EKG quiz 1

What is considered the main route of inter-atrial conduction?

Bachmann’s bundle

&0-80% of ventricular filling is passive, meaning …

no atrial contraction is needed

what are the 3 internal pathways making a connection between SA node and A node

superior anterior tract or fast tract

middle tract

inferior posterior tract or slow tract

In majority of the population, what is truly the only tract that attaches to the AV node?

fast tract (other two terminate somewhere in RA

What are the 3 zones of the AV node?

transition, compact, and trigger zones

In a normal heart, where is the only place where an impulse should be able to travel from the aria to the ventricles?

bundle of His

What is responsible for the depolarization of the interventricular septum?

intraventricular septal fascile

describe the left bundle branch

small piece of tissue that separates from His bundle, enters left vent and splits into 3 fascicles - left posterior fascicle (extents across posterior aspect), intraventricular septal fascicle (depolarizes inter ventricular septum), and left anterior fascicle (terminates into purkinje network

describe the right bundle branch

much longer piece of tissue than left bundle, separates from his bundle and enders right event, terminates into purkinje network

What is hearts 3rd pacemaker w/ intrinsic rate of 20-40 BPM?

purkinje network

phase 4

resting state / diastole; cardiac cells ready & can respond to impulse

more K inside cell, Na and Ca outside cell membrane

voltage = -90 mV

phase 0

upstroke (depolarization)

fast Na channels open & rapid influx of Na inside cell

causes positive voltage inside cell

K pours out of cell through open k channels at the same time

phase 1

early repolarization

na channels close and k channels re open; k slowly returns inside causing slight negative charge inside cell membrane

“notch”

phase 2

plateau

ca channels open and ca enters cell membrane causing contraction

influx of ca is matched by continuous influx of K

balance in voltage inside and outside cell

phase 3

rapid repolarization

Ca channels close

K channels remain open and allow influx of K inside cell membrane

inside cell returns to 90mV

absolute refractory period

short period of time after cardiac cell goes through AP, during which cell won’t respond to another stimuli

lasts 180ms

relative refractory

period of time during depolarization where a cardiac cell will respond to second stimuli, however cells are fragile

heart’s vector

true pathway of conduction thru heart is left and down towards the front of the body

which lead has a perfect view of hearts vector and is used for rhythm interpretation universally?

lead II

What is EKG paper printed at?

25 mm per second

what is size of small box

1mm tall and 0.04 s in duration

what is large box size

5mm tall and 0.2 s in duration (5 small boxes)

What are you measuring from left to right on EKG paper?

time

what are you measuring from up to down on EKG paper?

voltage

What is standard EKG machine calibration?

1 large box, or 0.2 s, in duration and 2 large boxes, or 10 mm tall

how many large boxes equals 3 seconds?

15

how many large boxes equals 6 seconds?

30

count down method

r wave on every large box = 300

r wave on every other large box = 150

as you continue to skip additional large boxes, HR becomes 100, 75, 60, 50

**not reliable for HR under 50

300 method

count number of large boxes between 2 consecutive R waves, divide 300 by that number to calculate HR

300 / # large boxes

1500 method

count number of small boxes between two consecutive R waves

1500 / # small boxes = HR

most accurate way to calculate HR

Normal sinus rhythm

rate: 60-100

regularity: regular

P waves: normal, present, married to QRS

PR interval: normal in duration 0.12 - 0.2 seconds

QRS complex: narrow

sinus bradycardia

rate: less than 60

regularity: regular

P waves: normal, present, married to QRS

PR interval: normal in duration 0.12 - 0.2 seconds

QRS complex: narrow or wide

sinus tachycardia

rate: over 100

regularity: regular

P waves: normal, present, married to QRS

PR interval: normal in duration 0.12 - 0.2 seconds

QRS complex: narrow or wide

sinus arrhythmia

rate: 60-100

regularity: irregular

P waves: normal, present, married to QRS

PR interval: normal in duration 0.12 - 0.2 seconds

QRS complex: narrow or wide

what happens in sinus arrhythmia

variations in the intervals of heart beats, MC in children

overall result is inc in inspiration and dec during exhalation

what happens in sinus exit block

sinus node fires normal, but impulses are being blocked

results in absence of cardiac cycles

P-P intervals march out across rhythm once electrical activity continues

Sinus exit block

rate: variable but typically less than 1

regularity: irregular

P waves: when present, normal and married to QRS

PR interval: normal in duration 0.12 - 0.2 seconds

QRS complex: narrow or wide

what happens during sinus pause

SA node stops firing and starts back up again

cardiac cycle reset after pause and P-P intervals will not march out across rhythm strip

sinus pause

rate: variable but typically less than 150

regularity: irregular

P waves: when present, normal and married to QRS

PR interval: normal in duration 0.12 - 0.2 seconds

QRS complex: narrow or wide

what happens in sinus arrest

SA node stops firing and starts back up again, at least 3 cardiac cycles have been missed

sinus node reset, P-P intervals will not march out across rhythm

sinus arrest

rate: variable but typically less than 150

regularity: irregular

P waves: when present, normal and married to QRS

PR interval: normal in duration 0.12 - 0.2 seconds

QRS complex: narrow or wide

PAC

ectopic impulse originates outside of SA node from; arrive early in cardiac cycle and will have P waves w/ diff morphologies

bigeminy / bigeminal complexes

premature beat occurs every other beat

trigeminal or trigeminy

every 3rd bead is a premature complex

WAP

rate: less than 100

regularity: irregular

P waves: at least 3 different morphologies, still married to QRS

PR interval: variable

QRS complex: narrow or wide

what happens in wap

at least 3 different areas w/in atria competing to be pacemaker

P waves w/ at least 3 diff morphologies

what happens in multifocal atrial tachycardia MAT

exact same as WAP except HR over 100

(at least 3 waves w/ diff morphologies)

