Basic EKG Flashcards
where is the SA node located?
junction of the superior vena cava and right atrium
what is the SA node inherent rate?
60-100 bpm
what is the AV node inherent rate?
40-60 bpm
what is the inherent rate of the ventricles/purkinje network?
20-40 bpm
what is the AV junction?
the conduction pathway between the atria and ventricles
what allows the atria to both contract at once?
intratrial pathways from the SA node in the right atrium to the left atrium
what are the phases of the cardiac conduction cycle?
-depolarization -repolarization -rest
what activates and completes each cardiac conduction cycle?
activated by the automaticity of the heart and completed through electrolyte changes (Na+/K+ ATP pump)
describe depolarization
-occurs by cell becoming “positive”, to a point of +30mV -Na+ enters cell, K+ leaves out (more Na+ going in making more positive) -Ca++ enters at slower rate, facilitating a prolonged conduction *electrical firing of the cell *continuous cycle to stimulate each heart beat
describe repolarization
-begins with Cl- entrance (making cell more negative) -retruns cell to its resting state (resets) -Na+ pumped back out, K+ begins to return in
how is the cardiac action potential (conduction cycle) depicted in graph form?
vertical line (depolarization) followed by a downward slope transition (repolarization)
describe the absolute refractory period
-as the cell is repolarizing, period of time where no matter the stimulus, cell can not depolarize again -insures a complete “re-charge” before the next cycle
describe the relative refractory period
-cell has completed a portion of the repolarization, but has not completed the process -can depolarize again, but is still more difficult to stimulate *certain stimulus during this time can precipitate the heart to change to lethal dysrhythmias *certain meds can predispose conduction during this period
what may cause dysrhythmias in relation to the relative refractory period?
-non pacemaker cells that suddenly discharge on their own similar to the automatic discharge of the SA node -these beats can land during the relative refractory period
what are other causes of dysrhythmias?
-may be created by complication with conduction pathway *re-entry rhythms may cause fast repeating beats that often require emergent care to break the cycle -alterations of the pacing sites (failure/impedance vs. hyper excitation) *AMI, drug action, hypoxia, electrolyte imbalance
what are non pacemaker cells that discharge to stimulate a beat called?
-ectopic sites or foci
what does the EKG provide?
-views the electrical activity of the heart -takes a picture between two electrodes (one lead) -time and voltage are measured
what are the various types of electrodes?
-internal (esophageal): pacing probe is placed down throat -epicardial (attached to heart): during open chest -surface (attached to skin)
how is electricity flowing towards a positive lead viewed on the EKG?
as an upward or positive line
what are the bipolar leads?
-limb leads -looks between the right are, left arm, and left leg -these leads allow to look from both (bipolar) directions -leads I, II, III
what are the unipolar leads?
-augmented leads *look b/w a reference point (unipolar) and right and left arms and left foot *leads aVR, aVL, aVF -precordial or chest/V leads *look b/w a reference point and chest lead (AV node)
what is Wilson’s Central Terminal?
determines where the heart is, creating a reference point for unipolar leads
what are modified chest leads? (MCL)
-modification of bipolar leads to mimic precordial views -used in absence of a 12 lead capable machine -set monitor to lead III (- left shoulder, + left leg); move left shoulder to reference point and move left leg electrode to anatomical points for V1-V6 -each site documented as MCL1 for V1, etc.
describe limb lead placement
-each lead labeled for the site (RA- white, LA-black, LL-red, RL-green ) -place on tissue, not bony surface -limb leads can be placed on wrists/ankles or shoulder/flanks **wrong electrode placement alters EKG
describe precordial lead placement
V1- 4th intercostal, right sternal border V2- 4 ICS, left sternal border V3- b/w V2 and V4 V4- 5th ICS @ left midclavicular line (MCL) V5- b/w V4 and V6 @ anterior axillary line (AAL) V6- 5th ICS @ midaxillary line (MAL) *under breast tissue
what lead is usually monitored for routine EKG monitoring?
II -monitor HR, regularity, conduction patterns
why is lead II good?
-views direction of travel of electricity from negative to positive electrode giving positive deflections -view follows normal pathway of heart conduction -looks from 60 degree angle (heart vector 59 degree)
what is diagnostic EKG monitoring used for?
