EKG Graphs

What is the 1500 method

count the number of small boxes between two R intervals

used for a standard speed of 25mm/sec

rhythm must be regular to use this method and works best for fast rhythms.

What is the sequence method

also known as the 300 method

calculated using large boxes rather than smaller ones

only used as an estimate for regular rhythms

what is the 6 second method

used for estimating rate when the rhythm is irregular

count the number of QRS complexes in a given tracing (between the hash marks) and multiply number by 10

Calculating max heart rate and target heart rate

220 - pt. age is max heart rate

target heart rate is (220 - pt. age) x 70%

How many seconds is required to establish regularity of waveforms

6 - 10 seconds

What is a caliper

tool to measure regularity of waveforms

P wave signifies…

atrial depolarization (contraction)

QRS waveform is …

ventricular depolarization (contraction)

regular rhythm…

QRS complexes separated by the exact same distance across EKG tracing

irregular rhythm…

difference between waveform spacing

regularly irregular rhythm…

noticeable irregular pattern that repeats throughout the tracing of a QRS complex

irregularly irregular rhythm…

varies without consistency throughout the tracing

dimensions of EKG paper

normal QRS waveform range

0.04 - 0.10 seconds

variations can be a sign of ventricular dysfunction

J point

point where ventricular depolarization stops and repolarization begins

during ischemia J point can elevate or depress below baseline

occurs at end of QRS or at start of ST segment

T wave

ventricular repolarization

U wave

not always visible but represents repolarization of the bundle of HIS and purkinje fibers

PR intervals

time it takes for the SA node to fire, atria to depolarize, and electricity to travel through the AV node

Beginning of atrial depolarization to beginning of ventricular depolarization

from P to Q wave

normal PR range

0.12 - 0.20 seconds

P-P interval

represents that amount of time between atrial depolarization cycles

used to analyze rhythms/rates

R-R interval

represents time between ventricular depolarization cycles

QT interval

one complete ventricular cycle (depolarization and repolarization)

PR segment

end of P wave to beginning of Q wave

time between the end of atrial contraction and beginning of ventricular contraction

caused by AV node slowing impulse to allow the ventricles to fill up properly

ST segment

represents early phase of ventricular repolarization

from end of s wave to beginning of t wave

time from end of ventricular depolarization to the beginning of ventricular repolarization

amplitude of ekg tracing

0.01 mV for each 1 mm square

two large squares (10 small boxes) equals 1 mV

what demonstrates atrial dysfunction

abnormalities in P waves and PR intervals

what demonstrates ventricular dysfunction

QRS and T wave abnormalities

low levels of potassium…

high levels of potassium

cause heart rate to decrease

cause abnormal heart rate/rhythm

low levels of calcium

high levels of calcium

causes heart to slow

longer than normal contractions

Characteristics of normal sinus rhythm

P wave present, upright and rounded, amplitude less than 2.5 mm, duration less than 110 ms, with QRS narrow

Characteristics of sinus bradycardia

less than 60 bpm

sinus tachycardia

greater than 100 bpm

usually normal for pt with hyperthyroidism

Sinus dysrhythmia

slight irregularity in the rhythm

associated with normal breathing patterns

sinus arrest

break in the normal pattern

usually SA node failed to fire

not significant unless the arrest lasts longers than 6 seconds

atrial flutter

atria contract at a rate much faster than the ventricles are contracting

has a sawtooth pattern

atrial fibrillation

more severe than flutter

no organized contraction of atria — quivering state which can cause a blood clot due to stagnation of blood in ventricles

junctional arrhythmias

occur at AV node or tissue — typically causes the p wave to be inverted because the AV node initiates impulses when the SA node is damaged

premature junctional complex

early impulse occuring before the next beat

P wave may be before, after, or buried within QRS complex = irregular rhythm

junctional escape rhythm

impulse originates from the AV node like a pacemaker.

