Differential diagnosis for syncope: 

- Slow onset, slow offset - hyperventilation, hypoglycemia

- Abrupt onset, slow offset - seizure 

- Abrupt onset, abrupt offset: 

a. Obstructive - aortic stenosis, HoCM, myxoma, severe pulmonary HTN (no LV preload) 

b. Arrhythmic - bradycardia, tachycardia. 

c. Vascular - vasovagal, orthostatic, hypertension, vertebro-basilar insufficiency (i.e. vasospasm/migraine)

- can have some crossover - hyperventilation can cause bradycardia, seizure can cause acidosis, vertebrobasilar dissection can cause increased vagal tone and AV block

Neurocardiogenic syncope: i.e. "vasovagal" 

- vasodepressor (blood pressure drops, HR goes up) + cardioinhibitory (body makes HR go down suddenly) - HR goes down too low, syncope. As soon as you fall down, increased preload - recovery 

- cardio inhibitory (carotid hypersensitivity) - i.e. in the hospital, people get suctioned, pressure on CN IX, transient asystole (same mechanism as carotid massage) 

- vasodepressor - decreased vascular tone. 

Arrhythmic syncope

- VT or Torsades + hypotension - in old person with structural heart defects, must r/o VT 

- Afib/flutter + RVR (i.e wpw)

- AV block

- Sinus arrest - syncope occurs every 3-5 years so there's no point in short term monitoring.

Rare causes of syncope 

- Bradybury eggleston - men 80s-90s with prostate disease, supine hypertension (200s systolic), orthostatic hypotension. Treat with avoiding extreme movements, +midodrine (alpha agonism) to maintain preload. 

- Platybasia - AV fistulas in occiput, so when you change position, you steal blood from vertebrobasilar system. 

- Platypnea orthodeoxia - reverse of orthopnea. pulmonary hypertension with PFO - right to left shunt when standing up. Either shunt within heart (PFO) or within lungs (pulmonary AVM) 

MI - peri-ischemic area is most likely to generate VT that then degenerates into VFib 

2nd degree AV block: 

- narrow qrs - 90% of the time it's mobitz 1 

- wide qrs - 90% of the time it's mobitz 2 

Precordial thump 

- defibrillation - extends the refractory period, so breaks the re-entrant rhythm of vfib 

- precordial thump is similar to defibrillation - can induce or break v-fib. if someone is coding, and you can't get the defibrillator, just hit the patient really hard in the chest