ECG Flashcards
what are the 3 unique properties of cardiac myotcytes
- automaticity
- rhythmicity
- conductivity
what is the inherent discharge rate of the SA node?
60-100 times per min
this rhythmicity creates the sinus rhythm
what is the inherent discharge rate of the AV node?
40-60x per minute
what is the inherent discharge rate of the His-Pukinje fibers?
30-40 times per min
T/F: the faster/higher discharge rate predominates
TRUE
autonomic influence > SA > AV > Purkinje fibers
what does the P wave depict?
atrial depolarization
the impulse is spread to the L atrium via the Bachmann bundle
what does the PR interval depict?
the spread of depolarization reaches the AV, there is a slight delay
where are bundle branches located?
interventricular septum
what does the QRS complex reflect?
ventricular depolarization
what does the T wave represent?
ventricular repolarization
what is the absolute refractory period?
the period in which the heart cannot be stimulated to contract
represented by the interval from the beginning of the QRS complex to the apex of the T wave
the standard 12 lead ECG consists of what?
6 limb leads + 6 chest leads
List the 6 different limb leads
- standard limb leads → I, II, III
- augmented limb leads → aVR, aVL, aVF
the limb leads provide a view of the heart in the ______________
frontal plane
where is V1 placed
4th intercostal space
R sternal border
where is V2 placed?
4th intercostal space
L sternal border
where is V3 placed?
between leads V2 and V4
where is V4 placed?
5th intercostal space in midclavicular line
where is V5 placed?
horizontally even with V4
but in the anterior axillary line
where is V6 placed?
horizontally even with V4 and V5 but in the midaxillary line
ECG chest leads provide a view of the heart in the ___________
horizontal plane
which leads are placed over the R side of the heart?
V1 and V2
which leads are placed over the interventricular septum?
V3 and V4
what do leads V5 and V6 demonstrate?
changes on the left side of the heart
phrase to remember where to place telemetry leads
white right
snow over grass
brown ground
smoke over fire
when performing a single lead assessment, what are you looking for?
- Heart rhythm or rate
- normal waveforms
- abnormal waveforms
which lead is frequently used if you perform a single lead assessment?
chest lead 5
OR
limb lead II
*they both provide a picture of the LV
on an ECG strip, how many squares equal 1 and 6 seconds?
5 big squares = 1 sec
30 big squares = 6 sec
Methods of determining heart rate from an ECG strip
- 300, 150, 100, 75, 60, 50 method
- count the number of large boxes between 2 adjacent R waves than 300/this count
T/F: single limb monitoring can accurately assess rate and rhythm only
TRUE
List steps of assessing the cardiac cycle on an ECG
- evaluate P wave (normal, upright, all look the same?)
- evaluate P-R interval
- evaluate QRS complex
- evaluate QRS interval
- evaluate T-wave
- evaluate R-R interval
- evaluate heart rate
- observe the pt and evaluate any symptoms
what is the normal duration for the PR interval?
0.12-0.20 seconds
what is the normal duration for the QRS interval?
0.06-0.10 seconds
ECG abnormalities that we can notice
- First Degree AV block
- Second Degree AV block
- Wenckeback (Mobitz I)
- Mobitz II
- Third Degree AV block
- Atrial arrhythmias
- paroxysmal atrial tachycardia
- paroxysmal supraventricular tachycardia
- atrial fibrillation
- Ventricular arrhythmias
- premature ventricular complexes
- ventricular tachycardia
- ventricular fibrillation
what is a first degree AV block?
occurs when the impulse is initiated in the SA node but is delayed on the way to the AV node
the delay may be initiated in the AV node itself, and the AV conduction time is prolonged
what does a first degree AV block look like on an ECG strip?
prolonged PR interval
“if the R is far from the P than you have first degree”
T/F: HR is usually within normal limits in a First Degree AV block
TRUE
may be lower than 60 bpm
what is a second degree AV block?
transient disturbance that occurs high in the AV junction and prevents conduction of some of the impulses through the AV node
what does a second degree AV block look like on an ECG?
initially P wave precedes each QRS complex but eventually a P wave may stand alone (conduction is blocked)
progressive lengthening of the PR interval occurs
as the PR interval increases a QRS complex will eventually be dropped
what is the difference between a Wenckebach and Mobitz 2?
both types of second degree AV blocks
- Wenckebach (Mobitz 1) = ECG signs of gradual exhaustion of impulse conduction. Manifests as a gradual increase of PR interval before a block occurs
- Mobitz II = sporadically occurring blocks, w/o any Wenckebach phenomenon
describe a second degree AV block (Mobitz II)
P waves “march through” at a constant rate
“if some p’s don’t get through, than you have Mobitz II”
what is a third degree AV block?
no impulses that are initiated above the ventricles are conducted to the ventricle
atria and ventricles fire at their own inherent rate
“If the Ps and Qs don’t agree, than you have 3rd degree”
how would the heart rate look in a 3rd degree AV block?
depends on the latent ventricular pacemaker and may range from 30-50 bpm
how are 1st degree AV blocks treated?
these are benign and usually not treated
how are 2nd degree AV blocks treated?
