ecg workshop - snapup tickets · 2016. 11. 9. · ecg workshop university health network emergency...
TRANSCRIPT
ECG Workshop
University Health Network
Emergency Medicine Conference 2016
Shirley Strachan-Jackman NP, MN, ENC(C)
Objectives
• Discuss the approach to the patient with chest pain
• Review heart blocks
• Take a step-by-step approach to ECG interpretation
• Identify normal and abnormal components on the ECG
• Determine how a 12/15 lead helps diagnose pathological conditions
• Identify EGC changes for ischemia, AMI, BBB, pericarditis, PE, LVH, and electrolyte imbalances
Most Importantly.....
• Have fun—and next time you take an ECG for a physician sign-off, you will be able to tell them what’s normal or abnormal...he or she will be impressed!
Chest pain is merely a symptom, not a diagnosis
Differential Diagnosis of Chest Pain
• Cardiac causes- CAD, stable angina, unstable angina, variant angina, STEMI, NSTEMI
• Pericarditis
• Valvular diseases- aortic stenosis, subaortic stenosis, mitral valuve prolapse
• Vascular causes- aortic dissection, PE, pulmonary hypertension
• Pulmonary causes- pleural irritation d/t infection, inflammation, infiltration, pneumothorax, tracheobronchitis
• MSK- costochondritis, muscle strain, cervical/thoracic spine problems
• GI causes- esophageal reflux/spasm, biliary colic, peptic ulcer disease, pancreatitis
• Miscellaneous causes-herpes zoster, chest wall tumours, anxiety
It’s not always a textbook presentation
• People who present with right-sided chest pain—50% AMI
• Elderly—cognitive impairment—be aware of fatigue, weakness, dizziness, NFW, SOB
• Diabetics—neuropathy, often do not have pain
Our goal is to…
• Identify those patients with life-threatening etiologies
- Aortic Dissection
- Myocardial Infarction
- Unstable Angina
- Massive PE
- Cardiac Tamponade
ECG…
…is the best single test available in the ED
…history is important with the physical examination
Conduction System
Pacemaker Rates
Lead Placement
• Lead placement is important—inaccurate placement of > 3/5 inch- can lead to inaccurate waveforms and an incorrect ECG interpretation
15 Lead Electrode Placement
Components of the ECG Complex
Pathological Q-Wave
ST Segment Depression
Injury- ST Elevation
QT Interval
Normal Coronary Arteries
RCA
- Inferior wall of LV - Posterior wall of LV - Right ventricle - Sinus node (55%) - AV node (85%)
LCA - Lateral wall LV
- SA node (45%)
- AV node (15%)
- Posterior division of the left branch
LADA
- Anterior wall of LV
- Anterior portion of the septum
- Right bundle branch
- Anterior division of left branch
Limb Leads vs. Chest Leads
• Limb leads- I, II, III, AVR, AVL, AVF
View the heart on the vertical plane- from the sides, above and below
• Chest leads- V1 to V6
View the heart on the horizontal plane- from the front and left side
Each lead views the heart at a unique angle
Heart Blocks
• First degree AVB
• Second degree AVB Type I; Mobitz I; Wenckebach
• Second degree AVB Type II; Mobitz II
• Third degree AVB; Complete Heart Block
First Degree AV Block
Second Degree AV Block Type I
• Each successive impulse from the SA node is delayed slightly longer than the previous impulse until the impulse fails to be conducted to the ventricles- and the cycle repeats itself. Think of… longer, longer, drop.
