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
