Cardiology Flashcards
ECG
Which leads point in the downward direction?
- aVF (straight down, 90 degrees)
- II (60 degrees)
- III (120 degrees)
Which lead is at 0 degrees?
I
What is a normal range for mean axis of depolarization?
-30 to 110
What is a quick way to know that the axis of depolarization is in the normal range?
“Thumbs up sign”
If pt is positive in lead I and positive in aVF, they are in normal range (0-90)
What part of electrical conduction of the heart does the P wave represent?
Atrial depolarization
What part of electrical conduction of the heart does the QRS complex represent?
Ventricular depolarization
What part of electrical conduction of the heart does the T wave represent?
Ventricular repolarization
If lead I is isoelectric, which lead do you look at to determine direction of the axis of depolarization?
aVF
- If (+), axis is +90
- If (-), axis is -90
If lead II is isoelectric, which lead do you look at to determine direction of the axis of depolarization?
aVL
- If (+), it is -30
- If (-), it is +150
If lead aVF is isoelectric, which lead do you look at to determine direction of the axis of depolarization?
Lead I
- If (+), it is 0
- If (-), it is +180
What does a long QT interval indicate?
Problems with repolarizing the ventricles
How is heart rate calculated?
Find an R wave which peaks on a heavy line – the next heavy black line is 300, followed by 150, 100, 75, 60 and 50
In normal sinus rhythms, the P wave is upright in which leads?
Leads I and II
What does the PR interval indicate?
Time it takes for stimulus to travel from the SA node to the ventricles
What does an inverted T wave represent?
Ischemia
How is the QT interval affected by LV hypertrophy?
Lengthened
How is the QT interval affected by digitalis?
Shortened
How is the QT interval affected by hypokalemia?
Lengthened
How is the QT interval affected by MI?
Lengthened
How is the QT interval affected by Hypercalcemia?
Shortened
How is the QT interval affected by myocarditis?
Lengthened
How is the QT interval affected by thyrocosis?
Shortened
How is the QRS complex affected by AV node escape rhythm?
Narrowed
How is the QRS complex affected by ventricular escape rhythm?
Widened
depolarization wave spreads slowly via abnormal pathway in the ventricular myocardium and not via the His bundle and bundle branches
What is the inherent HR of the following?
- Atria
- AV node
- Ventricles
- Atria: 75/min
- AV node: 60/min
- Ventricles: 30-40/min
What do you look for on an ECG to determine whether the patient has heart block?
Whether every P wave is followed by QRS
Yes => No heart block
What do you look for on an ECG to determine whether the patient has ischemia?
Inverted T wave
Diagnose:
Sinus bradycardia
- Sinus rhythm
- HR = 45
What are the characteristics of 1st degree heart block?
- P is followed by QRS
- PR interval is more than a box away (>250ms)
What are the characteristics of 2nd degree heart block type I?
PR prolongation but just drops a beat out of no where
What are the characteristics of 2nd degree heart block type II?
PR interval is the same before and after the block
(block is below the His-purkinje system)
What are the characteristics of 3rd degree heart block?
- QRS complexes are going at their own rate
- don’t always see a p wave at end b/c it is superimposed on QRS
What are the characteristics of a 2:1 AV block?
Pattern: P, QRS, P, (skip), P, QRS, P, (skip)
What are the characteristics of atrial fibrillation?
- Ventricular rate is irregularly irregular, no discernable P waves
- upper chambers are just quivering
- see slide 88
What are the characteristics of atrial flutter?
- Fast, but it is a circuit in the atrium going about 300 bpm
- See a saw-tooth pattern
Determining L from R bundle branch block
- Bundle branch block
- Widened QRS
- L or R?
- Look at lead V1
- Look at last part of QRS
- If most energy is above the isoelectric line => Right
- If most energy is below the line => Left
- ***Think of a turn signal
- Reference: ekg.academy
What are the characteristics of acute ischemia? How can you tell if it affects the anterior heart or the inferior heart?
- Acute ischemia:
- ST elevation
- Anterior heart
- Leads V2, V3
- Inferior heart
- Leads II, III, aVF
What are the characteristics of an old infarct?
Significant Q wave
- wider than 1 mm or
- length 1/3 QRS amplitude
What are the characteristics of ischemia?
- T wave inversion
- ST interval depression
- See slide 103
What are the characteristics of pericarditis?
- Diffuse ST elevation (everywhere)
- PR depression
- They will have a rub that is worse when they lean forward
Intro to CHF
Decreased perfusion to the kidney activates what system? What is the result?
- Activates Renin - Angiotensin - Aldosterone system
- Result:
- Na and water retention
- Vasoconstriction
What is abnormal about the beta receptors in CHF?
- Downregulate themselves
- not as affected by NE (doesn’t permit vasodilation for example)
What is the effect of the SNS in CHF?
- Increases afterload
- Increases HR
- Impairs contractility
- Increases O2 demand of the heart
- provokes ischemia
- Triggers arrhythmia
- Ca overload and apoptosis
What electrical abnormalities can be present in CHF?
- A-V dysynchrony
- Abnormal impulse propagation in the ventricules
- Atrial or ventricular arrhythmias