Heart Block Flashcards
Sinus rhythm details
Definition is normal rate and rhythm with all normal intervals
- normal heart rate will increase on inspiration and slow down during expiration in young healthy patients (not pathogenic)
Sinus pause/sick sinus
Failure of SA node to fire one or more beats (P-P intervals increase spontaneously and P wave may not be present)
- pace maker fixes this
SA exit block:
A type of sinus pause where the PP interval is 2:1 ratio from the rest of the normal PP intervals
- pace maker fixes this also
Why dont the SA node and AV node beat separately, even though the AV node can also fire automatically?
The SA node fires faster and better which overrides the AV node firing.
- AV node takes over for the SA node but results in either none or retrograde p waves with bradycardia
Beats per minute as it pertains to automaticity areas of the heart
SA node (60-100)
AV node (35-60)
His/ Purkinje cells (25-35)
Ventricular myocytes (<35)
goes in this order form top down if the previous areas are unresponsive
Escape rhythm/ AV junctional rhythm/ AV nodal rhythm/ junctional escape rhythm
QRS normal w/ P waves being opposite reflection or buried into the QRS complex.
- P waves can also be retrograde
Junctional tachycardia
Fast rate >100bpm
- often produces retrograde p waves in lead waves
Idioventricular escape rhythm
Slow rates (<35bpm) with very wide QRS complexes and P waves/T waves - requires compression
Bundle branch blocks
Occurs due to malfunction of one of the bundles which delays the conduction. Ventricles will beat separately
- RBBB = left -> right delayed
- LBBB = right -> left delayed
Causes of RBBB
Usually pulmonary issues or atrial septal defections
- shows rSR waves in lead V1 “rabbit ears”
- very depressed S wave in V6
Causes of LBBB
Usually a marker of underlying heart disease or LVH
- can also be mitral/aortic valve disease, CAD or injury due to cardiac surgery.
Shows “M” QRS complex that is deflected negative in V1, but positive in V6
1st degree heart block
Prolonged PR interval exceeding 200ms (5 small boxes)
- all P waves have a corresponding QRS complex
by itself, it does not require any treatment
2nd degree heart block
Not all atrial impulses are conducted through the AV node
- P waves dont always match up with QRS complexes
Type 1: PR intervals get increasingly longer until AV dissociation occurs
- does not require treatment
Type 2: PR intervals dont increase until AV dissociation occurs (however they are still prolonged)
- requires a pacemaker since it can often lead to 3rd degree heart block. And the problem usually in the bundle of His
How to tell the difference between PACs and an av block
PACs = p waves look different from each other since an ectopic foci is the cause
- the P-P interval between the preceding p wave and the PAC p wave is shorter.
What does the conduction ratio mean
The ratio between the # of P waves: # of QRS complexes
- if the ratio is consent over time the rhythm is considered regularly irregular
3rd degree heart block
No atrial impulses will conduct to the ventricles
- very obvious AV dissociation since the atria and the ventricles contract independently and have their own separate rate
Atria rate is always faster than ventricular rate
- can show wide or narrow QRS complex pending on where the origin of the block occurs
- narrow complex QRS<120ms = (closer to the AV node itself)
- wider complex QRS>120ms = (closer to the ventricles)
Requires pacemaker
