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Helm PA, Younes L, Beg MF, Ennis DB, Leclercq C, Faris OP, McVeigh E, Kass D, Miller MI, Winslow RL. Evidence of Structural Remodeling in the Dyssynchronous Failing Heart. Circ Res 2006; 98:125-32. [PMID: 16339482 DOI: 10.1161/01.res.0000199396.30688.eb] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ventricular remodeling of both geometry and fiber structure is a prominent feature of several cardiac pathologies. Advances in MRI and analytical methods now make it possible to measure changes of cardiac geometry, fiber, and sheet orientation at high spatial resolution. In this report, we use diffusion tensor imaging to measure the geometry, fiber, and sheet architecture of eight normal and five dyssynchronous failing canine hearts, which were explanted and fixed in an unloaded state. We apply novel computational methods to identify statistically significant changes of cardiac anatomic structure in the failing and control heart populations. The results demonstrate significant regional differences in geometric remodeling in the dyssynchronous failing heart versus control. Ventricular chamber dilatation and reduction in wall thickness in septal and some posterior and anterior regions are observed. Primary fiber orientation showed no significant change. However, this result coupled with the local wall thinning in the septum implies an altered transmural fiber gradient. Further, we observe that orientation of laminar sheets become more vertical in the early-activated septum, with no significant change of sheet orientation in the late-activated lateral wall. Measured changes in both fiber gradient and sheet structure will affect both the heterogeneity of passive myocardial properties as well as electrical activation of the ventricles.
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Affiliation(s)
- Patrick A Helm
- Centers for Cardiovascular Bioinformatics & Modeling, Johns Hopkins University, Baltimore, MD, USA.
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Sermesant M, Rhode K, Sanchez-Ortiz GI, Camara O, Andriantsimiavona R, Hegde S, Rueckert D, Lambiase P, Bucknall C, Rosenthal E, Delingette H, Hill DLG, Ayache N, Razavi R. Simulation of cardiac pathologies using an electromechanical biventricular model and XMR interventional imaging. Med Image Anal 2005; 9:467-80. [PMID: 16006170 DOI: 10.1016/j.media.2005.05.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Simulating cardiac electromechanical activity is of great interest for a better understanding of pathologies and for therapy planning. Design and validation of such models is difficult due to the lack of clinical data. XMR systems are a new type of interventional facility in which patients can be rapidly transferred between X-ray and MR systems. Our goal is to design and validate an electromechanical model of the myocardium using XMR imaging. The proposed model is computationally fast and uses clinically observable parameters. We present the integration of anatomy, electrophysiology, and motion from patient data. Pathologies are introduced in the model and simulations are compared to measured data. Initial qualitative comparison on the two clinical cases presented is encouraging. Once fully validated, these models will make it possible to simulate different interventional strategies.
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Affiliation(s)
- M Sermesant
- Cardiac MR Research Group, King's College London, 5th Floor Thomas Guy House, Guy's Hospital, London, UK.
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Ashikaga H, Mickelsen SR, Ennis DB, Rodriguez I, Kellman P, Wen H, McVeigh ER. Electromechanical analysis of infarct border zone in chronic myocardial infarction. Am J Physiol Heart Circ Physiol 2005; 289:H1099-105. [PMID: 15908463 PMCID: PMC2396317 DOI: 10.1152/ajpheart.00423.2005] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
To test the hypothesis that alterations in electrical activation sequence contribute to depressed systolic function in the infarct border zone, we examined the anatomic correlation of abnormal electromechanics and infarct geometry in the canine post-myocardial infarction (MI) heart, using a high-resolution MR-based cardiac electromechanical mapping technique. Three to eight weeks after an MI was created in six dogs, a 247-electrode epicardial sock was placed over the ventricular epicardium under thoracotomy. MI location and geometry were evaluated with delayed hyperenhancement MRI. Three-dimensional systolic strains in epicardial and endocardial layers were measured in five short-axis slices with motion-tracking MRI (displacement encoding with stimulated echoes). Epicardial electrical activation was determined from sock recordings immediately before and after the MR scans. The electrodes and MR images were spatially registered to create a total of 160 nodes per heart that contained mechanical, transmural infarct extent, and electrical data. The average depth of the infarct was 55% (SD 11), and the infarct covered 28% (SD 6) of the left ventricular mass. Significantly delayed activation (>mean + 2SD) was observed within the infarct zone. The strain map showed abnormal mechanics, including abnormal stretch and loss of the transmural gradient of radial, circumferential, and longitudinal strains, in the region extending far beyond the infarct zone. We conclude that the border zone is characterized by abnormal mechanics directly coupled with normal electrical depolarization. This indicates that impaired function in the border zone is not contributed by electrical factors but results from mechanical interaction between ischemic and normal myocardium.