• Causes- CAD, Inferior wall MI and rheumatic fever; as well as cardiac medications such as digoxin, Inderal, verapamil
Second Degree AV Block Type I
Second Degree AV Block Type II
• Less common than type I but more serious- ventricular rate is slower and cardiac output diminished- more likely to cause symptoms
• Generally caused from a anterior-wall MI, degenerative changes in the conduction system or severe CAD
• Strip will look like someone erased some QRS complexes- the PR interval will always be constant before the QRS complexes
• QRS complexes may be wide
Second Degree AV Block Type II
Third Degree AV Block
• Impulses are completely blocked at the AV node and can’t be conducted to the ventricles
• Potentially life-threatening
• Atria and ventricles act independently
– If block is right at the AV node- HR 40-60- QRS narrow
– If block is Purkinje system- HR < 40- QRS wide
Third Degree AV Block
Figuring it all out! Block Teams
Constant/ Fixed P wave Varied P wave
First Degree AVB
Second Degree AVB Type II
Second Degree AVB Type I
Third degree AVB
Think of Heart Blocks Like a Marriage
Ten Rules to a Normal ECG
Which Each Lead “Sees”
Lateral Septal/ Anterior
Anterior
Lateral Lateral
Lateral
Inferior
Inferior Inferior Anterior
Septal/ Anterior
Rule # 1
PR interval should be 3-5 small squares
Rule # 2
The width of the QRS complex is less than 3 small squares
Rule # 3
The QRS complex should be dominantly upright in leads I and II
Rule # 4
The QRS and T waves tend to have the same general direction in the limb leads
Rule # 5
All waves are negative in lead aVR
Rule # 6
The R wave in the precordial leads must grow from V1 to at least V4
Rule # 7
ST segment should be isoelectric
Rule # 8
P waves should be upright in leads I, II and V2-V6
Rule # 9
There should be no Q wave or a small Q wave (less than 0.04 secs. in width) in leads I, II and V2-V6
Rule # 10
T waves must be upright in leads I, II and V2-V6
ECG Approach
1. Assess heart rate and rhythm.
2. Determine electrical axis.
3. Examine R wave progression—normally the R wave gets taller from V1 to V4—gets slightly smaller in V6 (no R wave progression-??MI).
4. Check for ischemia or infarction pattern: Check inferior leads/ posterior leads
Check lateral leads
Check anterior leads
If needed, check right ventricular leads
Check V1 for RBBB & LBBB
Electrical Axis
Factors that influence electrical axis include:
position of heart
person’s body size and type
conduction pathways
force of the electrical impulse being generated
Electrical Axis
Causes of Left Axis Deviation
• Normal deviation
• Inferior wall MI
• Left anterior hemiblock
• Wolff-Parkinson-White Syndrome
• Mechanical shifts—pregnancy, ascites, tumors
• LBBB
• Left ventricular hypertrophy
• Aging
Causes of Right Axis Deviation
• Normal deviation
• Lateral wall MI
• Left posterior hemiblock
• RBBB
• Emphysema
• Right ventricular hypertrophy
Early Repolarization
• Produces an infarct-like pattern of healthy, asymptomatic patients
• ST-segment elevation is seen
• Produces tall T-waves
Early Repolarization
Bundle Branch Blocks
• BBB is caused by a block of the impulse of the right or left bundle branch
• Complete or incomplete
• Normally, the RBB quickly transmits the stimulus of depolarization to the right ventricle. The LBBB does the same to the left ventricle. This stimulus is transmitted to both ventricles at the same time.
Right Bundle Branch Block (RBBB)
• In RBBB, the initial impulse activates the interventricular septum from the left to right, just as in normal activation
• The LBB activates the left ventricle—the impulse then crosses the interventricular septum to activate the right ventricle—the right ventricle fires late
RBBB ECG Features
• Best seen in V1
• QRS complex > or = to .12 seconds
• QRS predominantly positive in V1
• Other features include slurred S wave in lateral leads
RBBB
How LBBB occurs
• In LBBB, the impulse first travels down the right bundle branch—the impulse activates the interventricular septum from right to left—the opposite of normal activation. Finally, the impulse activates the left ventricle—the left ventricle fires late
LBBB ECG Features
• Best seen in V1
• QRS complex > or = to .12 seconds
• QRS is predominantly negative in V1
• ST-T wave changes are more prominent than RBBB—often see T wave inversion in Lead I, V5 and V6
LBBB
Myocardial Ischemia & Infarction
Ischemia
Inferior AMI
Reciprocal Changes (Remote Ischemia)
• ST-segment depression in the wall of the heart opposite the location of the infarction
• Inferior MI’s—produce reciprocal changes in the anterior (V1-4) and high lateral (I and aVL)
• Anterior MI’s—produce reciprocal changes in the inferior wall (II, III, aVF)
Reciprocal Changes
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Anterior Wall MI
Lateral Wall AMI
Anterior Lateral Wall MI
ECG
Right Ventricular Wall MI
Diagnosing Right Ventricular AMI
When diagnosing a RV AMI—only need ½ mm ST-segment elevation because the muscle of the RV is thin compared to the muscle of the LV which is very thick.
