Arrhythmias Flashcards
The 2 mechanisms of arrhythmias are
ectopic foci
reentry circuit
Atrial flutter is
a re-entrant pathway in the atrium (usually right) causes supraventricular tachycardia
Characteristics of atrial flutter on ECG
‘saw-tooth’ shaped “flutter waves” (F waves)
No P-waves
Why is the ventricular rate of contraction slower than in the atria in?
due to the refractory period at the AVN
Atrial fibrillation is
Multiple ectopic sites around the atria (usually overriding the SAN) cause the atria to quiver causing ventricular tachycardia
Is the ventricular/pulse rate regular or irregular in atrial flutter
regular or irregularly irregular
Is the venticular/pulse rate regular or irregular in atrial fibrillation
An irregularly irregular pulse, both in the rhythm and volume, is characteristic
Atrial contraction rate is very high in atrial fibrillation but most of them don’t get through to the ventricles - why?
AVN refractory period
Characteristics of atrial fibrillation on ECG
No P-waves
Irregular, narrow QRS
Baseline is flatter the more ectopic sites there are
Ventricular tachycardia is
A rapidly firing ectopic foci or reentry circuit in the ventricle causes regular fast contractions (100-200bpm)
Characteristics of ventricular tachycardia on ECG
wide, bizarre looking QRS
No P-wave
Can occur in short episodes of ~30secs (sustained needs immediate treatment or cardiac arrest)
Heart rate in ventricular flutter
> 200bpm
Whats the relationship between the atrial and ventricular contractions in ventricular tachycardia and flutter like?
complete dissociation as ventricular depolarisation not triggered by atrial site
Ventricular fibrillation is
multiple weak ectopic sites in a ventricle giving unsynchronized chaotic signals causing the ventricles to quiver (fibrillate)
Characteristics of ventricular fibrillation on ECG
No identifiable P-wave, QRS, or T-wave
Irregular waveforms of varying amplitude
How does V-fib lead to death
Ventricles fibrillate, pump little/no blood, cardiac arrest
Treatment of arrhythmia
Anti-arrhythmic drugs - Na/K/Ca channel blockers to try and get back to sinus rhythm
Beta blockers and Ca channel blockers- alters autonomic influence on heart to lower HR
Anticoagulants - stops clots forming in stagnant blood in heart (thrombus > stroke)
Symptoms of ventricular tachycardia
SOB
Nausea
Dizziness
Chest pain
What is a re-entry circuit?
A unidirectional block in a conducting pathway causing localised of global self-perpetuating electrical loop
(global as in “global re-entry” = re-entry circuit between atria and ventricles)
most common AV block in atrial flutter is
2:1 AV block
the most common arrhythmia is
atrial fibrillation
Atrial bpm in atrial flutter
typically 250-320bpm
Atrial bpm in atrial fibrilation
300-600bpm
the main risk in atrial flutter and fib
embolic stroke - clots form in stagnant/slow moving blood
what is direct current (DC) cardioversion
procedure where patients heart is defibrillated to get it back into normal rhythm (done under general anaesthetic)
(can give anti-arrhythmic drugs to do this pharmacologically)
Atrial flutter and fibrillation can be assymptomatic and discovered incidentally or they can give the following symptoms
chest pain
palpitations
dyspnoea
faintness
