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Mitral annular (MA) excursion during diastole encompasses a volume that is part of total left ventricular (LV) filling volume (LVFV). Altered excursion or area variation of the MA due to changes in preload or inotropic state could affect LV filling. We hypothesized that changes in LV preload and inotropic state would not alter the contribution of MA dynamics to LVFV. Six sheep underwent marker implantation in the LV wall and around the MA. After 7-10 days, biplane fluoroscopy was used to obtain three-dimensional marker dynamics from sedated, closed-chest animals during control conditions, inotropic augmentation with calcium (Ca), preload reduction with nitroprusside (N), and vena caval occlusion (VCO). The contribution of MA dynamics to total LVFV was assessed using volume estimates based on multiple tetrahedra defined by the three-dimensional marker positions. Neither the absolute nor the relative contribution of MA dynamics to LVFV changed with Ca or N, although MA area decreased (Ca, P < 0.01; and N, P < 0.05) and excursion increased (Ca, P < 0.01). During VCO, the absolute contribution of MA dynamics to LVFV decreased (P < 0.001), based on a reduction in both area (P < 0.001) and excursion (P < 0.01), but the relative contribution to LVFV increased from 18 [+ or -] 4 to 45 [+ or -] 13% (P < 0.001). Thus MA dynamics contribute substantially to LV diastolic filling. Although MA excursion and mean area change with moderate preload reduction and inotropic augmentation, the contribution of MA dynamics to total LVFV is constant with sizeable magnitude. With marked preload reduction (VCO), the contribution of MA dynamics to LVFV becomes even more important. diastolic function; inotropic augmentation; mitral annular excursion; preload reduction; regional left ventricular filling properties

Background: Knowledge of normal cardiac kinematics is important when attempting to understand the mechanisms that impair the contractile function of the heart during disease. The complex kinematics of the heart can be studied by inserting radiopaque markers in the cardiac wall and study the pumping heart with biplane cineradiography. In order to study the local strain, the bead array was developed where small radiopaque beads are inserted along three columns transmurally in the left ventricle. Method: This paper suggests a straighforward method for strain computation, based on polynomial least-squares fitting and tailored for combined marker and bead array analyses. Results: This polynomial method gives small errors for a realistic bead array on an analytical test case. The method delivers an explicit expression of the Lagrangian strain tensor as a polynomial function of the coordinates of material points in the reference configuration. The method suggested in this paper is validated with analytical strains on a deforming cylinder resembling the heart, compared to a previously suggested finite element method, and applied to in vivo ovine data. The errors in the estimated strain components are shown to remain unchanged on an analytical test case when evaluating the effects of one missing bead. In conclusion, the proposed strain computation method is accurate and robust, with errors smaller or comparable to the current gold standard when applied on an analytical test case. [DO]: 10.1115/1.2746385] Keywords: finite strain, transmural, finite element, myocardial marker, bead array

Rapid early diastolic left ventricular (LV) filling requires a highly compliant chamber immediately after systole, allowing inflow at low driving pressures. The transmural LV deformations associated with such filling are not completely understood. We sought to characterize regional transmural LV strains during diastole, with focus on early filling, in ovine hearts at 1 week and 8 weeks after myocardial marker implantation. In seven normal sheep hearts, 13 radiopaque markers were inserted to silhouette the LV chamber and a transmural beadset was implanted into the lateral equatorial LV wall to measure transmural strains. Four-dimensional marker dynamics were obtained 1 week and 8 weeks thereafter with biplane videofluoroscopy in closed-chest, anesthetized animals. LV transmural strains in both cardiac and fiber-sheet coordinates were studied from filling onset to the end of early filling (EOEF, 100 ms after filling onset) and at end diastole. At the 8 week study, subepicardial circumferential strain ([E.sub.CC]) had reached its final value already at EOEF, while longitudinal and radial strains were nearly zero at this time. Subepicardial [E.sub.CC] and fiber relengthening ([E.sub.ff]) at EOEF were reduced to 1 compared with 8 weeks after surgery ([E.sub.CC]:0.02 [+ or -] 0.01 to 0.08 [+ or -] 0.02 and [E.sub.ff]:0.00 [+ or -] 0.01 to 0.03 +-0.01, respectively, both P Keywords: diastolic strain, early filling, myocardial mechanics, postoperative period, transmural heterogeneity

