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78 Cards in this Set
- Front
- Back
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what is electrocardiography?
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standard means by which the composite electrical activity of the heart is assessed from the surface of the body
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what is the standard means by which the composite electrical activity of the heart is assessed from the surface of the body?
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electrocardiography
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what is an electrocardiogram?
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tracing produced on a screen or paper
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what is an electrocardiograph?
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device used to produce the electrocardiogram
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what does ECG stand for?
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electrocardiogram
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what does EKG stand for?
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electrocardiogram
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what does an electrocardiogram record?
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the trace and its component entervals are the time-dependent representation of the evoked voltages (which have vectors comprised of magnitue and direction) from action potentials, produced in the specialized cardiac conduction system, and the contractile elements, which develop in a sequence
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what is used to take an electrocardiogram for diagnosis of cardiac rate and rhythm?
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three bipolar leads
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what are the leads called?
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RA, LA, and LL
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what does RA stand for?
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right antebracium
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what does LA stand for?
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left antebracium
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what does LL stand for?
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left hind leg
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what is Einthoven's triangle?
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the triangle whose points determine the placement of bipolar leads when recording an electrocardiogram
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the bipolar leads are placed on the points of what?
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einthoven's triangle
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what is measured by the bipolar leads?
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the voltage differences between the limb reference points from the current fluxes that comprise cardiac action potentials
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why are the leads bipolar?
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potential differences between two reference points; each lead designation has a unique orientation of positive and negatvie electrodes which are electronically determined by the circuitry of the ECG monitor and selectable by the user
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where are the negative and positive leads of ECG I?
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negative = RA, positive = LA
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where are the negative and positive leads of ECG II?
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negative = RA, positive = LL
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where are the negative and positive leads of ECG III?
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negative = LA, positive = LL
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which lead has negative = RA, positive LA?
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I
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which lead has negative = RA, positive LL?
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II
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which lead has negative = LA, positive LL?
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III
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when the wave of depolarization is propagated toward the positive electrode of any selected lead, where is the trace deflection?
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the trace deflection in that lead is desplayed upward
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the trace deflection in that lead is desplayed upward if what occurs?
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when the wave of depolarization is propagated toward the positive electrode of any selected lead
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if one knows the electrode orientation of the selected lead and the convention of trace deflection based upon the location of the positive electrode, one can do what?
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predict how a particular ECG pattern must reflect a given activation sequence in the myocardium
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what are augmented unipolar electrocardigraphic leads?
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leads aVR, aVL, and aVF utilize same limb lead positions but the ECG machine connects them in different combinationsthat percieves the electrical potential at one of the limb locations compared to the voltage between the others
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how do augmented unipolar electrocardigraphics leads inscribe on the ECG trace?
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electrod orientation of selected lead and the convention of trace deflection based upon the location of the positive electrode one can predict how at particular ECG pattern must reflect a given activation sequence in the myocardium
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what does NSR stand for?
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normal sinus rhythm
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what are the axis on an ECG plot?
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x-axis = time, y-axis= voltage amplitude
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what does a typical NSR sequence contan?
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P-wave, a QRS complex, and a T-wave
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what does a P-wave correspond to?
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atrial depolarization
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atrial depolarization is represented by what on an ECG?
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P-wave
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what does a QRS complex correspond to?
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ventricular depolarization
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what does a T-wave correspond to?
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ventricular repolarizaiton
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ventricular depolarization is represented by what on an ECG?
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QRS complex
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ventricular repolarization is represented by what on an ECG?
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T-wave
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what is important about ECG morphology?
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the amplitude of an ECG trace is directly related to the magniture of membrane ionic current occurating at any instant and the width of each component and the intervals between them are the real time representations of their respective durations
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the amplitude of an ECG trace is directly related to the magniture of membrane ionic current occurating at any instant and the width of each component and the intervals between them are the real time representations of their respective durations is illustrated by what?
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ECG morphology
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what determined the magnitue of membrane ionic current?
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the number of cells depolarizing or repolarizing
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what gives the P-wave its characteristic shape?
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on the rising phase more and more cells are depolarizaing and on the falling phase fewere and fewere cells are depolarizing at any given time as the wave of depolarization spreads across the atria
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what is the direction of an impulse propagation in the heart?
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right-left, cranial-caudal (toward the left leg)
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right-left, cranial-caudal describes what?
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impulse propagation in the heart
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what are clinically irrelevant abnormalities of impulse generation or conduction called?
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normal variants
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what are normal variants?
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clinically irrelevant abnormalities of impulse generation or conduction
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what is the first setep in evaluating an ECG?
