PubMed Health⌕ Search

Biomedical subjects

Mark A Fogel

Publications and source records attributed to Mark A Fogel.

16 recordsLinked to original sources
PubMed2006

Usefulness of magnetic resonance imaging for the diagnosis of right ventricular dysplasia in children.

Cardiac magnetic resonance (CMR) has been helpful in adults in the diagnosis of arrhythmogenic right ventricular dysplasia. Short of direct surgical observation or autopsy, no gold standard exists. CMR diagnostic criteria include right atrial and ventricular dilation, regional right ventricular (RV) wall motion abnormalities, outflow tract ectasia, and myocardial fatty infiltration. To determine whether adult diagnostic criteria are useful in children referred for CMR for this diagnosis, the images and records of 81 patients (aged 11.5 +/- 5.5 years) over an 8-year period were reviewed. Histories included ventricular tachycardia, palpitations, dilated right ventricle, syncope, near sudden death, or family history of RV dysplasia. Four families were studied with parents who had RV dysplasia diagnosed by surgery, explanted heart, or CMR. CMR imaging included T1-weighted imaging, cine, 1-dimensional RV myocardial tagging, and phase-encoded velocity mapping, and 2 patients underwent delayed-enhancement CMR. Only 1 of the 81 patients met 5 of the criteria. None of the others met >2 of the criteria, and only 2 patients met 1 or 2 criteria. For questionable regional wall motion abnormalities, RV myocardial tagging was helpful. In conclusion, CMR of patients with a history suspicious for the diagnosis of RV dysplasia is a low-yield test in children. This may be due to the evolving nature of the disease, which does not manifest itself from a morphologic or ventricular-function standpoint until later in development. Follow-up studies as patients age may be advantageous.

Cardiomyopathy, Dilated↗
PubMed2005

Total cavopulmonary connection flow with functional left pulmonary artery stenosis: angioplasty and fenestration in vitro.

BACKGROUND: In our multicenter study of the total cavopulmonary connection (TCPC), a cohort of patients with long-segment left pulmonary artery (LPA) stenosis was observed (35%). The clinically recognized detrimental effects of LPA stenosis motivated a computational fluid dynamic simulation study within 3-dimensional patient-specific and idealized TCPC pathways. The goal of this study was to quantify and evaluate the hemodynamic impact of LPA stenosis and to judge interventional strategies aimed at treating it. METHODS AND RESULTS: Simulations were conducted at equal vascular lung resistance, modeling both discrete stenosis (DS) and diffuse long-segment hypoplasia with varying degrees of obstruction (0% to 80%). Models having fenestrations of 2 to 6 mm and atrium pressures of 4 to 14 mm Hg were explored. A patient-specific, extracardiac TCPC with 85% DS was studied in its original configuration and after virtual surgery that dilated the LPA to 0% stenosis in the computer medium. Performance indices improved exponentially (R2>0.99) with decreasing obstruction. Diffuse long-segment hypoplasia was approximately 50% more severe with regard to lung perfusion and cardiac energy loss than DS. Virtual angioplasty performed on the 3-dimensional Fontan anatomy exhibiting an 85% DS stenosis produced a 61% increase in left lung perfusion and a 50% decrease in cardiac energy dissipation. After 4-mm fenestration, TCPC baffle pressure dropped by approximately 10% and left lung perfusion decreased by approximately 8% compared with the 80% DS case. CONCLUSIONS: DS <60% and diffuse long-segment hypoplasia <40% could be considered tolerable because both resulted in only a 12% decrease in left lung perfusion. In contrast to angioplasty, a fenestration (right-to-left shunt) reduced TCPC pressure at the cost of decreased left and right lung perfusion. These results suggest that pre-Fontan computational fluid dynamic simulation may be valuable for determining both the hemodynamic significance of LPA stenosis and the potential benefits of intervention.

Angioplasty↗
PubMed2005

Cardiac magnetic resonance imaging for accurate diagnosis of aortic arch anomalies in patients with 22q11.2 deletion.