Background: The ability to measure and quantify myocardial motion and deformation provides a useful tool to assist in the diagnosis, prognosis and management of heart disease. The recent development of magnetic resonance imaging methods, such as harmonic phase analysis of tagging and displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D kinematic analyses of human myocardium possible in the clinic and for research purposes. A robust analysis method is required, however., Methods: We propose to estimate strain using a polynomial function which produces local models of the displacement field obtained with DENSE. Given a specific polynomial order, the model is obtained as the least squares fit of the acquired displacement field. These local models are subsequently used to produce estimates of the full strain tensor., Results: The proposed method is evaluated on a numerical phantom as well as in vivo on a healthy human heart. The evaluation showed that the proposed method produced accurate results and showed low sensitivity to noise in the numerical phantom. The method was also demonstrated in vivo by assessment of the full strain tensor and to resolve transmural strain variations., Conclusions: Strain estimation within a 3D myocardial volume based on polynomial functions yields accurate and robust results when validated on an analytical model. The polynomial field is capable of resolving the measured material positions from the in vivo data, and the obtained in vivo strains values agree with previously reported myocardial strains in normal human hearts.

A quantitative analysis of myocardial mechanics is fundamental to the understanding of cardiac function, diagnosis of heart disease and assessment of therapeutic intervention. In clinical practice, most cardiac imaging analyses are performed in 2D because of the limited scan time available. However, the obtained information from a 2D measurement is limited. This study presents a method to obtain temporal evolutions of transmural 3D Lagrangian strains from two intersecting 2D planes of slice-followed cine displacement encoding with stimulated echoes (DENSE) data using a bilinear-cubic polynomial element to resolve strain from the displaced myocardial positions. The method was validated against an analytical standard and has been applied to in vivo data acquired on a 3 T magnetic resonance system from a healthy volunteer to quantify systolic strains at the anterior-basal region of left ventricular myocardium. The method demonstrates accurate results when validated in the analytical model, and the in vivo results agree within experimental accuracy with values reported in the literature. Even with a short scan time, this method provides the full 3D Lagrangian strain tensor from two 2D DENSE measurements., (© 2011 The Authors. Clinical Physiology and Functional Imaging © 2011 Scandinavian Society of Clinical Physiology and Nuclear Medicine.)

Left ventricular myofibers are connected by an extensive extracellular collagen matrix to form myolaminar sheets. Histological cardiac tissue studies have previously observed a pleated transmural distribution of sheets in the ovine heart, alternating sign of the sheet angle from epicardium to endocardium. The present study investigated temporal variations in myocardial fiber and sheet architecture during the cardiac cycle. End-diastolic histological measurements made at subepicardium, midwall, and subendocardium at an anterior-basal and a lateral-equatorial region of the ovine heart, combined with transmural myocardial Lagrangian strains, showed that the sheet angle but not the fiber angle varied temporally throughout the cardiac cycle. The magnitude of the sheet angle decreased during systole at all transmural depths at the anterior-basal site and at midwall and subendocardium depths at the lateral-equatorial site, making the sheets more parallel to the radial axis. These results support a previously suggested accordion-like wall-thickening mechanism of the myocardial sheets.

Introduction: With the reduction of administrative Regions in Denmark to a total of five, more focus has been given to prehospital services. Since access to and quality of prehospital treatment is not standardized, it may very well vary between regions., Material and Methods: Information was collected from all existing physician-based units in Denmark through official sources and subsequently verified by direct contact to the administrative unit's prehospital organization. Data was collected in the period 1 December 2007 to 31 January 2008., Results: There is great variation in coverage of Danish prehospital physician-based units. The number of dedicated prehospital units in significantly lower in Region North Jutland than in the remaining regions (measured as units pr. million inhabitants as well as is units per 10,000 square kilometers). Generally, the dedicated physician-based prehospital units are staffed with a specialist in anaesthesiology., Conclusion: There is considerable variation in the coverage of the physician-based prehospital units in Denmark. There are sound medical arguments for having a specialist in anaesthesiology staffing physician-based prehospital units. All administrative regions - except Region Nordjylland - offer advanced physician prehospital treatment on a 24-hours basis.