging
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    ABSTRACT: An increased tricuspid regurgitation jet velocity (TRV > 2.5 m/s) and pulmonary hypertension defined by right heart catheterization both independently confer increased mortality in sickle cell disease (SCD). We explored the usefulness of peripheral blood mononuclear cell-derived gene signatures as biomarkers for an elevated TRV in SCD. Twenty-seven patients with SCD underwent echocardiography and peripheral blood mononuclear cell isolation for expression profiling and 112 patients with SCD were genotyped for single-nucleotide polymorphisms. Genome-wide gene and miRNA expression profiles were correlated against TRV, yielding 631 transcripts and 12 miRNAs. Support vector machine analysis identified a 10-gene signature including GALNT13 (encoding polypeptide N-acetylgalactosaminyltransferase 13) that discriminates patients with and without increased TRV with 100% accuracy. This finding was then validated in a cohort of patients with SCD without (n = 10) and with pulmonary hypertension (n = 10, 90% accuracy). Increased TRV-related miRNAs revealed strong in silico binding predictions of miR-301a to GALNT13 corroborated by microarray analyses demonstrating an inverse correlation between their expression. A genetic association study comparing patients with an elevated (n = 49) versus normal (n = 63) TRV revealed five significant single-nucleotide polymorphisms within GALNT13 (P < 0.005), four trans-acting (P < 2.1 × 10(-7)) and one cis-acting (P = 0.6 × 10(-4)) expression quantitative trait locus upstream of the adenosine-A2B receptor gene (ADORA2B). These studies validate the clinical usefulness of genomic signatures as potential biomarkers and highlight ADORA2B and GALNT13 as potential candidate genes in SCD-associated elevated TRV.
    Full-text · Article · Jun 2012 · American Journal of Respiratory and Critical Care Medicine
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    ABSTRACT: Background: Sickle cell disease (SCD) is a hemoglobinopathy that affects one in 500 African Americans. Although it is well established that patients with SCD have left ventricular (LV) diastolic dysfunction, it is not clear whether they have subtle LV systolic dysfunction despite preserved ejection fraction (EF). We used three-dimensional speckle tracking echocardiography (3DSTE) to assess changes in both systolic and diastolic LV function in SCD. Methods: Transthoracic real time 3D images were obtained (Philips iE33) in 56 subjects, including 28 stable outpatients with SCD (age 33 ± 7 years) and 28 normal controls (age 35 ± 9 years). 3DSTE was performed using prototype software (4DLV Analysis, TomTec) to obtain LV volume and deformation time curves, from which indices of systolic and diastolic LV function were calculated. Results: In SCD patients, 3DSTE-derived LV filling parameters were significantly different from normal controls, reflecting an increase in both rapid and atrial filling volumes and prolonged active relaxation, depicted by a decrease in filling volume fractions at fixed times and an increase in rapid filling duration. Global LV systolic function was not only preserved but increased compared to controls, as reflected by significantly increased global longitudinal strain. Importantly, twist angle and torsion as well as radial and circumferential components of 3D strain were similar in both groups. Conclusions: 3DSTE was able to confirm diastolic dysfunction, as expected in some patients with SCD. However, 3DSTE strain analysis did not reveal any changes in LV systolic function. These findings provide novel insight into the pathophysiology of the cardiovascular complications of SCD.
    Full-text · Article · May 2012 · Echocardiography
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    ABSTRACT: -Cardiovascular disease is an important cause of morbidity and mortality in sickle cell disease (SCD). We sought to characterize sickle cell cardiomyopathy using multi-modality non-invasive cardiovascular testing and identify potential causative mechanisms. -Stable adults with SCD (n=38) and healthy controls (n=13) prospectively underwent same day multi-parametric cardiovascular magnetic resonance (cine, T2* iron, vasodilator first pass myocardial perfusion, and late gadolinium enhancement (LGE) imaging), transthoracic echocardiography, and applanation tonometry. Compared to controls, patients with SCD had severe dilation of the left ventricle (124±27 vs 79±12 ml/m(2)), right ventricle (127±28 vs 83±14 ml/m(2)), left atrium (65±16 vs 41±9 ml/m(2)), and right atrium (78±17 vs 56±17 ml/m(2)), p<0.01 for all. SCD patients also had a 21% lower myocardial perfusion reserve index than control subjects (1.47±0.34 vs 1.87±0.37, p=0.034). A significant subset of SCD patients (25%) had evidence of LGE while only one patient had evidence of myocardial iron overload. Diastolic dysfunction was present in 26% of SCD patients compared to 8% in controls. Estimated filling pressures (E/e', 9.3±2.7 vs 7.3±2.0, p=0.0288) was higher in SCD patients. Left ventricular dilation and the presence of LGE were inversely correlated to hepatic T2* times (i.e. hepatic iron overload due to frequent blood transfusions, p<0.05 for both); whereas, diastolic dysfunction and increased filling pressures were correlated to aortic stiffness (augmentation pressure and index, p<0.05 for all). -Sickle cell cardiomyopathy is characterized by 4-chamber dilation and in some patients myocardial fibrosis, abnormal perfusion reserve, diastolic dysfunction, and only very rarely myocardial iron overload. Left ventricular dilation and myocardial fibrosis are associated with increased blood transfusion requirements while left ventricular diastolic dysfunction is predominantly correlated with increased aortic stiffness. Clinical Trial Registration-http://www.clinicaltrials.gov. Unique identifier: NCT01044901.
