Basic ECG Flashcards
pacemaker cell
determine heart rate and initiate heart beats
SA and AV
electrical conducting cell
deliver the impulse to the myocardial cells
mycardial cells
contract and pump blood out of the heart
SA node
primary pacemaker of the heart (sets HR)
60-100 bpm
AV node
becomes the pacemaker if for some reason the SA node fails
AV node rate= 40-60bpm
narrow QRS complex means what for conduction
rapid conduction
normal pathway of conductance
do electrical conducting cells transmit current slow or fast?
quickly
What is the electrical conducting cells pathway? (6)
SA node anterior, posterior, middle fascicles AVN Bundle of His RBB and LBB Purkinje fibers
myocardial cells can initiate heat beats in what two situations?
1- SA and AV nodes fail
2- myocardium is irritated
what causes the myocardium to become irritated?
ischemia
electrolyte abnormality
acidosis
caffine
Do myocardial cells or electrical conducting cells transmit current quickly and more effectively?
electrical conducting cells
Wide QRS complex means what for conductance
slow conductance
current travels through the muscle, not normal pathway
what do ECG leads detect?
the electrical difference (voltage) between two limbs
Lead I provides a picture from what angle?
180 degrees
lead II provides a picture from what angle?
60 degrees
Where are the leads on a 3 lead ecg?
right arm, left arm, left leg
what is the limitation for the 3 lead system?
not as sensitive for detecting myocardial ischemia in the left ventricle
What does Lead I detect? What is the color-to-color for Lead I?
detects electrical difference between the right arm (-) and left arm (+)
white to black
What does Lead II detect? What is the color-to-color for Lead II?
electrical difference between right arm (-) and left leg (+)
white to red
What does Lead III detect? What is the color-to-color for Lead III?
electrical difference between the left arm (-) and left leg (+)
black to red
The green lead
neutral or ground lead
completes electrical circuit and doesn’t have anything to do with the EKG itself
brown lead
additional precordial lead
more sensitive for detecting LV ischemia
what helps make higher quality signal for the ECG electrodes
better connection
conductive gel on electrode
can clean skin
try not to place on hair
ECG paper 1mV= ___ small boxes?
10small boxes
ECG paper 1 large box
200msec
5mm
1 small box= ____ mseconds
40 msec
1mm
5 large boxes
1 second
300 large boxes
1 min
two ways to estimate the HR?
- count number of beats within a certain number of time (2 sec or 6 sec) and multiply to get number of beats in minute
- count # large boxes between beats
do segments or intervals of the ECG have waves?
intervals
P wave
atrial depolarization
duration <120msec (3 small boxes)
QRS complex
ventricular depolarization
duration <120msec (3 small boxes)
premature ventricular contractions are causes by what?
if the heart gets irritated and the ventricles start their own heart beat
ventricular escape rhythm
electrical conductance fails and ventricles take over as pacemaker
potential cause for wide QRS complex (not irritation or electrical failure)
current travels across myocardium instead of through purkinje fibers
Wolf Parkinson White Syndrome (WPW)
Right bundle branch block (RBBB)
Left bundle branch block (LBBB)
T wave
ventricular repolarization
height <5mm in leads I,II,III
U wave
follows t wave
not seen unless hypokalemia
J point
point at which S wave returns to baseline
Delta wave
upward slurring of Q wave seen in WPW syndrome
J wave (osborne wave)
“bump” on the S wave
seen in hypothermia
PR interval start
beginning of p wave
PR interval end
start of Q wave
PR interval normal time
120-200msec (3-5 small boxes)
Why is the PR interval time important?
shows conduction is delayed in the AV node and allows atria to finish contract before ventricles contract
OPTIMAL VENTRICLE FILLING
QT interval start
q wave
QT interval end
end of the t wave
What medications prolong the QT interval? When should these be avoided?