- dependent on the type of 2nd degree block
- no treatment necessary OR
- pacemaker placement
- result of an MI
how are 3rd degree AV blocks treated?
these are life threatening
- MI, degeneration of the conducting system
- permanent pacemaker placement
- medical emergency
how can atrial arrhythmias present on an ECG?
- P waves may be present but may be merged with the previous T wave
- PR intervals may be difficult to determine but are less than 0.2 seconds
- QRS complexes are identical unless there is an aberration
- QRS duration between 0.06 and 0.10 sec
- RR intervals are usually regular and may show starting and stopping of the PAT
factors that contribute to paroxysmal atrial tachycardia
- emotional factors
- overexertion
- hyperventilation
- K+ depletion
- caffeine
- nicotine
- aspirin sensitivity
- rheumatic heart disease
- mitral valve dysfunction
- PE
if paroxysmal atrial tachycardia continues for a period of time what symptoms may develop?
- dizziness
- weakness
- SOB
define atrial fibrillation
defined as an erratic quivering or twitching of the atrial muscle caused by multiple ectopic foci in the atria that emit electrical impulses constantly
describe how atrial fibrillation may look on an ECG
- P waves are absent, thus leaving a flat or wavy baseline
- the RR interval is characteristically defined as irregularly irregular
- the QRS duration is between 0.06 and 0.10 second
what does ventricular response look like in atrial fibrillation?
may be normal, slow or too rapid
but typically it is more rapid
atrial fibrillation is typically associated with what things?
- advanced age
- CHF
- ischemia or infarction
- cardiomyopathy
- digoxin toxicity
- drug use
- stress or pain
- rheumatic heart disease
- renal failure
atrial fibrillation is typically associated with what things?
- advanced age
- CHF
- ischemia or infarction
- cardiomyopathy
- digoxin toxicity
- drug use
- stress or pain
- rheumatic heart disease
- renal failure
T/F: atrial fibrillation is life threatening
FALSE
not considered life-threatening unless the HR is elevated at rest
what is an atrial kick?
decrease in CO by 15-30%
with atrial fibrillation there is a potential for developing _________
mural thrombi
what are PVCs?
premature ventricular complexes
occur when an ectopic focus originates an impulse from somewhere in one of the ventricles
what does the QRS look like in a PVC?
classically described as wide and bizzare looking QRS without a P wave and followed by a complete compensatory pause
how are PVCs treated?
depends on the underlying cause, the frequency and severity of the PVCs, and the symptoms associated with them
when are PVCs considered life threatening?
- paired together
- multifocal in origin
- more frequent than 6 per minute
- land directly on the T wave
- present in triplets or more
when are PVCs considered benign?
when they are isolated, w/o symptoms, and fewer than 6 per minute
what is V-tach?
ventricular tachycardia
- defined as a series of 3 or more PVCs in a row
- torsades de pointes
- occurs because of rapid firing by a single ventricular focus w/increased automaticity
how does V-tach look on an ECG?
- P waves are absent
- three of more PVCs in a row
- associated with a prolonged QT interval
- QRS complexes are wide and bizarre
- rate is between 100-250 bpm
V-tach can be a precursor to _______
ventricular fibrillation
what are some causes of V-tach?
- ischemia
- acute infarction
- CAD
- hypertensive heart disease
- reaction to meds
how is v-tach treated?
- cardioversion
- defibrillation
- lidocaine, bretylium tosylate (Bretylol) or procainamide (Pronestyl)
someone who remains conscious with V-tach may appear _______________
extremely lightheaded or near syncope
when is V-tach considered a medical emergency?
when CO is severely diminished and V-tach has converted to V-FIb
define V-Fib
Ventricular Fibrillation
an erratic quivering of the ventricular muscle resulting in no CO
caused by multiple ectopic foci firing creating asynchrony
how would an ECG look with V-Fib?
a grossly irregular up and down pattern fluctuating of the baseline in an irregular zigzag pattern
T/F: V-Fib is a medical emergency?
TRUE
treat with defibrillation as quickly as possible followed by cardiopulmonary resuscitation, supplemental O2 and injection of meds
how do you determine the presence of hypertrophy by looking at an ECG?
look at the voltage in V1 and V5
- R ventricular hypertrophy
- a large R wave in V1 which gets progressively smaller in V2, V3, and V4
- L ventricular hypertrophy
- a large S wave in V1 and a large R wave in V5 that have a combined voltage of greater than 35 mV
how do you determine the presence of ischemia via an ECG?
- an inverted T-wave
- S-T segment depression
