1. Basic Dysrhythmias Sinus Arrhythmias

2. Basic Rhythm Strip Interpretation
Use a systematic approach each and every time a strip is analyzed
Its 3:00 AM and your patient has chest pain. You call the ER who asks for a 12-lead EKG. Do you know what to look for? Your rapid interpretation could initiate immediate intervention and save the patient's life!

3. Basic Rhythm Strip Interpretation
First, and most important, look at your patient!
Read every strip from left to right.
Apply the five step systematic approach.
Avoid shortcuts.
Be consistent
What is the patient’s clinical picture and how is it significant to the rhythm noted on the monitor?
Avoid shortcuts and assumptions. A quick glance at a strip will often lead to an incorrect interpretation.
Be consistent. Ask and answer each question in the 5 step approach in the order that it is presented here

4. Basic Rhythm Strip Interpretation
Step 1: Heart rate & Rhythm
Step 2: P wave rate & Rhythm
Step 3: PR Interval
Step 4: QRS complex
Step 5: Interpretation
This 5 step approach looks first at heart rate and rhythm, followed by analysis of the graphic representations of activities as they occur in the electrical conduction system of the heart.

5. Step 1: Heart Rate
Six second method: count the number of QRS complexes in a six second interval on the EKG strip.
Large box method:count the number of large boxes between 2 consecutive R waves (R-R Interval) and divide into 300.
Small box method:count the number of small boxes between two consecutive R waves and divide into 1500.
Sequence method: select an R wave that falls on a dark vertical line, number the dark vertical lines following this as Note where the next R wave falls.
Heart rate is the number of electrical impulses (as represented by PQRST complexes) conducted through the myocardium in 60 seconds (one minute)
If atrial and ventricular rates are dissimilar, you need to calculate both.
Each I-mm box on the graph paper represents 0.04 seconds. There are 1500 boxes in one minute (60 seconds/min divided by 0.04 seconds/box=1500 boxes/minute. Time consuming, but accurate!

6. Step 1: Heart Rhythm Is the rhythm regular or irregular?
Measure the intervals between R waves to determine ventricular regularity.
Measure the intervals between P waves to determine atrial regularity.
If irregular, is it
1. Regularly irregular
2. Irregularly irregular
Regularly irregular—irregular rhythms that occur in a pattern.
Irregularly irregular—R-R intervals exhibit no similarity.

7. Step 2: the P wave Are P waves present?
Are the P waves occurring regularly?
Is there one P wave present for each QRS complex present?
What is the P-P rate?
Are the P waves smooth, rounded, and upright in appearance or are they inverted?
Do all the P waves look similar?
The p wave is produced when the right and left atria depolarize. Depolarization of the atria is produced when an electrical impulse spreads throughout the atria via the internodal pathways. The P wave is noted as the first deviation from the isoelectric line on the EKG strip.
If the p wave is not rounded and upright in lead II, then you are not looking at a sinus rhythm. Rhythm didn’t originate in the SA node.

8. Step 3: The PR Interval Are the PR Intervals greater than 0.20 second?
Are the PR Intervals less than 0.12 second?
Are the PR Intervals constant across the EKG strip?
PR Interval measures the time interval from the onset of atrial contraction to the onset of ventricular contraction, or the time necessary for the electrical impulse to be conducted through the atria and the AV node.
It is measured from the onset (or the beginning) of the P wave, to the onset of the Q wave of the QRS Complex.
Normal PR Interval is seconds.
Shortened PR Interval may be an indication that the usual progression of the impulse is outside the normal route.
Prolonger PRI may indicate a delay in the electrical conduction pathway or an atrioventricular (AV) block.
Each small block is 0.04 seconds. Normal PR interval is three to five small blocks.

9. Step 4: the QRS Complex
Are the QRS intervals greater than 0.12 second?
Are the QRS intervals less than 0.12 second?
Are the QRS complexes similar in appearance across the EKG strip?
The QRS Complex represents ventricular depolarization (or contraction).
Q wave: the first negative deflection of the complex. Q wave representing septal depolarization
R wave: the first positive or upward deflection following the p wave. R wave representing ventricular depolarization
S wave: the sharp negative or downward deflection that follows the R wave. S wave representing depolarization of the Purkinje fibres.
Normal width is 0.06 to 0.11 second.
Wide QRS may be ventricular in origin.
Narrow QRS is most probably supraventricular.