Zofran and Phenergan (antiemetics)
avoided in pts with prolonged QT syndrome
PR segment start
end of p wave
PR segment end
beginning of Q wave
ST segment start
J point
ST segment end
start of T wave
premature beat
heart beat that happens before it is expected to
examples of premature beats
premature atrial contraction
premature junctional contraction
premature ventricular contractions
escape beat
heart beat that comes after a long pause
examples of escape beats
ventricular escape beat
junctional escape beat
during systole what is and is not perfused?
Perfused: organs of the body
Not perfused: the heart (coronary arteries are closed by valve)
During diastole what is and is not perfused?
Perfused: the heart (coronary arteries drain blood from backflow)
Not perfused: everything else
Do patients with high or low heart rates have better coronary perfusion? why?
slower HR
- longer time coronary arteries open
- greater diastolic filling time
What is cardiac output determined by?
ventricular filling prior to contraction
What are the two ways that ventricular filling occurs and which is better?
active filling (atria contract)** BETTER passive filling (atria dont contract)
If the ventricular filling is passive will the volume be lower or higher than active filling?
lower
factors that can reduce ventricular filling (3)
1- heart beat that occurs without an atrial contraction (no P wave; passive)
2- premature heart beats (ventricles contract before being filled)
3- rapid HR (atrial or ventricular)
what happens when atria contract too quickly?
not enough time to fulling contract so reduces amount of blood forced to ventricles
What happens when ventricles contract too quickly?
dont have enough time to fill before contraction
Rapid heart rate leads to (3)
decreased cardiac output
hypotension
pulseless pt
ECG description of sinus bradycardia
p wave present
HR <60bpm
benefits of sinus bradycardia
normal/good for these patients:
healthy pt who exercises
CAD patients
sinus brady cardia in healthy patients
higher stroke volume
maintains adequate cardiac output
sinus brady cardia in patients with CAD
increased oxygen supply (diastolic filling)
decreased oxygen demand
What do patients with CAD normally take to maintain a slow HR?
beta blockers
what does the level of concern with sinus bradycardia depend on? (3)
1- age (children very bad)
2- severity (50 could be normal; 30 always concern)
3- how fast the drop in HR occured
treatment for bradycardia
1- drugs (glyco, atropine, epi)
2- if unresponsive to drugs then initiate cardiac pacing with pacemaker
temporary transcutaneous pacing
use defibrillator to pace the heart
set a HR and it will stimulate at that pace
permanent implantable pacemaker
permanent, under clavicle, delivers current to the pacing wires that are inside the heart
only works when the HR falls below a certain point
ECG description of sinus tachycardia
P wave present
HR > 100 bpm
etiology (causes) of sinus tachycardia
hypovolemia/hypotension
pain/light anesthesia
anesthetic concerns with sinus tachycardia (3)
increased cardiac oxygen demand (bad in CAD)
decreased cardiac oxygen supply (decreases diastolic filling; bad CAD)
indicates possible hypovolemia
treatment for sinus tachycardia
depends on cause:
1- fluids if bc hypovolemia
2- deepen anesthetic if light
3- consider beta blocker if not hypovolemic or light
ECG description of irregular sinus rhythm
looks like sinus but rate is irregular
faster during inspiration
slower during expiration
during spontaneous inspiration what happens to the intrathoracic pressure and preload
intrathoracic pressure decreases
preload increase
HR speeds up to pump excess out
during spontaneous expiration what happens to the intrathoracic pressure and preload?
intrathoracic pressure increases
preload decreases
HR slows does bc it doesnt have to pump out as fast
anesthetic concerns with irregular sinus rhythm
not as concerned
seen in healthy pts with deep breaths
ectopy
any heart beat that originates outside the SA node
ectopy is activated where? (3)
AV node
atrial myocardium
ventricular myocardium
Supraventricular ectopy (6)
premature atrial contraction (PAC) atrial flutter atrial fibrillation (Afib) Premature junctional contraction (PJC) Junctional rhythm junctional escape beat
ventricular ectopy (5)
premature ventricular contraction (PVC) escape ventricular contraction ventricular escape (idioventricular) rhythm ventricular tachycardia (Vtach) ventricular fibrillation (Vfib)