-presence and location of AMI -axis deviation -chamber enlargement
what leads look at the septum of the heart?
V1 and V2
what leads look at the anterior wall of the heart?
V3 and V4
what leads look at the lateral wall of the heart?
Lead I, aVL, V5, and V6
what leads look at the inferior wall of the heart?
Lead II, III, AVF
what may cause complications with electrodes?
-dry adherence glue -diaphoresis -body hair/oils -movement
what might skin prep include with monitoring leads?
-wiping skin with alcohol (not with defib pads!!) -tincture of benzoin to increase adherence -shaving hair
what is artifact?
ECG deflections caused by factors other than electrical activity of the heart *attempt to eliminate artifact when possible to improve readability and reduce risk of misinterpretation
what are causes of artifact?
-muscle tremors -shivering -patient movement -loose electrodes -60 Hz interference (electricity from bovie) -machine malfunction -chest compressions
what axis on the EKG graph represents time?
x- axis
what axis on the EKG graph represents voltage?
y-axis
what lines are used to measure time on EKG graph?
vertical lines (display time increments along the x axis)
what lines are used to measure voltage on EKG graph?
horizontal (display voltage increments along y axis)
how fast are EKG machines standardized to run graph paper across a stylus? calibrated at?
25 mm/sec; calibrated at 1 mV
with time, one small box equals? 1 large box (5 small)?
0,04 sec; 0.2 sec
with voltage, one small box equals? 2 large boxes (10 small)?
0.1 mV (1 mm in height); 1 mV
why is time measured?
to measure rates and intervals of the EKGs
why is voltage measured?
to determine the strength and direction of the EKGs
what is “size” in the EKG monitor?
-scale of the tracing -can be increased to enlarge the entire complex *allows for easier viewing, but may distort features like PR interval or ST elevation *standard calibration is 10mm or 2 large blocks
what is “gain” in the EKG monitor?
-sensitivity *most new monitors adjust automatically *more sensitivity allows greater reception, but may increase artifact *filter mode (usual mode opposed to monitor mode) filters out artifact
what are the five steps of EKG interpretation?
1) rate (slow, fast, normal?) 2) rhythm (consistently regular, regularly irregular?) 3) P waves (present? upright? 1 P: 1 QRS?) 4) PR interval (consistent? < .20 sec?) 5)QRS complex (<.12 sec)
what is regularly irregular?
the irregularity occurs regularly for example a skipped beat after every 3 beats
what intervals change with rate?
QT interval changes with rate *PR interval should not change
what is a quick way to note for prolonged QT interval?
-mark two consecutive R waves -mark half way between *if T wave occurs before the 50% mark, QT is normal; if T wave is on or after the 50% mark, QT is prolonged
what is the risk of a prolonged QT interval?
R on T phenomenon
changes in PR intervals usually indicate what?
heart block
what is the quickest method to measure rate?
count the number of QRS complexes in a 6 second strip and multiply by 10 *always check radial pulse (compare pulse ox to EKG) since an electrical rate may reflect more than the mechanical rate (ex: bigeminy, all beats don’t perfuse)
what is the triplicate method of measuring rate?
-locate R wave that falls on dark line bordering large box -assign 300, 150, 100, 75, 60, 50 in that order to next six dark lines to the right -number corresponding to dark line at peak of next R wave is rate
what is the same and what changes amongst different leads?
-intervals will be the same, but may be more easily measured in certain leads -picture/tracing from each lead will be different
what is the isoelectric line?
electrical tracing when no electrical activity (flat) *ST segment should be parallel to isoelectric line
what does the p wave represent?
depolarization of the atria
what does a normal p wave look like?
-upright except in aVR lead -0.06-0.1 sec duration (width) -< or equal to 2.5 mm in height **< or equal to 2.5 mm in width and height
what is the PR interval?
beginning from the p wave to the beginning of the QRS complex
how long is a normal PR interval?
0.12-0.2 sec **< or equal to 0.2 sec
what does the QRS complex represent?
depolarization of the ventricles
what components make up the QRS?
-Q wave: first downward deflection (septal depolarization) -R wave: positive deflection during ventricular depolarization -S wave: negative deflection following the R wave
what is the normal duration of the QRS complex?
