The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform

Rafael Beyar - One of the best experts on this subject based on the ideXlab platform.

  • Dynamics of Left Ventricular Apex Rotation During Angioplasty A Sensitive Index of Ischemic Dysfunction
    Circulation, 1997
    Co-Authors: Merril L. Knudtson, P. Diane Galbraith, Kathy L. Hildebrand, John V. Tyberg, Rafael Beyar
    Abstract:

    Background Apex rotation has been shown to provide a reliable index of the dynamics of Left Ventricular (LV) twist. In this study, we aimed to characterize twist at baseline and during acute ischemia in 20 patients undergoing percutaneous transluminal coronary angioplasty to the Left anterior descending (LAD) artery and to test whether an old myocardial infarction or collateral flow affected twist dynamics. Methods and Results Among patients with no previous infarction, five had no collaterals (group A) and six had angiographically visible collaterals (group B). Previous anterior infarction was present in nine patients (group C). Data were acquired with the LAD angioplasty wire passed beyond the Apex using a view aligned with the LV long axis. Frame-by-frame dynamics of Apex rotation were measured from the angular movement of the portion of the wire that traversed the Apex. Aortic pressure recordings allowed precise temporal definition of the cardiac cycle. Dynamics of Apex rotation were measured at fixed...

  • Effects of Ischemia on Left Ventricular Apex Rotation: An Experimental Study in Anesthetized Dogs
    Circulation, 1995
    Co-Authors: Carol A. Gibbons Kroeker, John V. Tyberg, Rafael Beyar
    Abstract:

    Background Left Ventricular (LV) twist has been defined as the counterclockwise rotation of the Ventricular Apex with respect to the base during systole. We recently showed that, since base rotation is minimal, measurement of Apex rotation reflects the dynamics of LV twist. Since ischemia is known to affect endocardial and epicardial fiber force and shortening and therefore the transmural balance of torsional moments, we hypothesized that ischemia has a significant effect on Apex-rotation amplitude and on untwisting during the isovolumic relaxation (IVR) period. Methods and Results With an optical device coupled to the LV Apex, Apex rotation was recorded simultaneously with LV pressure, ECG, LV segment length, and minor-axis diameters in 16 open-chest dogs. Ischemia was caused by a 1- to 2-minute snare occlusion of either the Left anterior descending (LAD) or circumflex (LCx) arteries. LAD ischemia had a pronounced effect on Apex rotation: an increase in Apex-rotation amplitude attributed to subendocardial dysfunction at 10 seconds of ischemia; maximum Apex rotation occurring later (during the IVR period) throughout the ischemia; a paradoxical relaxation pattern of initial untwisting followed by twisting and untwisting during the IVR period with ischemia; and a decrease in the amplitude of Apex rotation with ischemia, possibly due to transmural dysfunction. LCx occlusion had similar effects on Apex rotation, except that Apex-rotation amplitude was not increased at 10 seconds of occlusion and the amplitude of Apex rotation did not decrease with severe ischemia. Under control preischemic conditions, a linear relationship between Apex rotation and segment length was observed during ejection and a different, steeper relationship during IVR. With regionally ischemic segments, this relationship became nonlinear for both ejection and IVR. Conclusions Both LAD and LCx ischemia had profound effects on the dynamics of Apex rotation. A paradoxical relaxation pattern occurred with ischemia. We suggest that these observations are due to changes in the dynamic transmural balance of torsional moments that determine LV twist.

Larry W. Stephenson - One of the best experts on this subject based on the ideXlab platform.

  • Update 2001: Skeletal muscle ventricles: Left Ventricular Apex to aorta configuration
    The Annals of thoracic surgery, 2001
    Co-Authors: Gregory A. Thomas, Larry W. Stephenson
    Abstract:

    Abstract As Originally Published in 1993: Skeletal Muscle Ventricles: Left Ventricular Apex to Aorta Configuration Huiping Lu, MD, Robert Fietsam, Jr, MD, Robert L. Hammond, MD, Hidehiro Nakajima, MD, Frank W. Mocek, MD, Gregory A. Thomas, MD, Renato Ruggiero, MD, Hisako Nakajima, MD, Michael Colson, MS, and Larry W. Stephenson, MD Division of Cardiothoracic Surgery, Department of Surgery, Wayne State University, Detroit, Michigan, and Medtronics, Inc, Minneapolis, Minnesota Abstract—Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in 6 dogs. After 3 weeks of vascular delay followed by 6 weeks of 2-Hz continuous electrical conditioning, a valved conduit was placed between the Left Ventricular Apex and the SMV and a second valved conduit, between the SMV and the aorta. The SMV was stimulated to contract during diastole at a 1:2 ratio with the heart. The SMV pumped 47% of the systemic blood flow initially (0.73 ± 0.23 versus 1.54 ± 0.42 L/min) and 40% after 3 hours. Skeletal muscle ventricle stimulation resulted in a 58% increase in mean diastolic pressure initially (52 ± 9 to 82 ± 11 mm Hg; p