Atria and ventricles receive impulse simultaneously which causes an absent P wave or inverted P wave

heart rate does not exceed 60 bpm

pt exhibits reduced cardiac output

Accelerated junctional rhythm

same as escape rhythm but has 60 - 100 bpm

unlikely to have decreased cardiac output

junctional tachycardia rhythm

same as escape and accelerated but with 100 - 150 bpm

may experience palpitations or fluttering

Supraventricular tachycardia (SVT) or narrow complex tachycardia

impulse comes from any area above the ventricles - does not follow the normal electrical conduction pathway

heart rate is greater than 150 bpm and P waves are usually not visible

Premature Ventricular Complexes (PVCs)

ventricles contract out of the normal sequence by an ectopic focal point within the ventricles

P wave is not visible and QRS is wider than normal with an unusual shape

occasional PVCs

frequent PVCs

1-5 occur in one minute

6 or more occurring in one minute

Types of PVC Patterns (hint - there are 7)

unifocal: single early PVC indicates one irritable area

mulitfocal: PVCs with multiple shapes indicate more than one irritable area

interpolated: occurs with no interruption in the normal rhythm

bigeminy: occur every second beat

trigeminy: occur every third beat

quadgeminy: occur every fourth beat

coupling: two PVCs occur back to back

Ventricular Tachycardia

three or more PVCs occurring in a row with a rate greater than 100 bpm

Continuous state of relaxation and contraction of ventricles with poor cardiac output

no noticeable P waves in the tracing and QRS complexes are wide and unusual with the T wave in opposite direction

quickly progresses to fibrillation (w/decreased tissue oxygenation)

ventricular fibrillation

emergency state of ventricular quivering and no cardiac output

no discernable wave

tracing not compatible with life

can lead to asystole with no rhythm *heart stops

pt. typically will be unconscious

Idioventricular rhythm

when only a ventricular pacemaker is functioning with a rate of 20 - 40 bpm and no p waves

QRS is wide with an unusual appearance

HR between 40 - 100 bpm is accelerated idioventricular rhythm

agonal rhythm

when all pacemakers of the heart have failed

wide, unusual qrs complex w/ no P or T waves

ventricular rate is less than 20 bpm

Heart block

block somewhere in the electrical conduction pathway, results in delayed or absent ventricular depolarization

Bundle Branch Block (BBB)

interference in one of the bundle branches

Left BBB: current moves through right bundle for right ventricular contraction but does not go to left bundle and instead moves to left ventricle via the septum - abnormal right to left stimulation

Right BBB: septum depolarization normally and the left ventricle is still activated by the left bundle branch. Right side is blocked so the left ventricle is able to send impulses through myocardium to the right ventricle to depolarize it.

First-degree atrioventricular block

delay in conduction from SA to AV. Travel is normal but pathway is delayed

PR interval is greater than 0.20 seconds

symptoms are not likely to occur

Second degree atrioventricular block type 1

Also known as Mobitz 1 or Wenckebach

nonconducted or blocked impulses from the AV to the ventricles which causes missing QRS complexes

PR interval gets progressively longer until a QRS is dropped and then the pattern repeats

Second degree atrioventricular block, type 2

Also known as Mobitz 2

PR remain constant but there is a P wave and no QRS complex or T wave — AV node selectively block specific impulses

heart block tends to progress quickly into a complete heart block

Third degree atrioventricular block

Complete heart block (CHP)

all electrical impulses that originate above the ventricles are blocked with no pattern to the cardiac cycle as the atria and ventricles are contracting independently.

atria contract at a normal rate but ventricles contract at 20 - 40 bpm depending on where pacemaker site is originating.

Ventricular fibrillation symptoms

dizziness, feeling of impending doom, chest discomfort, SOB, seizure activity

Ventricular tachycardia symptoms

drop in BP and consciousness bc of decreased cardiac output, VT can continue to produce a pulse but usually becomes pulseless or VF

dizziness, impending doom, chest discomfort, SOB

Causes of asystole

pulmonary embolism, large myocardial infarction, respiratory arrest (hypoxia), overdose

hypothermia, acidosis, electrolyte abnormalities, tension pneumothorax, trauma

myocardial ischemia

exhibited through ST segment depression of 1 mm or greater occurring in two contiguous leads or T waves

*contiguous leads look at the same part of the heart (2, 3, and AVF or V1, V2, and V3)

Ischemia persists: myocardial injury occurs —> T wave inversion can occur w/ or w/o ST elevation which is more indicative of injury,

STEMI

ST elevation myocardial infarction

Current injury to heart but tissue has not yet died

ST Segment depression

non-STEMI or NSTEMI

myocardial infarction with pathological Q wave changes in two or more continuous leads

Q wave will measure 0.04 seconds and will be equal or greater than one-third the height of the R wave