1) ECGs Flashcards
P wave
- Atrial depolarization
- Impulse slows as it passes through AV node from atria to ventricles
- Allows atria time to finish filling ventricles
P-R segment
- P-R interval includes the p wave
- Impulse then rapidly travels through His-Purkinje system
- Seen as a flat line following P wave
QRS complex
- Ventricular depolarization
- Depolarization of septum and ventricular walls generates QRS complex and contraction of ventricles
T wave
- Repolarization of ventricles
- Represented on ECG by ST segment and T wave
Typical approach to reading a 12 lead ECG
- Rate
- Rhythm (P, QRS, and PR intervals)
- Axis
- Hypertrophy/Enlargement
- Ischemia
- Others: QT interval, T waves, bundle branch blocks etc.
300, 150, 100, 75, 60, 50 method
- If the second R wave does not fall on a bold line the heart rate is approximated
- Example: if it falls between the 4th and 5th bold line the heart rate is between 60 and 75 BPM
12 lead rhythm check
- “Rhythm strips” are usually Lead II or V5
- They are often run at the bottom of a 12 lead EKG
- Telemetry also provides rhythm strips
Normal sinus rhythm
- 60 to 100 BPM
- P for every QRS, QRS for every P
- Normal PR < 1 big box
- Normal P waves: symmetric, <2.5 small boxes
- Narrow QRS complexes
Narrow QRS complex in normal sinus rhythm
- Less than 0.12 seconds (120ms)=
- Less than 3 small boxes
Sinus bradycardia ECG
- Like NSR, < 60 BPM
Sinus tachycardia ECG
- Like NSR, > 100 BPM, arises from SA node
- P for every QRS, QRS for every P
- Normal PR < 1 big box
- Normal P waves- symmetric, <2.5 small boxes
- Narrow QRS complexes
Atrial flutter
- Atrial rate 250 to 350
- Many P waves in a sawtooth appearance
- QRS complexes (ventricular conduction) could be fast or slow- usually narrow
Atrial fibrillation
- Atrial rate > 350 so P waves may be indiscernible
- Ventricular rate could be fast or slow, usually narrow QRS complexes, almost always irregularly irregular
A fib can cause irregularly irregular ventricular rates
- Ventricular rates can be rapid or “controlled”
- AF with RVR, AF with controlled VR
- Can be paroxysmal - PAF
- Can cause clots to form in atria
If AF with RVR or PAF with RVR, patient may experience
- Palpitations
- SOB
- Dizziness
AF is diagnosed with
- EKG
- Holter monitor
AF is treated with
- Anticoagulation to prevent CVA (direct oral anticoagulant like dabigatran or Warfarin with INR 2-3)
- PLUS rate control (controls Vent rate)
AF my also be treated with restoration of normal sinus rhythm
- Radiofrequency or Cryo-ablation of reentry tract by electrophysiologist with cardiac cath
- Rhythm control with antiarrhythmic medications
- Cardioversion
Supraventricular tachyarrythmias
- General term not used if you know the more specific cause of the tachycardia
- All tachyarrhythmias that originate above the bundle of His technically could be called SVT
SVT characteristics
- Atrial rate must be >150 (V rate may be less if AV block)
- Narrow QRS (unless BBB or accessory pathway, “aberrant conduction”)
- May be acute or chronic
- Slowing down the rate may allow visualization of P waves
- No discernible P waves
Supraventricular tachyarrhythmias include many narrow complex arrhythmias like
- Paroxysmal supraventricular tachycardia (PSVT)
- AV reentrant tachycardia (AVRNT)
- Atrial tachycardia (with buried P waves. If P waves are visible must specify atrial tachycardia rate >150)
- Atrial fibrillation and flutter that are tachycardic (with rapid ventricular response)
- Multifocal atrial tachycardia (MAT)
Ventricular dysrhythmias key features
- Wide (> 0.12 seconds in duration), 3 small boxes bizarre QRS complexes
- T waves in the opposite direction of the R wave
- Absence of P waves
Ventricular rhythms
- PVC - “Premature beats”
- Ventricular escape (idioventricular) 20-40
