Matthew Janik

Effects of papillary muscles and trabeculae on left ventricular quantification: increased impact of methodological variability in patients with left ventricular hypertrophy.

Background Accurate quantification of left ventricular mass and ejection fraction is important for patients with left ventricular hypertrophy. Although cardiac magnetic resonance imaging has been proposed as a standard for these indices, prior studies have variably included papillary muscles and trabeculae in myocardial volume. This study investigated the contribution of papillary muscles and trabeculae to left ventricular quantification in relation to the presence and pattern of hypertrophy. Methods Cardiac magnetic resonance quantification was performed on patients with concentric or eccentric hypertrophy and normal controls (20 per group) using two established methods that included papillary muscles and trabeculae in myocardium (method 1) or intracavitary (method 2) volumes. Results Among all patients, papillary muscles and trabeculae accounted for 10.5% of ventricular mass, with greater contribution with left ventricular hypertrophy than normals (12.6 vs. 6.2%, P < 0.001). Papillary muscles and trabeculae mass correlated with ventricular wall mass (r = 0.53) and end-diastolic volume (r = 0.52; P < 0.001). Papillary muscles and trabeculae inclusion in myocardium (method 1) yielded smaller differences with a standard of mass quantification from linear ventricular measurements than did method 2 (P < 0.001). Method 1 in comparison with method 2 yielded differences in left ventricular mass, ejection fraction and volume in all groups, especially in patients with hypertrophy: the difference in ventricular mass index was three-fold to six-fold greater in hypertrophy than normal groups (P < 0.001). Difference in ejection fraction, greatest in concentric hypertrophy (P < 0.001), was independently related to papillary muscles and trabeculae mass, ventricular wall mass, and smaller ventricular volume (R2 = 0.56, P < 0.001). Conclusion Established cardiac magnetic resonance methods yield differences in left ventricular quantification due to variable exclusion of papillary muscles and trabeculae from myocardium. The relative impact of papillary muscles and trabeculae exclusion on calculated mass and ejection fraction is increased among patients with hypertrophy-associated left ventricular remodeling.

Left Ventricle: Automated Segmentation by Using Myocardial Effusion Threshold Reduction and Intravoxel Computation at MR Imaging

UNLABELLED This retrospective analysis of existing patient data had institutional review board approval and was performed in compliance with HIPAA. No informed consent was required. The purpose of the study was to develop and validate an algorithm for automated segmentation of the left ventricular (LV) cavity that accounts for papillary and/or trabecular muscles and partial voxels in cine magnetic resonance (MR) images, an algorithm called LV Myocardial Effusion Threshold Reduction with Intravoxel Computation (LV-METRIC). The algorithm was validated in biologic phantoms, and its results were compared with those of manual tracing, as well as those of a commercial automated segmentation software (MASS [MR Analytical Software System]), in 38 subjects. LV-METRIC accuracy in vitro was 98.7%. Among the 38 subjects studied, LV-METRIC and MASS ejection fraction estimations were highly correlated with manual tracing (R(2) = 0.97 and R(2) = 0.95, respectively). Ventricular volume estimations were smaller with LV-METRIC and larger with MASS than those calculated by using manual tracing, though all results were well correlated (R(2) = 0.99). LV-METRIC volume measurements without partial voxel interpolation were statistically equivalent to manual tracing results (P > .05). LV-METRIC had reduced intraobserver and interobserver variability compared with other methods. MASS required additional manual intervention in 58% of cases, whereas LV-METRIC required no additional corrections. LV-METRIC reliably and reproducibly measured LV volumes. SUPPLEMENTAL MATERIAL http://radiology.rsnajnls.org/cgi/content/full/248/3/1004/DC1.

EPICARDIAL ADIPOSE TISSUE VOLUME AND CORONARY ARTERY CALCIUM TO PREDICT MYOCARDIAL ISCHEMIA ON POSITRON EMISSION TOMOGRAPHY-COMPUTED TOMOGRAPHY STUDIES

Background There appears to be an association of epicardial adipose tissue (EAT) with coronary artery disease (CAD) and its risk factors. EAT is assumed to influence CAD development by altering vasomotor tone and via toxic paracrine effects. The relationship of EAT to myocardial perfusion has not been studied.

An Assessment of Time Dependence of Defibrillator Benefit After Coronary Revascularization

Background: Previous studies have suggested that the benefit of implantable cardioverter defibrillator (ICD) implantation in patients following coronary revascularization (CR) may be related to time elapsed since revascularization, with those receiving the device > 6 months after the procedure deriving the greatest benefit. Methods: We evaluated 163 patients (141 M/22 F, age 67 ± 11 y, LVEF 30 ± 8%) with a history of CR who underwent electrophysiology study (EPS) for risk stratification. ICD implantation was at the discretion of the treating physician. Oc- currence of arrhythmia in ICD patients was ascertained from regular device clinic follow-up. Vital status was assessed us- ing the National Death Index. Results: 101 patients (62%) had recent CR (� 6 months before EPS) vs 62 (38%) with remote CR (> 6 months). Median follow-up was 29 ± 17 months. There was no difference in arrhythmia-free survival (p = 0.89, 84 (83%) vs 52 (84%) at 12 months), time to appropriate ICD therapy (p = 0.35, 94 (93%) vs 55 (89%) at 12 months), or overall survival (p = 0.15, 91 (90%) vs 59 (95%) at 12 months) between recent and remote CR patients. Conclusions: Overall survival, arrhythmia-free survival, and time to first appropriate ICD therapy are similar between pa- tients with recent and remote CR undergoing an EPS-guided approach to risk stratification.

1124 Automated soft segmentation of the left ventricle using myocardial effusion threshold reduction and intravoxel computation (METRIC)

Introduction An automated partial voxel left ventricular segmentation algorithm is presented. The algorithm, termed LV-METRIC (Left Ventricular Myocardial Effusion Threshold Reduction with Intravoxel Computation), measures the blood volume of the LV from cardiac cine MRI images, for all phases and slices. Papillary muscle and trabecular muscles are accounted for through partial voxel interpolation. Minimal interaction is required in some basal slices for which the valve plane must be defined.