This Week in PBS&DCardiac Conduction SystemThe ElectrocardiogramThe ECGThe ECGThe Modern ECGElectrocardiographHolter MonitorDipole ModelStandard Locations?ECG Lead ConfigurationsFrontal Plane Bipolar LeadsEinthoven TriangleThe Einthoven TriangleLead ILead IILead IIICardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and IIICardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and IIICardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and IIICardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and IIIUnipolar Measurements:Wilson Central TerminalWilson’s Central TerminalAugmented Leads:aVRAugmented Leads aVLAugmented Leads aVFAll Frontal LeadsFrontal LeadsTransversal LeadsSummaryReferencesPrinciples of Biomedical Systems & DevicesPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Principles of Biomedical Systems & DevicesLecture 7: The ElectrocardiogramPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404This Week in PBS&D Cardiac conduction system Electrocardiography Cardiac vector model ECG leads and lead configurations Einthoven’s Triangle Measuring ECGPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Cardiac Conduction SystemPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404The ElectrocardiogramPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404The ECGPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404The ECGPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404The Modern ECGPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404ElectrocardiographPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Holter MonitorPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Dipole Model The electrical activity of the heart can be modeled with a vector quantity: an electric dipole, M whose magnitude and direction changes in time. Also called the cardiac vectorPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Standard Locations? Potentials generated by the heart appear throughout the body Measurements made at different locations will generate differentrecordings. Need standard positions for electrode placement so that clinicalevaluations of ECG can be madePBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404ECG Lead Configurations A pair of electrodes, or a combination of several electrodes through a resistive network that gives an equivalent pair is called a lead. A vector that connects a lead electrode pair is the lead vector. If the cardiac vector M is known, the voltage generated at any lead can be easily computed.υa1a2a1M+θiiv aMa⋅=PBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Frontal Plane Bipolar LeadsEinthoven Triangle0=+−IIIIIIPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404The Einthoven TrianglePBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Lead ILead I is the first of three standard limb leads (I, II, III). Limb leads measure cardiac depolarization in the frontal (coronal) plane.The negative electrode is connected to the RIGHT ARM.The positive electrode is connected to the LEFT ARM.The axis is 0 degrees.When an action potential starts on the right and proceeds toward the left side of the heart, a positive inflection will beseen in lead one. This holds true for all leads. Whenever a current proceeds toward a positive electrode, an upright inflection is seen on the EKG tracing.PBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Lead IILead II is used alone quite frequently. Normal rhythms present with a prominant P wave and a tall QRS. The negative electrode is connected to the RIGHT ARM.The positive electrode is connected to the LEFT LEG.The axis is +60 degrees.In all the limb leads, the electrodes may be positioned close to the torso. For convenience, they are often placed at the shoulders and hips.PBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Lead IIILead III is the last of the three standard limb leads. The negative electrode is connected to the LEFT ARM.The positive electrode is connected to the LEFT LEG.The axis is 120 degrees.Cardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and IIICardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and IIICardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and IIICardiac Vector Through the Cardiac Cycle As Seen By Leads I, II and IIIPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Unipolar Measurements:Wilson Central Terminal Three additional leads are used for frontal plane measurements.  These are the measurements at the specific electrode, with respect to a reference electrode One commonly used reference electrode is the Wilson Central Terminal, obtained through a resistive network, combining limb electrodes The new set of leads obtained by combining the standard limb electrodes to the Wilson terminal form the augmented leads These leads provide additional vector views of cardiac depolarization in the frontal plane. Unlike leads I, II, III, the augmented leads utilize WCT, a central negative terminal. This virtual "electrode" is calculated by the EKG computer to measurevectors originating roughly at the center of the heart. Note that the voltage at Wilson’s terminal is zero (why?)PBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Wilson’s Central TerminalPBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Augmented Leads:aVRAugmented Lead (RIGHT) avRThe negative electrode is the central terminal.The positive electrode is connected to the RIGHT ARM.The axis is -150 degrees.PBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Augmented LeadsaVLAugmented Lead (LEFT) avLThe negative electrode is the central terminal.The positive electrode is connected to the LEFT ARM.The axis is -30 degrees.PBS&D – Fall 2004 – Polikar http://engineering.rowan.edu/~polikar/CLASSES/ECE404Augmented LeadsaVFAugmented Lead (FEET) avFThe