This study demonstrates, in patients with 22q11.2 deletion, the wide variety of complex aortic arch anomalies that can be accurately defined by cardiac magnetic resonance imaging (MRI) compared with echocardiography. From May 1999 to August 2003, 17 of 68 patients (25%) with 22q11.2 deletion referred for cardiac evaluation required cardiac MRI, after echocardiography, to clarify aortic arch anatomy. Images of cardiac anatomy were obtained using steady-state free precession, half-Fourier acquired single turbo spin-echo dark blood sequences and gadolinium for 3-dimensional reconstruction. All MRI findings were abnormal, and in 16 of 17 cases, echocardiography was unable to define aortic arch anomalies correctly compared with MRI.

Adolescent↗
PubMed2005

Physics-driven CFD modeling of complex anatomical cardiovascular flows-a TCPC case study.

Recent developments in medical image acquisition combined with the latest advancements in numerical methods for solving the Navier-Stokes equations have created unprecedented opportunities for developing simple and reliable computational fluid dynamics (CFD) tools for meeting patient-specific surgical planning objectives. However, for CFD to reach its full potential and gain the trust and confidence of medical practitioners, physics-driven numerical modeling is required. This study reports on the experience gained from an ongoing integrated CFD modeling effort aimed at developing an advanced numerical simulation tool capable of accurately predicting flow characteristics in an anatomically correct total cavopulmonary connection (TCPC). An anatomical intra-atrial TCPC model is reconstructed from a stack of magnetic resonance (MR) images acquired in vivo. An exact replica of the computational geometry was built using transparent rapid prototyping. Following the same approach as in earlier studies on idealized models, flow structures, pressure drops, and energy losses were assessed both numerically and experimentally, then compared. Numerical studies were performed with both a first-order accurate commercial software and a recently developed, second-order accurate, in-house flow solver. The commercial CFD model could, with reasonable accuracy, capture global flow quantities of interest such as control volume power losses and pressure drops and time-averaged flow patterns. However, for steady inflow conditions, both flow visualization experiments and particle image velocimetry (PIV) measurements revealed unsteady, complex, and highly 3D flow structures, which could not be captured by this numerical model with the available computational resources and additional modeling efforts that are described. Preliminary time-accurate computations with the in-house flow solver were shown to capture for the first time these complex flow features and yielded solutions in good agreement with the experimental observations. Flow fields obtained were similar for the studied total cardiac output range (1-3 1/min); however hydrodynamic power loss increased dramatically with increasing cardiac output, suggesting significant energy demand at exercise conditions. The simulation of cardiovascular flows poses a formidable challenge to even the most advanced CFD tools currently available. A successful prediction requires a two-pronged, physics-based approach, which integrates high-resolution CFD tools and high-resolution laboratory measurements.

Blood Flow Velocity↗
PubMed2005

Quantifying regional right ventricular function in tetralogy of Fallot.

Right ventricular (RV) function is notoriously difficult to quantify. Patients with tetralogy of Fallot (TOF) have decreased systolic performance. We measure regional RV performance using MRI with 1-dimensional myocardial tissue tagging. By tagging cine-MRI in two views, we measured regional shortening in 12 regions throughout the RV. We image 32 pediatric patients: 21 normal patients and 11 patients with repaired TOF. We establish a normal range for each RV region. TOF patients have decreased shortening on a region-by-region basis. We conclude that regional RV performance can be measured using this technique, and that decreased performance can be demonstrated in TOF patients.

Adolescent↗
PubMed2005

Application of spatial modulation of magnetization (SPAMM) to children: the effect of image resolution on tagging pattern.

