ECG The Basics And Beyond

ANITA RALSTIN MS, FNP-BC 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). Cardiac Conduction System NORMAL ECG

One small box = .04 seconds One large box = .20 seconds

Conduction picture courtesy of New Mexico Institute Anatomy and the ECG

• 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.

Calculaon Of

• 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. The Rule Of 300

It may be easiest to memorize the following table:

# of big Rate boxes 1 300 2 150 3 100 4 75 5 60 6 50 Calculaon Of Heart Rate Queson

• Calculate the heart rate Definion of Normal

• 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 Cardiac Conduction System NORMAL ECG

Conduction picture courtesy of New Mexico Heart Institute Where Does The Impulse Come From?

Initiation Point SA Node, Atrial, Junction, Ventricles

Formation Rate Normal, Tachycardic, Bradycardic

Electrical Regularity Regular, Irregular, Irregularly irregular Impulse

Onset Passive escape, active Where/How Does The Impulse Travel?

Sinus Node SA Block

Atria Intra Atrial Block

Electrical I, II, III Impulse AV Junction

RBBB Complete, Incomplete Conduction Ventricular LBBB LAH, LPH Combined Flow Sheet

Initiation Point SA Node, Atrial, Junction, Ventricles

Formation Rate Normal, Tachycardic, Bradycardic

Regularity Regular, Irregular, Irregularly irregular

Onset Passive escape, active Electrical Impulse Sinus Node SA Block

Atria Intra Atrial Block

AV Junction I, II, III

RBBB Complete, Incomplete Conduction Ventricular LBBB LAH, LPH Sinus Rhythm

• 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

When Is The Rhythm Unstable

Four main signs • Signs of low – systolic hypotension < 90 mmHg, altered mental status • Excessive rates: <40/min or >150/min • Chest pain • • If unstable, electrical therapy: cardioversion for tachyarrhythmia, pacing for bradyarrhythmia Review Of Common Rhythms

1. Normal Sinus Rhythm

2. Review Of Common Rhythms

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4. Supraventricular

Review Of Common Rhythms

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6. 5. Review Of Common Rhythms

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8. 2nd Degree AV Block Type 1 (Wenckebach)

Cardiac Conduction System NORMAL ECG

Conduction picture courtesy of New Mexico Heart Institute Review Of Common Rhythms

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10. 8.

Cardiac Conduction System NORMAL ECG

Conduction picture courtesy of New Mexico Heart Institute Review Of Common Rhythms

9. Review Of Common Rhythms

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Review Of Common Rhythms

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12. Cardiac Conduction System NORMAL ECG

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 . • 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 , • 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

• • Hypomagnesaemia • Hypocalcemia • Hypothermia • Myocardial ischemia • Post- • 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 • • Magnesium • Hypermagnesaemia is rare but can cause condition problems and lead to 3rd degree AV block • Hypomagnesaemia may be proarrhythmic. THANK YOU

QUESTIONS?