Atrioventricular block Flashcards
what results in AV block?
block in conduction in either the AV node or the bundle of his.
How many forms of heart block are there?
Three.
what is first degree AV block?
Prolongation of the PR interval to >0.22s. every atrial depolarisation is followed by conduction to the ventricles but with delay (every P wave is followed by a QRS)
what is second degree AV block?
Some P waves conduct and others do not.
what are the different forms of second degree AV block called?
Mobitz I block, Mobitz II block and 2:1 or 3:1 block
what is Mobitz I AV block?
Progressive PR interval prolongation until a P wave fails to conduct. The PR interval before the blocked P wave is much longer than the PR interval after the blocked P wave.
what is mobitz II AV block?
occurs when a dropped QRS complex is not preceded by progressive PR interval prolongation. usually has a wide QRS complex (>0.12s)
What is 2:1 or 3:1 block?
occurs when every second or third P wave conducts to the ventricles
what is third degree heart block?
complete heart attack occurs when all atrial activity fails to conduct to the ventricles
what drug may be given to treat heart block?
IV atropine
what are congenital causes of complete heart block?
- autoimmune
- structural heart disease
what are idiopathic fibrosis causes of complete heart block?
- Lev’s disease
- Lenegre’s disease
what are the ischaemic heart disease causes of complete heart block?
- acute myocardial infarct
- ischaemic cardiomyopathy
what are the non-ischaemic heart disease causes of complete heart block?
- calcific aortic stenosis
- idiopathic dilated cardiomyopathy
- infiltrations (e.g. amyloidosis, sarcoidosis, neoplasia)
what types of surgery may result in complete heart block?
aortic valve replacement, CABG, VSD repair
what iatrogenic causes are there of complete heart block?
radiofrequency AV ode ablation and pacemaker implantatation
what drugs could cause complete heart block?
digoxin, beta-blockers, non-dihydropyridine calcium-channel blockers, amiodarone
what infections could cause complete heart block?
endocarditis, lyme disease and chagas’ disease
what autoimmune rheumatic disease causes of complete heart block are there?
SLE, rheumatoid arthritis
what neuromuscular disease causes complete heart block?
duchenne muscular dystrophy
what is bundle branch conduction delay?
slight widening of the QRS complex (up to 0.11s).
what is bundle branch conduction delay known as?
incomplete bundle branch block
what is complete block of bundle branch?
associated with a wider QRS complex (>0.12s).
what does the shape of the QRS depend on in complete BBB?
whether the right or the left bundle is blocked.
How is right bundle branch block seen on the ECG?
deep S waves in leads I and V6 and as a tall late R wave in V1
How is left bundle branch block seen on the ECG?
deep S wave in lead V1 and a tall late R wave in leads I and V6.
what is hemiblock?
delay or block in the divisions of the left bundle branch produces a swing in the direction of depolarisation of the heart.
what is bifascicular block?
a combination of a block of any two of the following - right bundle branch, the left antero-superior division and the left postero-inferior division.
what symptoms may be seen for bundle branch block?
none. it is usually asymptomatic.
what signs may be seen in bundle branch block?
Right BBB may cause splitting of the second heart sound.
left BBB may cause reverse splitting of the second heart sound.
what symptoms may patients with intraventricular conduction disturbances complain of?
syncope
what are the causes of right bundle branch block?
normal finding in about 5% of individuals. congenital cardiac disorders such as: - atrial and ventricular septal defects - pulmonary stenosis and Fallot's tetralogy - pulmonary embolism - pulmonary hypertension - MI - fibrosis of conduction tissue - chagas disease
what are the common causes of left bundle branch block?
aortic stenosis
hypertension
MI
severe coronary disease