  • Skeletal Muscle Ventricles, Left Ventricular Apex-to-Aorta Configuration 1 to 11 Weeks in Circulation
    Circulation, 1997
    Co-Authors: Kevin A. Greer, Robert L. Hammond, Ali D. Spanta, Larry W. Stephenson
    Abstract:

    Background Skeletal muscle ventricles (SMVs) have been used in animals in a variety of configurations to provide circulatory assistance. Long-term survival and function have been demonstrated. Our laboratory recently obtained promising short-term hemodynamic data in a Left Ventricular Apex-to-aorta model. Methods and Results SMVs were constructed from the Left latissimus dorsi muscle in five adult mongrel dogs. After a 3-week period of vascular delay and 5 to 7 weeks of electrical conditioning, valved conduits were used to connect the Left Ventricular Apex to the SMV and the SMV to the descending aorta. The SMV was then stimulated to contract during cardiac diastole. Initial measurements showed a significant increase in the mean femoral diastolic pressure (62±6 versus 51±5 mm Hg, P

  • skeletal muscle ventricles Left Ventricular Apex to aorta configuration 1 to 11 weeks in circulation
    Circulation, 1997
    Co-Authors: Kevin A. Greer, Robert L. Hammond, Ali D. Spanta, Larry W. Stephenson
    Abstract:

    Background Skeletal muscle ventricles (SMVs) have been used in animals in a variety of configurations to provide circulatory assistance. Long-term survival and function have been demonstrated. Our laboratory recently obtained promising short-term hemodynamic data in a Left Ventricular Apex-to-aorta model. Methods and Results SMVs were constructed from the Left latissimus dorsi muscle in five adult mongrel dogs. After a 3-week period of vascular delay and 5 to 7 weeks of electrical conditioning, valved conduits were used to connect the Left Ventricular Apex to the SMV and the SMV to the descending aorta. The SMV was then stimulated to contract during cardiac diastole. Initial measurements showed a significant increase in the mean femoral diastolic pressure (62±6 versus 51±5 mm Hg, P<.05). There was also a decrease in the Left Ventricular tension-time index (11.5±2.5 versus 14.6±2.1 mm Hg·s, P<.05), indicating a decrease in the work requirement of the Left ventricle. During SMV stimulation, the majority of ...

  • Skeletal muscle ventricles: Left Ventricular Apex to aorta configuration☆
    The Annals of thoracic surgery, 1993
    Co-Authors: Robert Fietsam, Robert L. Hammond, Hidehiro Nakajima, Frank W. Mocek, Gregory A. Thomas, Renato Ruggiero, Hisako O. Nakajima, Michael Colson, Larry W. Stephenson
    Abstract:

    Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in 6 dogs. After 3 weeks of vascular delay followed by 6 weeks of 2-Hz continuous electrical conditioning, a valved conduit was placed between the Left Ventricular Apex and the SMV and a second valved conduit, between the SMV and the aorta. The SMV was stimulated to contract during diastole at a 1:2 ratio with the heart. The SMV pumped 47% of the systemic blood flow initially (0.73 ± 0.23 versus 1.54 ± 0.42 L/min) and 40% after 3 hours. Skeletal muscle ventricle stimulation resulted in a 58% increase in mean diastolic pressure initially (52 ± 9 to 82 ± 11 mm Hg; p < 0.05) and a 73% increase (45 ± 7 to 78 ± 8 mm Hg) after 3 hours of continuous pumping. This was associated with a 68% increase in the endocardial viability ratio initially and a 63% increase at 3 hours. The systolic tension-time index decreased by 26% initially and 25% at 3 hours. This study indicates that the SMV configuration of Left Ventricular Apex to aorta may be particularly suitable for Left Ventricular assist.

John V. Tyberg - One of the best experts on this subject based on the ideXlab platform.

