Dysrhythmias Flashcards
what are the 4 properties of cardiac cells?
1) automaticity: ability to initiate an impulse spontaneously and continuously
2) contractility: ability to respond mechanically to an impulse
3) conductivity: ability to transmit an impulse along a membrane in an orderly manner
4) excitability - ability to be electrically stimulated
what is the automatic nervous system responsible for?
- rate of impulse formation
- speed of conduction
- strength of cardiac contraction
what does vagus nerve stimulation do?
1) decrease heart rate
2) slowing of impulse conduction
3) decreases force of contraction
what does the sympathetic nervous system do?
1) increase heart rate
2) increases force of contraction
what does an ECG do?
graphic tracing of electrical impulses produced in the heart
where do you place the ECG lead wires?
1) 12 - lead ECG - views surfaces of the left ventricle from 12 different angles
2) 6 leads ECG - measures electrical forces in the horizontal plane
can you put the stickers on hair?
no the area needs to be shaved before putting the stickers
clean the skin as well with alcohol to remove oiliness
if pt is diaphoretic, utilize skin protectant
what are the different types of monitoring?
1) telemetry: continous ECG monitoring to a centralized system
- alarms set for various parameters or dysrythmias
2) holter monitor : Records ECG while patient is ambulatory for 24-28 hours
- diary maintained by patient to record activities and symptoms
3) exercise treadmill testing : evaluation of cardiac rhythm response to exercise
what are the placements for leads?
review this on YouTube
What happens if the pt has a pace maker?
the lead needs to be put on the back because can disrupt the reading if placed in front
What is the P wave?
represents time for the electrical impulse that causes atrial depolarization (contraction) to pass through the atrium
- they should be upright and round and normal duration range is 0.06sec to 0.12sec
what is the PR interval
measures from the beginning of p wave to beginning of the QRS complex
- normal duration 0.12-0.20
what is the QRS interval
measured from beginning to end of QRS complex
duration: 0.06 -0.10 seconds
what is the T wave?
represents time for ventricular repolirazation
- should be upright
duration: N/A
what is the QT interval
- Represents time take for entire electrical depolarization and repolarization of the ventricles
- Measured from the beginning of QRS complex to end of T wave
duration: 0.34-0.43
if the heart rate is irregular how do you determine the heart rate?
count the number of R-R intervals and multiply by 10
how do you determine the heart rate if rhythm is regular?
Count the number of small squares between an R-R interval and divide this number by 1500
what is the pacemaker of the heart?
SA node
where can dysruthmias originate from?
- AV node or the His-purkinje system
- secondary pace maker discharging more rapidly than the normal pacemaker
discuss sinus bradycardia
sinus nodes fires <60bpm
has a normal sinus rhythm but SA node is firing slow
what are the manifestations of sinus bradycardia?
WEAK and SLOW
Why does sinus bradycardia occur?
hypothyroidism, sick sinus syndrome, medications, increased vagal tone
how does sinus bradycardia get treated?
-ine medications or a pacemaker
discuss sinus tachycardia
discharge from the sinus node is increased as a result of vagal inhibition or SNS stimulation so the heart beat is > 100 bpm
what are manifestations of sinus tachycardia?
increased myocardial oxygen consumption, angina, hypotension due to decrease CO
why does sinus tachycardia occur?
- exercise
- fever
- hypotension
- hyperthyroidism
how is sinus tachycardia treated?
adrenergic and calcium channel blockers to reduce HR and myocardial oxygen consumption
- if pt is unstable they may need synchronized cardioversion
discuss premature atrial contraction
contraction originating from ectopic focus in atrium in location other than SA node before the next expected beat
- travels across atria by abnormal pathway, creating distorted P wave
what causes premature atrial contraction?
stress, caffeine, hypoxia, hyperthyroidsim
what does it mean for someone to have premature atrial contraction?
in a healthy person = not too significant
in someone with heart disease = may be warning signs for more serious dysrhythmia
discuss paroxysmal supra ventricular tachycardia (SVT)
when the signal in the heart goes from the SA node to the AV node normally but the electrical signals have problem going to the ventricles and shoot into the atrium so it causes high heart rate
what causes PSVT?
Stimulants
Stress
Sepsis
what are symptoms of PSVT?
hypotension, dyspnea, angina
what is the treatment for PSVT?
1) vagal manoeuvrs : valsalva, coughing
2) drug therapy: IV adenosine
if both these fail, synchronized cardio version should be used
discuss atrial flutter
recurring, regular, sawtooth shaped flutter waves.
- originated from a SINGLE ectopic focus
- atrial rate (p wave frequency) = 250 - 350 bpm
- PR interval is unable to be measured
everything else normal
why does atrial flutter occur?
usually occurs with CAD, some sort of heart probelm
what is the clinical significance of atrial flutter/
the high ventricular rate and loss of the atrial “kick” can decrease CO and precipitate heart failure and angina
- risk for stroke due to risk of thrombus formation in the atria from stasis of blood
what is the treatment for atrial flutter?
primary goal is to slow ventricular response by increasing AV block
- drugs to slow HR such as calcium blockers
discuss atrial fibrillation
total disorganization of atrial electrical activity due to multiple ectopic foci, resulting in loss of effective atrial contraction
atrial rate = 600bpm while ventricular slow range 50 bpm - 180 bpm
p waves are replaced by chaotic, fibrillary waves, rhythm is irregular, PR not measurable BUT QRS is normal
what is usually associated with a fib?
usually occurs with some sort of heart disease and often acutely caused by thyrotoxicosis
what is so important about a fib that we must worry?
can result in decrease in CO due to ineffective atrial contractions (loss of atrial kick) and rapid ventricular response
- thrombi may form = blood stasis and embolus may develop and travel to the brain
how do we treat a-fib?
the Goal is to decrease ventricular rate and prevent cerebral embolic events
so drugs for rate control and long term anticoagulation therapy
what is premature ventricular contractions?
contractions originating in ectopic focus of the ventricles
why does premature ventricular contractions happen?
usually stimulants like caffeine, digoxin or alcohol
if you have premature ventricular contractions?
normal heart = usually benign
in heart disease = PVCs may decrease CO and precipitate angina
and HF if >10/minute
premature ventricular treatment
based on cause of PVCs
- oxygen therapy
what is ventricular tachycardia?
occurs when an ectopic focus or foci fire repetitively and the ventricle takes control of the pacemaker
run of 3 or more PVCs
- monomorphi, polymorphic, sustained (>30sec) and non sustained
how dangerous is ventricular tachycardia?
considered life-theartening because of decreased CO and the possibility of deterioration to ventricular fibrillation
