Analyzing a Rhythm
Component
Characteristic
Rate
•
•
•
•
The bpm is commonly the ventricular rate.
Normal: 60–100 bpm
Slow (bradycardia): <60 bpm
Fast (tachycardia): >100 bpm
Regularity
•
•
•
•
Measure R-R intervals and P-P intervals.
Regular: Intervals consistent
Regularly irregular: Repeating irregular pattern
Irregular: No pattern
P Waves
•
•
•
•
Same in size, shape, position
Precedes each QRS
Upright (positive), uniform, rounded
Absent: Rhythm is junctional or ventricular.
PR Interval
• Constant: Intervals are the same.
• Variable: Intervals differ
• Normal: 0.12–0.20 sec and constant
QRS
Interval
• Normal: 0.04–0.12 sec
• Wide: >0.12 sec
QT Interval
• Beginning of R wave to end of T wave
• Varies with HR.
• Normal: 0.36 - 0.44 seconds
Method 3: Six-Second ECG Rhythm Strip
The best method for measuring irregular rates with varying R-R intervals is
to count the number of R waves in a 6-sec strip and multiply by 10. This
gives the average number of bpm.
Using 6-sec ECG rhythm strip to calculate heart rate.
Formula: 7 × 10 = 70 bpm
 If a rhythm is extremely irregular, it is best to count the number of RR intervals per 60 sec (1 min).
Jones, MS ed, MHA, EMT-P, Shirley A. ECG Notes Interpretation and Management Guide. Philadelphia: FA Davis Company, 2005.
Normal ECG Criteria
Rate
Atrial and ventricular rates are the same.
Adults - 60 to 100 cycles/min
Rhythm
Regular
P Wave
Precedes the QRS
Shape
Uniformly rounded and upright without peaking or
notches
Size
Amplitude 2.0 - 3.0 mm
Duration of 0.06 - 0.12 seconds
Deflection
Upright in leads I, II, aVF, V2 through V6;
Inverted in aVR; may be flat, inverted
Biphasic in leads III, V1, and V2
PR Interval
Adults – Consistent 0.12 - 0.20 second
QRS
Follows the P wave
QRS interval is 0.06 - 0.10 second
Q Wave
Duration is <0.03 second
Depth is 1-2 mm in leads I, aVL, V5, and V6
Deep QR or QS in aVR and possibly in lead III
QT Interval
<0.42 second (men)
<0.43 second (women)
ST Segment
Follows isoelectric line
Slight curve at proximal portion of the T wave
Not depressed more than 1 mm
T Wave
Asymmetric and slightly rounded, without sharp
points or large notches
Deflection
Should be in the same direction as QRS;
Upright in leads I, II, aVF, V4 through V6;
Inverted in aVR;
Varied in all other leads
Sinus Bradycardia
Rate
P wave
QRS
Conduction
Rhythm
40-59 bpm
Sinus
Normal (.06-.10)
P-R normal or slightly prolonged at
slower rates
Regular or slightly irregular
This rhythm is often seen as a normal variation in athletes, during sleep, or in
response to a vagal maneuver.
Common causes:






Inferior wall MI
Hyperkalemia
Increase intracranial pressure
Hypothermia
Myocardial ischemia
Cardiac medication; Beta blockers, calcium channel blockers,
antiarrhythmics
Asymptomatic patient needs no treatment
Interventions include:
 Stopping medications that suppress the SA node; digoxin, beta blockers,
calcium channel blockers
 Identify the precipitating cause
 Medication; atropine, epinephrine, and dopamine
 Temporary or permanent pacing
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 http://www.rnceus.com.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams & Wilkins, 2007.
Sinus Tachycardia
Rate
P wave
QRS
Conduction
Rhythm
101-160/min
Sinus
Normal
Normal
Regular or slightly
irregular
The clinical significance of this arrhythmia depends on the underlying cause.
It may be normal.
Common causes:







Increased circulating catecholamine’s
CHF
Hypoxia
Pulmonary embolism
Increased temperature
Stress
Response to pain
Asymptomatic patient needs no treatment
Interventions include:
 Treatment of underlying cause
 Beta blockers
 Calcium channel blockers
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 <http://www.rnceus.com>.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams &
Wilkins, 2007.
Premature Atrial Contractions
Rate
P wave
QRS
Conduction
Rhythm
Irregular atrial and ventricular rates
Usually have a different morphology than sinus P
waves because they originate from an ectopic
pacemaker
Normal
Normal, however the ectopic beats may have a
different P-R interval.
Irregular - PAC’s occurring early in the cycle and
they usually do not have a complete compensatory
pause.
PAC's occur normally in a non diseased heart.
Common causes:







Coronary or valvular heart disease
Acute respiratory failure
Pulmonary disease
Electrolyte imbalances
Fever
Infectious diseases
Anxiety
Interventions include:
 Patient who are asymptomatic don’t need treatment
 Finding the underlying cause; fever, anxiety
 Digoxin, procainamide and quinidine
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 <http://www.rnceus.com>.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams & Wilkins, 2007.
Atrial Flutter
Rate
P wave
QRS
Conduction
Rhythm
Atrial 250-350/min; Ventricular conduction depends on the
capability of the AV junction (usually rate of 150-175
bpm).
Not present; usually a "saw tooth" pattern is present.
Normal
2:1 or 4:1 Atrial to Ventricular
Usually regular, but can be irregular if the AV block varies.
Common causes:





Mitral valve disease
Hyperthyroidism
Pericardial disease
Acute MI
After cardiac surgery
The treatment depends on the level of hemodynamic compromise. The
arrhythmia becomes more dangerous as the rate increases.
Interventions include:


Synchronized cardioversion is the treatment of choice.
Otherwise, antiarrhythmics, digoxin and calcium channel blockers.
Be alert for s/s of low cardiac output!
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 <http://www.rnceus.com>.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams & Wilkins, 2007.
Atrial Fibrillation
Rate
P wave
QRS
Conduction
Rhythm
Atrial rate: 400 bpm or greater; Ventricular: fast or
slow
Not present; wavy baseline is seen instead.
Normal
Variable AV conduction; if untreated the
ventricular response is usually rapid.
Irregularly irregular. (This is the hallmark of
this dysrhythmia).
Atrial fibrillation may occur suddenly, but it often becomes chronic.
Common causes:







Cardiac surgery
Mitral regurgitation
Mitral stenosis
Hyperthyroidism
Coronary artery disease
Acute MI
Pericarditis
Interventions include:


Digoxin, diltiazem, or other anti-dysrhythmic medications to control
the AV conduction rate and assist with conversion back to normal
sinus rhythm.
Cardioversion may also be necessary to terminate this rhythm.
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 <http://www.rnceus.com>.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams & Wilkins, 2007.
Paroxysmal Supraventricular Tachycardia
Atrial 160-250/min: Conducts to ventricles 1:1 unless
a block is present.
P wave
Abnormal, possibly hidden in previous T wave
Normal (unless associated with aberrant ventricular
QRS
conduction).
P-R interval depends on the status of AV conduction
Conduction tissue and atrial rate: May be normal, abnormal, or
not measurable.
Rate
Paroxysmal Supraventricular Tachycardia (PSVT) may occur in the normal
as well as diseased heart.
Common causes:







Stimulants
Electrolyte imbalances
Acute MI
Cardiomyopathy
Congenital anomalies
Valvular heart disease
Wolfe-Parkinson-White syndrome
This rhythm is often transient and usually requires no treatment.
Interventions include:
 Vagal maneuvers
 Digoxin, antiarrhythmics, adenosine
 Cardioversion
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 <http://www.rnceus.com>.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams & Wilkins, 2007.
Ventricular Tachycardia
Rate
P wave
QRS
Conduction
Rhythm
Usually between 100 to 220/bpm, but can be
as rapid as 250/bpm
Obscured if present and are unrelated to the
QRS complexes.
Wide and bizarre morphology
Same as with PVCs
Three or more ventricular beats in a row;
may be regular or irregular.
Ventricular tachycardia almost always occurs in diseased hearts.
Patients usually have symptoms with this dysrhythmia.
Ventricular tachycardia can quickly deteriorate into ventricular fibrillation
and sudden cardiac death.
Some common causes are:






Coronary artery disease
Acute MI
Drug intoxication from digoxin, procainamide, or cocaine
CHF
Valvular heart disease
Electrolyte imbalance such as Hypokalemia
Interventions include:


Immediate defibrillation and ACLS protocols.
Identification and treatment of the underlying cause is also needed.
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 <http://www.rnceus.com>.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams & Wilkins, 2007.
Ventricular Fibrillation
Rate
P wave
QRS
Conduction
Rhythm
Unattainable
May be present, but obscured by
ventricular waves
Not apparent
Chaotic electrical activity
Chaotic electrical activity
This arrhythmia results in the absence of cardiac output and sudden cardiac
death.
Common causes:







Myocardial ischemia
MI
Untreated ventricular tachycardia
Heart disease
Acid-base imbalance
Severe hypothermia
Electrolyte imbalances; hypokalemia, hyperkalemia, hypercalcemia
Intervention includes:


Immediate defibrillation and ACLS protocols.
Identification and treatment of the underlying cause is also needed.
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 <http://www.rnceus.com>.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams & Wilkins, 2007.
Asystole/Ventricular Standstill
Rate
P wave
QRS
Conduction
Rhythm
None
May be seen, but there is no
ventricular response
None
None
None
Asystole is ventricular standstill.
The patient is completely unresponsive, with no electrical activity in the
heart and no cardiac output.
Interventions include:





Identify the cause
CPR, 100% oxygen,
IV
Intubation
Epinephrine 1.0 mg., IV push, q3-5 minutes
Posey, RN, MSN, Andrea D. "Interactive Online Continuing Education for Nurse Professionals.Feb. 2009 http://www.rnceus.com.
Springhouse. ECG Interpretation Made Incredibly Easy! Philadelphia: Lippincott Williams & Wilkins, 2007.