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Affiliation(s)
- Hiroshi Ashikaga
- Laboratory of Cardiac Energetics, NHLBI, NIH, 10 Center Dr., MSC 1061, Bldg. 10, B1D416, Bethesda, MD 20892-1061, USA.
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Kerckhoffs RCP, Faris OP, Bovendeerd PHM, Prinzen FW, Smits K, McVeigh ER, Arts T. Electromechanics of paced left ventricle simulated by straightforward mathematical model: comparison with experiments. Am J Physiol Heart Circ Physiol 2005; 289:H1889-97. [PMID: 15964924 PMCID: PMC2396318 DOI: 10.1152/ajpheart.00340.2005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intraventricular synchrony of cardiac activation is important for efficient pump function. Ventricular pacing restores the beating frequency but induces more asynchronous depolarization and more inhomogeneous contraction than in the normal heart. We investigated whether the increased inhomogeneity in the left ventricle can be described by a relatively simple mathematical model of cardiac electromechanics, containing normal mechanical and impulse conduction properties. Simulations of a normal heartbeat and of pacing at the right ventricular apex (RVA) were performed. All properties in the two simulations were equal, except for the depolarization sequence. Simulation results of RVA pacing on local depolarization time and systolic midwall circumferential strain were compared with those measured in dogs, using an epicardial sock electrode and MRI tagging, respectively. We used the same methods for data processing for simulation and experiment. Model and experiment agreed in the following aspects. 1) Ventricular pacing decreased systolic pressure and ejection fraction relative to natural sinus rhythm. 2) Shortening during ejection and stroke work declined in early depolarized regions and increased in late depolarized regions. 3) The relation between epicardial depolarization time and systolic midwall circumferential strain was linear and similar for the simulation (slope = -3.80 +/- 0.28 s(-1), R2 = 0.87) and the experiments [slopes for 3 animals -2.62 +/- 0.43 s(-1) (R2 = 0.59), -2.97 +/- 0.38 s(-1) (R2 = 0.69), and -4.44 +/- 0.51 s(-1) (R2 = 0.76)]. We conclude that our model of electromechanics is suitable to simulate ventricular pacing and that the apparently complex events observed during pacing are caused by well-known basic physiological processes.
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Affiliation(s)
- R. C. P. Kerckhoffs
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - O. P. Faris
- Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - P. H. M. Bovendeerd
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - F. W. Prinzen
- Department of Physiology, Maastricht University, Maastricht, The Netherlands
| | - K. Smits
- Department of Lead Modeling, Medtronic Bakken Research Center, Maastricht University, Maastricht, The Netherlands
| | - E. R. McVeigh
- Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - T. Arts
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Department of Biophysics, Maastricht University, Maastricht, The Netherlands
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Abstract
Ventricular geometry and fiber orientation may undergo global or local remodeling in cardiac disease. However, there are as yet no mathematical and computational methods for quantifying variation of geometry and fiber orientation or the nature of their remodeling in disease. Toward this goal, a landmark and image intensity-based large deformation diffeomorphic metric mapping (LDDMM) method to transform heart geometry into common coordinates for quantification of shape and form was developed. Two automated landmark placement methods for modeling tissue deformations expected in different cardiac pathologies are presented. The transformations, computed using the combined use of landmarks and image intensities, yields high-registration accuracy of heart anatomies even in the presence of significant variation of cardiac shape and form. Once heart anatomies have been registered, properties of tissue geometry and cardiac fiber orientation in corresponding regions of different hearts may be quantified.