BACKGROUND AND OBJECTIVE: Spatial modulation of magnetization (SPAMM) is a valuable magnetic resonance imaging technique for studying ventricular biomechanics. In order to track the intersection points of the stripes to calculate regional wall motion and strain, the stripe spacing should be at most half the wall thickness, yet sufficiently larger than the image pixel size in order that the stripes be well resolved. These conflicting requirements, that the grid spacing be much smaller than the wall thickness yet much larger than the pixel size, are relatively easy to meet in adult subjects but are difficult in children because of their small size. The purpose of this study was to delineate the effect of pixel size relative to SPAMM grid spacing on the stripe pattern produced by SPAMM with application towards its use in children and to present a new approach to the analysis of these images. METHODS: We performed SPAMM imaging on a 1.5 Telsa Siemen's Vision MR system on a phantom, using an artificial ECG (R-R interval = 450 ms for triggering), holding the pixel size constant and varying the degree of stripe spacing. We used both square (1 mm) and rectangular (1 mm by 2 mm) pixels. We express the ratio of grid to pixel size as the ratio of the center-center spacing of the grid lines to the horizontal pixel size. We retrospectively reviewed the SPAMM images on 10 patients with a ratio of grid to pixel size approximately 4:1 and 10 with a ratio of grid to pixel size approximately 8:1. We further performed SPAMM imaging in four patients with different grid to pixel size ratios in the same patient. Finally, we tested a new algorithm to track the signal intense regions rather than the signal poor intersection points of the grid lines, which were compared on three ventricles with SPAMM tagging. RESULTS: In a phantom, the effect of decreasing the separation between stripes while keeping the resolution of the image constant changed the stripe pattern from a series of two parallel lines perpendicular to each other to a "checkerboard" pattern. With a relative grid:pixel ratio of 8:1 as used with adult studies, the dark bands and the crossing points are well defined. As the ratio decreases from 8:1 to 6:1, the black band is less well resolved. When the resolution is reduced further to a grid:pixel ratio of 4:1, the image appears to be a checkerboard of white and dark squares. This occurred with both square and rectangular pixels. The effect in vivo is similar. When the ratio is approximately 8:1, all patients demonstrated a stripe pattern as a set of parallel lines perpendicular to each other. When the ratio was approximately 4:1, all patients demonstrated the stripe pattern as checkerboard. This was found to be the case in the same patient, whether varying the pixel size by changing the field of view or matrix or by changing the grid spacing. We also found that tracking the signal intense regions was equivalent to tracking the signal poor intersection points of the grid, and this approach was much easier to implement. CONCLUSION: With decreasing ratio of grid spacing to pixel size, SPAMM stripe patterns change from a set of parallel lines perpendicular to each other to a "checkerboard" pattern. This effect has implications for tracking techniques to determine strain and wall motion. At smaller ratios, as is needed sometimes in children, it is easier to track the signal intense regions rather than the "intersection" points of the stripes. Both these approaches to tracking are equivalent.

Adolescent↗
PubMed2004

Brain versus lung: hierarchy of feedback loops in single-ventricle patients with superior cavopulmonary connection.

BACKGROUND: CO2 vasodilates and O2 vasoconstricts the cerebral vascular bed; the opposite is true in the lungs. When the brain and lungs are connected exclusively in series, which feedback loop predominates is unknown. The circulation of the superior cavopulmonary connection (SCPC) provides a unique physiology to answer this question. METHODS AND RESULTS: To determine cerebral and pulmonary blood flow and to establish the hierarchy of cerebral and pulmonary feedback mechanisms, 12 intubated, ventilated, single-ventricle patients in SCPC physiology (age 2.2+/-0.5 years) underwent magnetic resonance imaging velocity mapping of their jugular veins and aorta in room air, hypercarbia, and 100% O2. Flows in these vessels and arterial blood gases were measured. With 22+/-6 torr CO2 (Pco2) increased from 40 to 63 mm Hg, P<0.01), flow to the brain and lungs increased (1.5 to 2.7 L/min per m2, P=0.0003), Po2 improved (48 to 60 mm Hg, P=0.0004), and cardiac index increased (4.3 to 5.4 L/min per m2, P=0.0003). The increased cardiac index accounted for the increased cerebral and pulmonary blood flow (R=0.73, P=0.02) and cerebral O2 transport increased by 80% (P=0.0005) while preserving body O2 delivery. Hyperoxia did not change cerebral and pulmonary blood flow; Po2 increased 94% (P=0.01). CONCLUSIONS: The cerebral CO2 feedback loop predominates over the pulmonary one when they directly compete with each other. CO2 has a major impact on flow distribution whereas O2 has little impact. Increased CO2 improves cerebral oxygenation in SCPC patients. This may provide a clue in determining neurological sequelae in SC physiology and may influence timing of Fontan completion.

