Biomedical subjects

Frederick H Epstein

Publications and source records attributed to Frederick H Epstein.

23 records · Page 2Linked to original sources

PubMed2003

Stunned, infarcted, and normal myocardium in dogs: simultaneous differentiation by using gadolinium-enhanced cine MR imaging with magnetization transfer contrast.

PURPOSE: To simultaneously differentiate stunned, infarcted, and normal myocardial regions by using gadolinium-enhanced cine magnetic resonance (MR) imaging with magnetization transfer contrast. MATERIALS AND METHODS: Twelve dogs were imaged on days 1 and 8 after transient 90-minute coronary artery occlusion. A magnetization transfer contrast with echo-train readout (MTET) MR sequence was performed before and 30 minutes after gadolinium contrast enhancement. Ex vivo analysis consisted of MR imaging, microsphere blood flow analysis, and triphenyltetrazolium chloride (TTC) staining. A paired two-tailed t test was used to compare wall thickening from day 1 to day 8. Linear regression and Bland-Altman analyses were used to compare infarct size depicted with MTET imaging with that seen on TTC-stained tissue. RESULTS: Severe wall motion abnormalities were detected in all dogs. At TTC analysis, seven dogs had evidence of myocardial infarction and five had evidence of stunned myocardium. The mean percentages of left ventricular wall thickening in infarcted, stunned, and remote myocardial regions were 2% +/- 4 (SD), 4% +/- 8, and 33% +/- 5, respectively. Wall thickening did not improve in the infarcted zones, but it improved to nearly normal levels in the stunned region 1 week after induced occlusion (mean, 40% +/- 8; P <.02). MTET images clearly depicted infarcted myocardium as brighter than both the normal and stunned myocardial regions but darker than the blood pool. In vivo MTET infarct volume correlated with ex vivo TTC analysis data (y = 1.01x + 0.00, R = 0.98, standard error of the estimate = 0.019). CONCLUSION: One day after myocardial ischemia, MTET during one MR imaging examination enabled simultaneous differentiation of infarcted, stunned, and normal myocardial regions on the basis of gadolinium enhancement and regional function.

Animals↗

PubMed2002

Angiotensin II type 2 receptor overexpression preserves left ventricular function after myocardial infarction.

BACKGROUND: The role of the angiotensin II type 2 receptor (AT2-R) in left ventricular (LV) remodeling may depend on the underlying stimulus. We hypothesized that cardiac AT2-R overexpression in transgenic (TG) mice would attenuate remodeling after myocardial infarction (MI). METHODS AND RESULTS: Ten wild-type (WT) C57BL/6 mice and 12 TG mice that overexpress the AT2-R in the heart were studied by cardiac MRI at baseline and days 1, 7, and 28 post-MI induced by 1 hour of occlusion of the LAD followed by reperfusion. Short-axis imaging from apex to base was used to determine LV mass index, end-diastolic and end-systolic volume indices (EDVI, ESVI), regional wall thickness and thickening, and ejection fraction (EF). Gadolinium-DTPA was infused 20 minutes before day 1 imaging to assess infarct size. At baseline, heart rate, blood pressure, LV mass index, and EDVI were similar between groups. Baseline ESVI was lower (0.20+/-0.07 versus 0.45+/-0.15 microL/g, P<0.001) and EF higher (82.3+/-4.9% versus 67.7+/-5.3%, P<0.001) in TG than WT. Infarct size was similar (36.6+/-7.2% in WT, 34.0+/-7.8% in TG, P=NS). When controlled for baseline differences, ESVI was significantly less and EF significantly higher at all time points in TG versus WT. At day 28, ESVI was 1.05+/-0.32 microL/g in TG and 1.63+/-0.41 microL/g in WT, P<0.03, and EF was 47.3+/-5.8% versus 34.1+/-9.2%, P<0.003, respectively. Regional wall thickness and thickening were greater in TG both at baseline and at day 28. At day 28, blood pressure and LV dP/dt were higher in TG. CONCLUSIONS: Cardiac AT2-R overexpression improves LV systolic function at baseline and preserves function during post-MI remodeling.

Animals↗

PubMed2002

Multislice first-pass cardiac perfusion MRI: validation in a model of myocardial infarction.

The purpose of this study was to validate a first-pass MRI method for imaging myocardial perfusion with multislice coverage and relatively small analyzable regions of interest (ROIs). A fast gradient-echo (FGRE) sequence with an echo-train (ET) readout was used to achieve multislice coverage, and a high dose of a contrast agent (CA) was used to achieve a high signal-to-noise ratio (SNR). Dogs (N = 6) were studied 1 day after reperfused myocardial infarction, and fluorescent microspheres were used as a standard for perfusion. First-pass MRI correlated well vs. microsphere flow, achieving mean R values of 0.87 (range = 0.82-0.93), 0.71 (range = 0.46-0.85), and 0.72 (range = 0.49-0.95) for subendocardial ROIs, transmural ROIs, and the endocardial-epicardial ratio, respectively. Additionally, analysis of myocardial time-intensity curves (TICs) indicated that 15.8 +/- 6 sectors, corresponding to 260 microl of endocardium, can be analyzed (R(2) > 0.95).

Animals↗

PubMed2002

MR tagging early after myocardial infarction in mice demonstrates contractile dysfunction in adjacent and remote regions.

The purpose of this study was to use MR myocardial tagging to assess regional cardiac function after myocardial infarction (MI) in mice. Eight mice were imaged before and 1 day after MI. MRI included cine imaging, myocardial tagging, and contrast-enhanced imaging. Regional percent circumferential shortening (%CS) was measured from the tagged images, and the region of hyperenhancement on the contrast-enhanced images was used to determine the infarcted, adjacent, and remote zones. Ejection fraction (EF) fell from 59% +/- 6% at baseline to 32% +/- 6% after MI (P < 0.01). At baseline, %CS was 14.5% +/- 3.4%. After MI, %CS was 0.7% +/- 4.4% in the infarcted zone, 7.4% +/- 4.4% in the adjacent zone, and 11.8% +/- 4.2% in the remote zone. %CS was statistically different for all comparisons between the infarcted, adjacent, remote, and baseline groups (P < 0.01). MR tagging can detect regional differences in myocardial function post-MI in mice.

Animals↗

PubMed2002

Effects of phase encode order and segment interpolation methods on the quality and accuracy of myocardial tags during assessment of left ventricular contraction.

Tissue tagging can be implemented during cardiovascular magnetic resonance imaging exams to assist with the quantification of left ventriculargeometry, volume and ejection fraction, endocardial thickening and relaxation, and myocardial stress-strain relationships. During tagged cine gradient echo image acquisitions of left ventricular wall motion, rows of k-space data can be acquired with various phase-encoding orders, and the reconstruction of supplemental images can be accomplished using a variety of interpolation techniques. In this study, we investigated the utility of various phase order and segment interpolation methods for determining accurate tag displacement trajectories. Center-out phase order image acquisition with reconstruction using linear interpolation provided the highest tag position and displacement accuracy. Therefore, it is recommended that myocardial tagging exams be acquired with center-out phase encode order and reconstructed using linear segment interpolation when used for performing quantitative analysis of cardiovascular structure and function.

Humans↗