Function & Conduction
What are the 2 key components that the heart is responsible for?
What is electrical activity & mechanical activity.
What is the intrinsic firing rate of the SA node?
What is 60-100
Horizontal Lines:
Each small box represents:
Each large box represents:
small box = 0.04 seconds
large box = 0.20 seconds
What is a Sinus Rhythm?
any rhythm that originates from the sinoatrial (SA) node, the heart’s natural pacemaker
What is sinus arrhythmia and what is a result of?
A variation in heart rate resulting in a regularly irregular rhythm that occurs with respiration.
Name the 4 chambers of the heart.
What is: right atrium, right ventricle, left atrium, left ventricle
What is the intrinsic firing rate of the AV node?
What is 40-60
Vertical Lines
Each small box =
Each large box =
Each small box = 0.1 mV
Each large box = 0.5 mV
Name 4 key identifies of all sinus rhythms.
•A P wave before each QRS
•Upright, matching P waves in Lead II
•A consistent PR interval of 0.12–0.20 seconds
•A QRS duration of < 0.12 seconds
Name 2 types of sinus pauses?
Sinus Exit Block and Sinus Arrest
The ECG reflects what?
What is: the electrical activity of the heart.
What are 2 key functions of the AV node?
ØSlows conduction to allow atrial contraction and “atrial kick”
ØActs as a backup pacemaker at 40–60 bpm
ØBlocks excessively rapid atrial impulses
How many large boxes are there in a 6 second strip?
What is 30 boxes
Identify the ECG features of NSR
Rhythm, rate, P waves, PRI, QRS
•Rhythm: Regular (atrial & ventricular)
•Rate: 60-100 beats/minute
•P Waves: Lead II: Upright, uniform, precedes each QRS complex
•PRI: Normal (0.12-0.20 seconds or 3-5 small boxes)
•QRS: Normal (0.04-0.12 seconds or 1-3 small boxes)
How do you determine that the pause is a sinus exit block?
Pause is equal to exactly two or more previous cardiac cycles of the underlying rhythm
What are the 2 nodes that are located in the right atrium?
What is the SA node & the AV node.
What is the intrinsic firing rate of the purkinje fibers?
What is 20-40
Describe where the following leads go: white, black, red, green, brown
White: right arm
Black: left arm
Red: left leg
Green: right leg
Brown: right side of the sternum, 4th intercostal
What ECG feature changes with Sinus Bradycardia & Sinus Tachycardia compared to NSR
SB rate <60
ST rate >100
How do you determine that the pause is a sinus arrest?
The pause is NOT a multiple of the P-P/R-R interval & is unpredictable
Define the absolute refractory period vs the relative refractory period.
•Absolute refractory period: no stimulus can excite the cell.
•Relative refractory period: a stronger than normal stimulus may trigger a response
What are the 2 reasons that alternate pacemakers may assume pacing instead of the SA node?
What is escape & irritability.
What 2 ECG leads look at lead II?
right arm and left leg
What are the normal characteristics of Sinus Arrhythmia?
Rhythm, rate, P waves, PRi, QRS
•Rhythm: Regularly Irregular
•Rate: Normal (60-100 beats/minute), Slow (less than 60 beats/minute), or Fast (greater than 100)
•P Waves: Positive in lead II, normal in size, shape, direction, P wave precedes each QRS complex
•PRI: Normal (0.12-0.20 seconds or 3-5 small boxes)
•QRS: Normal (0.04-0.12 seconds or 1-3 small boxes)
What does sick sinus syndrome mean?
Umbrella term for any arrhythmia that is due to disruption in conduction pathway/disorder of SA, which controls the heartbeat. Sick sinus syndrome causes slow heartbeats, pauses (long periods between heartbeats) or irregular heartbeats (arrhythmias).