ECGs Flashcards
Arrhythmias (dysarrhythmia)
Abnormal cardiac rhythm
*Prompt assessment of abnormal cardiac rhythm and patients response is critical
12 - Lead ECG
Looks at 12 areas in the heart Anterior Lateral sides Septum NOT posterior or right ventricle
P
Atrium depolarization ( SA node fires causing atrium to contract) if patient has a P wave they are in sinus rhythm
PR interval
- What does it measure
- What is the normal PR interval
- What is the PR interval represent
- Measures from the beginning of the P wave to the beginning of the of the QRS complex.
- Normal PR interval is 0.12-0.20 (5 small squares)
- The PR interval represents atrial depolarization
QRS Complex
- What does it measure
- What is the normal QRS complex
- What is the QRS complex represent
- Measure this complex from the beginning of the Q wave until the end of the S wave.
- The normal QRS complex is 0.04-0.10 seconds (2 1/2 small squares)
- The QRS complex represents ventricular depolarization…… Atrium repolarization
NB: Remember that not all QRS complexes contain all the QRS waves! Q-first deflection is negative R- Postive deflection after a Q wave S- Negative deflection after an R wave
T wave
Repolarization of ventricles (relax and resting)
QT interval
- Where to measure it
- What does it measure?
- Normal?
- Prolonged QT interval means?
- Beginning of QRS till the end of the T wave
- Measures the length of the time it takes for the ventricle to contract and relax
- Normal QT interval: 0.35-0.45 seconds
- Can lead to life-threatening arrythmias ( low magnesium (alcohol can lower))
ST segment
- below the isoelectric line
- Above the isoelectric line
Place a ruler under the PR interval
1** If the bottom part of the ST segment line is more than one small square (1mm) below the PR interval, then the patient is having myocardial ischemia
2** If the bottom part of the ST segment is more than small square(1mm) above the PR interval, then the patient is probably having a MI
Small square seconds
0.04 second
Large square seconds
0.02 seconds
Number of large squares in a 6-second strip
30
Phases of Cardiac Action Potential
phase 0: Upstroke or rapid depolarization and corresponds with ventricular contraction
: Initial impulse
Phase 1,2,3 Repolarization
1: Overshot
2: plato (little change) opening of the Ca channels helps to sustain contraction… CCB work here
If someone has a low EF (
If the rhythm is regular 2 methods to estimate HR
1.
2.
- Count the number of QRS complexes in a 6 strip x 10
- Count number of small squares between two R waves and divide into 1500.
Count number of large squares between two R waves and divide into 300
Steps in assessing the Cardiac Rhythm
Steps 1-7
Step 1: Heart rhythm (regular vs irregular) P-P/ R-R intervals identical Step 2. Heart Rate Step 3. P waves Step 4. PR interval Step 5. QRS Complex Step 6. ST Segment Step 7. T wave
Normal Sinus rhythm ECG characteristics
Rate: 60-100 bpm P present P waves precede every QRS complex P-R ratio is 1:1 Causes: normal Tx: always be sure your patient has a pulse
The absolute refractory period
occurs when excitability is zero and the heart tissue cannot be stimulated. Nothing is strong enough to elicit another contraction
Beginning of the QRS complex till middle of the T wave
The relative refractory period
Heart is almost back to normal but is still unstable
Occurs from the middle of the T wave till the end.
If a strong enough impulse hits this area can cause life-threatening arrythmias… R on T phenomenon
ST- elevation
MI coronary artery is occluded
ST- depression
Ischemia or non stemi MI
Partically goes through whole ventricle
Deep and wide q waves (had a previous MI) St will go back to normal
Sinus Bradycardia
Rate: less than 60
P present
P waves precedes each QRS complex
P-R ratio is 1:1
Causes of Sinus Bradycardia
2.S/S
Carotid sinus massage Hypothermia Increased vagal tone Administration of parasympathomimetic drugs *Hypothyroidism * increased ICP *Obstructive jaundice * Inferior wall MI 2. Pale, cool skin, hypotension, weakness,angina,dizziness or syncope, confusion,or disorientation, SOB
Sinus Bradycardia TX
Asymptomatic and hemodynamically stable:NONE
Symptomatic: ATROPINE
Temporary pacing
Dopamine/Epinephrine infusion
Sinus Tachycardia
Rate: >100/min
P present
P waves precedes every QRS
P-R ratio 1:1
Sinus Tachycardia Causes
- S/S
Exertion Anxiety Fever Anemia Stimulants Hyperthyroidism pain Drugs 2. S/S: Dizziness, dyspnea, hypotension, angina
Sinus Tachycardia TX
Determined by underlying causes
- B-adrenergic blockers to reduce HR and myocardial oxygen consumption
(Gold Standard in HF and ST elevation MI)
Supraventricular Tachycardia/ Narrow complex tachycardia (normal QRS)
Arrhythmias originating in an Ectopic pacemaker site in the atria (not SA node)
Involves enhance automaticity of arterial tissue or conduction of the Ectopic impulse
Rhythm is regular
Ventricular response is greater than 150/min and generally less than 200/min
No P wave
NO PR interval
QRS complex: 0.04-0.10
(If normal QRS -ectopic foci is in atrium