Transport and Perfusion: Electrical Conduction - ECG (Week 4) Flashcards
four terms that describe the heart’s electrical properties?
1) Automaticity: Ability to initiate an impulse spontaneously and continuously.
2) Contractility: Ability to respond mechanically to an impulse.
3) Conductivity: Ability to transmit an impulse along a membrane in an orderly manner.
4) Excitability: Ability to be electrically stimulated.
What is Automaticity:
Ability to initiate an impulse spontaneously and continuously.
Contractility:
Ability to respond mechanically to an impuls
Conductivity:
Ability to transmit an impulse along a membrane in an orderly manner.
Excitability:
Ability to be electrically stimulated.
What does the autonomic system control in impulse formation?
1) The rate of impulse formation.
2) The speed of impulse conduction.
3) The strength of myocardial contraction.
What nerve in the parasympathetic system is responsible for the resting state?
The Vagus nerve
The intracellular region of the heart contains Sodium or potassium?
Potassium
The outside/ intersitial are of the heart contains Sodium or Potassium?
Sodium
What causes depolarization of the heart?
Upon stimulation, however, a flood of Na+ cations flow across the semipermeable cardiac cell’s membrane, making it more positive. The change in voltage that occurs with this flood of Na+ ions cause depolarization,
What causes repolarization?
Wen sodium comes out of the cell and potassium comes inside the cell. Voltage pumps return to normal
monitor oscilloscope.
The device that converts ECG voltage measurements to the visual representation, “rhythm-strips,”
What are artifacts?
Momentary disturbances in ECG pattern (pg 45 in Ryan’s notes)
Telemetry monitoring
monitoring of a client’s heartrate and rhythm to determine problems such as dysrhythmias, ischemia, or infarction. It can be performed by a telemetry technician or through computerized, automated, devices that are programmed to identify, and alarm to, specific problem-patterns.
Normal sinus rhythm
rhythm that originates in the SA node and follows the normal conduction pattern of the cardiac cycle.
isometric line.
A flat line extending through an ECG pattern i
isoelectric line.
A flat line within the ECG pattern, such as from the bottom of the P-wave to the Q-point
What are the automaticity Rate for the SA Node, AV Node, and the Purkinje Fibres??
Automaticity Rates
SA Node: 60-100 bpm
AV Node: 40-60 bpm Purkinje Fibres: 20-40 bpm
ectopic impulse.
an impulse that originates from a source outside of the normal cardiac conduction system.
What causes a premature beat?
When cardiac tissue damage occurs, i.e. ischemia/necrosis, the damaged tissues do not conduct the nervous impulse as quickly; it serves as a “conduction block.” Because of this delayed conduction, cardiac tissues adjacent to the block, that have already contracted, may repolarize out of their refractory period back to their excitable state.
How do you asses a cardiac ECG Rhythm? (9 steps)
1) Evaluate atrial and ventricular rhythms. (Regular or irregular?)
2) Determine the atrial and ventricular rates.
3) Assess the presence and configuration of P waves.
4) Calculate the duration of the PR interval.
5) Calculate the QRS duration.
6) Calculate the QT interval.
7) Assess for ST interval or T wave changes.
8) Interpret the rhythm. (i.e. atrial fib?)
9) Determine the clinical significance. (Is the client stable or unstable?)
10)
Determine course of treatment.
4 noninvasive ways to assess cardiac rhythms?
1) Holter monitering.
2) Event recorder monitoring.
3) Exercise treadmill (stress-) testing.
4) Signal averaged ECGs.
Electrophysiology (EPS) testing
invasive means of assessing cardiac rhythms, and involves the insertion of multiple catheters to the right side of the heart via the femoral vein. Performing this procedure can cause serious dysrhythmias
Sinus Bradycardia or Absolute Bradycardia
when the SA node fires at a rate of less than 60 beats per minutes
relative bradycardia
When the client is experiencing a HR that is less than their norm and is causing symptoms, and can be more than 60 bpm
what are the symptoms of bradycardia?
pale, cool skin, hypotension, angina, dizziness or syncope, confusion or disorientation, and
shortness of breath.
How do you treat Sinus bradycardia?
- anticholinergic medications.
- Atropine is used as first-line pharmacotherapy for bradycardia
- Pacemaker may be require
Sinus Tachycardia
- rate (>100bpm)
- can be absolute or relative as well.
- can occurs by either
(1) parasympathetic (vagus) nerve inhibition or
(2) sympathetic nervous system excitation.
Symptoms of Sinus Tachycardia
dizziness, dyspnea, and hypotension. The increased oxygen demands of the heart may cause angina.
How to treat Sinus Tachycardia
- If the cause is hypovolemia, fluid administration may suffice to correct the HR. If the cause is pain, analgesics can correct the rate.
- Beta-blockers may be used to slow the HR if the cause is identified as excessive SNS stimulation or consumption of exogenous stimulants (epi/norepi).
- Adenosine is used to correct tachycardia. It is an antiarrhythmic agent that works like a “chemical defibrillation.” It causes the heart to momentarily “stall-out,” in hopes that, when it re-engages, the rhythm will correct itself.
How does premature atrial contraction occur?
Occurs when an ectopic current originates in atrial tissues other than the SA node.
What can cause Premature atrial contractions?
from emotional stress, fatigue, or the use of drugs such as caffeine, alcohol, and nicotine. A PAC can also occur from hypoxia, electrolyte imbalances, and disease states such as hyperthyroidism, COPD, and CAD.
Paroxysmal Supraventricular Tachycardia
dysrhythmia originating from an ectopic focus between the AV node and the bundle of HIS. It occurs because of electrical re-entry of current into already contracted tissues after the absolute refractory period has passes.
How to diagnose Paroxysmal Supraventricular Tachycardia
HR must be 100-300 bpm. On the ECG, the P wave will often be absent as it is masked by the preceding T wave.