EKGs Flashcards
Criteria for sinus rhythm
1) P before each QRS
2) Upright P in lead II
3) Biphasic P in lead V1
Heart rate with 1 large box between Rs
300 bpm
Heart rate with 3 large boxes between Rs
100 bpm
Heart rate with 4 large boxes between Rs
75 bpm
Heart rate with 5 large boxes between Rs
60 bpm
Quick criteria for normal QRS axis
- QRS positive in lead aVF and positive in lead I (0 to +90 degrees)
- QRS positive in lead aVF, negative in lead I, and positive in lead II (0 to -30 degrees)
Quick criteria for left axis deviation
- QRS negative in lead aVF, positive in lead I, and negative in lead II
Quick criteria for right axis deviation
- QRS positive in lead aVF and negative in lead I
Quick criteria for indeterminate (Northwest) axis
- QRS negative in lead aVF and negative in lead I
Normal ST segment finding
Isoelectric
What physiological processes are represented in the QT interval?
Beginning of ventricular depolarization (QRS) to the end of ventricular repolarization (T)
Normal QT interval
400-440 ms (controversial)
Quick way to determine if QT interval is prolonged
T wave ends beyond the halfway point of RR interval
What does the QTc correct for?
Heart rate
What is a normal QTc interval?
< 450 ms in men; < 470 ms in women
Bezett’s formula
QTc = QT / √RR
Common electrolyte abnormalities leading to prolonged QT interval
- Hypocalcemia
- Hypomagnesemia
- Hypokalemia
Normal T wave findings
- Upright in most leads (exceptions include aVR and V1)
- Assymetric with steep decline (compared to incline)
What is a Q wave?
Any downward deflection immediately following the P wave
How long is an abnormal widened QRS complex?
120 ms
What is the S wave?
Downward deflection following R wave
Signs of pulmonary embolism on ECG
- Most commonly, sinus tachycardia
- Classically, McGinn-White (S1Q3T3) sign of acute cor pulmonale, consisting of a large S wave in lead I, a Q wave in lead III, and an inverted T wave in lead III
What is an R wave?
First upward deflection following the P wave
What is “normal R wave progression”?
- In lead V1, R «_space;S
- R:S ratio increases in precordial leads
- By lead V4, R > S
- In lead V6, R»_space; S
What is “poor R wave progression”?
R remains small in leads V3-V4
Causes for R > S in lead V1
- Wolff-Parkinson-White syndrome
- Right bundle branch block
- Acute posterior MI
- Right ventricular hypertrophy
- Isolated posterior wall hypertrophy (Duchenne’s MD)
ECG criteria for right bundle branch block
1) QRS > 120 ms
2) R and R’ waves with intervening S wave (rsR “bunny ears”) in leads V1-V3
3) Slurred (rounded) S waves in leads I and aVL (and often in V5 and V6)
Signs of pathologic Q waves
- More than one small box wide (40 ms)
- More than 2 mm (two small boxes) deep
- More than 25% of total QRS amplitude
- Present in leads V1-V3
What do pathologic Q waves indicate?
Myocardial infarction (usually OLD, developing hours to days after, particularly when revascularization does not occur)
Sequence of ECG changes in transmural myocardial infarction
1) Hyperacute T waves (transient, usually missed)
2) ST elevation at the J point (“tombstoning”)
3) Resolution of ST elevation; development of pathologic Q waves
What is the J point?
Junction of the QRS complex and ST segment
What can PR segment depression indicate?
Pericarditis or atrial infarction
What physiological process is occurring during the P wave?
Atrial depolarization
Why is the ventricular rate in atrial fibrillation slower than the atrial rate of 400-600 bpm?
AV node is intermittently refractory (this causes irregularly irregular rhythm)
Best lead to see P waves when evaluating irregularly irregular rhythm (i.e. suspected atrial fibrillation)
Lead II (sometimes V1)
Which arrhythmia has a sawtooth appearance on ECG?
Atrial flutter
Criteria for multifocal atrial tachycardia (MAT)
- Ventricular rate above 100 bpm
- At least 3 different P wave morphologies (wandering atrial pacemaker)
Four characteristics of premature atrial contractions
1) Premature
2) Ectopic, with altered P wave morphology
3) Narrow complex
4) Compensatory pause
Signs of Wolff-Parkinson-White syndrome on ECG
- Shortened PR interval (due to accessory pathway)
- Delta wave (slurring of QRS upstroke) in some individuals
What is the pharmacologic treatment for WPW? What should NOT be given if the patient has WPW + A fib? Why not?
- Give procainamide for WPW
- Do NOT give amiodarone, adenosine, beta-blockers, calcium channel blockers, or digoxin (ABCD)
- Blocking the AV node causes atrial action potentials to use the faster accessory pathway, potentially causing ventricular fibrillation
What type of arrhythmia is Wolff-Parkinson-White syndrome? (category)
Atrioventricular Reentrant Tachycardia (AVRT); congenital
What is an atrioventricular nodal reentrant tachycardia (AVNRT)?
There is a reentrant circuit present within the AV node itself (two pathways through AV node)
Signs of AVNRT on ECG
1) Narrow complex tachycardia
2) In some patients, P wave after QRS complex (pseudo-S on lead II; pseudo-R on V1)
3) P wave absent in most cases
4) Tachycardia that quickly terminates with AV blocking maneuvers (carotid massage, adenosine)
What is a first degree AV block?
When conduction is slowed through the AV node, producing a prolonged PR interval on ECG ( > 1 big box)
What occurs in a Wenckenbach/ Mobitz I/ type 1 second degree AV block?
AV conduction is slowed and increases with each beat until P wave fails to conduct through the AV node (progressive elongation of PR interval)
What occurs in a Mobitz II/ type 2 second degree AV block?
AV node becomes completely refractory to conduction on an intermittent basis (NO progressive elongation of PR interval)
What occurs in third degree AV block (complete heart block)?
No conduction through AV node, so there is complete dissociation between atrial and ventricular rhythms (P and QRS are unrelated)
Left bundle branch blocl (LBBB) criteria
1) QRS Duration greater than 120 ms
2) Lead V1 should have either a QS or a small r wave with large S wave (large V appearance)
3) Lead V6 should have a notched (or ‘slurred’) R wave and no Q wave
Criteria for right ventricular hypertrophy (RVH)
1) R wave > 7 mm in lead V1
- OR-
2) R > S in lead V1
Sokolow-Lyon Criteria for left ventricular hypertrophy (LVH)
[S wave in lead V1] + [R wave in V5 or V6] > 35 mm
What is the Brugada criteria/algorithm used for? What are the signs that it assesses?
Used for diagnosing ventricular tachycardia.
1) Concordance in precordial leads (V1-V6)
2) RS interval > 100 ms (wide complex)
3) AV dissociation
4) LBBB, RBBB, etc. morphology patterns