Posterior AMI
• Horizontal ST depression
• Tall, broad R waves
• Upright T waves
• Dominant R wave (R/S ratio > 1) in V2
Electrolyte Imbalances
Hyperkalemia
Serum Potssium (mmol/L) Predicted ECG status 5.5-6.5 Tall tented T waves 6.5-7.5 Loss of P waves 7.5-8.5 Widening QRS 8.5 QRS continues to
widen, approaching to sine wave
Pericarditis
• Widespread ST elevation throughout all leads and without remote ischemia
• PR segment depression
• Q-waves never develop
Pericarditis
• Stage 1 – widespread STE and PR depression with reciprocal changes in aVR (occurs during the first two weeks)
• Stage 2 – normalization of ST changes; generalized T wave flattening (1 to 3 weeks)
• Stage 3– Flattened T waves become inverted (3 to several weeks)
• Stage 4 – ECG returns to normal (several weeks onwards)
Lead II is Helpful
Pulmonary Emboli
ECG
Hypothermia
• Hypothermia is defined as a core body temperature of < 35 degrees centigrade
• Mild hypothermia is 32-35 degrees
• Moderate hypothermia is 29-32 degrees
• Severe hypothermia is < 29 degrees
Hypothermia- ECG Changes
• Bradyarrhythmias
• Osborne Waves (= J waves)
• Prolonged PR, QRS and QT intervals
• Shivering artefact
• Ventricular ectopics
• Cardiac arrest due to VT, VF or asystole
Left Ventricular Hypertrophy (LVH)
• Compare V1 & V2 and determine which lead has the deepest “S” wave- determine depth mm
• Compare V5 & V6 and determine which leads has the tallest “R” wave- determine in mm
• Add the height of the tallest “R” wave and the deepest “S” wave
• If number is equal to or > than 35 mm, suspect LVH
• Or “R” in aVL is equal to or > 11 mm
Wolffe-Parkinsons-White Syndrome (WPW)
• Syndrome is a congenital abnormality associated with SVT
• There are accessory pathways outside the normal conduction system that bypass the slowing effect of the AV node and rapidly conduct impulses from the atria directly to the ventricles
• Involves activation of the ventricles that occurs earlier than expected (preexcitation)
• Bypasses the AV node- the most common bypass tract is an accessory AV pathway otherwise known as a Kent bundle
WPW
WPW Patients
• Potentially at an increased risk for dangerous ventricular arrhythmias due to extremely fast conduction across the bypass tract
WPW-ECG Finding
• A shortened PR interval (<.12 secs.)- early depolarization of the ventricles
• Delta wave- sloping
• Narrow QRS complex-impulse travels down the AV and travels
up the accessory pathway (more common)
• Wide QRS complex-impulse travels down the accessory pathway and up the AV node
• 25%- normal ECG
WPW- ECG Findings
Practice Time
Brugada Syndrome
• Is a syndrome consisting of syncopal episode(s) and/ or sudden cardiac death in patients with a structurally normal heart
• ECG changes: incomplete RBBB; ST segment elevation in the V1-V3 leads and terminal T wave inversion
• Genetic disposition and predominately affects males
Diagnostic Criteria
• Type 1 (Coved ST segment elevation >2mm in >1 of V1-V3 followed by a negative T wave) is the only ECG abnormality that is potentially diagnostic. This has been referred to as Brugada sign.
Summary
• ECG is the best single test available in the ED
• History is important
• Take your time…don’t jump to the obvious- use a systematic approach