cardiac rhythm monitors and equipment Flashcards
which pathway depolarizes left atrium
bachmann bundle (anterior internodal)
outline the conduction system pathway in the heart
SA node –> internal tracts –> AV node –> bundle of his –>bundle branches –> purkinje fibers
outline the internal tracts
anterior internodal tract
middle internodal tract (winkebach)
posterior internodal tract (thorel tract)
conduction velocity in SA and AV nodes
0.02-0.1 m/sec (slow conduction)
conduction velocity in myocardial muscle cells
.3-1 m/sec (intermediate conduction)
conduction velocity in his bundle, bundle branches, and purkinje fibers
1-4 m/sec (fast conduction)
conduction velocity is a function of (3)
- RMP
- amplitude in the AP
- rate of change in membrane potential during phase 0
conduction velocity is affected by (5)
ANS tone
hyperkalemic induced closure of fast Na channels
ischemia
acidosis
anti arrhythmic drugs
what does the james fiber accessory pathway connect
atrium to AV node
what does the atrio hisian fiber accessory pathway connect
atrium to his bundle
what does the kents bundle accessory pathway connect
atrium to ventricle
what does the mahaim bundle accessory pathway connect
av node to ventricle
review 5 phases of ventricular AP and how it corresponds to EKG
0= rapid depol (QRS)
1= initial repol (QRS)
2=plateau phase (QT interval)
3= final repol (T wave)
4= resting phase (T–> QRS)
when does the absolute and relative refractory period occur during ventricular AP?
ion movement during each phase
ID the electrical event
atrial depol begins
ID the electrical event
atrial depol complete
ID the electrical event
atrial repol, ventricular depol begins
ID the electrical event
ventricular depol complete
ID the electrical event
ventricular repol begins
ID the electrical event
repolarization complete
ID red, blue, green lines on wiggers diagram
review left ventricular volume in relation to mechanical events in the heart
biphasic p waves in lead II suggests
left atrial enlargement. think mitral stenosis
tall P waves suggests
RA enlargement. think cor pulmonale
duration and amplitude of
P wave
PR interval
Q wave
QRS complex
PR interval depression suggests
pericarditis
atrial infarction
Q wave: consider MI if
amplitude is > 1.3 of R wave
DOA > .04 seconds
depth is >1mm
if QRS complex increased, consider
LVH, BBB, ectopic beat, WPW
duration and amplitude for
QTc
ST segment
T wave
U wave
Osborn wave
ST segment: consider MI if
elevation or depression >1mm
ST segment elevation also caused by (2)
endocarditis
hyperkalemia
T wave points in opposite direction of QRS if repolarization is prolonged by
MI, RBBB
peaked T waves are caused by (3)
ischemia, LVH, intracranial bleed
if U wave is > 1.5mm, consider
hypokalemia
describe osborn wave
small positive deflection immediately after QRS complex (at beginning of ST segment), may occur with hypothermia
you measure J point relative to
PR segment. isoelectric line
J point and ST elevation/depression
greater than 1.0mm increase or decrease is significant
how does hyperkalemia affect EKG
narrow and peaked T
short QT
wide QRS
low p amplitude
wide PR
nodal block
sine wave fusion of QRS and T –> VF or asystole
how does hypokalemia affect EKG
U wave
ST depression
flat T wave
long QT interval
hypercalcemia versus hypocalcemia and the EKG
hypercalcemia –> short QT
hypocalcemia –> long QT
hypermagnesemia and EKG
no significant effect unless very high. heart block, cardiac arrest
hypomagnesemia and EKG
no effect unless very low, long QT
review positive, negative, biphasic vector of depolarization and where the current travels
(+) deflection occurs when vector of depol travels towards positive electrode
(-) deflection occurs when vector or depol travels away from positive electrode
biphasic deflection: vector of depol travels perpendicular to positive electrode
vector of depolarization - QRS complex
heart depolarizes from base to apex and endocardium to epicardium
polarity: myocytes go internally (-) to internally (+). produces a positive electrical current
which are the bipolar leads
I, II, III
limb leads
aVr, aVL, aVF
precordial leads
V1-V6
outline where aVR, aVL, lead I-III, aVF are
outline V1-V6