MAT

rate: over 100

regularity: irregular

P waves: at least 3 different morphologies, still married to QRS

PR interval: variable

QRS complex: narrow or wide

what is atrial flutter

rapid atrial rate caused by reentry circuit caused by chamber enlargement, scarred, or ischemic tissue unique sawtooth pattern

;

atrial flutter

rate: atrial: 200-350; vent: variable

regularity: regular or irregular

P waves: none, flutter waves present

PR interval: none

QRS complex: narrow or wide

what is atrial fibrillation

most treated; irregular activity of multiple sites w/in atria which suppress SA node; loss of atrial kick; 3 types

paroxysmal: in and out of afib, converts w/o intervention

persistent: responds to intervention

permanent: chronic doesnt respond to interventions

atrial fibrillation

rate: atrial: indeterminate, vent: variable

regularity: irregularly irregular

P waves: none, F waves present

PR interval: none

QRS complex: narrow or wide

what is AV nodal reentrant tachycardia AVNRT / SVT

regular, narrow, complex tachy that’s a consequence of reentrant circuit b/t internodal pathways of SA and AV node

triggered by ectopic focus such as PAC near fast or slow track

AVNRT

rate: 150-300

regularity: regular

P waves: not visible or retrograde

PR interval: none or RP interval

QRS complex: narrow

typical avnrt

circuit travels counter-clockwise down the slow tract and up the fast tract; either no P waves or P waves are retrograde and buried at end of QRS complex

pseudo S wave

p wave that’s retrograde and buried at end of QRS complex

atypical AVNRT

circuit travels down fast tract and up slow tract; retrograde p waves are clearly visible are clearly visible, might be RP interval and not PR interval

junctional escape beat (JEB)

rate: 40-60

regularity: regular

P waves: absent, or inverted, either before or after QRS

PR interval: if present, less than 0.12

QRS complex: narrow or wide

what happens during JEB

occur where next expected R wave should have been

SA node fails to fire or is firing too slowly

av node takes over as main pacemaker and suppresses SA node

ventricular rhythms

wide, abnormal looking, t waves typically contralateral (opposite of R waves), duration typically over 0.12 s, no p wave

PVC

early, before next expected R wave, originates in vents, no p wave, wide ERs, ectopic, contralateral t wave

group of 6 known as run of V tach and requires intervention

idioventricular rhythm (IVR) or agonal rhythm

rate: 20-40

regularity: regular

P waves: none

PR interval: none

QRS complex: wide, longer than 0.12 s

occurs when purkinje takes over; regular, wide w/ no detectable P

v-tach

rate: 100-300

regularity: regular

P waves: none. if present, dissociated and not married to QRS

PR interval: typically non

QRS complex: wide

v fib

rate: 300-500

regularity: irregular

P waves: none

PR interval: none

QRS complex: not measurable

atrial paced rhythm

pacer spike is followed by normal PQRST cycle

vent pacemaker

p wave followed by pacer spike, wide QRS, contralateral T wave

first degree HB

rate: slow or normal

regularity: regular

P waves: present

PR interval: longer than 0.2 s

QRS complex: narrow or wide

benign PR interval delay as result of slowed conduction thru AV, hallmark is sinus rhythm and PR interval beyond 0.2 s

second degree type I wenckebach

rate: slow or normal

regularity: irregular

P waves: normal, present, married to QRS except for dropped beat

PR interval: increasing intervals

QRS complex: narrow or wide

dropped QRS complexes, prolongation of PR interval until a P wave is not conducted

second degree type II / mobitz

rate: slow or normal

regularity: irregular

P waves: normal, present, married to QRS except for dropped QRS

PR interval: normal or wide, but always constant across strip

QRS complex: wide or narrow

consistent PR w/ dropped QRS

3rd degree Hb

rate: atrial: normal vent: slower than atrial

regularity: regular

P waves: present, normal, not married to QRS

PR interval: none

QRS complex: narrow or wide depending on origin

no p waves thru AV junction, regular P-P intervals that are unrelated to regular R-R intervals, P waves appearing to “march through” QRS-T; atrial rate faster than vent;; two independent pacemakers- SA node and AV junction or purkinje / bundle branch fibers

what is p wave

depol of atria, regardless of morphology

duration 0.1 s

PR interval

time from onset of P wave to beginning of QRS complex

duration 0.12 to 0.2 s (3-5 small boxes)

QRS complex

represents vent depol

should be less than 0.12 s

Q wave

first negative deflection following PR interval

represents depol of interventricular septum

must be less than 0.04s (1 small box) w/ low amplitude

R wave

first positive deflection following PR interval or Q wave

represents depol of anterior LV

S wave

first negative deflection following R wave

represents depol of lateral wall of LV

must extend below baseline

J point

where QRS complex ends and ST segment begins

should be baseline, can 1mm variance

ST segment

represents time in between vent depol and vent repol

should be baseline

begins at beginning of J points and terminates at onset of T wave

T wave

represents vent repol

normally should be asymmetric w/ slow, positive upstroke and sharp, terminal down stroke

peak of this wave is dividing line b/t absolute refractory and relative refractory

QT interval

represents all of vent activity during one cardiac cycle

begins at start of QRS and ends at end of T wave

350-450 ms in males; 360-460 ms in females

U wave

deflection immediately after T wave and in same direction as T wave

prominent U waves seen in hypokalemia and hyperthyroidism

TP segment

represents resting state of cardiac cells

end of T wave to beginning of next P wave

best place for assessment of isoelectric line (true baseline)

R-R and P-P intervals

used for assessment of rhythm rate & regularity and heart blocks