Imaging Electrical Activit y of the Heart

Imaging Electrical ActivitImaging Electrical Activityy of the Heartof the Heart

Özlem Özmen OkurÖzlem Özmen Okur

BM573 CARDIOVASCULAR IMAGINGBM573 CARDIOVASCULAR IMAGING

Student PresentationStudent Presentation

28.11.200528.11.2005 Imaging Electrical Activity of the HeartImaging Electrical Activity of the Heart 22/21/21

Contraction of a Cardiac Muscle CellContraction of a Cardiac Muscle Cell

In the heart:In the heart:Iionic current triggers the rhythmic muscle contractions that pump blood in and out. Iionic current triggers the rhythmic muscle contractions that pump blood in and out.

http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/06.htm http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/06.htm

bumil

In the heart muscle cell, or myocyte, electric activation takes place by means of the same mechanism as in the nerve cell - that is, from the inflow of sodium ions across the cell membrane. The amplitude of the action potential is also similar, being about 100 mV for both nerve and muscle. The duration of the cardiac muscle impulse is, however, two orders of magnitude longer than that in either nerve cell or skeletal muscle. A plateau phase follows cardiac depolarization, and thereafter repolarization takes place. As in the nerve cell, repolarization is a consequence of the outflow of potassium ions. The duration of the action impulse is about 300 ms, as shown in Figure 1.Associated with the electric activation of cardiac muscle cell is its mechanical contraction, which occurs a little later. Figure 2 illustrates the electric activity and mechanical contraction of frog cardiac muscle.


The The DDifferent ifferent WWaveforms for aveforms for EEach of ach of the the SSpecialized pecialized CCells ells

http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/06x/conducti/0607i.htm http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/06x/conducti/0607i.htm


Need for Mapping of Electrical Need for Mapping of Electrical ActivityActivity

To understand the mechanisms responsible for the normal cardiac rhythm To understand the mechanisms responsible for the normal cardiac rhythm and for the initation and maintenance of arrhythmias.and for the initation and maintenance of arrhythmias.

http://www.comsol.com/stories/heart/http://www.comsol.com/stories/heart/http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/06x/isochron/65.htm http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/06x/isochron/65.htm


Problems (1)Problems (1) Normal Sinus Rhythm (: All Normal Sinus Rhythm (: All

complexes normal, evenly complexes normal, evenly spacedspacedRate 60 - 100/min Rate 60 - 100/min

Sinus Bradycardia: All Sinus Bradycardia: All complexes normal, evenly complexes normal, evenly spacedspacedRate < 60 - 100/minRate < 60 - 100/min

Sinus Tachycardia: All Sinus Tachycardia: All complexes normal, evenly complexes normal, evenly spacedspacedRate > 100/min Rate > 100/min

Sinus Arrythmia: All Sinus Arrythmia: All complexes normal, rhythm is complexes normal, rhythm is irregularirregular


Problems (2)Problems (2) WANDERING WANDERING

PACEMAKERPACEMAKER (Impulses (Impulses originate from varying points originate from varying points in atria): Variation in P-wave in atria): Variation in P-wave contour, P-R and P-P interval contour, P-R and P-P interval and therefore in R-R intervals and therefore in R-R intervals

ATRIAL FLUTTER ATRIAL FLUTTER (Impulses travel in circular (Impulses travel in circular course in atriacourse in atria)): Rapid : Rapid flutter waves, ventricular flutter waves, ventricular response irregularresponse irregular

ATRIAL FIBRILLATION ATRIAL FIBRILLATION (Impulses have chaotic, (Impulses have chaotic, random pathways in atria): random pathways in atria): Baseline irregular, Baseline irregular, ventricular response ventricular response irregularirregular

VENTRICULAR VENTRICULAR FIBRILLATIONFIBRILLATIONChaotic ventricular Chaotic ventricular depolarizationdepolarization


Wave pattern (a single spiral) on the ventricular Wave pattern (a single spiral) on the ventricular surface, during monomorphic tachycardia surface, during monomorphic tachycardia

http://www.math.utah.edu/~keener/lectures/maw/slide8.html http://www.math.utah.edu/~keener/lectures/maw/slide8.html


Surface View of FibrillationSurface View of Fibrillation

http://www.math.utah.edu/~keener/lectures/maw/slide13.html http://www.math.utah.edu/~keener/lectures/maw/slide13.html


Imaging Electrical Activity of the HeartImaging Electrical Activity of the Heart

Reconstruction from internally located Reconstruction from internally located electrodeselectrodes