  • Dynamics of Left Ventricular Apex Rotation During Angioplasty A Sensitive Index of Ischemic Dysfunction
    Circulation, 1997
    Co-Authors: Merril L. Knudtson, P. Diane Galbraith, Kathy L. Hildebrand, John V. Tyberg, Rafael Beyar
    Abstract:

    Background Apex rotation has been shown to provide a reliable index of the dynamics of Left Ventricular (LV) twist. In this study, we aimed to characterize twist at baseline and during acute ischemia in 20 patients undergoing percutaneous transluminal coronary angioplasty to the Left anterior descending (LAD) artery and to test whether an old myocardial infarction or collateral flow affected twist dynamics. Methods and Results Among patients with no previous infarction, five had no collaterals (group A) and six had angiographically visible collaterals (group B). Previous anterior infarction was present in nine patients (group C). Data were acquired with the LAD angioplasty wire passed beyond the Apex using a view aligned with the LV long axis. Frame-by-frame dynamics of Apex rotation were measured from the angular movement of the portion of the wire that traversed the Apex. Aortic pressure recordings allowed precise temporal definition of the cardiac cycle. Dynamics of Apex rotation were measured at fixed...

  • Effects of Ischemia on Left Ventricular Apex Rotation: An Experimental Study in Anesthetized Dogs
    Circulation, 1995
    Co-Authors: Carol A. Gibbons Kroeker, John V. Tyberg, Rafael Beyar
    Abstract:

    Background Left Ventricular (LV) twist has been defined as the counterclockwise rotation of the Ventricular Apex with respect to the base during systole. We recently showed that, since base rotation is minimal, measurement of Apex rotation reflects the dynamics of LV twist. Since ischemia is known to affect endocardial and epicardial fiber force and shortening and therefore the transmural balance of torsional moments, we hypothesized that ischemia has a significant effect on Apex-rotation amplitude and on untwisting during the isovolumic relaxation (IVR) period. Methods and Results With an optical device coupled to the LV Apex, Apex rotation was recorded simultaneously with LV pressure, ECG, LV segment length, and minor-axis diameters in 16 open-chest dogs. Ischemia was caused by a 1- to 2-minute snare occlusion of either the Left anterior descending (LAD) or circumflex (LCx) arteries. LAD ischemia had a pronounced effect on Apex rotation: an increase in Apex-rotation amplitude attributed to subendocardial dysfunction at 10 seconds of ischemia; maximum Apex rotation occurring later (during the IVR period) throughout the ischemia; a paradoxical relaxation pattern of initial untwisting followed by twisting and untwisting during the IVR period with ischemia; and a decrease in the amplitude of Apex rotation with ischemia, possibly due to transmural dysfunction. LCx occlusion had similar effects on Apex rotation, except that Apex-rotation amplitude was not increased at 10 seconds of occlusion and the amplitude of Apex rotation did not decrease with severe ischemia. Under control preischemic conditions, a linear relationship between Apex rotation and segment length was observed during ejection and a different, steeper relationship during IVR. With regionally ischemic segments, this relationship became nonlinear for both ejection and IVR. Conclusions Both LAD and LCx ischemia had profound effects on the dynamics of Apex rotation. A paradoxical relaxation pattern occurred with ischemia. We suggest that these observations are due to changes in the dynamic transmural balance of torsional moments that determine LV twist.

Thierry Carrel - One of the best experts on this subject based on the ideXlab platform.

  • Ideal site for Ventricular anchoring of artificial chordae in mitral regurgitation
    The Journal of Thoracic and Cardiovascular Surgery, 2012
    Co-Authors: Alberto Weber, Samuel Hurni, Stijn Vandenberghe, Andreas Wahl, Thierry Aymard, Rolf Vogel, Thierry Carrel
    Abstract:

    Objective Surgical treatment of mitral leaflet prolapse using artificial neochordae shows excellent outcomes. Upcoming devices attempt the same treatment in a minimally invasive way but target the Left Ventricular Apex as an anchoring point, rather than the tip of the corresponding papillary muscle. In this study, cine cardiac magnetic resonance imaging was used to compare these 2 different anchoring positions and their dynamic relationship with the mitral leaflets. Methods Eleven healthy volunteers (mean age, 31 years; 6 female; mean ejection fraction, 62%) were examined by cardiac magnetic resonance imaging (3 Tesla, cine steady free precession technique with retrospective gating), whereby dedicated software enabled assessment of the physiologic distances among 3 anchoring sites (anterior papillary muscle, posterior papillary muscle, and Apex) and the plane of the mitral annulus at the level of leaflet coaptation. These distances were measured in systole and diastole, and the performance of virtual neochordae was analyzed for the 3 potential anchoring sites. Results Length difference between systole and diastole for the 3 measured distances were 0.19 ± 0.11 cm (5.9% ± 3.4%) for the anterior papillary muscle, 0.19 ± 0.09 cm (6.7% ± 3.6%) for the posterior papillary muscle, and 1.52 ± 0.18 cm (17.8% ± 2.8%) for the Left Ventricular Apex ( P  = .001). Virtual neochordae between the leaflet and the Left Ventricular Apex were first adjusted in systole to achieve leaflet coaptation. Leaflet tear in diastole can only be avoided if the width of the attached leaflet is larger than the systole–diastole length difference. On the other hand, if virtual neochordae are adjusted in diastole to avoid leaflet tear, residual leaflet prolapse during systole can result. Because the systole–diastole length difference for papillary muscle anchored chordae is smaller than for apical chordae by a factor 10, there is a strongly reduced risk of prolapse or tearing and the leaflet width is unimportant. Furthermore, if the neochordae attached to the anterior mitral leaflet uses the Apex as a distal anchoring site, the angle α between the aortic valve plane and this mitral leaflet is significantly reduced in diastole and therefore increases the risk of systolic anterior motion. Conclusions Anchoring of neochordae at the papillary muscles, thereby mimicking the real anatomy, should be preferred over the Left Ventricular Apex. Further analysis of dilated hearts and papillary muscle displacement is necessary to include the whole spectrum of pathologies.

  • Ideal site for Ventricular anchoring of artificial chordae in mitral regurgitation.
    The Journal of thoracic and cardiovascular surgery, 2011
    Co-Authors: Alberto Weber, Samuel Hurni, Stijn Vandenberghe, Andreas Wahl, Thierry Aymard, Rolf Vogel, Thierry Carrel
    Abstract:

    Surgical treatment of mitral leaflet prolapse using artificial neochordae shows excellent outcomes. Upcoming devices attempt the same treatment in a minimally invasive way but target the Left Ventricular Apex as an anchoring point, rather than the tip of the corresponding papillary muscle. In this study, cine cardiac magnetic resonance imaging was used to compare these 2 different anchoring positions and their dynamic relationship with the mitral leaflets. Eleven healthy volunteers (mean age, 31 years; 6 female; mean ejection fraction, 62%) were examined by cardiac magnetic resonance imaging (3 Tesla, cine steady free precession technique with retrospective gating), whereby dedicated software enabled assessment of the physiologic distances among 3 anchoring sites (anterior papillary muscle, posterior papillary muscle, and Apex) and the plane of the mitral annulus at the level of leaflet coaptation. These distances were measured in systole and diastole, and the performance of virtual neochordae was analyzed for the 3 potential anchoring sites. Length difference between systole and diastole for the 3 measured distances were 0.19 ± 0.11 cm (5.9% ± 3.4%) for the anterior papillary muscle, 0.19 ± 0.09 cm (6.7% ± 3.6%) for the posterior papillary muscle, and 1.52 ± 0.18 cm (17.8% ± 2.8%) for the Left Ventricular Apex (P = .001). Virtual neochordae between the leaflet and the Left Ventricular Apex were first adjusted in systole to achieve leaflet coaptation. Leaflet tear in diastole can only be avoided if the width of the attached leaflet is larger than the systole-diastole length difference. On the other hand, if virtual neochordae are adjusted in diastole to avoid leaflet tear, residual leaflet prolapse during systole can result. Because the systole-diastole length difference for papillary muscle anchored chordae is smaller than for apical chordae by a factor 10, there is a strongly reduced risk of prolapse or tearing and the leaflet width is unimportant. Furthermore, if the neochordae attached to the anterior mitral leaflet uses the Apex as a distal anchoring site, the angle α between the aortic valve plane and this mitral leaflet is significantly reduced in diastole and therefore increases the risk of systolic anterior motion. Anchoring of neochordae at the papillary muscles, thereby mimicking the real anatomy, should be preferred over the Left Ventricular Apex. Further analysis of dilated hearts and papillary muscle displacement is necessary to include the whole spectrum of pathologies. Copyright © 2012 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Kazuhisa Uchiyama - One of the best experts on this subject based on the ideXlab platform.