    Full-text · Article · Feb 2012 · Journal of Cardiovascular Magnetic Resonance
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    ABSTRACT: Left ventricular (LV) volumes and ejection fraction derived from two-dimensional echocardiography are two measures of adverse LV remodeling, which predict survival in patients with systolic heart failure. However, the geometric assumptions and image foreshortening that can occur with two-dimensional echocardiography reduces measurement accuracy and thus predictive value. By its nature, three-dimensional (3D) echocardiography allows the entire LV shape to be studied, providing a methodology to examine LV remodeling through LV curvature on a global and regional scale. The aim of this study was to correlate changes in global and regional LV shape to LV ejection fraction. Full-volume, 3D transthoracic echocardiographic studies of the left ventricle were performed in 106 consecutive patients with either normal left ventricles (n = 59) or cardiomyopathies (n = 47). Customized software (QLAB) was used to extract segmented 3D LV endocardial shells at end-systole and end-diastole and to analyze these shells to determine global and regional LV shape analysis. Independent t tests were used for intergroup comparisons, and linear regression was used to correlate regional shape changes with systolic performance. Derivation and analysis of the 3D LV shells was possible in all patients. Patients with dilated cardiomyopathy had significantly smaller curvature values, indicating rounder global LV shape throughout the cardiac cycle. Regional analysis identified a loss of septal and apical curvatures in these patients. Systolic apical mean curvature was well correlated with LV ejection fraction (r = 0.89). This is the first study to demonstrate that regional remodeling measured by regional 3D LV curvature correlates well with LV function. As well, this methodology is independent of the geometric assumptions that limit the predictive value of two-dimensional echocardiographic measures of LV remodeling. Overall, this is a novel tool that may have applications in the assessment and prediction of outcomes of different forms of dilated cardiomyopathy.
    No preview · Article · Jan 2012 · Journal of the American Society of Echocardiography: official publication of the American Society of Echocardiography
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    ABSTRACT: Background: Assessment of right ventricular (RV) function is difficult due to the complex shape of this chamber. Tricuspid annular plane systolic excursion (TAPSE) measured with M-mode echocardiography is frequently used as an index of RV function. However, its accuracy may be limited by ultrasound beam misalignment. We hypothesized that two-dimensional (2D) speckle tracking echocardiography (STE) could provide more accurate estimates of RV function. Accordingly, STE was used to quantify tricuspid annular displacement (TAD), from which RV longitudinal shortening fraction (LSF) was calculated. These STE derived indices were compared side-by-side with M-mode TAPSE measurements against cardiac magnetic resonance (CMR) derived RV ejection fraction (EF). Methods: Echocardiography (Philips iE33, four-chamber view) and CMR (Siemens, 1.5 T) were performed on the same day in 63 patients with a wide range of RV EF (23-70% by CMR). TAPSE was measured using M-mode echocardiography. TAD and RV LSF were obtained using STE analysis (QLAB CMQ, Philips). TAPSE, TAD and RV LSF values were compared with RV EF obtained from CMR short axis stacks. Results: STE analysis required <15 seconds and was able to track tricuspid annular motion in all patients as verified visually. Correlation between RV EF and TAD (0.61 free-wall, 0.65 septal) was similar to that with M-mode TAPSE (0.63). However, STE-derived RV LSF showed a higher correlation with CMR EF (r = 0.78). Conclusion: RV LSF measurement by STE is fast and easy to obtain and provides more accurate evaluation of RV EF than the traditional M-mode TAPSE technique, when compared to CMR reference. (Echocardiography 2012;29:19-24).
