5.1 ECG1 Flashcards
What are the 2 main coronary arteries?
Where do they supply blood to?
LMCA - supplies blood to left side of heart
- divides into LAD (supplies to front of left side of heart and bulk of LV) and LCx (supples left lateral and posterior)
RCA - supplies blood to right atrium, right ventricle, and SA and AV nodes that regulate heart rhythm
What coronary artery is most likely to contain electrical conduction system?
right coronary artery
What are the intrinsic factors of the autonomic control?
SA node - pacemaker of the heart
What are the extrinsic factors of the autonomic control?
neural function (chronotropic)
- balance of sympathetic and parasympathetic stimulation
- hormonal control (catecholamines)
Sympathetic vs. parasympathetic?
sympathetic = fight or flight
parasympathetic = rest and digest
What is the conduction system?
special electrical (pacemaker) cells in the heart that are arranged in a system of pathways.
What controls the heart?
Normally, the pacemaker site with the fastest firing rate
What is the idea around vectors in the heart?
Electrical activity goes off in many different directions - we sum them up to get an average of the vectors
In a healthy heart, the sum of vectors should lead through where?
What is this called?
the left ventricle
called the electrical axis
What does lead 2 / rhythm strip look at?
Blood going towards the LV
What does p-wave represent?
atrial contraction (atrial depolarization)
SA node is firing off
What does the QRS complex represent?
ventricular depolarization
(atrial repolarization occurs too, but isn’t seen b/c it is lesser magnitude)
What does the T-wave represent?
ventricular repolarization
When does diastole occur in an ECG?
between the beats
What are the intrinsic rates of pacing cells?
SA node?
Atrial cells?
AV node?
His bundle?
Bundle branch?
Purkinje cells?
Myocardial cells?
SA node = 60-100 BPM
Atrial cells = 55-60 BPM
AV node = 45-50 BPM
His bundle = 40-45 BPM
Bundle branch = 40-45 BMP
Purkinje cells = 35-40 BMP
Myocardial cells = 30-35 BMP
Which direction does a current flowing towards a positive electrode deflect?
Current flowing away from positive electrode?
Current flowing towards a positive electrode deflects upward
Current flowing away from positive electrode deflects downward
On an ECG recording paper, what do/does 1 square, 3 small squares, and 5 small squares measure?
1 small square = 0.04s
3 small squares = 0.12s
5 small squares = 0.20s
What numbers demonstrate heart rate from thick-lined box to the next thick line?
300
150
100
75
60
50
43
38
33
30
What are sinus rhythms?
What are the 7 called?
all rhythms whose origin is the sinus node
sinus ryhthm
sinus bradycardia
sinus tachycardia
sinus arrhythmia
sick sinus syndrome
sinus arrest
sinus block
What are sinus bradycardia
and sinus tachycardia?
sinus bradycardia <60bpm
sinus tachycardia >100bpm
How do you calculate atrial rate vs ventricular rate?
Atrial rate - calculate from p-wave to p-wave
Ventricular rate - QRS to QRS
What is sinus arrhythmia?
Describe rate, regularity, p-wave, QRS ratio, PR interval, QRS width, grouping, and dropped width.
Rate: 60-100 bpm
Regularity: changes with breathing; Slower during exhalation and faster during inhalation
P-wave = normal
QRS ratio: 1:1
PR interval = normal; 0.12-0.20s
QRS width: normal
grouping: none
dropped beats: none
What is the length for a normal PR interval?
0.12-0.20s
Sinus arrhythmia has identical features to a normal sinus rhythm except what?
except the rate varies more than 10%
(shorter and longer distances between beats / diastole)
What is sinus bradycardia?
Rate <60bpm
Normal otherwise
PR interval and QRS width are normal to slightly prolonged
What can cause sinus bradycardia?
vagal stimulation leading to nodal slowing
or medicines such as beta blockers
also seen in some highly conditioned athletes
What is sinus tachycardia?
Rate >100 bpm
Normal otherwise; PR interval and QRS width may be normal to slightly shortened
What has caused sinus tachycardia?
can be caused by medications or by conditions that require increased cardiac output, such as exercise, hypoxemia, hypovolemia, hemorrhage and acidosis
What is hypoxemia and hypovolemia?
Hypoxemia – low level of oxygen in the blood
Hypovolemia – a decreased volume of circulating blood in the body
What is premature atrial contraction?
- rate depends on sinus rate
- irregular
- p-wave is present but may be in a different shape
- P-P intervals are different lengths
- multifocal p-wave stimuli
- sometimes grouping
What are multifocal PACs?
premature atrial contractions that are generated in different places of the atria so they have different shapes
What is ectopic atrial tachycardia?
- rate of 100-180bpm
- ectopic = in abnormal place
- p-wave –> different ectopic focus
- QRS width can be abnormal
What is SVT?
supraventricular tachycardia
- regular rhythm
- 160-250bpm
- p-wave is often not visible
- PR interval is usually not measurable
- QRS is usually normal
What are the causes of supraventricular tachycardia?
atrial flutter with rapid ventricular response
atrial fibrillation with rapid vent response
atrial tachycardia
AV node re-entry tachycardia
accessory pathway mediated SVT
What is atrial flutter?
a single irritated focus of the atria that is firing rapidly; creates a reentry circuit that depolarizes the atria and gains control as pacemaker of the heart
p-wave appears saw-toothed (very peaked)
atrial rate is often 250-250bpm
ventricular rate is commonly 125-175 bpm
variable QRS width
Describe how the AV node works as a gatekeeper.
AV node = gatekeeper to the ventricle that comes in as it determines how many impulses reach the ventricles
What might cause atrial flutter?
often occurs in people with heart disease
acute myocardial infarct, congestive cardiomyopathy, hyperthyroidism, cor pulmonale (right-sided heart failure), valve disease
What is occurring in atrial fibrillation?
multiple ectopic foci in the atria firing, causing the atria to depolarize in a chaotic manner
atria is quivering
AV node is bombarded with many impulses
always irregularly irregular
wavy baseline, can’t see p-wave
A-fib versus A-flutter… which is irregularly irregular and which is regularly irregular?
A-fib = irregularly irregular
A-flutter = regularly irregular
What is a controlled rate of atrial fibrillation?
rate <100bpm = controlled with medication
What are causes of artifact?
Patient Movement
Muscle Tremor
Poor or Lost Electrode Contact
Electrical Interference from Other Electrical Equipment
External chest compressions
Or:
muscle tremor, alternating current (AC) interference, poor electrode contact with the skin, interference related to biotelemetry, and external chest compression
What is artifact?
Abnormal waves and spikes in an ECG that result from sources other than the electrical activity of the heart and interfere with or distort the components of the ECG.
What is the difference between sinus pause and sinus block?
sinus pause = varied time period of which there is no sinus pacemaker working; tie interval is not a multiple of the normal P-P interval
sinus block = picks back up on time in some multiple of the P-P interval; after a dropped beat, cycle continues as scheduled
- sinus has fired but the impulse has not made it out of the SA node
What is a WAP? What is occurring?
regularly irregular or irregularly irregular?
wandering atrial pacemaker - multiple atrial pacemakers are firing at their own pace. Results in an ECG with at least 3 different p-wave morphologies.
100bpm
irregularly irregular
variable PR interval
What is multifocal atrial tachycardia?
> 100bpm (lower than Afib)
irregularly irregular
clear p-wave but different morphologies
