Q2-CB15/Cardiac Arrhythmias Flashcards
What type of information does the ECG provide about the events in the cardiac cycle?
it provides info about the rate, rhythm, and timing
What info can the ECG provide abt heart muscle?
ischaemia, damage, hypertrophy
an increased voltage/height on an ECG suggest what?
increased muscle mass
what do wider waves or intervals on an ECG suggest?
slowed conduction
What does this diagram suggest about the individual?
What does a left axis deviation mean?
What does a right axis deviation mean?
from what parts of the ECG can you tell that there is a delayed conduction?
elongated PR interval, QRS, or QT
From what part of the ECG can you tell that there is ischaemia?
There is an ST depression. (note that this is only seen in leads pointing towards damage)
From what part of the ECG can you tell that there is an infarction?
ST elevation (only seen in leads pointing towards damage)
What bpm constitues tachycardia?
more than 100 bpm
What bpm constitues bradycardia?
less than 60 bpm
If the rhythm is not regular, then it is irregular. This means that there is an arrhythmia. What are the 2 types of irregular rhythms?
regularly irregular and irregularly irregular
What do conduction problems means in regards to arrhythmia?
the rate and rhythm are ok, but the conduction is either too fast or too slow
Sinus rhythm comes from the _______ node.
Sinoatrial (SA)
sinus rhythm ______ at the AV node and fastest through the _________
slows down, Bundle of His/Purkinje fibers
what is sinus tachycardia?
increased rate but normal rhythm
what is sinus bradycardia?
decreased rate but normal rhythm
What is sinus arrhythmia?
a regular irregular rhythm from the SA node
What happens at all the arrows and at 1 and 2?
What 3 things may cause arrhythmias?
changes in automaticity, triggered activity after depolarization, and conduction delay + appearance of re-entry circuits
What is the depolarization rate of the SA node?
60-100/min, it depends on the ANS
What is the depolarization rate of the AV node?
40-50/min
what is the depolarization rate of purkinje fibers?
about 35/min
What are afterdepolarizations?
abnormal depolarizations of cardiac muscle cells
What are the 2 types of afterdepolarizations?
early afterdepolarizations and delayed afterdepolarizations
When do EADs occur?
EADs occur when stimulation occurs during the plateau (Phase 2) or repolarisation phase (Phase 3)
When do DADs occur?
DADs occur during Phase 4 (resting) and trigger depolarisation, but
before the time normally expected. this is due to elevated Ca++ levels
Explain re-entry circuits.
not all parts of the heart will depolarize (ex. blood vessels, damaged fibrotic tissue)
when depolarization hits these areas it cant go through the heart, so it has to go around the heart (think of crows avoiding an obstacle)
if the route is the same length as the original then there is no problem; but if the route is longer, then problems may arise
What are ex of longer routes in re-entry circuits?
What is a paroxymal tachycardia?
it is a burst of tachycardia due to re-entry pathways
what are the 2 types of paroxysmal tachycardia?
ventricular and supraventricular
explain ventricular paroxysmal tachycardia.
- serious
- may lead to fibrillation or death
- usually due to ischaemic damage or drugs
Explain supraventricular paroxysmal tachycardia.
- supraventricular means above the ventricles so its either atrial or AV node
- if its atrial, then the P wave is inverted
- if its the AV node, then the P wave is hidden
- more common in young people
- usually is not deadly
What is fibrillation?
uncoordinated and sporadic depolarizations throughout the heart
Explain atrial fibrillation.
- since there is no coordinated depolarization of the atria, there is no P wave.
- irregularly irregular tachycardia
Explain ventricular fibrillation.
- individual myocytes are depolarizing, so there is no distinct waveform that can be seen
- there is no coordinated contraction, so there is no cardiac output
What is another term for ectopic?
abnormal
What can cause ectopic beats in the atria?
an extensive stretch of muscle fibers
What are ectopic beats in the atria?
they are premature contractions due to abnormal impulses from ectopic foci
Are premature atrial contractions common or rare?
they are fairly common
How do ectopic beats in the atria show up on an ECG?
they show up as an extra P wave and a weak pulse on the ectopic beat
What is similar to ectopic beats in the atria?
A premature AV node contraction; it also has a weak pulse but there is no P wave because depolarization travels to the atria AND the ventricles
(the P wave is lost in the resulting QRS complex)
What is another name for ectopic beats in the ventricle?
premature ventricular contractions (PVC’s)
How can you tell on an ECG that someone has PVCs?
It is seen as a widened QRS complex and an inverted T wave
- conduction through muscle is slower than the main conducting system. the slow conduction means that fibers that depolarize first also repolarize first.
What is heart block?
decreased or total block of AV conduction
What things can cause heart block?
ischemia/compression/inflammation of AV node
What are the 3 types of heart block?
1st degree, 2nd degree, 3rd degree
What is first degree heart block?
it is a delay in conduction; characterized by an increased PR interval (greater than 0.2 sec)
What is second degree heart block?
increased delay, some of the PQRSs get dropped completely
What is 3rd degree heart block?
it is the complete block; ventricles contract but slower (40 bpm), the SA node is still firing but there is no relationship between P and QRS