Electrocardiographic ImagingElectrocardiographic Imaging Optical ImagingOptical Imaging Magnetocardiographic ImagingMagnetocardiographic Imaging


Ventricular Ventricular JJacket acket AArrayrray

VahlhausVahlhaus, Christian, et al; “, Christian, et al; “Direct epicardial mapping predicts the recovery of left ventricular dysfunction in chronic ischaemic Direct epicardial mapping predicts the recovery of left ventricular dysfunction in chronic ischaemic myocardiummyocardium”; European Heart Journal; v. 25; n. 2; pp. 151-157; 2003.”; European Heart Journal; v. 25; n. 2; pp. 151-157; 2003.

bumil

Ventricular jacket array consisting of 102 gold-plated bipolar electrode pairs, arranged in 12 strips of printed copper layers on flexible plastic material: six strips with 10 pairs of electrodes and six strips with seven pairs of electrodes. (B) 102 bipolar epicardial electrograms simultaneously recorded with CardioMapp


IInternally nternally LLocated ocated DDefibrillation efibrillation EElectrodeslectrodes

LeftLeft: : anterioranterior, r, rightight: : posterior view of the posterior view of the heart and the major heart and the major vessels of the heart. vessels of the heart.

RedRed: : regions of large regions of large current densitiescurrent densities

BBluelue: : regions of regions of relatively lower current relatively lower current densities.densities.

http://www.http://www.liblib..utahutah.edu/.edu/gouldgould/2000/lecture00.html/2000/lecture00.html

bumil

The two images show the electric current density magnitudes resulting from a defibrillation simulation using small, internally located defibrillation electrodes. The left image is an anterior view and the right image is a posterior view of the heart and the major vessels of the heart. Red denotes regions of large current densities and blue denotes regions of relatively lower current densities.


Electrocardiographic ImagingElectrocardiographic Imaging

NoninvasiveNoninvasive Using body surface Using body surface

measurementsmeasurements RReconstructeconstructionion on the on the

heart's surface using heart's surface using geometrical information geometrical information from computed from computed tomography (CT) and a tomography (CT) and a mathematical algorithm. mathematical algorithm.

Burnes, John, et al; "A Noninvasive Imaging Modality for Cardiac Burnes, John, et al; "A Noninvasive Imaging Modality for Cardiac Arrhythmias"; Nature Medicine; n. 10; pp. 422-428; 2004.Arrhythmias"; Nature Medicine; n. 10; pp. 422-428; 2004.


Optical Imaging of Electrical Optical Imaging of Electrical Activity in the HeartActivity in the Heart

Cardiac action potentials are recorded using Cardiac action potentials are recorded using voltage-sensitive dyes to monitor voltage-sensitive dyes to monitor

cellular potential, cellular potential, cell to cell interactions, and cell to cell interactions, and propagation and repolarization "patterns" propagation and repolarization "patterns"

underlying cardiac arrhythmias. underlying cardiac arrhythmias.

http://www.http://www.metrohealthresearchmetrohealthresearch.org/.org/hvrcresearchelectrophyshvrcresearchelectrophys.html.html


Optical Properties of Membrane-Bound Dyes That Have Been Used to Measure

Membrane Potential Changes

Fluorescence, Absorption, Dichroism, Birefringence, Fluorescence resonance energy transfer, Nonlinear second harmonic generation, and Resonance Raman absorption.

considerably less sensitive to movement artifacts generated by muscle contractions

Efimov, Igor, et al; "Optical Imaging of the Heart"; Circ. Res.; n.95; pp. 21-33; 2004.Efimov, Igor, et al; "Optical Imaging of the Heart"; Circ. Res.; n.95; pp. 21-33; 2004.

bumil

Fluorescence is a luminescence which is mostly found as an optical phenomenon in cold bodies, in which a molecule absorbs a high-energy photon, and re-emits it as a lower-energy (longer-wavelength) photon. The energy difference between the absorbed and emitted photons ends up as molecular vibrations (heat). Usually the absorbed photon is in the ultraviolet, and the emitted light (luminescence) is in the visible range, but this depends on the absorbance curve and Stokes shift of the particular fluorophore. Fluorescence is named after the mineral fluorite (calcium fluoride), which exhibits this phenomenon.In optics absorption refers to the absorption of photons by a materialA dichroic material is one which either causes visible light to be split up into distinct beams of different wavelengths (colours), Birefringence, or double refraction, is the division of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on the polarization of the light. Fluorescence resonance energy transfer (or Förster resonance energy transfer) describes an energy transfer mechanism between two fluorescent molecules. A fluorescent donor is excited at its specific fluorescence excitation wavelength. By a long-range dipole-dipole coupling mechanism, this excited state is then nonradiatively transferred to a second molecule, the acceptor. The donor returns to the electronic ground state. The described energy transfer mechanism is termed "Förster resonance energy transfer" (FRET), named after the German scientist Theodor Förster. When both molecules are fluorescent, the term "fluorescence resonance energy transfer" is often used, although the energy is not actually transferred by fluorescence.


