Ch. 5 Notes: Rhythm Strip Interpretation and Sinus Rhythms Flashcards
What is used to determine the cardiac rhythm?
Waveform, segments, and intervals
What are the 5 steps to identifying components of the rhythm?
- Atrial rhythm and rate
- Ventricular rhythm and rate
- P wave morphology
- PR interval
- QRS duration and morphology
What lead is generally used for rhythm evaluation?
Lead II
What are the two options for rhythms?
Irregular or regular
How do you determine if the rhythm is regular or irregular?
Regular rhythms have equal spacings and irregular rhythms don’t
How do you measure the atrial rhythm?
From the beginning of the P wave to the beginning of the next P wave (P-P interval)
How do you measure the ventricular rhythm?
From the R wave to the next R wave (R-R interval)
How do you calculate atrial and ventricular rates?
Count the number of small boxes between the P-P or R-R intervals and divide 1500 by that number (or look on chart)
What method should you use to calculate the atrial and ventricular rates for irregular rhythms?
Use the 6-second method; count the number of P or R waves in a 6 second strip and multiply by 10
What is normal P wave morphology?
Upright and rounded
What should normally follow every P wave?
QRS complex
How do you measure the PR interval?
From the start of the P wave to the start of the QRS complex
How do you measure the QRS duration?
From the beginning of the Q wave to the end of the S wave (J point)
What are signs of decreased cardiac output?
Confusion, dizziness, syncope, chest pain, low BP, decreased pulse volume, nausea, cramping, pallor, cool skin, diaphoresis, mottled skin, tachypnea, shortness of breath
Which rhythm is used to compare to other rhythms?
Normal sinus rhythm
Where does the normal sinus rhythm originate from?
The SA node
What is the criteria for normal sinus rhythm?
- Atrial rhythm/rate: regular, 60-100 bpm
- Ventricular rhythm/rate: regular 60-100 bpm
- P wave morphology: uniform, upright, rounded, before every QRS complex
- PR interval: 120-200 ms or 0.12-0.20 s
- QRS duration and morphology: 60-120 ms or 0.06-0.12 s, consistent and without variations
What is the criteria for sinus bradycardia?
The same as normal sinus except for the atrial and ventricular rates which are less than 60 bpm
What treatment may be needed for sinus bradycardia?
Medication or a pacemaker
What does a pacemaker do?
Create artificial electrical impulses that are delivered to the heart muscle
What is the criteria for sinus tachycardia?
The same as normal sinus rhythm except for the atrial and ventricular rates which are greater than 100 bpm
Why can sinus tachycardia cause low cardiac output?
There isn’t enough time for the ventricles to fill with blood before the heart contracts because it is pumping too fast
What might a patient complain of if their HR is too fast?
Palpitations or heart fluttering
Why is tachycardia dangerous for patients with severe coronary artery disease or a recent heart attack?
The heart muscle needs more oxygen the faster it beats which it will not get because the coronary arteries do not receive enough blood during diastole because of the fast HR
What causes a sinus dysrhythmia?
Pressure on the heart from respiratory cycle and increased vagal tone (HR also slows when patient breathes in)
How do you identify sinus dysrhythmia?
QRS complexes have different widths, narrower and wider, in the same strip
What is the criteria for sinus dysrhythmia?
The same as normal sinus rhythm except for its irregularity in sequence with respirations
What is the usual overall rate for sinus dysrhythmia?
60-100 bpm
Does the patient usually show visible signs for sinus dysrhythmia?
No
Sinus dysrhythmia is common in what demographics?
Children and young adults
What can severe rhythm irregularity cause?
Dizziness or palpitations due to slow rate
What should you do with the ECG strip of a patient with sinus dysrhythmia?
Place a copy of the rhythm strip in the patient’s record for documentation
What is sinus arrest?
The SA node stops firing which causes a pause in electrical activity
What does not occur during the pause in a sinus arrest?
Ventricular contractions
What happens during a sinus exit block?
The SA node initiates an impulse but it is blocked from exiting the SA node
What can cause sinus exit block?
Acute myocardial infarction, ischemia, drugs (digitalis or quinidine)
What is the difference between sinus exit block and sinus arrest on the ECG strip?
“Marching” the caliper through the pause in a sinus exit block shows that the rhythm has not changed but the rhythm does change for sinus arrest
Sinus exit block and sinus arrest are ____________ dysrhythmias
“add-on” (they interrupt an underlying rhythm)
What must the interpretation begin with in regards to a sinus exit block or sinus arrest?
The underlying rhythm that was interrupted
What is the criteria for sinus exit block and sinus arrest?
The same as normal sinus rhythm BUT it can occur in bradycardia or tachycardia as well so the rates could be above or below the usual 60-100 bpm
What should you note about the rhythm in sinus arrest and sinus exit block?
The rhythm is regular before and after the arrest or block
How do you calculate QRS duration and PR interval?
Count the number of small boxes between the Q and S waves or the P and R waves and multiply that number by 40 ms or 0.04 s
How do you calculate the length of a pause in a sinus exit block or sinus arrest?
Count the number of small boxes between the R-R interval around the pause and multiply that number by 40 ms or 0.04 s
What does a pause of 6 seconds or more indicate?
Medical emergency (code blue) and patient would most likely become unconscious so resuscitation measures may be needed
What do more frequent and longer pauses indicate?
Patient is more likely to show signs of low cardiac output
What can pauses as short as 2 seconds that occur frequently cause?
Periods of low cardiac output
What cannot be determined from a 6-10 second strip?
Frequency of pauses
What are treatment options for sinus exit block or sinus arrest?
Oxygen, pacemaker, or discontinuing medication if it is caused by drug toxicity
Why can oxygen help a patient with sinus exit block or sinus arrest?
It improves ischemia which results from a reduction of blood (oxygen) to a region of the heart tissue
