ECG INTERPRETATION

Sinus Tachycardia

- is a heart rhythm with elevated rate of impulses originating from the sinoatrial node, defined as a rate greater than 100 beats/min (bpm) in an average adult.

Causes of Sinus Tachycardia

ExerciseAnemiaDehydration or shockFever/sepsis/infectionHypoxiaChronic pulmonary disease

HyperthyroidismPheochromocytomaMedications/stimulantsCongestive heart failurePulmonary embolus

1. What is the heart rate?

Rhythm Strip Quiz

2. Conditions that lead to this type of heart rate include:a) Increased vagal toneb) Stress, fear, and anxietyc) Rapid firing of the atriad) A pacemaker that arises outside the SA node

125 bpm

Sinus Bradycardia

- is a heart rhythm that originates from the sinus node and has a rate of under 60 beats per minute.

The quickest way of assessing the heart rate of this dysrhythmia is the 6 second x 10 method.

Normal P, QRS, T wave

Causes of sinus bradycardia include:

-AV blocking medications (beta-blockers, calcium channel blockers, digoxin).- Heightened vagal tone (i.e. well trained athlete)- Sick sinus syndrome- Hypothyroidism- Hypothermia- Obstructive sleep apnea- Hypoglycemia

Contraindications :

A- AdenosineB- Beta- blockersC – Calcium Channel BlockersD - Digoxin

- refers to a changing sinus node rate with the repiratory cycle (inspiration and expiration).

-This is quite common in young, healthy individuals and has no clinical significance. The heart rate increases with inspiration (due to the Bainbridge reflex) and decreases with expiration.

Sinus arrhythmia

- Normal sinus P waves (upright in leads I and II) with a constant morphology

- P-R interval is constant (no evidence of AV block).

Characteristics :

- The P-P interval gradually lengthens and shortens in a cyclical fashion, usually corresponding to the phases of the respiratory cycle

Sinus arrhythmia

Sinoatrial exit block

- occurs when the action potential initiated by the sinoatrial node (SA node) is inhibited or completely blocked before it is able to leave the SA node and reach the atrium, thus no P wave will appear on the ECG.

Sinoatrial exit block

A Premature Atrial Contraction (PAC)

1. They are premature. That is they occur earlier than you would expect if you were to measure the previous P to P intervals. A premature beat arising from an ectopic focus within the atria. There is an abnormal P wave, usually followed by a normal QRS complex.

2. They are ectopic. Meaning originating outside of the SA node. Thus the P wave morphology would be different than the normal sinus P wave.

Causes of PAC’s - Anxiety.- Sympathomimetics.- Beta-agonists.- Excess caffeine.- Hypokalaemia.- Hypomagnesaemia- Digoxin toxicity- Myocardial ischaemia

Premature Atrial Contractions

Patterns: PACs often occur in repeating patterns:

Bigeminy — every other beat is a PAC.Trigeminy — every third beat is a PAC.Quadrigeminy — every fourth beat is a PAC.Couplet – two consecutive PACs.Triplet — three consecutive PACs.

Atrial Bigemany (PAC)

Atrial fibrillation (AF)

is the most common chronic arrhythmia and is characterized by erratic atrial electrical activity with atrial rates of 400-600 beats per minute.

The P wave is absent on the surface electrocardiogram which can at times be replaced with “fibrillatory waves”

Atrial fibrillation (AF)

Red arrow – indicates Fibrillatory wavesPurple arrow – Indicates normal P wave/ ECG

Atrial fibrillation (AF)

Cause of atrial fibrillationP - Pulmonary embolus, pulmonary disease, post- operative, pericarditisI -Ischemic heart disease, idiopathic (“lone atrial fibrillation”), intravenous central line (in right atrium)R - Rheumatic valvular disease (specifically mitral stenosis or mitral regurgitation)A - Anemia, alcohol (“holiday heart”), advanced age, autonomic tone (vagally mediated atrial fibrillation)T - Thyroid disease (hyperthyroidism)E - E levated blood pressure (hypertension), S - Sleep apnea, sepsis, surgery