NUR 240 ch 22 arrhythmias Flashcards
arrhythmia definition
are disorders of the formation or conduction (or both) of the electrical impulse within the heart
arrhythmias are diagnosed by
analyzing the ECG waveform
sinus node (SA node)
the electrical impulse that stimulates and paces the cardiac muscle normally originates here. electrical impulse usually occurs at a rate of 60 to 100 times per minute
conduction
transmission of electrical impulse from one cell to another
ie. from the SA node to the AV node
depolarization
cardiac muscle cells change from a more negative charge to a more positive charge (still neg, but just a little less neg)
what happened during depolarization
contraction!! (systole)
influx of Na+ into the heart cell
repolarization
cardiac muscle cells return to a more negatively charged intracellular condition, their resting state
what happens during repolarization
REpolarization = RElaxation
(diastole)
P wave
part of an ECG that reflects conduction of an electrical impulse through the atrium
atrial depolarization
PR interval
the part of an ECG that reflects conduction of an electrical impulse from the sinoatrial node through the atrioventricular node
atrial depolarization complete
QRS complex
the part of an ECG that reflects conduction of an electrical impulse through the ventricles
ventricular depolarization
ST segment
the part of an ECG that reflects the end of the QRS complex to the beginning of the T wave
ventricular depolarization complete
QT interval
the part of an ECG that reflects the time from ventricular depolarization through repolarization
Sinus rhythm
electrical activity of the heart initiated by the sinoatrial node (SA)
U wave may be seen with a deficiency in which electrolyte
potassium
how can Potassium effect heart rhythm
heart rate is influenced by the
autonomic nervous system
Stimulation of the sympathetic nervous system causes
- positive chronotropy (increased heart rate)
- positive dromotrophy (increased AV conduction)
- positive inotropy (increased force of myocardial contraction)
- constricts peripheral blood vessels– increasing blood pressure
parasympathetic stimulation causes
negative chronotropy (reduces heart rate)
negative dromotropy (reduced AV conduction)
reduces force of atrial myocardial contraction
dilation of arteries– decreasing blood pressure
increased sympathetic stimulation can lead to
increased incidence of arrhythmias
causes of increased sympathetic stimulation
exercise, anxiety, fear, or administration of catecholamines such as dopamine, aminophylline, or dobutamine
causes of decreased sympathetic stimulation
with rest, anxiety reduction methods such as therapeutic communication or meditation, or administration of beta-adrenergic blocking agents
decreases incidence of arrhythmias
poor electrode adhesion can cause
significant artifact (distorted, irrelevant ECG waveforms)
wash skin with soap and water, do not wash sign with alcohol swab - hinders detection of cardiac electrical signal
skin prep for ECG electrodes
wash skin with soap and water
do not wash sign with alcohol swab - hinders detection of cardiac electrical signal
Arrhythmias can cause a disturbance of
both the rate and rhythm (or just one)
Atrial flutter
occurs because of a conduction defect in the atrium and causes rapid, REGULAR atrial impulse at a rate between 250 and 400 bpm
atrial fibrillation
results from abnormal impulse formation that occurs when structural or electrophysiologic abnormalities alter the atrial tissue causing rapid, disorganized, and uncoordinated twitching of the atrial musculature
causes of sinus bradycardia
lower metabolic needs (sleep, athletic training, hypothyroidism)
vagal stimulation (vomiting, suctioning, severe pain)
medications (calcium channel blockers [nifedipine, amiodarone], beta blockers [metroprolol])
idiopathic sinus node dysfunction
increased cranial pressure
CAD
MI
acute decompensated heart failure
acute altered mental status
unstable and symptomatic bradycardia is frequently due to
hypoxemia (low blood oxygen)
what med MAY be given if bradycardia produces signs and symptoms of clinical instability (acute AMS, chest discomfort, hypotension)
atropine
sinus tachycardia causes
physiological or psychological stress (acute blood loss, shock, hypervolemia, hypovolemia, heart failure, pain, hyper metabolic states, fever, exercise, anxiety)
medications that stimulate sympathetic response (catecholamines, aminophylline, atropine), stimulants (caffeine and nicotine) and illicit drugs (amphetamines, cocaine, ecstasy)
autonomic dysfunction (Postural orthostatic tachycardia syndrome)
Postural orthostatic tachycardia syndrome (POTS)
tachycardia without hypotension
presyncopal symptoms- palpitations, lightheadedness, weakness, and blurred vision that occurs with sudden postural changes
As the heart rate increases, the diastolic filling time decreases, possibly resulting in reduced cardiac output and subsequent symptoms of syncope (fainting) and low blood pressure
If the rapid rate persists and the heart cannot compensate for the decreased ventricular filling, the patient may develop acute pulmonary edema
medical management of tachycardia
Vagal maneuvers- such as carotid sinus massage, gagging, bearing down against a closed glottis (as if having a bowel movement)
forceful and sustained coughing
applying a cold stimulus to the face (such as applying an ice-cold wet towel to the face)
administration of adenosine
if tachycardia is causing hemodynamic instability (acute AMS, chest discomfort, hypertension) what should be done?
