Chapter 3 Flashcards
Why do P waves have to look the same in a regular rhythm?
Impulse created in SA node will be in same place, take same path, they’re always going to look alike
The time will also be the same
Taking same steps (in a sense) so a QRS will always follow
What characteristics does a rhythm that begins in the SA node have?
- Positive (upright) P wave before each QRS complex (always)
- P waves that look a like
- A constant PR interval
- A regular arterial and ventricular rhythm (usually)
What can affect the electrical impulse of the SA node?
- Medications
- Diseases or conditions that cause the heart rate to speed up, slow down, or beat irregularly.
- Diseases or conditions that delay or block the impulse from leaving the SA node
- Diseases or conditions that prevent an impulse from being generated in the SA node
SA node has the ability to change rate to the situation. Need more blood? Moving more? Less?
Normal Sinus Rhythm (NSR)
Reflects normal electrical activity - that is, the rhythm starts in the SA node and then heads down the normal conduction pathway through the aria, arioventricular (AV) node and bundle, right and left bundle branches, and purkinje fibers.
In adults and adolescents, the SA node usually fires at a regular rate of 60-100bpm
How do you recognize NSR?
- P waves look the same. Spacing is the same. Upright.
- Following after P wave will always be a QRS.
- R-R regular / P-P regular
- PRI measurement is the same
- 60-100bpm
Sinus Bradycardia (SB)
If SA node fires at a rate slower than normal for the patient’s age, the rhythm is called sinus bradycardia
In adults and adolescents, SB has a heart rate of less than 60bpm
Severe SB is less than 40bpm
What causes SB?
- Occurs in adults and children during sleep
- Common in well-conditioned athletes
- Vagus nerve stimulation (makes everything go slow - parasympathetic stimulation)
-coughing
-vomiting
-straining to have a bowel movement
-sudden exposure of the face to cold water
Examples of what causes SB
-diseases in SA node
-hyperkalemia
-hypokalemia
-hypothermia
-hypothyroidism
-hypoxia
-increased intracranial pressure
-inferior myocardial infraction (MI)
-medications
-obstructive sleep apnea
-post heart transplant
-posterior MI
-tracheal suctioning
-vagal stimulation
What can be done to treat SB?
- No treatment if asymptomatic
- If symptomatic because of the slow rate, treatment may include
-pulse oximeter
-supplemental oxygen, if indicated
-vascular access
-12 - lead ECG
-Atropine
Atropine
Given to patients with low (severe) heart rate
Blocks chemicals at endings of vagus nerves
Allows more sympathetic activity
-rate at which the SA node can fire is increased
-increases rate of impulse conduction through AV node
Sinus Tachycardia (ST)
If the SA node fires at a rate faster than normal for the patients age
Sinus tachycardia begins and ends GRADUALLY (no spikes, goes up at a constant pace)
Over 100bpm
What causes ST?
-acute myocardial infection
-caffeine-containing beverages
-dehydration, hypovolemia
-drugs such as cocaine, amphetamines, ecstasy, cannabis
-exercise
-fear and anxiety
-fever
-heart failure
-hyperthyroidism
-hypoxia
-infection
-medications (epinephrine, atropine, dopamine)
-nicotine
-pain
-pulmonary embolism
-shock
-sympathetic stimulation
Inappropriate Sinus Tachycardia (IST)
- Occurs for no apparent physiological cause
- Heart rate may rapidly increase to more than 100bpm with minimal exertion, at rest or both
- Accompanying symptoms are usually nonspecific
- Mechanisms responsible for IST are not entirely understood
- Diagnosis is made only after other causes for the tachycardia have been ruled out
What to do about ST?
- Physiological ST:
-directed at correcting the underlying cause
_fluid replacement
_relief of pain
_removal of offending medications or substances
_reducing fever or anxiety - Inappropriate ST:
-Lifestyle modifications
-pharmacological treatment may be tried
-surgical ablation may be performed in severe causes
Sinus Arrhythmia (SA)
When SA node fires IRREGULARLY, the resulting rhythm is called sinus arrhythmia
Respiratory SA - associated with the phases of breathing and changes in intrathoracic pressure
Non-respiratory SA - not related to the ventilatory cycle
How do you recognize SA?
- Doesn’t have the same patter - IRREGULAR
- Normal P wave followed by QRS
IRREGULAR rhythm, but has all the other normal characteristics of NSR
What causes sinus arrhythmia?
Non respiratory SA
Can be seen in people with normal hearts, but is more likely to be found in older individuals and in those with heart disease
Common after inferior wall MI
May be seen with increased intracranial pressure
May be a result of the effects of medications or carotid sinus pressure