AV Dysrhythmias and AAA
1.
Atrial Fibrillation - Occurs when there us chaotic, asynchronus firing of multiple
areas within the atria. This completely suppresses the SA node output and causes the
atria to quiver instead fo contract. The atria fire greater than 350 beats per minute. These
impulses bombard the AV ose but are only conducted to the ventricles in an irregular and
sporadic fashion.
Because of a loss of atrial kick, the ventricular filling is decreased up to 30%.
Client’s experiencing atrial fib may deveop intra atrial emboli as the atria are not
contracting and blood stagnates in the atrial chambers forming a thrombus. This
predisposes the client to systemic emboli- particularily stroke. A ventricular response
within the nirmal rate (60 to 100 beats per minute) is often well-tolerated. A fast
ventricular response can result in decreased cardiac output that leads to heart failure,
angina, or syncope. Client’s who have preexisting heart disease, such as hypertrohic
obstructive cardiomyopathy, mitral stenosis, rheumatic heart disease, and mitral
prosthetic valves, are less tolerant of atrailf ibrillation and may experience shoch and
severe heart failure.
Atrial fib is more common than atrial tachycardia or atrial flutter. It can occur in
healthy persons after excessive caffeine, alcohol, or tobacco ingestion or because of
fatigue and acute distress. It can also be caused by the catecholamines released during
exercise. Atrial fib may also be seen with other conditions including rheumatic heart
diasease, CHF (atrial dilation), and atherosclerotic heart disease. Less commonly, atrial
fibrillation may offur with cardiomyopathy, acute myocarditisa nd pericarditis, and chest
trauma.
Atrial Fibrillation
Causes of Atrial Fibrillation
Cardiac disorders
Examples
Following cardiac surgery, mitral
regurgitation, mitral stenosis, chronic
coronary artery disease, myocardial
infarction, pericarditis, atrial septal defects,
pulmonary embolism
Use of certain drugs
Digitalis toxicity, aminophylline
Increased vagal tone
Valsalva’s maneuver, carotid sinus
massage, vomiting
Others
Hypoxia, hyperthyroidism, infecrtion,
catecholamine release during exercise; may
also occur in healthy people who use
coffee, alcohol, or cigarettes to excess or
who are fatigued and under stress
Review of Characteristics Associated with Atrial Fibrillation
Rate
Ventricular rate may be slow, normal, or
fast; atrial rate is greater than 350 beats per
minute
Regularity
Totally (chaotically) irregular
P waves
Absent, instead there is a chaotic looking
baseline
QRS complexes
Normal
PR Interval
Absent
QT interval
Unmeasurable
Treatment of Atrial Fibrillation (dependent on cardiac output and symptomatology):
Heparin, Lovenox, and Coumadin.
Chemical Cardioversion – Cardizem IV
Electrical (elective) cardioversion
Difference between defibrillation and cardioversion??????
Atrial Flutter
1.
A rapid depolarization of 1 focus in the atria at a rate of 250-350 beats per minute.
On the EKG the P waves loose their distinction due to the rapid atrial rate. The
waves blend together in a saw-tooth or picket fence pattern and are called flutter
waves.
It can occasionally occur in healthy hearts, but usually is caused by conditions
that enlarge the atria and elevate atrial pressures. Commonly seen in clients with
severe mitral valve disease, hyperthyroid disease, pericardial disease, and primary
myocardial disease. It is often well tolerated, but the number of impulses
conducted through the AV node determines the ventricular rate. Slower rates
(fewer than 50) or faster ventricular rates (greater than 150) can compromise
cardiac output.
The key feature is saw-tooth flutter waves. These flutter waves correspond to the
rapid atrial rate of 250-350 beats per minute. The ventricular rate may be regular
or irregular.
Review of Key Characteristics Associated with Atrial Flutter
Rate
Ventricular rate may be slow, normal or
fast; atrial rate is between 250 and 350
beats per minute
Regularity
May be regular or irregular (depending on
whether the conduction ration stays the
same or varies)
P waves
Absent, instead there are flutter waves; the
ratio of atrial wave-forms to QRS
complexes may be 2:1, 3:1, or 4:1. An
atrial to ventricular rate of 1:1 is rare.
QRS complexes
PR interval
QT interval
Normal
Not measurable
Not measurable
Causes of Atrial Flutter
Causes
Cardiac disorders
Examples
Conditions that enlarge atrial tissue and
elevate atrial pressures, following cardiac
surgery, severe mitral valve disease,
cardiomyopathy, pericarditis, myocarditis,
hypertrophy, CHF, acute infarction
Others
COPD, hypoxia, digitalis toxicity,
hyperthyroidism, infection, catecholamine
release during exercise; may also occur in
healthy people who use coffee, alcohol, or
cigarettes to an excess or who are fatigued
and under stress