    No preview · Article · Oct 2011 · Echocardiography
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    ABSTRACT: The ability of multidetector computed tomography (MDCT) to detect stress-induced myocardial perfusion abnormalities is of great clinical interest as a potential tool for the combined evaluation of coronary stenosis and its significance. However, stress testing requires repeated scanning that is associated with additional radiation exposure and iodine contrast. Our goal was to determine the effects of reduced tube voltage and contrast dose on the ability to detect perfusion abnormalities. We studied 40 patients referred for coronary CT angiography (CTA) who agreed to undergo additional imaging after administration of an A(2A)-agonist (regadenoson 0.4 mg). Images were acquired at rest and during hyperemia with prospective gating with 120 kV tube voltage with 80-90 mL of contrast in 20 patients (group 1) and 100 kV with 55-70 mL of contrast in the remaining 20 patients (group 2). Custom 3D analysis software was used to define 3D myocardial segments and measure x-ray attenuation in each segment. In each group of patients, myocardial attenuation was averaged for segments supplied by coronary arteries with stenosis causing >50% luminal narrowing on coronary CTA and separately for segments supplied by arteries without significant stenosis. Coronary CTA detected stenosis >50% in 23 of 120 coronary arteries in 16 of 40 patients. In all patients combined, myocardial attenuation increased from 86 ± 9 at rest to 110 ± 17 HU with stress, reflecting an increase in tissue blood flow, despite the decrease in left ventricular cavity attenuation (347 ± 72 to 281 ± 55 HU), reflecting an increase in cardiac output. Importantly, in both groups, myocardial attenuation was equally reduced in segments supplied by diseased arteries (group 1: 119 ± 19 vs 103 ± 14 HU, P < 0.05; group 2: 108 ± 20 vs 97 ± 16 HU, P < 0.05), despite the 74% reduction in radiation (from 7.4 ± 2.8 to 1.9 ± 0.45 mSv) and the 28% reduction in contrast dose (from 84 ± 7 to 60 ±7 mL) (both P < 0.05). Regadenoson stress MDCT imaging can detect hypoperfused myocardium even when imaging settings are optimized to provide a significant reduction in radiation and contrast doses.
    No preview · Article · Jul 2011 · Journal of cardiovascular computed tomography
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    ABSTRACT: Accurate segmental mitral valve (MV) analysis is essential for surgical planning. Although real-time three-dimensional (3D) transesophageal echocardiography has improved the ability to visualize the MV, accurate localization of MV pathology from 3D transesophageal echocardiographic images still remains experience dependent. Three-dimensional parametric maps of the MV obtained from these images further simplify the visualization of MV anatomy. The aims of this study were to examine whether 3D parametric maps of the MV could improve the diagnostic accuracy in localizing pathology and to determine their usefulness for readers with different levels of training. Five novice (American Society of Echocardiography [ASE] level 2), three intermediate-level (ASE level 3; <500 MV cases), and two expert (ASE level 3; >500 MV cases) readers interpreted MV segmental anatomy in 50 patients (30 with degenerative MV disease, 20 with normal MVs). All readers reviewed two-dimensional and 3D transesophageal echocardiographic and 3D parametric maps at sequential weekly sessions. The results were compared with surgical findings. Expert readers were the most accurate irrespective of image type. Novice readers were the least accurate and commonly misinterpreted P2 and P3 scallops. Their accuracy was highest when interpreting 3D parametric maps (from 87% with two-dimensional transesophageal echocardiography to 92%). Intermediate readers' accuracy fell between the other two groups irrespective of image type and showed no change with the use of parametric maps. This is the first study to show that the interpretation of 3D parametric maps improves the accuracy of localization of MV pathology by novice readers. Therefore, parametric maps should be used routinely by less experienced readers during the assessment of degenerative MV disease.