- Accelerated Ventricular rhythm 40-100
- Ventricular Tachycardia 100-250 (Torsades de Pointes is a special VT)
- Ventricular Fibrillation 300-500, chaotic
Torsades de Pointes VT
- Polymorphic VT that twists on itself like a ribbon
- Can result from long QT syndrome
Long QT interval
- Predisposes patients to Torsades de Pointes
- The prolonged interval between ventricular depolarization and repolarization
- Congenital is rare
- Acquired, including drug-induced, electrolyte imbalances is common cause
Long QT interval symptoms
- Palpitations
- Presyncope
- Syncope
- Sudden death
Common causes of increased QT interval
- Hypocalcemia
- Hypokalemia
- Hypomagnesemia
- Quinidine
- Sotalol
- Amiodarone
- Antineoplastics
- Antipsychotics
QT calculation
- By machine
- QT/square root of cycle
Ventricular fibrillation is so chaotic there is
- No cardiac output
MI progression
- Ischemia
- Injury
- Infarction
Changes in MI progression
- T wave changes
- Acute MI, STEMI (ST elevation MI)
- Acute Q-wave MI
- Old MI
Myocardial ischemia characteristic signs
- T wave changes
- Inverted T wave
- Tall, peaked T wave
- Depressed ST segment
Testing for ST changes
- Stress test (rest vs. walk)
- Look for ST depressions
ECG tombstoning
- J point for ST elevation
Pathologic Q waves
- Indicate presence of irreversible myocardial damage or myocardial infarction
MI locations in heart/EKG
- Anterior- V1-4 or 6
- Lateral I, AVL, and/or V5, V6
- Inferior II, III, AVF
- Posterior is different- large R and ST depression in V1 and V23 “reverse anterior”
EKG lead-heart locations
- Lateral = I, aVL, V
- Inferior = II, III, aVF
- Left main = aVR
- Septal = V1, V2
- Anterior = V3, V4
Inferior MI lead
- Facing = II, III, aVF
- Reciprocal = I, aVL
High lateral MI lead
- Facing = I, aVL
- Reciprocal = II, III, aVF
Anterior MI lead
- Facing = V1, V2, V3, V4
- Reciprocal = NONE
Posterior MI lead
- Facing = NONE
- Reciprocal = V1, V2, V3, V4
Most change seen in EKG with MI
- ST elevations are more concerning than ST depressions
Anterior myocardial infarction
- Involves anterior surface of LV
- Best identified in leads V1, V2, V3, and V4
Lateral myocardial infarction
- Involves left lateral heart wall
- ST segment elevation, T wave inversion, and the development of pathologic Q waves in leads I, aVL, V5,V6
Inferior myocardial infarction
- Involves inferior surface of the heart
- ST segment elevation, T wave inversion, and development of pathologic Q waves in leads II, III, aVF
Posterior myocardial infarction
- Involve posterior surface of the heart
- Look for reciprocal changes in leads V1 and V2
Posterior STEMI
- Large R in V1 or V2 (like RVH)
- ST depression in V1
- Basically, ST depression in V1 or V2 primarily should give you suspicion for acute posterior MI
- Although usually ST depression indicates ischemia, in these leads it may indicate posterior infarction
Pericarditis symptoms
- Chest pain is sudden onset, sharp, retrosternal
- Pain relieved by leaning forward
- Fever, myalgia
- Pericardial friction rub indicates pericarditis
- EKG changes are diffuse, across most leads
ECG changes in pericarditis
- T wave initially upright and elevated but then during recovery phase it inverts
- ST segment elevated and usually flat or concave
ECG findings that warrant cancellation of elective surgery
- Acute axis deviation
- New bundle branch block
- Acute ST-segment elevation (STEMI or Pericarditis)
- Acute ST-segment depression (myocardial ischemia or subendocardial injury
- Type II second degree atrioventricular block or third degree atrioventricular block
- Tall peaked T waves (hyperkalemia)
- Prolonged of the corrected QT (QTc) interval (hypokalemia, hypomagnesemia, hypocalcemia)
- Narrow complex supraventricular tachyarrhythmias
- Wide complex supraventricular tachyarrhythmias