Schematics of a Typical Optical Schematics of a Typical Optical Mapping SystemMapping System


Mapping of Activation and Repolarization

bumil

from the anterior surface of a Langendorff-perfused guinea pig heart. An optical trace at the right illustrates that the quality of optical recordings approaches that of the goldstandard: microelectrode recordings. When movement artifacts are a concern, activation and repolarization times can be still be determined by calculating the maximum first derivative of the action potential upstroke and the maximum second derivative of the downstroke, respectively. Activation and repolarization data are usually presented as isophasic or isochronal maps (see Figure 3)4,19,37,50–52 or a vector field of conduction in the cardiac muscle (see Figure3),53,54 allowing quantitative assessment of spread of activation and repolarization in highly anisotropic heart muscle under normal and pathological conditions.


Magnetocardiographic ImagingMagnetocardiographic Imaging

http://www.hitachi.com/ICSFiles/afieldfile/2004/06/08/r2001_01_103.pdfhttp://www.hitachi.com/ICSFiles/afieldfile/2004/06/08/r2001_01_103.pdf

MMagnetocardiographs taken from the front and back of the heartagnetocardiographs taken from the front and back of the heart ..UUsing a special magnetic sensor called SQUIDsing a special magnetic sensor called SQUID (8100 fT to severeal tens of pT is emitted from the (8100 fT to severeal tens of pT is emitted from the heart)heart) WWhile clothed.hile clothed.


Ischemic Heart Disease ExampleIschemic Heart Disease Example

http://www.hitachi.com/ICSFiles/afieldfile/2004/06/08/r2001_01_103.pdfhttp://www.hitachi.com/ICSFiles/afieldfile/2004/06/08/r2001_01_103.pdf

bumil

The total current distribution flowing through the heart musclecan be visualized as an image by using an iso-integral map. Thefigure reveals the occurrence of an abnormal repolarizationprocess (ST-T) current distribution due to ischemia.


MMagnetocardiographagnetocardiographicic 3-D 3-D VVisualization of isualization of HHeart eart CCurrent urrent DDistributionistribution


ReferencesReferences

Burnes, John, et al; "A Noninvasive Imaging Modality for Cardiac Burnes, John, et al; "A Noninvasive Imaging Modality for Cardiac Arrhythmias"; Nature Medicine; n. 10; pp. 422-428; 2004.Arrhythmias"; Nature Medicine; n. 10; pp. 422-428; 2004.

Vahlhaus, Christian, et al; “Direct epicardial mapping predicts the Vahlhaus, Christian, et al; “Direct epicardial mapping predicts the recovery of left ventricular dysfunction in chronic ischaemic recovery of left ventricular dysfunction in chronic ischaemic myocardium”; European Heart Journal; v. 25; n. 2; pp. 151-157; 2003.myocardium”; European Heart Journal; v. 25; n. 2; pp. 151-157; 2003.

Efimov, Igor, et al; "Optical Imaging of the Heart"; Circ. Res.; n.95; pp. Efimov, Igor, et al; "Optical Imaging of the Heart"; Circ. Res.; n.95; pp. 21-33; 2004.21-33; 2004.

http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/ http://www.comsol.com/stories/heart/http://www.comsol.com/stories/heart/ http://www.math.utah.edu/~keener/lectures/maw/http://www.math.utah.edu/~keener/lectures/maw/ http://www.lib.utah.edu/gould/2000/lecture00.htmlhttp://www.lib.utah.edu/gould/2000/lecture00.html http://www.nature.com/nm/journal/v10/n4/abs/nm1011.html http://www.nature.com/nm/journal/v10/n4/abs/nm1011.html http://www.metrohealthresearch.org/hvrcresearchelectrophys.htmlhttp://www.metrohealthresearch.org/hvrcresearchelectrophys.html http://www.hitachi.com/ICSFiles/afieldfile/2004/06/08/r2001_01_103.pdf http://www.hitachi.com/ICSFiles/afieldfile/2004/06/08/r2001_01_103.pdf


Thank You...Thank You...

Imaging Electrical Activit y of the Heart

Documents

Transcript of Imaging Electrical Activit y of the Heart