ECG Flashcards
What is the normal speed of an ECG strip
25mm/sec
What does one small block represent
40ms or 0.04 secs
What does a big block represent
200ms
How do you calculate the heart rate
You count the number of QRS complexes in the rhythm strip and then multiply by 6
What is the other method for calculating the heart rate using the big blocks
You count the number of big blocks and then divide by the 300
What is the formula for the max sinus rhythm
220- age of the patient
Which are the normally negative leads on an ECG
AVR, V1 and V2
Which area of the heart does Lead 1 AVL and V5 and 6
Lateral side of the heart
What does the leads 2 3 and AVF look at
Inferior side of the heart
Which leads look at the anterior area of the heart
V1 2 3 4
Which leads look at the septum of the heart
V1 and V2
How do you know that a P wave is originating in the SA node
In the inferior leads 2 3 and AVF the P waves are positive and then in the AVR it is negative
Which 2 waves are used to check the morphology of a P wave
2 and V1
What are the general measures of a P wave
Smaller than 2.5 mm and less than 0.12sec
How do you know that a patient has P pulmonale or RA enlargement
Increased more than 2.5mm [2.5 small blocks] in lead 2. There will also be a biphasic p wave in V1 with the positive portion being larger
How do you know that a patient has P mitralle or LA enlargement
Increased more than 2.5mm [2.5 small blocks] in lead 2. There will also be a biphasic p wave in V1 with the negative portion being larger
What does the PR segment represent
This is the depolarisation of the atria and the delay of the AV node
What is a normal PR segment length
3-5 small blocks or 120 - 200msec
What are you worried about when there is shortening of PR segment
Pre excitation problems like WPW and Ectopic focuses near the AV node
What are the concerns when there is the lengthening of the PR segment
Heart blocks
What is the normal length of a QRS complex
105ms or less and not above 120ms
What are the 4 things that we look at in a QRS complex
- Axis
- Width
- Height
- Presents of a pathological Q waves
What is the normal range for the axis
90 to -30
What is the axis of the AVL
-30
What is the axis of leads 1 2 and 3
- 0
- 60
- 120
What is the axis of AVR
-150
What is the axis of AVF
90
What are the possible causes of a left axis deviation
L anterior hemiblock
Inferior MI
What are the causes of a right axis deviation
- Right Ventricular Hypertrophy
- Right Bundle Branch Block
- Lateral Myocardial Infarction
- Cor Pulmonale
- Left Posterior Fascicular Block
- Wolff-Parkinson-White (
- Normal in Children and Young Adults
What does supraventricular mean
It tells the impulse originates from above the ventricles, but the QRS is widened due to abnormal conduction through the ventricle
What are supraventricular causes of wide QRS complexes
Right or left BBB or hypothermia
What are the ventricular causes of wide QRS complexes
- Ventricular ectopics
- Pre excitation
- Ventricular Pacemaker
What are the 3 criteria for a RBBB
- Tall slurred R waves in V1
- Deep slurred S waves in V6 and Lead 1
- Inverted T waves in V1-3
What are the 3 criteria in a LBBB
- Negative QRS complexes in the septal leads V1-3
- M shaped R waves in V6
- T wave inversion in V5 and 6
What causes a hemiblock
Occurs when there is a blockage or delay in one of the two main branches of the left bundle branch of the heart’s conduction system
What does a bifascicular block look like
RBBB + Left axis (L ant hemi-block)
What does a trifascicular block look like
RBBB + left axis + Mobitz 2
How to diagnose LVH with the cornell criteria
Add the R waves in AVL + S wave in V3
If it is over 28 mm in male and 20 in female then it is pathological
What are the criteria for RVH
Tall R wave in V1 (must have this criteria plus at least 1 of the other 3)
1. T wave inversion in V1-3
2. Right axis
3. P pulmonale
What is the normal Q waves
A normal Q wave is the negative deflection that precedes a the positive of an R wave
What are the 3 criteria for a pathological Q wave
Width of more than 1 block
Deeper than 3 blocks
More than 25% of the R wave
What does a pathological Q wave indicate
It indicates an infarct but for it to indicate a infarct then there must be pathological Q waves in more than 2 leads
What are the possible causes of ST segment depression 4
- Myocardial ischemia
- NSTEMI
- Posterior infarct
- Digoxin (Nike tick sign in V4-6)
What are the causes of an ST segment elevation 3
- Acute MI
- Pericarditis
- Ventricular aneurysms
In which leads is it normal to have inverted T waves
AVR, Lead 3 and V1
What are the causes of a peaked T wave 2
Hyperacute MI or Hyperkalemia
How can you distinguish strain from LVH
combination of ST ↓, T neg in V1 or V6
Where are U waves normally seen and what are their normal size
The normal size is less than 0.5 mm and are best seen in lead V2 and 3
What are the usual causes of U waves
Anything that slows the heart rate
What are things that cause U waves 6
- Bradycardia
- Severe hypokalemia
- Hypothermia
- LVH
- Hypocalaemia
- Digoxin
What causes an inverted U wave 3
Heart disease
Hyperthyroidism
Raised ICP
What is the normal length of a QT interval
Under 440 in males and 460 in females
What causes a prolonged QT interval
Congental abnormalies
Hypo K Mg or Ca
Drugs
Ischemia and infarction
What causes a shortened QT interval
Hypercalcemia
What are the criteria for a sinus bradycardia
All the QRS are preceded by a p and the HR is less than 60
In which lead is the p wave biphasic
V1
What is the general size of a normal p wave
3 block high and 3 blocks long
