A N I TA R A L S T I N M S , F N P - B C
ECGTheBasicsAndBeyond
I have no conflicts of interest.
Pearls
• Treat the patient not the paper. • Electrical activity triggers mechanical activity. No
electrical activity = no mechanical activity • But electrical activity does not guarantee
mechanical activity. • The more cells involved the larger the deflection on
the ECG. • If the wave of electrical activity is moving toward
the electrode, the wave will be positive (above the baseline); if the wave is moving away from the electrode the wave will be negative (below the baseline).
NORMAL ECG Cardiac Conduction System
Conduction picture courtesy of New Mexico Heart Institute
One small box = .04 seconds One large box = .20 seconds
AnatomyandtheECG
• The P wave = atrial activation (SA node to AV node).
• The PR interval = onset of atrial activation to onset of ventricular activation.
• The QRS complex = electrical ventricular activation.
• The ST-T segment = ventricular repolarization.
• The QT interval = the duration of ventricular activation and recovery.
Calcula8onOfHeartRate
• Method 1: Count the number of large (0.2-second) time boxes between two successive R waves, and divide the constant 300 by this number OR divide the constant 1500 by the number of small (0.04-second) time boxes between two successive R waves.
• Method 2 best for irregular rhythms: Count the number of cardiac cycles that occur every 6 seconds, and multiply this number by 10.
TheRuleOf300
It may be easiest to memorize the following table:
# of big boxes
Rate
1 300
2 150
3 100
4 75
5 60
6 50
Calcula&onOfHeartRate
Ques&on
• Calculate the heart rate
Defini8onofNormalSinusRhythm
• Heart rate • 60-100 Adult • 80-160 Infant • 80-130 Toddler • 75-115 6 year old
• Regular rhythm • P waves round, same shape and before each QRS • Normal PR interval (0.12-0.20 sec or 3-5 small boxes) • Normal QRS interval (< 0.12 sec or < 3 small boxes) • QRS positive in leads I, II, aVF, V3-V6
NORMAL ECG Cardiac Conduction System
Conduction picture courtesy of New Mexico Heart Institute
WhereDoesTheImpulseComeFrom?
Electrical Impulse
Formation
Initiation Point
Rate
Regularity
Onset
SA Node, Atrial, Junction, Ventricles
Normal, Tachycardic, Bradycardic
Regular, Irregular, Irregularly irregular
Passive escape, active
Where/HowDoesTheImpulseTravel?
I, II, III
RBBB
Electrical Impulse
Conduction
Sinus Node
Atria
AV Junction
Ventricular
SA Block
Intra Atrial Block
LBBB
LAH, LPH
Complete, Incomplete
CombinedFlowSheet
I, II, III
RBBB Conduction
Sinus Node
Atria
AV Junction
Ventricular
SA Block
Intra Atrial Block
LBBB
LAH, LPH
Complete, Incomplete
Electrical Impulse
Formation
Initiation Point
Rate
Regularity
Onset
SA Node, Atrial, Junction, Ventricles
Normal, Tachycardic, Bradycardic
Regular, Irregular, Irregularly irregular
Passive escape, active
SinusRhythm
• The P wave is upright in leads I and II • Each P wave is usually followed by a Q • The heart rate is 60--100 beats/min
WhenIsTheRhythmUnstable
Four main signs • Signs of low cardiac output – systolic hypotension
< 90 mmHg, altered mental status • Excessive rates: <40/min or >150/min • Chest pain • Heart failure
• If unstable, electrical therapy: cardioversion for tachyarrhythmia, pacing for bradyarrhythmia
ReviewOfCommonRhythms
1. Normal Sinus Rhythm 2.
ReviewOfCommonRhythms
3. 4. Supraventricular Tachycardia
ReviewOfCommonRhythms 4. 6. Atrial Flutter 5.
ReviewOfCommonRhythms 6. 8. 2nd Degree AV Block Type 1 (Wenckebach)
NORMAL ECG Cardiac Conduction System
Conduction picture courtesy of New Mexico Heart Institute
ReviewOfCommonRhythms 7. 10. 8.
NORMAL ECG Cardiac Conduction System
Conduction picture courtesy of New Mexico Heart Institute
ReviewOfCommonRhythms
9.
ReviewOfCommonRhythms
10.
ReviewOfCommonRhythms 11. 12.
NORMAL ECG Cardiac Conduction System
Conduction picture courtesy of New Mexico Heart Institute
LONG QT
• The QT interval is from the start of the Q wave to the end of the T wave.
• Represents ventricular depolarization and repolarization (electrical) and ventricular contraction and relaxation (mechanical)
• QT changes with heart rate
LONG QT
• Abnormally prolonged QT increases the risk of ventricular arrhythmias, torsades de pointes
• QT can be measured and calculated; it is reported on the ECG. • There are multiple QT calculator apps
• QT will be affected by abnormal ventricular conduction.
• QTc is prolonged if > 440ms in men and > 460 ms in women
• QTc > 500 is associated with increased risk of torsades de pointes
CAUSES OF PROLONGED QT
• Hypokalemia • Hypomagnesaemia • Hypocalcemia • Hypothermia • Myocardial ischemia • Post-cardiac arrest • Increased intracranial pressure • Congenital long QT syndrome • DRUGS!!!
QT PROLONGING DRUGS
• Crediblemeds.org • Antiarrhythmic medications • PPIs • Antidepressants, many • Antibiotics and antifungals, many
• List included in handouts.
ELECTROLYTE AND ECG
• Potassium • Hyperkalemia 6.0 mmol/L or higher
• Pointed T waves in the V leads • ST elevation in V1-V3 • QRS widens at higher K+ levels
ELECTROLYTE AND ECG
• Potassium • Hypokalemia
• T waves widen and lower amplitude
• ST segment depression • T wave inversion • U wave
• Magnesium • Hypermagnesaemia is
rare but can cause condition problems and lead to 3rd degree AV block
• Hypomagnesaemia may be proarrhythmic.
THANKYOUQUEST IONS?