    No preview · Article · Jun 2011 · Journal of the American Society of Echocardiography: official publication of the American Society of Echocardiography
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    ABSTRACT: Myocardial deformation measurements using two-dimensional speckle-tracking echocardiography (STE) are known to vary among vendors. The intervendor agreement of three-dimensional (3D) deformation indices has not been studied. The goals of this study were to determine the intervendor agreement of 3D STE-based measurements of left ventricular (LV) deformation parameters to investigate the intrinsic variability of these measurements and identify the sources of intervendor differences. Real-time full-volume images obtained in 30 subjects with normal LV systolic function using two vendors' equipment (V1 and V2) on the same day were analyzed by two independent observers using two software packages (S1 and S2). Agreement between three technique combinations (V1/S1, V2/S2, and V1/S2) and their intrinsic reproducibility (interobserver and intraobserver agreement) were assessed using intraclass correlation coefficients. Parameters of LV deformation included global longitudinal strain, twist, 3D displacement, and 3D strain and its radial, longitudinal, and circumferential components. For all three combinations, intertechnique agreement was poor (intraclass correlation coefficient < 0.4), always beyond the intrinsic variability. For all measured parameters, the intertechnique agreement was better when the same software package was used with images from different vendors (V2/S2 vs V1/S2) than when images from same vendor were analyzed using different software (V1/S2 vs V1/S1). Three-dimensional STE-derived LV deformation parameters are highly vendor dependent, and the discordance levels are beyond intrinsic measurement variability of any of the tested combinations of imaging equipment and analysis software. This intervendor discordance must be taken into account when interpreting 3D deformation data.
    No preview · Article · Jun 2011 · Journal of the American Society of Echocardiography: official publication of the American Society of Echocardiography

  • No preview · Conference Paper · May 2011

  • No preview · Conference Paper · May 2011
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    ABSTRACT: The ability of multidetector computed tomography (MDCT) to detect stress-induced myocardial perfusion abnormalities is of great clinical interest as a potential tool for the combined evaluation of coronary stenosis and its significance. However, stress testing requires repeated scanning, which is associated with additional radiation exposure and iodine contrast. Our goal was to determine the effects of reduced tube voltage and contrast dose on the ability to detect perfusion abnormalities. We studied 40 patients referred for CT coronary angiography (CTCA). Images were acquired at rest and during regadenoson stress (256-channel scanner, Philips) using 120kV tube voltage with 80–90 ml contrast in 20 patients and 100kV with 55–70 ml contrast in the remaining 20 patients. Custom software was used to define 3D myocardial segments and measure segmental x-ray attenuation. In each group of patients, myocardial attenuation was averaged for segments supplied by arteries with stenosis causing >50% narrowing on CTCA, and separately for segments supplied by arteries without significant stenosis. In both groups, myocardial attenuation was equally reduced in segments supplied by diseased arteries, despite the 74% reduction in radiation and the 28% reduction in contrast. Regadenoson stress MDCT imaging can detect hypoperfused myocardium even when imaging settings are optimized to provide a significant reduction in radiation and contrast doses.
    Full-text · Article · Jan 2011
  • Homaa Ahmad · Roberto M. Lang

    No preview · Article · Oct 2010 · Current Cardiovascular Imaging Reports
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    ABSTRACT: Left ventricular (LV) ejection fraction (EF) by transthoracic two-dimensional echocardiography is time-intensive and highly dependent on image quality. Mitral annular displacement (MAD) qualitatively correlates with EF and can be measured in patients with poor image quality and dropout. The authors hypothesized that speckle-tracking echocardiography (STE)-derived MAD could quantify EF accurately and tested this hypothesis using cardiac magnetic resonance (CMR) as a reference. One hundred eighteen patients undergoing clinical transthoracic echocardiography were screened, and 110 whose mitral annuli was sufficiently well-defined irrespective of LV endocardial visualization underwent CMR within 6 days (85 of 110 in 1 day). Reference CMR EF values were obtained using standard methodology. STE was used to track annular motion throughout the cardiac cycle in the apical 2-chamber and 4-chamber views. To establish the relationship between MAD and CMR EF and to obtain a formula to estimate EF from MAD, regression analysis was performed in a study group of 60 patients with a wide range of EFs. This formula was then used in an independent test group of 50 patients by comparing estimated MAD EF against CMR EF values using Pearson's correlation and Bland-Altman analyses. In the study group, STE MAD correlated highly with CMR EF and resulted in a formula relating MAD to EF. In the test group, estimated EF correlated well with CMR EF (4-chamber, R(2) = 0.64; 2-chamber, R(2) = 0.55), with near-zero bias and acceptable limits of agreement. Intraobserver and interobserver variability were between 5.8% and 12.7%. STE MAD is a clinically useful tool for quick, easy, robust, and accurate estimates of EF irrespective of LV endocardial definition.
    Full-text · Article · Mar 2010 · Journal of the American Society of Echocardiography: official publication of the American Society of Echocardiography