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?