Comparison of 2D and 3D calculation of left ventricular torsion as circumferential-longitudinal shear angle using cardiovascular magnetic resonance tagging

<p>Abstract</p> <p>Purpose</p> <p>To compare left ventricular (LV) torsion represented as the circumferential-longitudinal (CL) shear angle between 2D and 3D quantification, using cardiovascular magnetic resonance (CMR).</p> <p>Methods</p> <p>CMR tagging was performed in six healthy volunteers. From this, LV torsion was calculated using a 2D and a 3D method. The cross-correlation between both methods was evaluated and comparisons were made using Bland-Altman analysis.</p> <p>Results</p> <p>The cross-correlation between the curves was <it>r</it>²= 0.97 ± 0.02. No significant time-delay was observed between the curves. Bland-Altman analysis revealed a significant positive linear relationship between the difference and the average value of both analysis methods, with the 2D results showing larger values than the 3D. The difference between both methods can be explained by the definition of the 2D method.</p> <p>Conclusion</p> <p>LV torsion represented as CL shear quantified by the 2D and 3D analysis methods are strongly related. Therefore, it is suggested to use the faster 2D method for torsion calculation.</p

The Role of the Frank–Starling Law in the Transduction of Cellular Work to Whole Organ Pump Function: A Computational Modeling Analysis

We have developed a multi-scale biophysical electromechanics model of the rat left ventricle at room temperature. This model has been applied to investigate the relative roles of cellular scale length dependent regulators of tension generation on the transduction of work from the cell to whole organ pump function. Specifically, the role of the length dependent Ca2+ sensitivity of tension (Ca50), filament overlap tension dependence, velocity dependence of tension, and tension dependent binding of Ca2+ to Troponin C on metrics of efficient transduction of work and stress and strain homogeneity were predicted by performing simulations in the absence of each of these feedback mechanisms. The length dependent Ca50 and the filament overlap, which make up the Frank-Starling Law, were found to be the two dominant regulators of the efficient transduction of work. Analyzing the fiber velocity field in the absence of the Frank-Starling mechanisms showed that the decreased efficiency in the transduction of work in the absence of filament overlap effects was caused by increased post systolic shortening, whereas the decreased efficiency in the absence of length dependent Ca50 was caused by an inversion in the regional distribution of strain

Rationale, design and methodology for Intraventricular Pressure Gradients Study: a novel approach for ventricular filling assessment in normal and falling hearts

<p>Abstract</p> <p>Background</p> <p>Intraventricular pressure gradients have been described between the base and the apex of the left ventricle during early diastolic ventricular filling, as well as, their increase after systolic and diastolic function improvement. Although, systolic gradients have also been observed, data are lacking on their magnitude and modulation during cardiac dysfunction. Furthermore, we know that segmental dysfunction interferes with the normal sequence of regional contraction and might be expected to alter the physiological intraventricular pressure gradients. The study hypothesis is that systolic and diastolic gradients, a marker of normal left ventricular function, may be related to physiological asynchrony between basal and apical myocardial segments and they can be attenuated, lost entirely, or even reversed when ventricular filling/emptying is impaired by regional acute ischemia or severe aortic stenosis.</p> <p>Methods/Design</p> <p><it>Animal Studies: </it>Six rabbits will be completely instrumented to measuring apex to outflow-tract pressure gradient and apical and basal myocardial segments lengthening changes at basal, afterloaded and ischemic conditions. Afterload increase will be performed by abruptly narrowing or occluding the ascending aorta during the diastole and myocardial ischemia will be induced by left coronary artery ligation, after the first diagonal branch.</p> <p><it>Patient Studies: </it>Patients between 65-80 years old (n = 12), both genders, with severe aortic stenosis referred for aortic valve replacement will be selected as eligible subjects. A high-fidelity pressure-volume catheter will be positioned through the ascending aorta across the aortic valve to measure apical and outflow-tract pressure before and after aortic valve replacement with a bioprosthesis. Peak and average intraventricular pressure gradients will be recorded as apical minus outflow-tract pressure and calculated during all diastolic and systolic phases of cardiac cycle.</p> <p>Discussion</p> <p>We expect to validate the application of our method to obtain intraventricular pressure gradients in animals and patients and to promote a methodology to better understand the ventricular relaxation and filling and their correlation with systolic function.</p

Cardiac resynchronization therapy guided by cardiovascular magnetic resonance

Cardiac resynchronization therapy (CRT) is an established treatment for patients with symptomatic heart failure, severely impaired left ventricular (LV) systolic dysfunction and a wide (> 120 ms) complex. As with any other treatment, the response to CRT is variable. The degree of pre-implant mechanical dyssynchrony, scar burden and scar localization to the vicinity of the LV pacing stimulus are known to influence response and outcome. In addition to its recognized role in the assessment of LV structure and function as well as myocardial scar, cardiovascular magnetic resonance (CMR) can be used to quantify global and regional LV dyssynchrony. This review focuses on the role of CMR in the assessment of patients undergoing CRT, with emphasis on risk stratification and LV lead deployment

High-resolution MRI of the carotid arteries using a leaky waveguide transmitter and a high-density receive array at 7 T

\u3cp\u3eA setup for 7T MRI of the carotid arteries in the neck was designed and constructed. Separate dedicated arrays were used for transmit and receive. For the transmit array, single-side adapted dipole antennas were mounted on a dielectric pillow, which was shown to serve as a leaky waveguide, efficiently distributing B1 into the neck. Risk assessment was performed by simulations. Phantom measurements were performed to establish optimal positions of the antennas on the pillow. Using two antennas, a dual transmit setup was created. In vivo B1 (+) maps with different shim configurations were acquired to assess transmit performance. This effective transmit array was used in combination with a dedicated 30 channel small element receive coil. High-resolution in vivo turbo spin echo images were acquired to demonstrate the excellent performance of the setup.\u3c/p\u3