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assess the technical quality of the record and determine the paper speed and calibration
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how is paper speed determined or an ECG?
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may be writen on the record or may have 1-second time markers
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what should each lead of the ECG produce on the tracing?
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a visible calibration signal (square wave)
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what must one watch out for in terms of the calibration signal?
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artifacts created by the superimposition of the calibration signal on a P or QRS comples
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What happens if a complex get to near an edge?
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they will appear clipped and voltage measurements will be inaccurate
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what are common artifacts in an ECG tract?
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respiratory or recordal movement (wandering baseline), 60-cycle interference from other electrical appliances or a poorly isolated wall outlet, muscle tremor, movement of the patient, touching of the electrodes during recording
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how do we calculate the heart rate from an ECG tracing?
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ventricular rate = # of QRS complexes in 3 or 6 seconds or RR interval in mSec/60,000 and atrial rate = # P-waes in same and for sinus rhythms, ventricular rate = atrial rate
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what questions shold be answered to diagnose rhythm?
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is the atrial & ventricular rate normal for the species, and equal?, is there a P-wave for every QRS-T?, Are the QRS-T and P wave consistently related?, are the R-R intervals regular?, Are there patterns to irregularities?, Are the P-P intervals regular?, Do all the Pwaves and QRS-T complexes look alike? are the reasonable fore the lead and species?
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what else must be done to evaluate the P-QRS-T complex configuration?
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measure intervals, amplitudes, and durations of complexes
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what is the average heart rate for dogs?
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60-160
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what is the average heart rate for cats?
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140-220
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what is the average P wave duration and amplitude in the dog?
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0.04sec/0.4mV
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what is the average P wave duration and amplitude in the cat?
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0.035sec/0.3mV
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what is the average PR interval duration in the dog?
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0.130sec
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what is the average PR interval duration in the cat?
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0.080sec
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what is the average QRS duration in the dog?
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0.06sec
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what is the average QRS duration in the cat?
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0.04sec
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what is the average amplitude of R measured in lead II in the dog?
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<2.5-3.0mV
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what is the average amplitude of R measured in lead II in the cat?
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<0.9mV
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On the ECG trace, what does a sinus rhythm look like?
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a P for every QRS & a QRS for every P, regular P-QRS-T complexes occur within normal range for species and generally look the same and regular, with normal interavals between P and QRS complex
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On the ECG trace, what does a sinus arrhythmia look like?
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like a normal sinus rhythm but with a cyclic irregularity to the P-P & R-R intervals, usually at a normal or slow (bradycardia) heart rate
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On the ECG trace, what does a sinus tachycardia look like?
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sinus rhythm at a rate faster than the normal range for the species
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On the ECG trace, what does a sinus arrest look like?
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sudden loss of SA node function, so no P appears for a pause > 2 normal P-P intervals, and an excape comples may appear to end pause w/out P wave
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On the ECG trace, what does a 1st Degree AV block look like?
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prolonged P-R interval beyond normal for the species without any nonconducted P waves
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On the ECG trace, what does a 2nd Degree AV block look like?
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some P occur w/out accompanying QRS complexes (unable to pentrate AV node), ventricular escape complese may occur after
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On the ECG trace, what does a 3rd Degree AV block look like?
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no definable relationship between P wave and QRS complexes, ventricular escape rhythm is slow (bradycaardic)
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on the ECG trace, what does a supraventricular premature complex look like?
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normal looking QRS that interrupts the normal P-P and R-R interval, may have abnormal P wave, often accompany atrial stretch or disease
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what does SVPC stand for?
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supraventricular premature complexes
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on the ECG trace, what does an atrial fibrillation look like?
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rapid, irregular rhythm w/out identifiable P waves (irregular baseline) w/normal looking QRS, minor variability in QRS morphology, sign of generally serious atrial stretch disease
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on the ECG trace, what does ventricular premature complex look like?
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wide, bizarre, QRS comples with T wave in opposite direction that interrupts underlying rhythm. Look like ventricular escape complese except for their timing (interrupt normal rather than end a pause). May be isolated, occur 2 ata time (couplet), alterante with sinus complexes (ventricular bigeminy) or occur as paroxysms or sustained periods of tachycardia
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what does VPC stand for?
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ventricular premature complex
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on the ECG trace, what does ventricular fibrillation look like?
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no P waves or QRS complexes, rapidly undulating baseline, no organized electrical activity, no heartbeat/pulse. Fatal unless defibrillation can be accomplished
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what does VF stand for?
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ventricular fibrillation
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what is the ECG?
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a record of activation sequence of myocardial tissues; when direction/speed of impulse propagation is altered from normal, the ECG changes in predictable manner reflective of those changes
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