Quantitative Imaging of Diastolic Function using Cardiac Magnetic Resonance Imaging

• Author / Creator

  Cheng Baron, June

• Diastolic dysfunction is the primary cause of 40–50% of all heart failure cases and is a contributing factor in many cardiac conditions, resulting from delayed or slowed muscle relaxation, increased stiffness of the relaxed heart or from poor systolic function which reduces the elastic recoil of the heart. The study of diastolic function has been hampered by a lack of simple, quantitative, parameters describing diastolic performance. The current standard of evaluation consists of echocardiography-derived blood and tissue velocities. Magnetic resonance imaging (MRI) provides better spatial coverage and soft tissue contrast, but is relatively unexplored in the context of diastolic function. Goals of this thesis were to improve current and develop new quantitative measures of diastolic function using MRI. Left ventricular deformation during isovolumic relaxation was studied to reveal that measured changes in left ventricular volume during this interval reflect changes in myocardial strain and are balanced by the inward bowing of the mitral valve leaflets which maintains the isovolumic condition. Next, aspects of the filling portion of the cardiac cycle were studied including mitral blood velocity and flow, left atrial propagation velocity and atrio-ventricular pressure gradients. Mitral blood velocity and flow were found to have distinct time-courses that become more similar with increasing severity of diastolic dysfunction. Velocity propagation, a wave-like pressure wave phenomenon, was observed in the left atrium during systole, early filling and atrial contraction, providing a new measure of diastolic function reflecting atrial stiffness and pressure. Atrio-ventricular pressure gradients however, were not found to provide additional information beyond blood velocity measures. Finally, there is growing interest in measuring systolic strain in the presence diastolic dysfunction with preserved ejection fraction, where strains appear abnormal despite normal volumetric function. Conventional MRI-derived strain requires specialized acquisition protocols and onerous post-processing. A method was developed to measure strains from standard anatomical MRI. MRI is a promising tool for the comprehensive characterization of diastolic function. However, this field of study is still relatively un-established and further studies, similar to those presented here, in larger patient groups are necessary to establish the role of MRI for diastolic function in research and clinically.

• Subjects / Keywords

  • Magnetic resonance imaging
  • Cardiac
  • Diastolic function

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3GG82

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.