synchronized cardioversion (if vagal maneuvers and adenosine are unsuccessful)
additionally:
IV beta blockers or calcium channel blockers
cardioversion
electrical current given in synchrony with the patients own QRS complex to stop an arrhythmia
atrial arrhythmias: premature atrial complexes (PAC)
a single ECG complex that occurs when an electrical impulse starts in the atrium before the next normal impulse of the sinus node
what causes PAC
caffeine, alcohol, nicotine, stretched atrial myocardium (as in hypervolemia), anxiety, hypokalemia, hypermetabolic states (pregnancy), atrial ischemia, injury, infection, or infarction
risk factors for a fib
INCREASING AGE**
COPD
*Hypertension
*Diabetes
*Obesity
*Valvular heart disease
*Heart failure
*Obstructive sleep apnea
*Alcohol abuse
*Hyperthyroidism
*Myocardial infarction
*Smoking
*Exercise
*Cardiothoracic surgery
*Increased pulse pressure
*European ancestry
*Family history
common complication of a fib
blood pools in the atria which can lead to a stroke
p waves in a fib
p waves are not present before the QRS complex
p waves are replaced with irregular fibrillary waves (F waves)
atrial rate in a fib
very fast and irregular (300 to 600 bpm)
uncontrolled a fib
ventricular rate is greater than 100 bpm, complications such as HF can develop
patients with a fib should be on what medications
antithrombotic medications (anticoagulants and anti platelet drugs) because it reduces the risk of stroke
(to control HR) for persistent or permanent a fib- beta-blocker or non-dihydropyridine calcium channel blocker
medications that can convert the heart rhythm or prevent atrial fibrillation
Medications that may be given to achieve pharmacologic cardioversion to sinus rhythm include flecainide, dofetilide, propafenone, amiodarone, and IV ibutilide
** dofetilide- monitor renal function and QT interval
atrial flutter important feature
Because the atrial rate is faster than the AV node can conduct, not all atrial impulses are conducted into the ventricle, causing a therapeutic block at the AV node. This is an important feature of this arrhythmia. If all atrial impulses were conducted to the ventricle, the ventricular rate would also be 250 to 400 bpm, which would result in ventricular fibrillation, a life-threatening arrhythmia
Atrial flutter signs and symptoms
chest pain, shortness of breath, low blood pressure
medical management of atrial flutter
vagal maneuvers or administration of adenosine
atrial fibrillation doesn’t allow for complete __
filling
physical assessment of a patient with an arrhythmia
skin (pale and cool)
signs of fluid retention (JVD, lung auscultation)
rate and rhythm of apical and peripheral pulses
heart sounds
blood pressure, pulse pressure
assess indicators of ___ and ____ in the assessment of patients with an arrhythmia
cardiac output
oxygenation
pacemakers
electronic devices that provides electrical stimuli to heart muscle
set at a certain rate
cardioversion vs defibrillation
cardioversion: delivery of electrical impulse is synchronized with patients ECG
defibrillation: delivery is unsynchronized
If cardioverting, turn synchronizer ____
If defibrillating, turn synchronizer _____
on
off
Ventricular arrhythmias: premature ventricular complex (PVC)
impulse that starts in the ventricle and is conducted through there ventricles before the next sinus impulse
can occur in healthy people with intake of caffeine, nicotine or alcohol
PVCs are a common occurrence and may increase in frequency with age
ventricular tachycardia (VT)
defined as three of more PVCs in a row, occurring at a rate exceeding 100 bpm
Patients with larger MIs and lower ejection fractions are at higher risk of lethal VT.
VT is an emergency because the patient is nearly always unresponsive and pulseless.
V tach looks like (on ECG)
tombstones
treatment of choice for pulseless VT
defibrillation
Torsades de pointes
a polymorphic VT preceded by a prolonged QT interval, which could be congenital or acquired
what happens to cardiac output in V fib
decreases
V fib is deadly if not reversed or treated
ventricular fibrillation
the electrical conduction system is sending out an abnormal electrical signal that is causing the ventricles to quiver
ventricles quiver, not squeezing enough blood out
what does V fib look like on a ECG
scribbles
chaotic, rapid rhythm that has no real organization to it
V Fib: coarse fibrillatory waves
patient has a better chance at being revived
V Fib: fine fibrillatory waves
slim chance for patient to be revived
looks similar to asystole on ECG
Ventricular fibrillation is always characterized by the absence of an audible heartbeat, a palpable pulse, and respirations.
medical management of V fib
early defibrillation is critical to survival with CPR
for refractory V fib- administration of amiodarone and epi may facilitate the return of a spontaneous pulse after defibrillation
