MRI-derived Ejection Fraction Research Articles

Aortic valve timing is critical for accurate estimation of MRI-derived ejection fraction

Background We aim to investigate the effect of utilizing aortic valve timing in the measurement of cardiac magnetic resonance (CMR)-derived ejection fraction (EF). Although CMR-derived left ventricular (LV) EF is the gold-standard for volumetric evaluation of the heart, it always reports higher values when compared to other modalities such as echocardiography and radionuclide ventriculography. The higher EF has often been attributed to better endocardial definition by CMR. In the ACCF/ACR/ AHA/NASCI/SCMR 2010 Expert Consensus Document on CMR, a 1987 paper is cited with utilizes the “maximal and minimal left ventricular cross-sectional area at the mid-ventricle” to identify end-systole and end-diastole. The 2013 CMR Guideline suggests phases with the largest and smallest global LV blood volume be utilized to identify end-diastole and end-systole. The same guideline also suggests aortic valve timing be utilized when arrhythmia or mitral regurgitation is encountered. We investigated the effect of different schemes on measured LVEF. Methods Standard retrospectively EKG-gated bSSFP short axis and LVOT cine images in 46 clinical patients in normal sinus rhythm with a range of EF (5.8 75.8 %) were acquired and analyzed. Scan parameters were as follows: in-plane resolution: 1.25 2.08 mm, slice spacing: 8 mm with a gap of 2 mm, reconstructed temporal resolution: 18.2 58.8 ms. Aortic valve opening and closing as a percentage of cardiac cycle was identified on LVOT images. Volumetric evaluation of short axis images was performed via semi-automated segmentation for all phases and all left ventricular slices (ITK-SNAP, Philadelphia PA). The schemes (shown in Table 1) were used to quantify LVEF. Scheme G was considered “true EF” and usied aortic valve opening and closing. Scheme F is intended to mimic real-time methods, which acquire slice-by-slice data and do not incorporate aortic valve timing or other external measures such as EKG.

Angiotensin-Converting Enzyme Inhibition Prevents the Release of Monocytes From Their Splenic Reservoir in Mice With Myocardial Infarction

Monocytes recruited to ischemic myocardium originate from a reservoir in the spleen, and the release from their splenic niche relies on angiotensin (Ang) II signaling. Because monocytes are centrally involved in tissue repair after ischemia, we hypothesized that early angiotensin-converting enzyme (ACE) inhibitor therapy impacts healing after myocardial infarction partly via effects on monocyte traffic. In a mouse model of permanent coronary ligation, enalapril arrested the release of monocytes from the splenic reservoir and consequently reduced their recruitment into the healing infarct by 45%, as quantified by flow cytometry of digested infarcts. Time-lapse intravital microscopy revealed that enalapril reduces monocyte motility in the spleen. In vitro migration assays and Western blotting showed that this was caused by reduced signaling through the Ang II type 1 receptor. We then studied the long-term consequences of blocked splenic monocyte release in atherosclerotic apolipoprotein (apo)E(-/-) mice, in which infarct healing is impaired because of excessive inflammation in the cardiac wound. Enalapril improved histologic healing biomarkers and reduced inflammation in infarcts measured by FMT-CT (fluorescence molecular tomography in conjunction with x-ray computed tomography) of proteolytic activity. ACE inhibition improved MRI-derived ejection fraction by 14% on day 21, despite initially comparable infarct size. In apoE(-/-) mice, ischemia/reperfusion injury resulted in larger infarct size and enhanced monocyte recruitment and was reversible by enalapril treatment. Splenectomy reproduced antiinflammatory effects of enalapril. This study suggests that benefits of early ACE inhibition after myocardial infarction can partially be attributed to its potent antiinflammatory impact on the splenic monocyte reservoir.

Noninvasive Assessment of Repaired Tetralogy of Fallot by Magnetic Resonance Imaging and Dynamic Radionuclide Studies

This study was designed to validate the diagnostic accuracy of magnetic resonance imaging (MRI) in evaluating biventricular ejection fraction and to quantify pulmonary regurgitant fraction (PRF) in patients after repair of tetralogy of Fallot. Two hundred and eighty survivors of repaired tetralogy of Fallot aged 42 months to 40 years (mean, 142.2 +/- 85.3 months) underwent cardiac MRI, first-pass and gated radionuclide ventriculography (RNV) for the assessment of biventricular function, and PRF after 89.26 +/- 42.40 months. The receiver operating characteristic curve analysis was done to quantify the diagnostic accuracy of MRI. There was statistically significant agreement between MRI and RNV in evaluating right and left ventricular function. An MRI-derived right ventricular ejection fraction 47.2% or greater than normal was associated with a sensitivity of 92.3% and a specificity of 92.3%. An MRI-derived left ventricular ejection fraction 53.9% or greater than normal was associated with a sensitivity of 93.2% and a specificity of 93.3%. Area analysis indicated that 97.34% (standard error [SE] = 0.0118) and 98.56% (SE = 0.0052) of the time values of right and left ventricular ejection fraction were higher for patients with normal right and left ventricular functions, respectively, compared with abnormal. There was a strong agreement between velocity-encoded and stroke volume-derived PRF [(r = 0.886, p < 0.001; d = 2.62 +/- 1.12, p < 0.0001; r' = 0.121, p = 0.051; b = 0.96 (SE = 0.012); p < 0.0001; ICC = 0.98, p < 0.0001). Higher PRF was associated with increased indexed right ventricular dimensions and inversely correlated with biventricular ejection fractions. The MRI-derived ejection fraction values predictably separate patients with normal ventricular function from abnormal. Velocity-encoded MRI can accurately quantitate PRF in tetralogy of Fallot.

Accuracy of echocardiographic right ventricular parameters in patients with different end-stage lung diseases prior to lung transplantation

Background: Because there are few data available on the accuracy of 2D-echocardiography to assess right ventricular (RV) size and function in patients with far-advanced lung disease, in this prospective study, we compared various echocardiographic RV parameters with RV volumes derived from magnetic resonance imaging (MRI). Methods In 32 patients (18 male, 17 female) presenting for lung transplantation, we measured RV end-diastolic and end-systolic area as well as derived RV fractional area change, long-axis diameter, short-axis diameter, tricuspid valve anulus diameter (using 2D apical or sub-costal 4-chamber view), and RV end-diastolic diameter (using M-mode in the parasternal short-axis view). These values were compared with RV end-diastolic and end-systolic volumes derived by MRI, serving as the gold standard. Results Right ventricular end-diastolic area was the most accurate echocardiographic parameter of RV size (correlation to MRI: r = 0.88, p < 0.001), followed by RV end-diastolic short-axis diameter ( r = 0.75, p < 0.001), long axis diameter ( r = 0.66, p < 0.001), and tricuspid valve anulus diameter ( r = 0.63, p < 0.001). In contrast, M-mode measurement of RV end-diastolic diameter was possible in only 24/35 (68%) patients and showed a weak correlation to MRI-derived RV end-diastolic volume ( r = 0.56, p = 0.004). Right ventricular fractional area change correlated well with MRI-derivedRV ejection fraction ( r = 0.84, p < 0.0001). In a sub-group analysis, patients with vascular lung disease showed best agreement between both methods for RV end-diastolic area and RV fractional area change compared with patients with restrictive or obstructive lung disease. Conclusion This study shows that in patients with far-advanced lung diseases, RV end-diastolic area demonstrated the best correlation with MRI-derived measurement of RV end-diastolic volume, and RV fractional area change compared favorably with MRI-derived ejection fraction. Despite reduced image quality, especially in patients with obstructive lung disease, these parameters can yield clinically valuable information.