10. Step 5: Interpretation
Now you are ready to interpret the rhythm.

12. Sinus Rhythms Normal Sinus Rhythm Sinus Bradycardia Sinus Tachycardia
Sinus Arrhythmia
Sinus Arrest

13. Sinus Rhythm Is it Sinus Rhythm?
To ascertain whether a rhythm is sinus or not you need to be able to identify key features:
There must always be a P wave.
The P wave should be a rounded shape
Each P wave should be the same shape
Each P wave should be followed by a QRS
The P-R interval should be 0.12 to 0.20 seconds (3-5 small squares) and constant
The rhythm should be regular.
You do not need to be able to recognise a "T wave" for it to be sinus rhythm. Many abnormalities obscure the t wave. Suffice to say, if the patient is alive then the ventricles are definitely repolarising.

14. Normal Sinus Rhythm

16. Sinus rhythm is the name given to the normal rhythm of the heart where electrical stimuli are initiated in the SA node, and are then conducted through the AV node and bundle of His, bundle branches and Purkinje fibers.
Depolarization and repolarization of the atria and ventricles show up as 3 distinct waves on ECG. A unique labeling system is used to identify each wave.
Although the diagram shows 5 waves, we will concentrate on 3 waves. You will not always see a Q wave or an S wave on an ECG.

17. Remember, different leads may have waves pointing in different directions. Eg. Lead AVR (right shoulder/right arm/wrist) will always see the electrical stimulus travelling away from it, therefore the waves expressed in AVR for sinus rhythm, pqrst, will all point downwards.

18. Sinus Bradycardia R-R intervals constant and regular
All waveforms are present, and there is 1 P-wave to each QRS complex
The rate is <60bpm but not usually <40bpm
Patients usually asymptomatic and no treatment is required
Often caused by beta-blockers / calcium channel blockers
May also be seen in athletes and occur during sleep.
Sinus Bradycardia
The job of the heart is to pump blood around the body carrying oxygen and nutrients to organs, muscles and tissues, and transporting waste such as carbon dioxide to the lungs for expiration. The cardiovascular system is under the control of the nervous system which increases and decreases the workload of the heart depending on the body's requirements.
So, if a person is involved in exercise, their muscles and organs require more blood and oxygen to function, so the heart and lungs go faster. If a person is resting or sleeping then the body's requirements drop considerably and the heart and lungs slow down.
Anything below 60 bpm is known as Bradycardia. Sinus Bradycardia is not a changed rhythm, it is simply normal sinus rhythm slowed down.

20. Sinus Tachycardia R-R intervals constant and regular
One P-wave per QRS complex
All waveforms present
Rate is > 100bpm, but not usually > 130bpm at rest
Occurs normally in exercise / stress. Patient is usually asymptomatic.
Other causes may be hypovolemia / underlying medical problems
Sinus Tachycardia
During exercise, it is common for a person's heart rate to go above 100bpm. This is known as Tachycardia and, if the rhythm is sinus, it is known as Sinus Tachycardia.
Sinus tachycardia is not a different rhythm, it is simply sinus rhythm going faster than 100 bpm

22. Sinus Arrhythmia
Sinus arrhythmia is not commonly seen but the same evaluation procedure is used:
Is there a P wave?
Is each P wave the same shape?
Is each P wave followed by a QRS complex?
Is the P-R interval between 3-5 small squares?
Is the rhythm regular?
If the answer to the first four questions is "yes", but the answer to the last is "no" then you have sinus arrhythmia.
Sinus Arrhythmia
Sinus Arrhythmia, or "regularly irregular" sinus rhythm, is a variation on sinus rhythm where the P-P interval ( the distance between consecutive P waves) varies by more than 10%.
It can be naturally occurring or due to heart damage.
Causes can be:
Respiratory-where the P-P interval lengthens and shortens with inspiration and expiration.
Non-respiratory - where the process occurs seemingly for no reason.
Sometimes seen in association with Complete Heart Block

23. Irregular
Rate 75
P waves upright
PR 0.20 seconds
QRS Narrow
Sinus Arrhythmia

24. Sinus Arrest
In disease (e.g. sick sinus syndrome) the SA node can fail in its pacing function. If failure is brief and recovery is prompt, the result is only a missed beat (sinus pause). If recovery is delayed and no other focus assumes pacing function, cardiac arrest follows.