Aorta↗
PubMed2003

Flow volume asymmetry in the right aortic arch in children with magnetic resonance phase encoded velocity mapping.

BACKGROUND: The right aortic arch is not uncommon in pediatrics. Flow dynamics in this type of aortic arch, which is important for cardiac energetics, organ perfusion, and Doppler flow calculations, have not been defined. Although there are complex secondary flow patterns, bulk axial flow makes up most of the energy use. METHODS: We examined 14 children with a right aortic arch by using through-plane phase-encoded magnetic resonance velocity mapping in the ascending and descending aorta to determine flow volume symmetry and velocity. The aortic cross section was divided into 4 quadrants aligned along the long axis of the aorta. Significance was defined as a P value <.05. RESULTS: In the ascending aorta, the posterior right quadrant demonstrated significantly greater blood flow than the other quadrants across the entire cardiac cycle (28% vs 23%-25%) and at the point of maximum flow (29% vs 22%-25%). Flow asymmetry was also present in the descending aorta; there was significantly more flow in the posterior quadrants than the anterior quadrants in total flow across the cardiac cycle (28% vs 21%-23%) and at the point of maximum flow (27%-28% vs 20%-24%). The time to maximum flow was significantly shorter in the ascending than the descending aorta (18% vs 24% of the cardiac cycle). In 10 of 14 patients, maximum velocity occurred in the right half of both the ascending and descending aorta. Flow reversal at end-systole was haphazard, occurring in all quadrants. CONCLUSION: Flow volume asymmetry exists in the ascending and descending portions of the right aortic arch, which has implications for cardiac energetics, organ perfusion, and Doppler scanning flow calculations. This information may be useful in designing improved aortic surgical reconstructions in cases of congenital heart disease.

Analysis of Variance↗
PubMed2002

Mid-term follow-up of patients with transposition of the great arteries after atrial inversion operation using two- and three-dimensional magnetic resonance imaging.

BACKGROUND: Older patients with transposition of the great arteries who have undergone an atrial inversion procedure (ATRIAL-INV) are difficult to image by echocardiography. The surgical baffles are spatially complex. OBJECTIVE: To test the hypothesis that two- and three-dimensional MRI can elucidate the spatially complex anatomy in this patient population. MATERIALS AND METHODS: Twelve patients with ATRIAL-INV, ages 16+/-4.5 years, underwent routine T1-weighted spin-echo axial imaging to obtain a full cardiac volumetric data set. Postprocessing created three-dimensional shaded surface displays and allowed for multiplanar reconstruction. Routine transthoracic echocardiography was available on all patients. RESULTS: Three-dimensional reconstruction enabled complete spatial conceptualization of the venous pathways, and allowed for precise localization of a narrowed region in the upper limb of the systemic venous pathway found in two patients. This was subsequently confirmed on angiography. Routine MRI was able to image the full extent of the venous pathways in all 12 patients. Routine transthoracic echocardiography was able to visualize proximal portions of the venous pathways in eight (67%), the distal upper limb in five (42%), and the distal lower limb in four (33%) patients, and it was able to visualize the outflow tracts in all patients. CONCLUSION: Three-dimensional reconstruction adds important spatial information, which can be especially important in stenotic regions. Routine MRI is superior to transthoracic echocardiography in delineation of the systemic and pulmonary venous pathway anatomy of ATRIAL-INV patients at mid-term follow-up. Although transesophageal echocardiography is an option, it is more invasive.