0.06-0.1 sec **< 0.12 sec
what does the ST segment represent?
time between depolarization and repolarization of the ventricles *J point= level at which ST segment begins from QRS *should be isoelectric with the baseline
what does the T wave represent?
ventricular repolarization
what can influence T wave changes?
-drugs -ischemia -electrolytes
describe normal sinus rhythm
-60-100 bpm -regular rhythm -P waves present and upright, 1:1 with QRS -PR interval less than 0.2 sec -QRS present, < .12 sec, 1:1 with P wave
describe sinus bradycardia
only difference from NSR is rate < 60 bpm
describe sinus tachycardia
only difference from NSR is rate > 100 bpm but < 150 and an abbreviated ST segment (time b/w depolarization and repolarization shorter)
when can sinus dysrhythmias commonly be seen?
- vent patients r/t lungs filling and impeding vena cava (HR decrease) then exhale allows blood flow (HR increase)
- dehydrated younger patients (give fluid)
- younger patients
what is a wandering pacemaker?
sinus dysrhythmia where each p wave looks different showing that the electrical impulse is not only originating at the SA node, but also coming from multiple ectopic areas in the atria
*PR and QRS remain intact and normal
describe atrial rhythms
- originate outside SA node
- issue is above the ventricles in atria so QRS comples remains narrow and maintains constant form
describe atrial flutter
- rate: variable; may be extremely fast (a-250, v-150)
- regularity: QRS is regular; P to P is regular
- P waves: present and upright; multiple P waves per QRS (2:1 conduction or 4:1)
- PR interval: constant
- QRS complex: narrow and maintains constant form
describe atrial fibrillation
- rate: variable; may be slow or fast (dont rely on monitor, count manual pulse)
- regularity: very irregular (key identifier)
- P waves: not visible, may have wavering baseline
- PR interval: undetermined d/t no true P wave
- QRS: <.12 sec; same morphology BUT irregular interval
describe Supraventricular tachycardia (SVT)
- rate: > 150 bpm (not sinus)
- regularity: regular (not a-fib)
- P waves: probably not visible d/t rate
- PR interval: indiscernible d/t rate
- QRS: narrow complex, <.12 sec (indicates origin of complex is above the ventricle)
describe atrial tachycardia
*can be considered SVT
- rate: 180-250 bpm
- regularity: regular
- P waves: present but may not be visible
- PRI: <.20 sec but probably not visible
- QRS: <.12 sec (narrow complex)
describe wandering pacemaker
rate: variable
regularity: irregular
P waves: present, 1:1 with QRS; different in origin
PRI: <.20 sec and consistent
QRS: <.12 sec
*morphology of each P wave is different indicating a changing pacer site
what is paroxysmal SVT?
sudden start and stop of SVT
what are junctional rhythms?
-characterized by retrograde conduction of the atria
*impulse travels towards the negative electrode, making the P wave inverted (may be late P wave hidden in QRS complex so not visible)
-occurs secondary to an inadequately firing AV node
*inherent rate 40-60 bpm
*accelerated junctional rhythm: 60-100 bpm
*junctional tachycardia >100 bpm
describe junctional escape rhythm
- rate: 40-60 bpm
- regularity: regular QRS
- P waves: usually present but inverted; may be found after QRS
- PR interval: variable but <.20 sec
- QRS: <.12 sec, normal with 1:1 ratio
describe ventricular tachycardia
rate: usually very fast, always > 100 bpm
regularity: regular
P waves: not present
PRI: undetermined d/t no P waves
QRS: > 0.12 sec, wide symmetrical complexes
describe ventricular fibrillation
rate: no complete complexes to determine rate
regularity: very irregular chaotic baseline
p wave: none
PRI: N/A
QRS: none
describe ventricular escape rhythm
AKA idioventricular rhythm; agonal rhythm; dying heart rhythm
- rate: 20-40 bpm
- regularity: regular
- P waves: none visible
- PRI: N/A
- QRS: >.12 sec, widely spaced, symmetrical complexes
describe sinus rhythm with bigeminy of PVCs
- rate: 60-100 (electrical, mechanical may be 30-50!!)
- regularity: regularly irregular; PVCs are too early to be regular
- P waves: present and upright on baseline SR, not visible on PVCs
- PRI: <.20 sec on baseline sinus rhythm
- QRS: <.12 sec on baseline; wide complexes (PVCs) with different site of origin
what is seen with SR with multifocal PVCs?
different ectopic sites indicated by different complexes
what is considered a run of V-tach?
