Sinus and Atrial Rhythms Flashcards
PR interval?
Normal length?
beginning of P to beginning of QRS complex
0.12-0.20
normal QRS?
0.6-0.11 (usually anything less than 0.12 is good)
How would you identify a sinus dysrhythmia? what may cause this?
RR intervals that vary by more than 0.12 seconds
Respiratory cycle association (increase in SA discharge with inspiration and decrease with expiration)
is sinus dysrhythmia pathologic?
No, it is normal, especially in in younger people with lower heart rates.
enhancement of vagal tone (slowing of HR variability) can cause this
What is sinus arrest?
What compensates for sinus arrest?
Sinus arrest is a disruption in the SA node conduction which results in a discrepancy in the PP interval.
Escape pacemakers will take over (usually the AV junction) or the SA node will pick back up.
Can you tell the difference between sinus block and sinus arrest on an ECG strip?
Not usually.
if an AV block is complete, how do you count the PP interval?
if the block is complete count the delay az part of the PP interval
what can cause sinus arrest or a sinus block?
Infarction
degenerative fibrotic changes
drugs (beta-blockers, digoxin, calcium channel blockers)
excessive vagal stimulation
Are sinoatrial block or sinus arrest clinically significant?
When do you treat? What are some treatments?
Not unless a lower pacemaker fails to control ventricular contraction
If patient is symptomatic, atropine or in serious cases a pacemaker.
What is sick sinus syndrome?
How do you treat it?
Sick sinus syndrome is a disease of the sinoatrial node. It can cause sinus brady, sinus block, or sinus arrest. There are also periods of rapid atrial dysrhythmias such as atrial flutter and atrial fibrillation.
for the sinus depression a pacemaker is often implanted, drug therapy for the rapid atrial dysrhythmias are also usually used.
What are PACs?
Describe the P wave in a PAC.
QRS?
Premature atrial contractions - a premature impulse is generated in the SA node that is sent throughout the entire conduction system in most cases.
The P wave often looks different than the sinus P wave, and is sometimes hidden in the T wave.
QRS usually has normal configuration but may be wide or bizarre (aberrant) depending on the timing of impulse conduction. A blocked PAC can occur (no QRS) if the atrial impulse doesn’t get conducted throughout the ventricles.
Do PACs occur in most people?
Why would they?
Yes
Various stimuli like emotions, caffeine, alcohol, rheumatic heart diease, ischemic heart disease, mitral stenosis, HF, hypokalemia, hypomagnesemia, medications, hyperthyroidism these disease processes may be the underlying cause, may be diagnostic tool)
Although PACs occur among healthy people, what can they be a precursor to?
a-tach, a-fib, a-flutter
What do patients feel with PACS? Are they treated?
A pause or skip, and no it is not treated directly, although any underlying condition causing it may be treated.
What is the definition of PSVT?
paroxysmal supraventricular tachycardia - a rapid atrial rhythm of 150-250 bpm. Usually begins abruptly with a PAC beforehand and end abruptly.
usually caused by the AV node.
What do P waves look like in someone with PSVT?
P waves can either be before the QRS complexes, hidden inside the QRS complexes, or even occur before the T waves.
P waves may look negative in some leads where it should be positive because of retrograde conduction of the atria that can occur.
What happens if someone is in PSVT and has some P waves that do not follow with a QRS complex?
This is called PSVT with block and is indicative of digoxin toxicity in most cases.
What are the different narrow QRS tachycardias?
sinus tachycardia
PSVT
atrial flutter
atrial fibrillation
What are some ways to identify PSVT over ST?
PAC often initiates PSVT (PSVT can happen in healthy people)
tachycardia begin abruptly with PSVT
PSVT is often a faster rate than ST and is mroe regular from minute to minute
vagal maneuvers (carotid massage or valsalva) either don’t effect or revert PSVT to normal (all or nothing), ST slows slightly due to vagal maneuvers
What are some mild symptoms of PSVT?
palpitations
light headedness
Other than vagal stimulation. how can PSVT be treated?
adenosine
if drug therapy isnt successful cardioversion or pacing may be indicated.
What is the BPM for atrial flutter?
250-350
What does atrial flutter look like on an ecg?
sawtooth or picket fence, flutter is commonly hidden in the T wave or QRS complex
What can be done if the ventricular rate is too fast to see atrial flutter on an ecg?
use vagal maneuvers, administer adenosine,
these things incrase the AV block which will make it more visible
What is the ratio of atrial fluttter to ventricular contraction?
2:1, 3:1, 4:1
Does atrial flutter effect CO?
yes it can if the ventricular rate is either too fast or too slow.
What is the big concern with rhythms like atrial flutter and a-fib?
the lack of contraction in the atria cause clots to from which then get thrown into the lungs.
What are some treatments for atrial flutter?
What is the ultimate goal of treatment?
The goal is to establish a sinus rhythm and control ventricular rate.
drug therapy can control ventricular rate as well as revert to a sinus rhythm
If drugs don’t cardiovert, electrical cardioversion is the next step, patient needs to be NPO prior to procedure due to required sedation
when is anticoagulation therapy indicated for atrial flutter?
After it has been going on for more than 72 hours before any procedure attempting to reverse it.
what are some long-term treatments for atrial flutter?
ablation, pacing, and implantable devices
What is the rate for atrial fibrillation?
350-500 BPM
What is one of the key differences between atrial flutter and a-fib?
a-fib does not have a P wave
Can a-fib effect ventricular rate?
yes is may, it all depends on its ability to pass the AV junction gatekeeper
Can a-fib be transient?
yes, it can also be pathologic.
How is atrial fibrillation treated?
same as atrial flutter -
anticoagulation therapy for chronic form (risk of mural thrombi)
cardioversion if drug therapy fails or if hemodynamic compromise occurs
ablation, pacing, and implantable devices are also options.
What disease processes is atrial fibrillation commonly seen in?
HF, ischemic and rheumatic heart disease, pulmonary disease, after open heart surgery, and congenital heart disease
What is multifocal atrial tachycardia?
rapid atrial rhythm that is caused by the firing of three or more areas in the atria causing a varied P wave and PR interval.
how does the QRS complex look with multifocal atrial tachycardia?
they usually look normal unless the impulse is conducted with aberrancy.
Where is multifocal atrial tachycardia commonly seen?
What do these patients exhibit and how is it treated?
Patients with pulmonary disease.
Patients commonly exhibit hypoxemia, hypokalemia, pH changes, pulmonary HTN
Since symptoms are usually due to the underlying disease process rather than the rhythm, the disease process is the main concern for treatment, if the ventricular rate is being effected badly it may be treated.
What happens with a junctional rhythm?
AV node takes control for SA node, normal rate for this is between 50-70 bpm.
What are the three waves a junctional rhythm can manifest?
AV node fires and retrograde conduction occurs in atria before moving to the ventricles (inverted P wave before QRS complex)
AV node conducts impulse that travels backwards to atria and forwards to ventricles at the same time (inverted P wave hidden in QRS) AV synchrony lost
Impulse travels to ventricles first before going backwards to atria (normal QRS with inverted P wave afterwards) AV synchrony lost
Why would a junctional rhythm patient become symptomatic?
because of the slower heart rate
