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Transmural Strains in the Ovine Left Ventricular Lateral Wall During Diastolic Filling
Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.ORCID-id: 0000-0003-2198-9690
Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.ORCID-id: 0000-0001-5526-2399
Stanford University.
Visa övriga samt affilieringar
2009 (Engelska)Ingår i: JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, ISSN 0148-0731, Vol. 131, nr 6Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

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-CC) had reached its final value already at EOEF, while longitudinal and radial strains were nearly zero at this time. Subepicardial E-CC and fiber relengthening (E-ff) at EOEF were reduced to 1 compared with 8 weeks after surgery (E-CC:0.02 +/- 0.01 to 0.08 +/- 0.02 and E-ff:0.00 +/- 0.01 to 0.03 +/- 0.01, respectively, both P < 0.05). Subepicardial E-CC during early LV filling was associated primarily with fiber-normal and sheet-normal shears at the 1 week study, but to all three fiber-sheet shears and fiber relengthening at the 8 week study. These changes in LV subepicardial mechanics provide a possible mechanistic basis for regional myocardial lusitropic function, and may add to our understanding of LV myocardial diastolic dysfunction.

Ort, förlag, år, upplaga, sidor
2009. Vol. 131, nr 6
Nyckelord [en]
biomechanics, biomedical measurement, cardiology, diagnostic radiography, medical disorders, strain measurement
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
URN: urn:nbn:se:liu:diva-18556DOI: 10.1115/1.3118774OAI: oai:DiVA.org:liu-18556DiVA, id: diva2:220588
Tillgänglig från: 2009-06-01 Skapad: 2009-06-01 Senast uppdaterad: 2016-03-14
Ingår i avhandling
1. Invasive and Non-Invasive Quantification of Cardiac Kinematics
Öppna denna publikation i ny flik eller fönster >>Invasive and Non-Invasive Quantification of Cardiac Kinematics
2010 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

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. Myocardial motion can be measured by means of several different types of data acquisition. The earliest myocardial motion tracking technique was invasive, based on implanting radiopaque markers into the myocardium around the left ventricle, and recording the marker positions during the cardiac cycle by biplane cineradiography. Until recently, this was the only method with high enough spatial resolution of three-dimensional (3D) myocardial displacements to resolve transmural behaviors. However, the recent development of magnetic resonance imaging techniques, such as displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D transmural kinematic analyses of human myocardium possible in the clinic and for research purposes.

Diastolic left ventricular filling is a highly dynamic process with early and late transmitral inflows and it is determined by a complex sequence of many interrelated events and parameters. Extensive research has been performed to describe myocardial kinematics during the systolic phase of the cardiac cycle, but not by far the same amount of research has been accomplished during diastole. Measures of global and regional left ventricular kinematics during diastole are important when attempting to understand left ventricular filling characteristics in health and disease.

This thesis presents methods for invasive and non-invasive quantification of cardiac kinematics, with focus on diastole. The project started by quantification of changes in global left ventricular kinematics during diastolic filling. The helical myocardial fiber architecture of the left ventricle produces both long- and short-axis motion as well as torsional deformation. The longitudinal excursion of the mitral annular plane is an important component of left ventricular filling and ejection. This was studied by analyzing the contribution of mitral annular dynamics to left ventricular filling volume in the ovine heart.

In order to quantify strains for a specific body undergoing deformation, displacements for a set of internal points at a deformed configuration relative to a reference configuration are needed. A new method for strain quantification from measured myocardial displacements is presented in this thesis. The method is accurate and robust and delivers analytical expressions of the strain components. The developed strain quantification method is simple in nature which aids to bridge a possible gap in understanding between different disciplines and is well suited for sparse arrays of displacement data.

Analyses of myocardial kinematics at the level of myocardial fibers require knowledge of cardiac tissue architecture. Temporal changes in myofiber directions during the cardiac cycle have been analyzed in the ovine heart by combining histological measurements of transmural myocardial architecture and local transmural strains.

Rapid early diastolic filling is an essential component of the left ventricular function. Such filling requires a highly compliant chamber immediately after systole, allowing inflow at low driving pressures. Failure of this process can lead to exercise intolerance and ultimately to heart failure. A thorough analysis of the relation between global left ventricular kinematics and local myocardial strain at the level of myocardial fibers during early diastole in the ovine heart was performed by applying the method for strain quantification and the technique for computing temporal changes in myocardial architecture on measures of myocardial displacements and tissue architecture in the ovine heart.

As data acquisition technologies develop, quantification methods for cardiac kinematics need to be adapted and validated on the new types of data. Recent improvements of DENSE magnetic resonance imaging enable non-invasive transmural strain analyses in the human heart. The strain quantification method was first tailored to displacement data from a surgically implanted bead array but has been extended to applications on non-invasive DENSE data measured in two and three dimensions. Validation against an analytical standard reveals accurate results and in vivo strains agree with values for normal human hearts from other studies.

The method has in this thesis been used with displacement data from invasive marker technology and non-invasive DENSE magnetic resonance imaging, but can equally well be applied on any type of displacement data provided that the spatial resolution is high enough to resolve local strain variations.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2010. s. 49
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1322
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:liu:diva-60202 (URN)978-91-7393-375-9 (ISBN)
Disputation
2010-08-17, sal C3, Hus C, Campus Valla, Linköpings universitet, Linköping, 10:15
Opponent
Handledare
Tillgänglig från: 2010-10-07 Skapad: 2010-10-07 Senast uppdaterad: 2016-03-14Bibliografiskt granskad

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