3 or more PVCs together
what are ectopic beats?
- premature beats that come from non-pacemaker sites
- the individual beat may or may not initiate a mechanical pulse
- source is determined by the shape of the complex
*p wave=PAC
*wide complex=PVC
*junction= PJC
describe ventricular asystole
- rate: QRS= 0 (may have P waves present but still asystole)
- regularity: N/A
- P wave: upright, regular
- PRI: N/A
- QRS: not present
describe pulseless electrical activity (PEA)
*no pulse with complexes
- can be an organized rhythm that does not have a pulse
- often a slower, wide complex rhythm
what are heart blocks?
- also known as AV blocks or atrioventricular delays
- occurs d/t a slowed or blocked conduction of electrical current from the SA node through the AV junction to the ventricles
- classified as first degree, second degree (type I/Wenckebach or type II/classical), and third degree
what elements need to be identified in order to classify the heart block?
- determine the PRI
- determine the P:P and QRS:QRS timing
describe a first degree heart block
**PR interval: constant, but > .20 sec (1 big box)
- rate: 60-100
- regularity: regular
- p waves: present, upright, 1:1 with QRS
- QRS: <.12 sec, normal
describe second degree, type I (Wenckebach) heart block
rate: variable, commonly slow (60-100)
**regularity: QRS irregular
P waves: present, upright; *multiple p waves per QRS BUT p-p constant
PR interval: *widening PRI, before resetting (cyclic)
QRS: <.12 sec, conducts only behind portion of p waves
describe second degree, type II (classical) heart block
rate: variable, usually slow
regularity: *QRS and P waves are regular
P waves: present, upright; multiple p waves per QRS
PR interval: constant for last p wave, <.20 sec
QRS: narrow complex, conduction only to last p wave
describe third degree heart block
- complete block
- characterized by complete dissociation b/w P and QRS complexes
rate: QRS rate slow (20-40); P rate 60-100
regularity: P:P regular; QRS:QRS regular; P:QRS very irregular
P waves: present, upright, multiple P waves per QRS
PRI: variable at each measurement
QRS: usually wide and evenly spaced far apart
describe pacer rhythms
-pacers can be for atria, ventricles, or both
*look for pacer spikes
*ventricular pacer always creates a wide complex rhythm
*cant determine ischemia on a 12 lead when paced
how are magnets used with pacers?
-defibrillators can be disabled by placing a magnet directly over the AICD unit until it beeps
*re-activate unit with the magnet again
*re-activation may set the unit to a “default” mode rather than previous programming
-pacing settings can be changed to “non sensing” with a magnet
**recommendation is to have rep disable and reactivate pre-op and post-op
what are the categories of each letter in the pacer type?
I. chambers paced
II. chamber(s) sensed
III. response to sensing
IV. programmability, rate modulation
V. antitachyarrythmia function (AICD or not?)
ex: VOO= ventricle paced with no chamber sensing
ex: DA= dual chambers paced, atria sensed
what EKG changes are seen with pericarditis?
elevated, concave ST segment
what EKG changes are seen with hyperkalemia?
- tall, peaked T waves (> 1/3 ht. QRS)
- wide, flat P waves
- widening QRS
- disappearing ST segment
- merging QRS
what EKG changes are seen with hypokalemia?
- U wave
- depressed ST segment
- flattening T waves
- widening QRS
What EKG changes are seen with hypercalcemia?
short QT intervals
what EKG changes are seen with hypocalcemia?
prolonged QT intervals
what EKG changes are seen with digitalis effect?
- depressed “scooped” ST segment
- flat, inverted, or biphasic T waves
- short QT intervals
what is seen with Wolff-Parkinson-White?
- more of a gradual incline with an upstroke of the QRS rather than a sharp upstroke
- upstroke is curved (delta wave) compared to downstroke of QRS
what can determine if elevated T wave is d/t hyperkalemia or AMI?
elevated T waves are noted throughout entrie EKG in all leads in hyperkalemia
with cardioversion of SVT, what should be checked?
-in synchronized mode
if monitoring an EKG and see ST elevation, what should you check?
check the red lead, if placed high on the chest, you will see false ST elevation
