Session 7-ECG Abnormalities Flashcards
Which rhythms are classified as supraventricular rhythms?
1) sinus node
2) atrial
3) AV node
Which system conducts supraventricular rhythms into and within the ventricles?
His-Purkinje system
True or false: supraventricular rhythms have a broad complex
FALSE - narrow complex, ventricular rhythms have broad complex
Where do ventricular rhythms arise from?
Focus/foci in ventricle
True or false: the conduction of ventricular rhythms is not via usual His-Purkinje systems
TRUE
Describe atrial fibrillation
Impulses have chaotic, random pathways in atria
What do atria do in atrial fibrillation rather than contract?
Quiver
True or false: ventricles depolarise and contract normally in atrial fibrillation
TRUE
Describe the characteristics of an atrial fibrillation ECG (2)
1) absent p waves - wavy baseline
2) narrow QRS complexes which are irregularly irregular
What is an AV conduction block or ‘heart block’?
Delay/failure of conduction of impulses from atria to ventricles via AV node and bundle of Hiss
What is the most common cause of an AV conduction block?
Acute myocardial infarction
What are the three types of heart block?
1) first degree heart block
2) second degree heart block (mobitz 1 and mobitz 2)
3) third degree heart block or complete heart block (CHB)
Describe the characteristics of first degree heart block
1) p wave normal
2) slow conduction in AV node and His bundle
3) PR interval prolonged > 5 small squares
4) QRS Norma
What is another name for Mobitz type 1 (2nd degree heart block)?
Wenkebach phenomenon
Describe the characteristics of Mobitz type 1, second degree heart block
progressive lengthening of PR interval until one P is not conducted (allowing time for AV node to recover)
Describe the characteristics of Mobitz type 2, second degree heart block
1) PR interval normal
2) sudden non-conduction of a beat (dropped QRS)
3) high risk of progression to complete heart block
Describe the characteristics of third degree heart block
1) normal atrial depolarisation but impulses not conducted to ventricle
2) ventricular pacemaker takes over (ventricular escape rhythm) and this rate is very slow (~30-40bpm)
3) usually wide QRS complexes
4) HR often too slow to maintain BP and perfusion
What is the relationship between P waves and QRS complexes in third degree heart block?
No relationship
What happens in ventricular ectopic beats?
1) Ectopic focus in ventricle muscle
2) Impulse not spread via fast His-Purkinje system therefore much slower depolarisation of ventricle and therefore wide QRS complex