Background Cardiovascular magnetic resonance (CMR) strain imaging is an established technique to quantify myocardial deformation. However, to what extent left ventricular (LV) systolic strain, and therefore LV mechanics, reflects classical hemodynamic parameters under various inotropic states is still not completely clear. Therefore, the aim of this study was to investigate the correlation of LV global strain parameters measured via CMR feature tracking (CMR-FT, based on conventional cine balanced steady state free precession (bSSFP) images) with hemodynamic parameters such as cardiac index (CI), cardiac power output (CPO) and end-systolic elastance (Ees) under various inotropic states. Methods  Ten anaesthetized, healthy Landrace swine were acutely instrumented closed-chest and transported to the CMR facility for measurements. After baseline measurements, two steps were performed: (1) dobutamine-stress (Dobutamine) and (2) verapamil-induced cardiovascular depression (Verapamil). During each protocol, CMR images were acquired in the short axisand apical 2Ch, 3Ch and 4Ch views. MEDIS software was utilized to analyze global longitudinal (GLS), global circumferential (GCS), and global radial strain (GRS). Results Dobutamine significantly increased heart rate, CI, CPO and Ees, while Verapamil decreased them. Absolute values of GLS, GCS and GRS accordingly increased during Dobutamine infusion, while GLS and GCS decreased during Verapamil. Linear regression analysis showed a moderate correlation between GLS, GCS and LV hemodynamic parameters, while GRS correlated poorly. Indexing global strain parameters for indirect measures of afterload, such as mean aortic pressure or wall stress, significantly improved these correlations, with GLS indexed for wall stress reflecting LV contractility as the clinically widespread LV ejection fraction. Conclusion GLS and GCS correlate accordingly with LV hemodynamics under various inotropic states in swine. Indexing strain parameters for indirect measures of afterload substantially improves this correlation, with GLS being as good as LV ejection fraction in reflecting LV contractility. CMR-FT-strain imaging may be a quick and promising tool to characterize LV hemodynamics in patients with varying degrees of LV dysfunction.

Cardiovascular magnetic resonance feature tracking (CMR-FT) is a novel technique for non-invasive assessment of myocardial motion and deformation. Although CMR-FT is standardized in humans, literature on comparative analysis from animal models is scarce. In this study, we measured the reproducibility of global strain under various inotropic states and the sample size needed to test its relative changes in pigs. Ten anesthetized healthy Landrace pigs were investigated. After baseline (BL), two further steps were performed: (I) dobutamine-induced hyper-contractility (Dob) and (II) verapamil-induced hypocontractility (Ver). Global longitudinal (GLS), circumferential (GCS) and radial strain (GRS) were assessed. This study shows a good to excellent inter- and intra-observer reproducibility of CMR-FT in pigs under various inotropic states. The highest inter-observer reproducibility was observed for GLS at both BL (ICC 0.88) and Ver (ICC 0.79). According to the sample size calculation for GLS, a small number of animals could be used for future trials.

Right ventricular biopsy represents the gold standard for the assessment of myocardial fibrosis and collagen content. This invasive technique, however, is accompanied by perioperative complications and poor reproducibility. Extracellular volume (ECV) measured through cardiovascular magnetic resonance (CMR) has emerged as a valid surrogate method to assess fibrosis non-invasively. Nonetheless, ECV provides an overestimation of collagen concentration since it also considers interstitial space. Our study aims to investigate the feasibility of estimating total collagen volume (TCV) through CMR by comparing it with the TCV measured at histology. Seven healthy Landrace pigs were acutely instrumented closed-chest and transported to the MRI facility for measurements. For each protocol, CMR imaging at 3T was acquired. MEDIS software was used to analyze T1 mapping and ECV for both the left ventricular myocardium (LV myo) and left ventricular septum (LV septum). ECV was then used to estimate TCV CMR at LV myo and LV septum following previously published formulas. Tissues were prepared following an established protocol and stained with picrosirius red to analyze the TCV histo in LV myo and LV septum. TCV measured at LV myo and LV septum with both histology (8 ± 5 ml and 7 ± 3 ml, respectively) and T1-Mapping (9 ± 5 ml and 8 ± 6 ml, respectively) did not show any regional differences. TCV histo and TCV CMR showed a good level of data agreement by Bland-Altman analysis. Estimation of TCV through CMR may be a promising way to non-invasively assess myocardial collagen content and may be useful to track disease progression or treatment response.

LDL-C) methods using samples from a previously reported randomized, clinical trial.Methods: This was an analysis of data from a previously reported multicenter, randomized double-blind, study in 948 hyperlipidemic patients in which patients received ezetimibe/simvastatin (Eze/Simva) (10/20 mg) + extendedrelease niacin (ERN) (to 2 g) or Eze/Simva (10/20 mg) for 24 and 64 weeks, and ERN to 2 g for 24 weeks then Eze/ Simva (10/20 mg) + ERN 2 g or Eze/Simva 10/20 mg for 40 weeks more. The RLP-C analysis included patients randomized to the Eze/Simva+ERN and Eze/Simva treatment arms for 24 and 64 weeks; patients randomized to N 2 g alone were not included. RLP-C levels, change from baseline and % change from baseline were evaluated by the IM, VAP, and Calculated methods. The relationships and agreement among the three methods used in the measurement of these parameters were assessed by Pearson correlation coefficients and Bland-Altman plots, respectively.Results: Cholesterol mass at baseline measured by the VAP and Calculated methods was w3-4X higher than by IM; all declined with treatment by 24 weeks with little further reduction at 64 weeks (see table). RLP-C change and % reduction from baseline were larger when measured by VAP versus Calculated and IM methods (Table). Although the three methods were moderately to strongly correlated (r 5 0.37 to 0.79) for RLP-C levels and changes, Bland-Altman plots showed little agreement between the methods for RLP-C levels and slightly better agreement for RLP-C changes (not shown).