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Electrophysiology

basic electrophysiology

TermDefinition
Absolute refractory period corresponds with the onset of the QRS complex to approximately the peak of the T wave; cardiac cells cannot be stimulated to conduct an electrical impulse, no matter how strong the stimulus
Action potential a five-phase cycle that reflects the difference in the concentration of charged particles across the cell membrane at any given time
Altered automaticity a disorder of impulse formation in which cardiac cells fire and initiate impulses before a normal SA node impulse
Amplitude height (voltage) of a waveform on the ECG
Arrhythmia abnormal heart rhythm
Artifact distortion of and ECG tracing by electrical activity that is non-cardiac in origin
Atrioventricular bundle the bundle of His
Atrioventricular node a group of cells that conduct and electrical impulse through the heart; located in the floor of the right atrium immediately behind the tricuspid valve and near the opening of the coronary sinus
Augmented limb lead leads aVR, aVL, and aVF; these leads record the difference in electrical potential at one location relative to the electrical potential of another extremity
Automaticity ability of cardiac pacemaker cells to spontaneously initiate an electrical impulse without being stimulated from another source (such as a nerve)
AV bundle the bundle of His
AV node specialized cells located in the lower portion of the right atrium; delays the electrical impulse in order to allow the atria to contract and complete filling of the ventricles
Axis imaginary line joining the positive and negative electrodes of a lead
Baseline straight line recorded on ECG graph paper when no electrical activity is detected
Biphasic waveform that is partly positive and partly negative
Bipolar limb lead ECG lead consisting of a positive and negative electrode
Bundle of His fibers located in the upper portion of the interventricular septum that receive and electrical impulse from the AV node and conduct the impulse to the right and left bundle branches
Complex several waveforms
Conduction system a system of pathways in the heart composed of specialized electrical (pacemaker) cells
Conductivity ability of a cardiac cell to receive and electrical stimulus and conduct that impulse to an adjacent crdiac cell
Contractility ability of cardiac cells to shorten, causing cardiac muscle contraction in response to and electrical stimulus
Depolarization movement of ions across a cell membrane, causing the inside of the cell to become more positive, and electrical event expected to result in contraction
Dysrhythmia abnormal heart rhythm
Ectopic impulse originating from a source other than the SA node
Effective refractory period period of the cardiac action potential that includes the absolute refractory period and the first half of eh relative refractory period
Electrode and adhesive pad that contains a conductive gel and is applied at specific locations on the patient's chest wall and extremities and connected by cable to and ECG machine
Electrolytes elements or compounds that break into charged particles (ions) when melted or dissolved in water or another solvent
Enhanced automaticity abnormal condition in which cardiac cells not normally associated with the property of automaticity begin to depolarize spontaneously or when escape pacemaker sites increase their firing rate beyond that considered normal
Excitability the ability of cardiac muscle cells to respond to an outside stimulus
Ground electrode third ECG electrode (the first and second are the positive and negative electrodes), which minimizes electrical activity from other sources
His-Purkinje system portion of the conduction system consisting of the bundle of His, bundle branches, and Purkinje fibers
Indicative changes ECG changes observed in leads that look directly at the affected area of the heart; indicative changes are significant when they are seen in two anatomically contiguous leads
Inherent natural, intrinsic
Interval waveform and a segment; in pacing, the period, measured in milliseconds, between any two designated cardiac events
Intrinsic rate rate at which a pacemaker of the heart normally generates impulses
Ion electrically charged particle
Isoelectric line absence of electrical activity; observed on the ECG as a straight line
J point point where the QRS complex and ST segment meet
Lead electrical connection attached to the body to record electrical activity
Membrane potential difference in electrical charge cross the cell membrane
millivolt (mV) difference in electrical charge between two points in a circuit
Myocardial cells working cells of the myocardium that contain contractile filaments and form the muscular layer of the trial walls and the thicker muscular layer of the ventricular walls
Pacemaker cells specialized cells of the heart's electrical conduction system, capable o spontaneously generating and conducting electrical impulsed
Permeability ability of a membrane channel to allow passage of electrolytes once it is open
Polarized state period after repolarization of a myocardial cell (also called the resting state) when the outside of the cell is positive and the interior of the cell is negative
PR interval P wave plus the PR segment; reflects depolarization of the right and left atria (P wave) and the spread of the impulse through the AV node, AV bundle, right and left bundle branches, and the Purkinje fibers (PR segment)
Purkinje fibers fibers found in both ventricles that conduct and electrical impulse through the heart
P wave first wave in the cardiac cycle; represents atrial depolarization and the spread of to electrical impulse throughout the right and left atria
QRS complex several waveforms that represent the spread of and electrical impulse though the ventricles (ventricle depolarization)
R wave on an ECG, the first positive deflection in the QRS complex, representing ventricular depolarization; in pacing, R wave refers to the entire QRS complex, denoting and intrinsic ventricular event
Reciprocal change ECG changes observed in leads in leads opposite the affected area of the heart; also called mirror image changes
Reentry spread of and impulse through tissue already stimulated by that same impulse
Refractoriness period of recovery that cells need after being discharged before they are able to respond to a stimulus
Relative refractory period corresponds with the down slope of the T wave; cardiac cells can be stimulated to depolarize if the stimulus is strong enough
Repolarization movement of ions across a cell membrane in which the inside of the cell is restored to its negative state
Segment line between waveforms; named by the waveform that precedes and follows it
Sinoatrial node normal pacemaker of the heart that normally discharges at a rhythmic rate of 60 to 100 bpm
ST segment portion of the ECG representing the end of ventricular depolarization (end of the R wave) and the beginning of ventricular repolarization (T wave)
Supranormal period period during the cardiac cycle when weaker than normal stimulus can cause cardiac cells to depolarize; extends from the end of phase 3 to the beginning of phase 4 of the cardiac action potential
T wave waveform that follows the QRS complex and represents ventricular repolarization
TP segment interval between two successive PQRST complexes during which electrical activity of the heart is absent; begins with the end of the T wave through the onset of the following P wave and represents the period from the end of ventricular repolarizton to the
Triggered activity a disorder of impulse formation that occurs when escape pacemaker and myocardial working cells fire more than once after stimulation by a single impulse resulting in atria or ventricular beats that occur alone, in pairs, in runs, or as a sustained ectopic
Unipolar lead that consists of a single positive electrode and a reference point
Voltage difference in electrical charge between two points
Waveform movement away from the baseline in either a positive or negative direction
Created by: pnkrangr87