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Affiliation(s)
- Mirza Faisal Beg
- Center for Imaging Science, The Whitaker Biomedical Engineering Institute, Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland
| | - Patrick A. Helm
- Center for Cardiovascular Bioinformatics & Modeling, The Whitaker Biomedical Engineering Institute, Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland
| | - Elliot McVeigh
- Laboratory of Cardiac Energetics, National Heart Lung Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Michael I. Miller
- Center for Imaging Science, The Whitaker Biomedical Engineering Institute, Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland
| | - Raimond L. Winslow
- Center for Cardiovascular Bioinformatics & Modeling, The Whitaker Biomedical Engineering Institute, Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland
- *Correspondence to: Raimond L. Winslow, Rm. 201B Clark Hall, Johns Hopkins University, 3400 N. Charles St., Baltimore MD 21218. E-mail:
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Kerckhoffs RCP, Faris OP, Bovendeerd PHM, Prinzen FW, Smits K, McVeigh ER, Arts T. Timing of depolarization and contraction in the paced canine left ventricle: model and experiment. J Cardiovasc Electrophysiol 2004; 14:S188-95. [PMID: 14760923 DOI: 10.1046/j.1540.8167.90310.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
INTRODUCTION For efficient pump function, contraction of the heart should be as synchronous as possible. Ventricular pacing induces asynchrony of depolarization and contraction. The degree of asynchrony depends on the position of the pacing electrode. The aim of this study was to extend an existing numerical model of electromechanics in the left ventricle (LV) to the application of ventricular pacing. With the model, the relation between pacing site and patterns of depolarization and contraction was investigated. METHODS AND RESULTS The LV was approximated by a thick-walled ellipsoid with a realistic myofiber orientation. Propagation of the depolarization wave was described by the eikonal-diffusion equation, in which five parameters play a role: myocardial and subendocardial velocity of wave propagation along the myofiber cm and ce; myocardial and subendocardial anisotropy am and ae; and parameter k, describing the influence of wave curvature on wave velocity. Parameters cm, ae, and k were taken from literature. Parameters am and ce were estimated by fitting the model to experimental data, obtained by pacing the canine left ventricular free wall (LVFW). The best fit was found with cm = 0.75 m/s, ce = 1.3 m/s, am = 2.5, ae = 1.5, and k = 2.1 x 10(-4) m2/s. With these parameter settings, for right ventricular apex (RVA) pacing, the depolarization times were realistically simulated as also shown by the wavefronts and the time needed to activate the LVFW. The moment of depolarization was used to initiate myofiber contraction in a model of LV mechanics. For both pacing situations, mid-wall circumferential strains and onset of myofiber shortening were obtained. CONCLUSION With a relatively simple model setup, simulated depolarization timing patterns agreed with measurements for pacing at the LVFW and RVA in an LV. Myocardial cross-fiber wave velocity is estimated to be 0.40 times the velocity along the myofiber direction (0.75 m/s). Subendocardial wave velocity is about 1.7 times faster than in the rest of the myocardium, but about 3 times slower than as found in Purkinje fibers. Furthermore, model and experiment agreed in the following respects. (1) Ventricular pacing decreased both systolic pressure and ejection fraction relative to natural sinus rhythm. (2) In early depolarized regions, early shortening was observed in the isovolumic contraction phase; in late depolarized regions, myofibers were stretched in this phase. Maps showing timing of onset of shortening were similar to previously measured maps in which wave velocity of contraction appeared similar to that of depolarization.
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Affiliation(s)
- Roy C P Kerckhoffs
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
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Faris OP, Evans FJ, Dick AJ, Raman VK, Ennis DB, Kass DA, McVeigh ER. Endocardial versus epicardial electrical synchrony during LV free-wall pacing. Am J Physiol Heart Circ Physiol 2003; 285:H1864-70. [PMID: 12855422 PMCID: PMC2396262 DOI: 10.1152/ajpheart.00282.2003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac resynchronization therapy has been most typically achieved by biventricular stimulation. However, left ventricular (LV) free-wall pacing appears equally effective in acute and chronic clinical studies. Recent data suggest electrical synchrony measured epicardially is not required to yield effective mechanical synchronization, whereas endocardial mapping data suggest synchrony (fusion with intrinsic conduction) is important. To better understand this disparity, we simultaneously mapped both endocardial and epicardial electrical activation during LV free-wall pacing at varying atrioventricular delays (AV delay 0-150 ms) in six normal dogs with the use of a 64-electrode LV endocardial basket and a 128-electrode epicardial sock. The transition from dyssynchronous LV-paced activation to synchronous RA-paced activation was studied by constructing activation time maps for both endo- and epicardial surfaces as a function of increasing AV delay. The AV delay at the transition from dyssynchronous to synchronous activation was defined as the transition delay (AVt). AVt was variable among experiments, in the range of 44-93 ms on the epicardium and 47-105 ms on the endocardium. Differences in endo- and epicardial AVt were smaller (-17 to +12 ms) and not significant on average (-5.0 +/- 5.2 ms). In no instance was the transition to synchrony complete on one surface without substantial concurrent transition on the other surface. We conclude that both epicardial and endocardial synchrony due to fusion of native with ventricular stimulation occur nearly concurrently. Assessment of electrical epicardial delay, as often used clinically during cardiac resynchronization therapy lead placement, should provide adequate assessment of stimulation delay for inner wall layers as well.
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Affiliation(s)
- Owen P Faris
- Laboratory of Cardiac Energetics, NHLBI/National Institutes of Health, 10 Center Drive, Rm. B1D416, Bethesda, MD 20892, USA
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