12- Ecg Basic Disturbances Of Rhythm Flashcards
How are bradycardia and tachycardia defined
Bradycardia (heart rate < 60)
• Tachycardia (heart rate > 100)
Give examples of cardiac conduction abnormalities
Supraventricular Arrhythmias:
Atrial fibrillation, atrial flutter, atrio-ventricular nodal reentrant
tachycardia (AVNRT)
• Ventricular Arrhythmias:
Ventricular tachycardia, ventricular fibrillation
Describe the standard display on an ecg
- Typically the ECG comes at a standard sweep speed of 25 mm/s
- 1 mm = 0.04s = small square
- 5mm=0.2s=BIGsquare
- Yaxis:1mm=0.1mV
Describe sinus tachycardia
The form of the waves is normal but the rate is fast
• You have NORMAL P waves and NORMAL PR intervals
• The only thing that’s abnormal is that the sinus node is firing faster than it
should
• Summary of the features of sinus tachycardia:
P waves have normal morphology Atrial rate = 100-200 bpm
Regular ventricular rhythm Ventricular rate = 100-200 bpm
A P wave precedes every QRS complex - there is no loss to conduction
• This is often physiological - could be the body’s way of responding to some
external insult
Describe atrial fibrillation
Absent P waves - you may get oscillating baseline (fibrillation waves - f waves) Atrial Rate = 350-600 bpm Irregular ventricular rhythm Ventricular Rate = 100-180 bpm Normal QRS
Describe atrial flutter
Undulating saw-toothed baseline (F (flutter) waves)
Atrial Rate = 250-350 bpm
Regular ventricular rhythm
Ventricular Rate = 150 bpm (with 2:1 atrioventricular block)
4:1 atrioventricular block is also common (3:1 and 1:1 are uncommon)
What are the 2 types of svt
Supraventricular Tachycardia (SVT) = Atrioventricular Nodal Reentrant Tachycardia (AVNRT)/Atrioventricular Reentrant Tachycardia (AVRT)
Atrioventricular Nodal Reentrant Tachycardia
•
The depolarisation is rotating within the AV node
• You get SIMULTANEOUS depolarisation of the atria and the
ventricles
• So the QRS complex and the P wave are instantaneous
• As the depolarisation of the ventricles shows a larger voltage,
this overlies the P wave
Summary of Atrioventricular Nodal Reentrant Tachycardia
- Narrow-complex tachycardia
- Regular QRS complexes
- P waves are often buried within the QRS or are just after the QRS
- Re-entrant circuit within the AV node
- Atria and ventricles depolarise at the same time
Describe preexcitation syndrome
congenital connection between the atria and the ventricles called an ACCESSORY PATHWAY
• This allows the atrial conduction to come down to the ventricles via two paths - via the normal AV nodal pathway and via the accessory pathway
Abnormal connection manifests as the delta wave on the QRS
• This can be recognised by the abnormally short PR interval which signifies an abnormal connection between the atria and the ventricles
What is Wolff-Parkinson-White Syndrome
accessory pathway
with a short PR interval leading to ventricular
preexcitation
What are the 3 degrees of av node block
1st Degree = prolonged PR interval
2nd Degree = some conduction gets through but it’s slow
• Mobitz Type 1 (Wenckebach)- some p waves don’t pass into ventricles, gradual increase in PR interval
• Mobitz Type 2 - normal PR interval
3rd Degree = complete heart block - nothing gets through to the ventricles -ventricles
• The ventricles start firing on their own as an escape mechanism
• The P waves and the QRS complexes are COMPLETELY DISSOCIATED
Describe bundle branch blocks
QRS complex widens (>0.12s) QRS morphology changes (varies depending on the ECG lead, and if it is right or left bundle branch block) LBBB: V1 = W V6 = M • RBBB: V1 = M V2 = W
Describe ventricular tachycardia
ventricular tachyarrhythmia can kill you
• Ventricular tachyarrhythmia has a broad QRS
• So you get a rapid, regular, broad QRS complex pattern
Describe ventricular fibrillation
There are broad, irregular QRS complexes
• The irregularity is in the QRS complex showing that the problem is in the ventricles
• Broad complexes that are void of any pattern
• Irregular in terms of amplitude and rhythm