25. This may occur in individuals with healthy hearts
This may occur in individuals with healthy hearts. It may also occur with increased vagal tone, myocarditis, MI, and digitalis toxicity.
If the pause is prolonged, escape beats may occur.
The treatment of this dysrhythmia depends on the underlying cause.
If the cause is due to increased vagal tone and the patient is symptomatic, atropine may be indicated.

28. Sinus Bradycardia
Rate: Below 60 beats per minute.
Rhythm: Regular. P wave: Normal contour and precedes each QRS complex.
P wave: round, upright
PR interval: Normal and constant.
QRS complex: Normal and constant.
Interpretation: The impulse originates in the SA node and follows the normal conduction pathways. Since the rate is below 60 beats per minute, this is a bradyarrhythmia. No medical treatment is necessary unless the rate is extremely slow and the patient becomes symptomatic (e.g., dizziness, hypotension, fainting). If treatment is necessary to increase heart rate, atropine is the drug of choice.

29. Regular
Rate 50
P wave present round upright
PRI 0.16 seconds
QRS narrow
Sinus Bradycardia

30. This is not one to worry about, as far as I know
This is not one to worry about, as far as I know. Sinus arrhythmia is when the normal sinus rate speeds up and slows down slightly, as the person breathes in and out. In 22-odd years I've never seen any physician show the slightest concern about this one. (Yes, this is a strip from a French website)

31. Sinus Tachycardia
Rhythm: regular
Rate: 130
P wave: round, upright
PR Interval 0.16 seconds
QRS: narrow

32. Regular
Rate 130
P wave round upright
PRI 0.14 seconds
QRS narrow
Sinus Tachycardia

33. Normal Sinus Rhythm
Rate: beats per minute.
Rhythm: Regular.
P wave: Normal contour and precedes each QRS complex.
PR interval: Normal and constant ( sec.).
QRS complex: Normal and constant ( sec.). The impulse originates in the SA node and travels through the AV node and ventricles in a normal fashion.
By following these steps, arrhythmias can be categorized according to their origin and mechanism. Let's evaluate the ECG strips below.

34. Sinus Bradycardia
Regular
Rate 50
P wave upright
PR 0.16 seconds
QRS Narrow

35. Sinus Arrhythmia

37. Rhythm regular
Rate 140
P wave round, upright
PR Interval0.18 seconds
QRS narrow
Sinus Tachycardia

38. Irregular
Rate 100
P wave upright rounded
PR Interval 0.12 seconds
QRS narrow
Sinus arrest (sinus pause)

39. Sinus Arrhythmia
Rate: May vary, but usually slower than normal.
Rhythm: Irregular.
P wave: Normal contour and precedes each QRS complex.
PR interval: Normal.
Interpretation: This rhythm is benign and requires no medical treatment. Phasic increases and decreases in heart rate are usually associated with inspiration and expiration, and are most noticeable during sleep.

40. Sinus Tachycardia
Rate: Above 100 beats per minute.
Rhythm: Regular.
P wave: Present and precedes each
QRS complex. In very rapid rates, the P wave may be difficult to identify if it is buried within the preceding T wave.
PR interval: Normal and constant.
QRS complex: Normal duration.
Interpretation: The impulse originates in the SA node and follows normal conduction pathways. Since the rate is above 100 beats per minute, this is a tachyarrhythmia. In most individuals, stress, excitement, or exercise increases heart rate. Problems arise when this increased rate places a burden on a damaged heart. The goal of treatment is to lower the rate using drug therapy.

41. Sinus Rhythm
Sinus Tachycardia
Sinus Arrhythmia
Sinus Arrest to Junctional Rhythm