What is a junctional escape
Junctional Escape refers to a type of heart rhythm originating from the junctional area (AV node)
What are the 3 criteria for a junctional escape
- Bradycardia 40-60
- Narrow QRS complexes
- Retrograde P waves
What is a retrograde P wave
It is an atrial contraction that is conducted in the opposite pathway to the normal contractions
What does a retrograde p wave look like
In Lead 2 it is negative and is positive in AVr
What is the normal PR interval
It is 3-5 blocks 120-200ms
What causes a shortened PR interval
WPW
What are the 3 criteria for WPW
Broad QRS
Shortened PR interval
Delta waves
What causes prolonged constant PR interval
First degree heart block
What are the 3 criteria for a first degree heart block
- Prolonged PR
2.PR interval is constant - Each P wave has a QRS
What causes PR interval becomes progressively longer until p-wave
is not followed by QRS (‘dropped beat’)
Second degree heart block type 1
Which type of heartblock causes grouped beats
Second degree mobitz type 1
What is the difference between a mobitz type 1 and a type 2
In a type 2 the PR interval is fixed and there is just an occasional dropped QRS
What is a second decree heart block with a 2:1 conduction
This is where the PR interval ifs fixed but every second P wave is not followed by a QRS
What are the 2 criteria of a 3rd degree heart block
- There is no relationship between the P and the QRS
- The ventricular rate is regular
What is the normal length of a QRS segment
Less than 120ms thus 3 small blocks
What is considered left axis deviation
Less than -30
What is considered right axis deviation
More than 90
How to identify a left bundle branch block
There is an W present in V1 and M in V6
How is a right bundle branch block identified
M pattern in V1 and a W in V6
What are the 5 possible differentials for a RBB
- Pulmonary hypertension
- IHD
- Conduction system fibrosis
4.Cardiomyopathy - Congenital heart disease
What are the 3 main criteria of left ventricular hypertrophy with strain pattern
- Tall QRS
- Inverted T waves
- LAD
What are the 3 criteria for RVH
- Dominant r wave in V1
- RAD
- T wave abnormalities in V1 and 2
What are the 2 criteria for spotting a PVC
- Narrow complexes with P waves
- Wide complex without a p wave
Where is the normal location of the ST segment
On the isoelectric line
What is considered abnormal depression or elevation of the ST segment
1 block on the normal leads and 2 on the limb leads
What does ST elevation or depression mean
MI
Which 4 leads look at the lateral aspect of the heart
Lead 1, aVL,V5 and V6
What are the 3 leads that look at the inferior segmant of the heart
Lead 2,3, and aVF
What are the 2 septal leads
V1 and 2
Which 2 leads look at the anterior segment of the heart
V3 and 4
What are the 4 criteria for a pericarditis
- Sinus tachycardia
- Prolonged PR in lead 1 and 2
- ST segment elevation
- No Q waves
What are the 2 criteria for a STEMI
- ST elevations
- Q waves
What is the normal height of a T wave
In the limb leads it is less than 5 mm and in the chest leads it is less than 10mm
What are the primary causes of large T waves
1.Hyperkalaemia
2. Hyperacute STEMI
What causes a flat T wave
It is a nonspecific finding that can show signs of ischemia or electrolyte imbalances
Where is a t wave inversion normal
V1 and lead 3
What causes a biphasic T wave
Hypokalemia
What is the normal range for QT interval
440ms for men and 460 for women
What are the acquired causes of long QT interval
- Low on electrolytes like calcium, k or Mg
2 Medications: Psychiatric and antibiotics and antihistamines
What is the cause of a left axis deviation 2
- Left anterior hemiblock
- Inferior MI
What does one small block represent
40 ms
What does a large spiked p wave indicate
Right artrial enlarement
What does a double peaked p wave mean
Left atrial enlargement
What is a pathological q wave and what does it indicate
A q wave present in V1-3 that is wider than 40ms and higher than 2mm and more than 25% of the r waves
What does a pathological Q wave indicate
Damaged or dead myocardium normally from a previous infarct
What is a ventricular pacemaker and when does it occur
This is when there is a 3rd degree heart block and so there is no connection between the atria and ventricles and so the ventricles need to take over contraction initiation
What are the 4 criteria for a ventricular pacemaker from the purkinje fibers
- Rate is 15-40
- Narrow QRS
- The QRS have bizarre shapes
- There is no connection between the P and the QRS
What is the main 2 criteria that are used to diagnose a high infranodal pacemaker
- No p QRS relationship
- The rate is 40-60
What is a common misdiagnosis in the presents of an artificial pacemaker
A pseudo LBBB with an axis of -60 to -90 and negative complexes in V6
What is the difference between a monomorphic and a polymorphic ventricular tachy
A polymorphic arises from 2 or more origins or reentry circuits
What are the 5 differencials for a regular narrow complex tachy
- Sinus tachy
- Atrial tachy
- Atrioventricular nodal reentry tachy
- Atrioventricular reentry tachy
- Atrial flutter
What is the differential for an irregular narrow tachy
A fib
What is the differential for a wide tachy
V tach
Which are the best leads for P waves
2 and V1
Which are the best leads for PR interval
2 and V1
Which are the best leads for QRS
V1 and 6 and Lead2
Which are the best leads for ST segment
V3 and 4 and lead 2
Which are the best leads for T waves
V2 3 and lead 2
Which are the best leads for QT interval
Lead 2 V5 and V6
What is the best wave for T wave abnormalities
V2 and 3 and lead 2
