ARRYTHMIAS Flashcards
What are the most common symptoms experienced by patients with arrythmias?
Often no symptoms at all Palpatations Light headedness Syncope Angina
What is a palpitation?
The sensation of ones own heartbeat
What is the mnemonic HIS DEBS and what does each later mean?
The causes or precipatating factors for arrythmias.
H - hypoxia (underlying pulmonary disorders)
I - ischemia and irritability
S - sympathetic stimulation
D - drugs
E - electrolyte disturbances
B - bradycardia (presdiposes to arrythmias)
S - stretch (of myocardium)
What is a Holter monitor?
A portable ECG machine used to assess arrythmic activity over prolonged periods such as 24 or 48 hours.
What is an event monitor?
This is a portable ECG machine which is initiated by the patient when they begin to experience symptoms. The rhythm strip then lasts for the next 3-5 minutes.
What are the five types of rhythm disturbance in the heart?
Arrythmias of sinus origin Ectopic rhythms Reentrant arrythmias Conduction blocks Preexcitation syndromes
What is sinus tachycardia?
If the rhythm of the heart speeds up beyond 100 beats per minute
What is sinus bradycardia?
If the rhythm of the heart slows down beyond 60 beats per minute
What conditions might be associated with sinus tachycardia?
Infections Hyperthyroidism Heart failure Hypoxic related conditions (such as COPD and asthma) Pain Shock Anemia Pheochromocytoma PE Myocardial infarction Kawasaki disease
What conditions might be associated with sinus bradycardia?
Early sign of myocardial infarction Enhanced vagal tone Hypothyroidism Hypothermia Intrinsic disease of the SA node (sick sinus syndrome) Increased intracranial pressure
What is a sinus arrythmia?
When the ECG reveals a rhythm that is normal in all respects except that it is slightly irregular. It is most often caused by the difference in rate whilst breathing in compared with breathing out.
Why does heart rate increase during inspiration?
Negative pressure in the thorax during inspiration leads to decreased filling time and hence increased heart rate.
Why does heart rate decrease during expiration?
Positive pressure in the thorax from expiration leads to increased filling time and hence decreased heart rate.
What is an escape beat?
A wave of electrical activity that does not originate from the SA node. This might be because the SA has stopped firing.
When the SA node does not fire, which pacemaker most often takes over?
The junctional pacemaker cells around the AV node which fire at about 40-60 times per minute.
Which wave is missing from the ECG strip when the junctional pacemaker cells are setting the rhythm of the heart?
The p wave
What is a retrograde p wave?
When the electrical activity spreads back through the atria having been discharged from the junctional pacemaker cells. The axis of the wave is reversed by 180˚.
What is the theoretical difference between sinus arrest and sinus block?
Sinus arrest is a failure of the SA to fire.
Sinus block is a failure of the tissue surrounding the SA node to conduct the electrical activity.
Because the ECG leads cannot pick up SA node depolarization, these two pathologies will present in the same way.
What are ectopic rhythms?
Abnormal rhythms that arise from elsewhere in the heart than the sinus node. In this way, they resemble escape beats, but here we are talking about sustained rhythms, not just one or a few beats. They arise from enhanced automaticity of a nonsinus node site, either a single focus or a roving one.
What is the most common cause of ectopic rhythms?
Digitalis toxicity (foxglove)
Are re-entrant rhythms a disorder of impulse formation or impulse transmission?
Impulse transmission
Describe how a reentry loop works with regard to cardiac electrical impulses?
Ischemic or other myocardial damage can mean that two adjacent pathways through the myocardium conduct impulses at different speeds. This is not a problem normally as each impulse cancels each other out when they reach the same point in the loop, as they each find themselves in the refractory period of the other. The problem occurs when a second impulse that comes either prematurely or very soon after the first impulse. The fast conducting pathway will have a relatively long refractory period whereas the slow conducting route has a much faster refractory period. This means that the second impulse cannot go down the fast conducting pathway but is allowed down the slow one. As a result this second impulse that travels initially down the second pathway is not cancelled out by its equivalent impulse coming down the fast pathway and a reentry loop has been established. The impulse can now travel back up the heart in a retrograde fashion which severely limits the hearts capability to pump in unison.
What are the four questions used to assess any ECG strip?
Are P waves present and normal?
Are the QRS complexes narrow or wide?
What is the relationship between the P waves and the QRS complexes?
Is the rhythm regular or irregular?
What might you see on an ECG that would indicate an atrial premature beat?
A P wave with an abnormal contour.
The timing might also be irregular.
The PR interval may be decreased as well.
What might you see on an ECG that would indicate a junctional premature beat?
A narrow QRS complex that is not preceeded by a P wave at all or a retrograde (upside down) P wave.
What is the difference between a junctional premature beat and a junctional escape beat?
The junctional premature beat happens too early but the junctional escape happens too late as a result of a lack of atrial impulse.
