RHYTHM STUDY GUIDE

Normal Sinus Rhythm:


Looking at the ECG you'll see that:


• Rhythm - Regular
• Rate - (60-100 bpm)
• P Wave - Visible before each QRS complex, small and rounded
• P-R Interval - Normal (5 small squares or less/ 0.20 seconds or less****Anything above
and this would indicate some type of AV-Block)
• QRS shape/duration – Normal measuring 0.12 seconds or less (3 small squares or less)
• Indicates that the electrical signal is generated by the sinus node and travelling in a
normal fashion in the heart.
• Patient response- Hemodynamically stable




SA node rhythms




Sinus Tachycardia


• Rhythm - Regular
• Rate - More than 100 beats per minute (100-150 beats)
• P wave- visible before each QRS complex, small and rounded

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,• P-R Interval - Normal (5 small squares or less/ 0.20 seconds or less****Anything above and
this would indicate some type of AV-Block)
• QRS shape/duration- Normal measuring 0.12 seconds or less (3 small squares or less)
• Indicates that an electrical signal is generated by the sinus node at a faster than normal
rate/pace, however, it still travels in a normal fashion through the heart.
• Causes include hyperthyroidism, hypovolemia, heart failure, anemia, exercise, fever, use of
stimulants, or sympathetic response to fear, pain, or anxiety.
• Treatment- The rhythm itself is usually not treated, but the cause is identified and treated
accordingly. For example, pain medications may be administered to treat sinus tach related
to patient’s pain response.
• Patient response- The fast rhythm may cause a decrease in cardiac output because of shorter
filling time for the ventricles. Patient’s with ischemic heart disease may be at greater risk for
complications.




Sinus Bradycardia

• Rhythm - Regular
• Rate - less than 60 beats per minute
• P wave- visible before each QRS complex, small and rounded
• P-R interval Normal (5 small squares or less/ 0.20 seconds or less****Anything above
and this would indicate some type of AV-Block)
• QRS duration/shape-Normal measuring 0.12 seconds or less (3 small squares or less)
• Indicates that an electrical impulse generated by the sinus node at a slower than normal
rate/pace, however, it still travels in a normal fashion through the heart. Usually benign
and often caused by patients on beta blockers.
• Causes include Can also be caused by vagal response, certain medications/drugs,
hypoglycemia, athletes (normal), disease of the sinus node, increased intracranial

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, pressure, hypoxemia, hypothermia and hypotension/decreased organ perfusion in non-
compensatory shock states.
• Treatment required only if patient is symptomatic. May give Atropine (unless caused by
hypothermia), may need to pace the heart, may give epinephrine. Continue to assess for
hemodynamic stability.
• Patient response will vary. Some patients tolerate well. If patient shows s/sx of decreased
cardiac output due to low heart rate treat cause.




Sinus Arrhythmia Looking at the ECG you’ll see that:


• Rhythm – Slightly irregular; cyclically irregular. Rate usually increase with inspiration and
decreases with expiration. The rhythm will be regular with inspiration/regular with
expiration and will create a pattern of irregularity that can be seen with the patient’s
breathing pattern.
• Rate - (60-100 bpm)
• P Wave - Visible before each QRS complex, small and rounded
• P-R Interval - Normal (5 small Squares or les/ 0.20 seconds or less.
• QRS duration/shape – Normal measuring 0.12 seconds or less (3 small squares or less)
• Cause unknown; benign
• Treatment is usually not required.
• Patient is hemodynamically stable




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