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ECG - Interpreting
RT EGANS Repository, Module 17: Interpreting the Electrocardiogram
Question | Answer |
---|---|
Normal Sinus Rhythm | •Heart rate: between 60 and 100 beats/min•PR interval: 0.12–0.20 s•QRS complex: <0.12 s•T wave: upright•ST segment: flat•R to R interval: regular (varying less than 0.12 s between QRS complexes) |
Sinus Tachycardia | one abnormality—an elevated heart rate.•Heart rate: >100 beats/min•PR interval: 0.12–0.20 s•QRS complex: <0.12 s•T wave: upright•ST segment: flat•R to R interval: regular (varying less than 0.12 s between QRS complexes) |
Sinus Bradycardia | one abnormality—a decreased heart rate.•Heart rate: < 60 beats/min•PR interval: 0.12–0.20 s•QRS complex: <0.12 s•T wave: upright•ST segment: flat•R to R interval: regular (varying less than 0.12 s between QRS complexes) |
Sinus Dysrhythmia | A sinus dysrhythmia has an irregular R to R interval. The heart is usually normal but may result in a sinus bradydysrhythmia (too slow) or sinus tachydysrhythmia (too fast).•Heart rate: may be normal, slow, or fast•PR interval: 0.12–0.20 s•QRS com |
Dyrhythmia - Sinus tachycardia | Anxiety, pain, fever, hypovolemia, hypoxemia; also side effect of bronchodilator medication |
Dyrhythmia - Sinus bradycardia | Hypothermia and abnormalities in SA node |
Dyrhythmia - Sinus arrhythmia | Varies with breathing (increased rate during inspiration, decreased rate during expiration)—more pronounced with lung disease; associated with inferior wall myocardial infarction and increased intracranial pressure; also affected by medications. |
In heart block, there is a problem with conduction between the SA node and the AV node. The width of the QRS complex provides information about the location of the ventricular pacemaker | •A normal QRS interval (<0.12 s) indicates pacing from the AV junction—a junctional ectopic beat.•A wide QRS interval (>0.12 s) indicates pacing from cells in the ventricles—a ventricular ectopic beat; ventricular beats normally produce slower heart rate |
First-Degree Heart Block | •Heart rate: usually between 60 and 100 beats/min•PR interval: >0.20 s, but constant•QRS complex: <0.12 s•T wave: upright•ST segment: flat•R to R interval: regular (varying less than 0.12 s between QRS complexes |
Second-Degree Heart Block Type I | •Heart rate:irregular, usually between 60 and 100 beats/min•PR interval:the PR interval gradually gets longer after each beat until a P wave is not conducted to the ventricles (no QRS complex)•QRS complex:<0.12 s•T wave:upright•ST segment:flat•R2R:Irreg |
Second-Degree Heart Block Type II | •Heart rate: irregular and lower than normal•PR interval: normal or slightly prolonged•QRS complex: <0.12 s if block at bundle of His, wider complex if block below the bundle of His•T wave: upright•ST segment: flat•R to R interval: irregular |
Third-Degree Block | •Heart rate: irregular and lower than normal•PR interval: variable•QRS complex: <0.12 s if block at bundle of His, wider complex if block below the bundle of His•T wave: upright•ST segment: flat•R to R interval: regular |
Causes of Heart Blocks - First-degree | Inferior wall MI, complication of medications such as digoxin or beta-blockers |
Causes of Heart Blocks - Second-degree type I | Abnormality in AV junction, ischemia to right coronary artery |
Causes of Heart Blocks - Second-degree type I | Left coronary artery ischemia or anterior wall MI |
Causes of Heart Blocks - Third-degree | Acute MI (more common with inferior and posterior wall MI), drug toxicity (digitalis) |