Lecture 12: ECG Assessing Cardiac Function Flashcards
What is the SA nodes rate in bpm?
60-80 bpm
What is the goal of the conducting system?
To coordinate pumping of the cardiac muscle
What is the AV nodes rate in bpm?
40 to 60bpm
What are the ventricular nodes rate in bpm?
20 to 40 bpm
What is an ectopic focus?
Any cardiac cell can depolarize on it’s own
Loner atrial cell
What is the normal time of the PR interval?
0.12 to 0.2 seconds
What is the PR interval?
The area between the p wave and the QRS complex
What does a longer PR interval indicate?
If the pr interval is longer than 0.2 seconds then there is a delay in conduction between the SA node and the ventricle (AVblock)
What is the normal time of the QRS complex?
0.04 to 0.12 seconds
What position should the ST segment be?
Isoelectric or at baseline
What is the beginning of the ST segment called?
The J point
When is the ST segment significant?
Depression more than 1mm and at least 0.08 seconds (2 small boxes)
What is a lead?
A combination of electrodes to give you a view of the heart (a combination of three electrodes)
What are the chest leads in a 12 lead EKG? What part of the heart do they look at?
V1, V2 right side of the heart
V3,V4 inter ventricular septum
V5, V6 left side of the heart
What should you start with when interpreting the ECG?
Determine the ventricular rate
How do you determine the ventricular rate?
Look from R wave to R wave
After looking at ventricular rate on an ECG, what is the next step in interpretation?
Look at the p wave. Is there a pave before each QRS?
A QRS complex should have a duration of…
Less than 0.12 seconds or 3 small boxes
What does ST segment elevation indicate?
Myocardial infarction
What does ST segment depression indicate?
(>2 mm) myocardial ischemia
What is a normal sinus rhythm?
Electrical conduction from the SA node through the normal conduction pathways
Sinus tachycardia is greater than 100
Sinus bradycardia is less than 60
What is a sinus arrhythmia? What are the two kinds?
Normal conduction but irregular rhythm. Respiratory and non respiratory arrhythmia
What are the characteristics of a sinus arrhythmia in order to be considered to be a respiratory sinus arrhythmia?
HR accelerates during inspiration and decelerates during expiration
What is an atrial premature depolarization/contraction?
An atrial premature beat caused by an ectopic focus
Will a PAC trigger the AV node?
Yes
Does a PAC result in a normal CO?
Yes. It is considered a benign heart condition
What is a saw tooth pattern?
An atrial flutter
How many p waves per minute can occur in an atrial flutter?
250 - 300
What are 2 possible causes of an atrial flutter?
(1) ischemic heart disease
(2) after surgery
What feature on the ECG is missing when someone has atrial fibrillation?
P waves
Will Afib disrupt cardiac output?
Yes
What is the cause of Afib?
Multiple atrial cells depolarizing on their own
What do the atria look like in an individual with Afib?
The atria quiver (looks like a bag of worms)
What is a concern in someone with Afib?
Afib leads to blood stasis which may cause clot formation (which may lead to stroke)
What are three clinical clues that someone may have AFib?
(1) irregular rhythm on palpation
(2) weak pulse
(3) clot risk increased
What are junctional rhythms?
Tissue next to AV node (junctional tissue) taking over pacing and QRS depolarization
Does the SA node fire in junctional rhythm?
No
If the SA node doesn’t fire in junctional rhythm, what is the heart rate?
40 - 60 bpm
Ventricular premature depolarization or contraction is caused by…
One ectopic focus in the ventricles before atrial depolarization
What is the result of PVC on the ECG?
The QRS will become wide and larger in magnitude
Are PVCs considered normal?
Yes, until there are more than 6 per minute
What is a unifocal PVC?
A PVC with one ectopic focus (the PVCs look the same)
What is a multifocal PVC?
A PVC with different ectopic foci (so the PVCs look different)
What is bigeminy?
When every other beat is a PVC.
What is trigeminy?
Every third beat is a PVC
What is a couplet?
When there are 2 PVCs in a row.
What is a triplet?
3 PVCs in a row
Can PT be done if the patient has a couplet? Triplet?
Yes- couplet
No- triplet
If there are 3 PVCs in a row it greater than 6 PVCs in one minute what is the patient at risk for?
Ventricular tachycardia
What is ventricular tachycardia?
(Can be sustained or not sustained) I don’t know what it is
V-Tach can become…
V Fib
What is ventricular fibrillation?
When multiple ectopic foci are in the ventricle
No ventricular pumping
What is a block?
I don’t understand
Atrioventricular blocks or (AV blocks) have 3 different kinds…
First degree AV block
Second degree AV block
-Type I (Mobitz Type I, Wenckebach phenomenon)
-Type II (Mobitz Type II)
Third degree AV block (Complete AV block)
What is a First degree AV block?
Conduction delay in AV node
PR interval > 0.20 sec (5 small boxes) and consistent
benign
What’s a Second degree AV block, Type I (Mobitz Type I, Wenckebach phenomenon)?
PR intervals get progressively longer and longer until one P wave is not conducted through to ventricles (skipped QRS)
usually benign
What’s a Second degree AV block, Type II (Mobitz Type II)?
Block in Bundle of His
PR intervals tend to be long but of consistent duration conduction often does not go through to ventricles;
may have P:QRS of 2:1, 3:1, 4:1, etc.
Ventricular rate tends to be irregular; pacemaker often required.
Pacemaker often required!
What’s a Third degree AV block (Complete AV block)?
Atrial and ventricular depolarization are independent (completely dissociated).
P waves and QRS complexes are not coordinated, so PR intervals have no consistent duration.
QRS may be wider than normal.
Ventricular rate tends to be regular.
Needs a pacemaker!!!
What’s a bundle branch block (BBB)?
Blockage between AV bundle (bundle of His) and Purkinje fibers leading throughout one ventricle.
QRS > 0.12 sec
What’s a Right bundle branch block (RBBB)?
Left ventricle contracts first
Will be seen with leads V2 V3!
What’s a Left bundle branch block (LBBB)?
Will be seen with leads V5 V6!
