cardiovascular physiology: ECG pathophysiology

Question 1

what is the order of electrical conduction through the heart

Answer 1

sa, internodal pathways, av, av bundle, bundle branches, purkinje fibres

Question 2

where are the autorhythmic cells located in the heart

Answer 2

sa node, av node, purkinje fibres

Question 3

what mechanical event initiates during the latter part of the P wave and continues throughout the p-r segment

Answer 3

atrial systole

Question 4

what mechanical event initiates just after the Q wave and continues throughout the the s-t segment

Answer 4

ventricular systole

Question 5

what electrical event occurs during the T wave of an ECG

Answer 5

ventricular repolarization

Question 6

what signals does the vagus nerve carry?

Answer 6

parasympathetic

Question 7

what 2 forces are balanced to control HR

Answer 7

parasympathetic, sympathetic

Question 8

what is vagus withdrawal and what does it cause

Answer 8

decrease in parasympathetic activity, increase in HR

Question 9

one little square of the ECG corresponds to what length of time?

Answer 9

.04 sec

Question 10

one large square of ECG corresponds to what length of time?

Answer 10

.2 seconds

Question 11

What is the purpose of an ECG

Answer 11

used to test for clinical abnormalities

Question 12

if the P-R segment of the ECG is abnormal, what could be going wrong

Answer 12

AV node and Av bundle conductivity

Question 13

what are intervals?

Answer 13

combination of segments and waves

Question 14

What does the PR interval represent

Answer 14

the time between atrial depolarization and ventricular depolarization

Question 15

what does the QT interval represent

Answer 15

it represents the time between when the ventricles start depolarising and when they finish repolarizing

Question 16

What is Einthoven’s triangle

Answer 16

it consists of a pair of electrodes being placed in both arms and a leg. Each pair of electrodes between limbs represents a lead.

Question 17

What is Einthoven’s triangle lead 1?

Answer 17

it is between the electrodes placed on each arm. The left corresponds with a positive charge. Right is a negative charge.

Question 18

when a downward deflection is recorded on an ECG what does this mean.

Answer 18

it means a current is flowing towards the negative lead (right side).

Question 19

when a upward deflection is recorded on an ECG what does this mean?

Answer 19

it means a current is flowing towards the positive lead ( left side).

Question 20

if the R wave of a ECG is unusual, what is the mechanical event that is correspondingly unusual?

Answer 20

Ventricular systole

Question 21

What is the normal range of HR

Answer 21

60-100 bpm

Question 22

How do you calculate HR from an ECG?

Answer 22

1500/# of small squares between R waves

Question 23

What is tachycardia

Answer 23

HR>100 at rest

Question 24

what is bradycardia

Answer 24

HR<60 at rest

Question 25

what does the presence of arrhythmias indicate?

Answer 25

It can indicate the presence of electrical generation or conductive problems.

Question 26

what is atrial fibrillation, its symptoms and what does it look like on an ECG

Answer 26

it is when the SA node is not acting as a pacemaker. On the ECG it looks like the p wave is replaced with very little and frequent irregular spikes. can have no symptoms but can also be associated with classic symptom of heart failure

Question 27

What is a PVC and what are its symptoms and ECG pattern

Answer 27

A premature ventricular contraction is when there are extra beats that originate from outside of the SA node. on an ECG, the QRS complex and t wave look abnormal. it can feel like a skipped beat and can also cause heart failure symptoms

Question 28

When do PVCs need to be treated?

Answer 28

when they occur more than 6 a minute

Question 29

Several PVCs in a row at more than 120bpm is called what

Answer 29

ventricular tachycardia VT

Question 30

describe ventricular flutter

Answer 30

A form of VT but at increased HR of 250-350bpm no discernable QRS complex or T waves looks like a sine wave in an rapid organised rhythm

Question 31

what can VT progress into

Answer 31

Ventricular fibrillation

Question 32

what's the difference between ventricular flutter and ventricular fibrillation

Answer 32

ventricular flutter is still organised. ventricular fibrillation is uncoordinated and unable to push blood.

Question 33

describe ventricular fibrillation (VF)

Answer 33

uncoordinated contraction of the ventricles. the contractions are too weak to eject blood into the aorta

Question 34

What can an S-T elevation indicate?

Answer 34

Myocardial infarction (heart attack)

Question 35

What can an S-T depression indicate

Answer 35

Myocardial ischemia (obstructed blood flow in the coronary arteries by atherosclerosis. if they rupture then myocardial infarction may occur)

Question 36

what is a first degree AV block and what does it look like on an ECG graph

Answer 36

it looks like an increase in duration of the PR interval. To count as a first degree AV block then the delay must be longer than .2 sec. This is caused by reduced conduction in between the two nodes.

Question 37

What is a Second degree AV block and what does it look like on an ECG graph

Answer 37

It's when there is a skipped ventricular contraction every 2-5 beats. this looks like a missing QRS complex every 2-5 beats. This is due to a slowed and sometimes blocked conduction to the AV node meaning it is sometimes disconnected from the SA node.

Question 38

describe a third degree AV block and what does it look like on an ECG graph.

Answer 38

It is when there is no more conduction or communication in-between the two nodes. this means that atrial and ventricular contractions happen independent of one another and not coordinated as they are supposed to be. This will look like the P wave and QRS complex happening at different rates.

Question 39

How is bradycardia most commonly corrected?

Answer 39

It is corrected through the placement of an artificial pacemaker Bradycardia: resting HR<60bpm

Question 40

How is tachycardia most commonly corrected?

Answer 40

Medication Cardioversion (electrical shock therapy or defibrillation can help reset heart rhythm) Ablation therapy (destruction of cardiac tissue responsible for arrhythmia)

Question 41

what are other examples of treatments for arrhythmias?

Answer 41

surgery -Coronary artery bypass -maze procedure Implantable Cardioverter-Defibrillator (ICD) -corrects bradycardia like a normal pacemaker -can act as defibrillator if VT or VF detected