ECG Flashcards
What’re the stages of assessing an ECG?
- Name and calibration (1 big box wide, 2 big boxes tall)
- Rate (ventricular then atrial)
- Rhythm - Space between QRS complexes regular? Sinus rhythm? P waves before QRS complexes? Prolonged PR interval? T waves normal? Any Abnormal U waves?
- Axis - R-wave progression
What’s the conducting pathway of the heart?
SAN / AVN / L. or R bundle branch / Pukinje fibers
What physiological delay happens at the AV node?
30ms to from SA to AV node
90ms delay before enting the penetrating portion of the AV bundle
40ms delay in the penetrating bundle
= 160ms delay in the AV network
What is Heart Block?
Electrical signal from the atrium to the ventircle is slowed or blocked
1st degree = signal delayed
2nd degree = signal is intermittently blocked
3rd degree = signal is always blocked
1st degree Heart Block
PR interval >5 little boxes
Young people
Rarely treated
2nd Degree Heart Block Type 1
Some P waves without QRS complex
Increased PR interval
No treatemnt
2nd Degree Heart Block - Type 2
PR interval stable
Bundle of His
High risk of 3rd degree block
Implant a pacemaker
Third Degree Heart Block
Atrial signals don’t arrive at the ventricles
Ventricles beat at their own pace
Atrial Fibrillation
Irregular QRS Complexes
(irratic or not visable P-waves)
Atrial Flutter
Sawtooth Appearance
300 BPM
Single re-entrant circuit in the right atrium
What drug can be used for Supraventricular Tachycardiacs
Adenosine
Activates specific ligand-gated K+ channels reducing exitability
Administered IV can cause transient HB at the AV node
What does the ECG have to show for the axis to be in the Northwest Territory?
Both I and II are negative
What’re some of the casues of Axis Deviation?
**Diaphragm pushing upwards **
Hypertrophy of one of the ventricles
Conduction Anomalies (axis moves towards undepolarised tissue)
Causes of Right Axis Deviation?
COPD / PE
Child or Tall Thin Person
Right Ventricular Hypertrophy
Causes of Left Axis Deviation?
Conduction pathologies
Obese person / pregnant
Artifical Cardiac Pacemaker
What is R-Wave progression?
V1 = Small R Wave (QRS complex negative)
V2, V3 = Zone of transition. The QRS is equally positive and negative
V6 = R Wave is dominant (QRS complex is Positive)
What can cause anomalies of R Wave progression?
Anterior Myocardial Infarction
LBBB
Wolff-Parkinson White Syndrome
What is Bundle Branch Block?
Conduction Pathology
One Bundle branch fails to conduct
That side of the heart is delayed in depolaristion (that side must be stimulated by the other)
What causes broad notched QRS Complexes?
Left Bundle Branch Block
What is Ischaemia? What signs are there on the ECG?
Relative lack of blood supply to tissues. Although there is no tissue infarct.
Causes ST depression on the ECG
What’re the signs of Acute Injury on an ECG?
ST Elevation
What sings would there be on an ECG of infarction?
Q-Waves
Potential Inverted T-waves
What’re the signs of Acute Coronary Syndrome on an ECG?
**ST elevation **
Receiprocal St depression
**Pathological Q waves **
T wave inversion
What’re pathological Q-waves?
Occur in an MI
Pathological Q waves lack R waves
What are normal Q-waves called?
Septal Q-waves
What leads supply the Septal Region of the Heart?
V1 + V2
What leads supply to Anterior Section of the Heart?
V3 + V4
What leads supply the inferior region of the heart?
aVF + II + III
What leads supply the lateral region of the heart?
I + V5 + V6
What artery supplies the anterior of the heat?
left anterior descending
What artery supplies the lateral region of the heart?
Left Circumflex Artery
What artery supplies the inferior of the heart?
Right dominant (90%) = Right Coronary Artery
Left dominant is supplied by the Left Circumflex
What artery supplies the posterior region of the heart?
Posterior Descending Artery
What artery supplies the SA & AV node?
Right Coronoary Artery
Which region of an MI has a worse prognosis?
Anterior MI has a worse outcome than a Posterior MI
What’s the prognosis of an MI (first and second time)?
First time = 1/3 die before discharge
Second time = > 50 die before discharge
What’s the differential diagnosis of an MI?
**Bengin Early Repolarisation **
(normal varient in the young)
Can T waves be depressed?
No
They can be inverted or negative! NOT inverted
What can cause tenting of T-waves?
Hyperkalemia
What can cause U waves?
Present in Hypokalaemia
What is a Broad Complex Tachycardia?
Wide QRS complexes
What’s a Supraventricular Tacycardia?
Arrhythmias that originate above the ventricles
What’s Junctional Tacycardia?
AV node involvement
Can occur in junctional pacemakers
Describe the image
Atrial Flutter with Carotid Sinus Pressure
What’re the 3 scources of Arrhythmias?
- Re-Entry
- Enhanced Automaticity
- Triggered Activity
What’re the symptoms of Long QT Syndrome?
Syncope & Sudden Death
What is the mechainsm of Long QT Syndrome? (i.e what’s the also called?)
Torsades de pointes
A Polymorphic Ventricular Tachyarrhythmia
How is Long QT Syndrome treated?
Pacemaker
Beta-blockers
Stop drug administration
Torsades De Points
(Long QT syndrome)
How long is a long QT?
Men > 440ms
Women > 460 ms
What’s the basis of Atrial Flutter?
Re-entery arrhythmia
Typically the right atrium
What is the basis of Fibrillation?
Abnormal automaticity of tissue in pulmonary veins
Re-entrant sources at posterior of left atrium
What does Sinus Rhythm mean?
Normal heart rhythm
Electrical signals start in the SA node
P wave is followed by a QRS complex (fixed PR interval - <5 squares)
What is sinus tachcardia?
Rate > 100 BPM
What is Sinus Bradycardia?
< 60 BPM
What two ways can atrial flutter occur?
Fixed degree block e.g a 3-to-1 block
Variable block e.g varies
Secondary Degree Heart Block Type 1
Gradually increasing PR interval, the most prolonged one is not followed by a QRS complex.
Second Degree Heart Block Type 2
PR interval is constant (either prolonged or normal)
Periodically there is no conduction between the atrium and the ventricle
What do Tall P and bifid waves indicate?
P Pulomnale, P waves are Peaked (right atrium enlargement)
P Mitrale, P waves are Bifid and look like the letter M (mitral stenosis)
Can you comment on the ST segment when LBBB is present?
NO!
What’re the two emergency Shockable Rhythms?
**Ventricular Fibrillation **(trace all over the place)
**Ventricular Tachycardia **(regular contractions)
What Rhythms are Non-Shockable?
Pulseless electrical activity
Asystole (no identifyable electrical activity)
P-wave asytole
How can you determine if a person has a pacemaker or not from an ECG?
Pacing spikes are seen
If directly to the ventricle, then wide QRS complexes are seen.
