Bradycardia Flashcards
2 main causes of bradycardia (<60 bpm)
- insufficient impulse formation (sinus node dysfunction)
- insufficient impulse conduction (AV block)
SSS s
sick sinus syndrome– symptoms due to sinus node dysfunction (not every bradycardia is bad). Sinus pauses and sinus arrest, or inappropritate HR response to exertion.
SSS is associated with 3 things
- ectopic atrial rhythms, junctional rhythm
- AV block
- atrial tachyarrthmias– AF and atrial flutter.
a sinus pause is commonly seen in normal people while ___ but it’s abnormal while ____

a sinus pause is commonly seen in normal people while SLEEPING but it’s abnormal while AWAKE
symptoms of SSS or bradycardia in general
- intermittent syncope and presyncope, dizzieness ,light headedness, falls i nthe elderly, palpitations.
- fatigue
- dyspnea and eercise intolerance.
how do you diagnose SND (sinus node dysfunction)
record inappropriately slow sinus rate on ECG. may need to do it on ECG

how do you diagnose SSS?
- record inappropriately slow sinus rate during symptoms.
- SYMPTOM RHYTHM CORRELATION ON ECG.
- this can be very difficult to achieve. diagnosis can be a judgement call. based on available evidence.
“Chronotropic incompetence”:
inadequate heart rate in response to metabolic demand. Failure to achieve 80% of age predicted HR (220-16e)
- is another feature of snius node dysfunction.
for primary sinus node dysfunction, the main cause is:
disease affecting the SAN like age/fibrosis, or paroxysmal AF“tachy-brady syndrome”, coronary disease, infiltrative diseases (sarcoid, amyloid)
causes of secondary sinus node dysunction
- drugs (beta blockers, calacium channel blockers, digoxin, amiodarone, autonomic issues (carotid hypersensitivity, vasovagal syncope), hyperkalemia
SSS treatment
- revesre the reverseible cuases – reduce the rate-limiting dugs if you can.
- check to see if they’re not hypothyroid or marked electrolyte disturbances. - permanent pacemaker.
- beware vasovagal syncope: can be profound sinus pauses and bradycardia– almost never requires a permanent pacemaker.
tachy-brady syndrome:
combination of ____ ___ and ____ conversion pauses at the termination of AF.
combination of paroxysmal AF and at other times, bradycardia (conversion pauses)
how do you treat tachy-brady syndrome?
tachycardia treatment: rate limiting or antiarrhthmic drugs. these will likely make the brady cardia worse.
- bradycardia treated with permanent pacemakers.
SND summary

note

first degree AV block
- just an AV delay. the PR interval is longer than nomral (>200ms). EVERY P WAVE conducts to the ventricles, just slowly.

third degree of AV block
- complete AV block/complete heart block. No P wave conducts to the venricles, not even one.
the atria and ventricles are not communicateing at all- they are dissociated from each other. they might both be regular but one isn’t conducting/controlling the other.
Some rhythm is driving the atria
sinus rhythm, sinus tachycardia, sinus
bradycardia, atrial fibrillation etc
Hopefully, some other rhythm is driving the ventricles
junctional escape rhythm, ventricular escape
rhythm, paced rhythm


AV complete heart block. third degree. the P waves are regular and the QRS complexes are normal but one is not causing the other.
Sinus rhythm (70 bpm), with third degree
(complete) AV block and a junctional
escape rhythm (39 bpm)
JVP changes in heart block
cannon A waves
note: second degree AV block

Type I second degree block (mobitz I)
the PR interval gradually lengthens before the P wave blocks, and the cycle begins agaain. this can be normal.
Sinus rhythm with 3:2 AV Wenckebach

Mobitz type II second degree heart block
Type II (aka Mobitz II) The PR interval remains constant before a P wave blocks, and the cycle begins again-- but still, some beats get "dropped"














