Cardiac numbers (exam 4) Flashcards
How often does the SA node generate an action potential in a normal adult? (in seconds)
0.83 seconds
Normal HR
72 BPM
If we took out all the influence from the vagus nerve and sympathetic chain on the SA node, what would our HR be? (SA node by itself)
110 BPM
What would the HR be if the SA node and SNS were impacting it? (No vagal influence)
120 BPM
What would our HR be if it was only impacted by SA node and vagus nerve? (NO SNS input)
60-62 BPM
What would our HR be if it was controlled by the AV node?
40-60 BPM
What would our HR be if it was controlled by the purkinje fibers?
15-30 BPM
Vrm of SA node
-55 mV
Threshold potential for SA node
-40 mV
What phases are in a slow (nodal) action potential?
4,0,3 (maybe 2)
How many internodal pathways are there?
3 (anterior, middle and posterior)
Time it takes for an AP to move from SA node to AV node
0.03 seconds
How long does it take for the entire right atria to depolarize under normal conditions?
0.07 seconds
How long does it take for the very last part of the left atrium to depolarize?
0.09 seconds
How long does it take for the very last part of the left ventricle to depolarize?
0.22 seconds
How long is the delay for an action potential to make it through the AV node?
0.12 seconds
How long is the delay in the bundle of His?
0.01 seconds
Duration of the P wave
0.09 seconds
Total delay of AV node + Bundles of His
0.13 seconds
Total time it takes for an action potential to get from SA node to the interventricular septum where we have the two main bundle branches
0.16 seconds
Angle of electrical current during a typical heartbeat
59 degrees
Magnitude of depolarization of a fast action potential
100 mV
QRS complex magnitude of deflection
1.5 mV
How many boxes tall x long is the P wave?
2.5 X 2.5 small boxes
P-R interval duration
0.16 seconds
Ideal duration of QRS complex
0.06 seconds
How do we do the math for the ideal QRS complex duration?
0.22 seconds (entire left ventricle depolarized) - 0.16 seconds (AP reaches interventricular septum) = 0.06 seconds
This is how long it took for the ventricles to depolarize
Duration of endocardial fast action potential
0.25-0.35 seconds
QT interval duration
0.25-0.35 seconds
Normal R-R interval
0.83 seconds
How to calculate HR with RR interval?
60 seconds / RR interval = HR
How many mV is a big box on an EKG?
0.5 mV
How many mV is a small box on an EKG?
0.1 mV
How many seconds is a big box on an EKG?
0.2 seconds
How many seconds is a small box on an EKG?
0.04 seconds
How quickly was paper fed into EKG machines in the olden days?
25 mm/second
Vrm of purkinje fibers
-90 mV
Vrm of ventricular muscle
-80 mV
Threshold potential of ventricular muscle
-70 mV
Threshold potential of purkinje fibers
-70 mV
If you have a heart block, how long will it take for the ventricles to initiate their own action potential the first time?
30 seconds
Cranial nerve V
trigeminal nerve
Cranial nerve X
vagus nerve
What is it called when a surgeon operates on an eyeball and it generates a complete heart block in the patient?
Five and dime reflex (V + X)
Ohm’s law
V = IR
What is the peak of an action potential in a ventricular myocyte?
+20 mV
Angle of lead II
60 degrees
Angle of lead III
120 degrees
Angle of lead I
0 degrees
Angle of aVF
90 degrees
This augmented lead gives you a view that looks in the middle of leads II and III
aVF
This augmented lead is rarely used
aVR
Angle of aVL
150 degrees
Angle of aVR
210 degrees
How many “extra” leads are the precordial leads
6 extra leads (V1-V6)
What are the anterior chest leads (#)?
V3 and V4
These precordial leads are placed on either side of the sternum
V1 and V2
These are known as the septal leads
V1 and V2
These are known as the lateral chest leads
V5 and V6
Where are leads V4, 5 and 6 located?
5th intercostal space on the patient’s left side
Where is lead V3 located?
sandwiched in-between lead V4 and V2
Where is V1 located?
Right side of the sternum, fourth intercostal space
Where is V2 located?
Left side of the sternum, fourth intercostal space
This precordial lead helps us differentiate if we have an anterior or posterior injury to the heart
V2
This precordial lead will see almost all of the electrical activity of the heart and will have a big deflection
V4
In incomplete heart block the PR interval is > ____ seconds
> 0.20 seconds
In second degree heart block the PR interval increases ___ to ____ seconds
0.25-0.45 seconds
Which is more dangerous - Mobitz one or Mobitz 2?
Mobitz type 2
What are the ratios in Mobitz Type II; P waves: QRS complexes
2:1
3:2
3:1
What is the ventricular escape in BPM in a complete heart block?
15-40 BPM
In Stokes-Adams syndrome ventricular escape is delayed __ - __ seconds
5-30 seconds
What is the threshold (in seconds) for maintaining consciousness without a heartbeat?
7-8 seconds
What is the length in ms of a fast action potential?
~200 milliseconds
In which phase are you most permeable to calcium in a fast action potential?
Phase 2
This % of the population has a bundle of Kent
0.2%