Adolescent↗
PubMed2002

Nonuniform flow dynamics in the aorta of normal children: a simplified approach to measurement using magnetic resonance velocity mapping.

PURPOSE: To determine regional flow dynamics in the normal aorta (Ao) in children. Understanding flow dynamics in children is important in cardiovascular energetics, in designing improved aortic reconstructions by crafting the surgery to mimic normal aortic flow, and in Doppler flow calculations. The objective of this study was to determine regional flow dynamics in the normal Ao in children. MATERIALS AND METHODS: We performed magnetic resonance velocity mapping on 13 subjects (ages 7.2 +/- 6.2 years) with normal Aos to determine flow dynamics in four equal quadrants in the ascending (AAo) and descending aorta (DAo) aligned along the long axis of the Ao. Statistical significance was set at P <.05. RESULTS: In the AAo, the left posterior quadrant displayed significantly less blood flow (16% +/- 5%) than the other quadrants (26-29%) over the cardiac cycle. In the DAo, both anterior quadrants carried significantly less blood flow (20% and 21%) than the posterior quadrants (27% and 32%). At maximum flow (15% +/- 5% into the cardiac cycle for the AAo; 27% +/- 15% for the DAo), there was significantly more flow in the right posterior quadrant (28% +/- 2%) than other quadrants (22-23%) in the AAo. In the DAo, both posterior quadrants had significantly higher flow rates (27% and 30%) than the anterior quadrants (21% and 22%). Maximum velocity in both the AAo and the DAo occurred in the left posterior quadrant in 10/13 at 16-24% into the cardiac cycle. At end-systole, a short flow reversal was noted in the posterior quadrants in the AAo in 11/13; in the DAo, this occurred in the anterior quadrants in 10/13. CONCLUSION: Flow dynamics in the normal Ao in children are not symmetrical; the flow distributions are asymmetric in both the AAo and the DAo throughout systole, including flow reversal related to the dicrotic notch. These results may help improve Ao surgery.

Analysis of Variance↗
PubMed2002

Use of ejection fraction (or lack thereof), morbidity/mortality and heart failure drug trials: a review.

Ejection fraction (EF) is an ejection phase parameter used to assess the performance of the heart in normal individuals and pathologic states such as myocardial infarction, dilated cardiomyopathy, and congestive heart failure (CHF). It can be measured by radionuclide ventriculography, angiocardiography, echocardiography and magnetic resonance imaging. EF is dependent on the loading conditions of the heart as well as contractility of the myocardium which makes it a less useful measure of cardiac performance. Nevertheless, it has been widely utilized and discussed for years. EF has been used as an entry criteria for many trials in CHF and has been used to characterize the hemodynamic effects of various classes of drugs which are used in treating CHF. How predictive an increase in EF on therapy is of morbidity and mortality is a matter of debate. This review outlines the utilization (or lack thereof), of EF in various CHF drug trials, its relationship to symptomatic improvement and morbidity/mortality.

Heart Failure↗
PubMedDate not supplied

Preliminary investigations into a new method of functional assessment of the fetal heart using a novel application of 'real-time' cardiac magnetic resonance imaging.

OBJECTIVES: Because of quantitative echocardiographic limitations of fetal ventricular volumes as well as poor windows, we sought to determine if real-time magnetic resonance imaging (MRI) could be used. METHODS: Real-time, functional, true fast imaging with steady-state precession, cardiac MRI was performed on 2 fetuses (one with hypoplastic left heart syndrome and one with ductal constriction). Fetal echocardiography was performed and cardiac index by Doppler was used to validate volume measures by MRI. RESULTS: This technique was able to visualize the beating heart and assess ventricular volumes. Cardiac index and assessment of right ventricular hypertrophy and dilation by echocardiography were consistent with the ventricular volumes and right ventricular hypertrophy obtained by cardiac MRI. CONCLUSION: Real-time, functional fetal cardiac MRI is possible and can be used to quantitatively assess ventricular volumes and cardiac index in utero.

Adult↗