Fast Arrhythmias 

Sinus rhythm
- Meaning that the source of atrial depolarization is the sinus node. You can have "sinus rhythm" with block.
- P wave direction is inferior, anterior, and to the L (assuming no dextrocardia) -- i.e. upright in II, upright in I. In AvF and III - it may be biphasic or even inverted, depending on the positioning of the heart
- When you're lying down, you use the inferior part of the sinus node (more R to L, so flatter in II, sharper in I). when you exercise, you use the superior part of the node (more superior to inferior -- higher peaks in II). Additionally, p-waves are bigger in exercise because more of the sinus node is being used. Downsloping PR intervals can reflect atrial depolarization after a large p-wave

Placement of leads
- V1 = 4th intercostal space (move to 2nd to look for brugata)

Negative P wave in V1-- left atrial enlargement, as the L atria is slightly posterior to the R, and when it gets larger this positioning is exaggerated.

Types of Arrhythmia
- Increased automaticity
- Re-entry
- Triggered activity (rare in normal people without dig toxicity) - impulses that occur during phase 3 or 4. "delayed after depolarization"

AV node
- fast pathway (SA directly to AV node) and slow (SA to tissue inferior and posterior to AV node) that conducts.
- Fast pathway conducts fast, recovers slow, slow pathway conducts slow, recovers fast.
- SA node always hits both slow and fast pathways. So do PACs--- setting up potential for re-entry

Aberrancy - wide qrs (>120ms) 
- conduction outside of his-purkinje system.
- Bundle branch block - R vs L, fixed vs rate-dependent, rate-of-change related BBB (ashman's phenomenon). Ashman's - sudden decrease in R-R interval. The right bundle's refractory period is dependent on the previous R-R interval. When you get a sudden decrease in R-R, the R bundle can't handle it and it will block. But then by the next short R-R interval it's learned and it will conduct the next one
- Drugs (TCA, Class I antiarrhythmic)
- Electrolytes (hyperkalemia-- extremely wide QRS ie. >200
- Pacemakers
- Non specific IVCD - conduction slowed through ventricular tissue because of cardiomyopathy, sarcoid, etc,
- Channelopathy
- Hypothermia
- Accessory pathways

Adenosine 
- When used in a transplanted heart, there are increased adenosine receptors, so they are hypersensitive to adenosine and administration may lead to prolonged asystole.

AV disassociation
- Complete heart block (more P's than R's) - atrial rate > ventricular rate, both are regular.
- Junctional tachycardia (more R's than P's)

Afib with accessory pathway
- sometimes conducts through the node (narrow QRS)
- sometimes conducts through the pathway (wide QRS)
- sometimes its both and its a slurred wave
- you don't want to block the node because as long as some impulses go through the node, they'll go retrograde up the accessory pathway and cause a refractory period -- when you block (with adenosine) there is unchecked conduction through the accessory pathway => vfib

Pacemakers: 
- RV pacing alone over time leads to cardiomyopathy, so biventricular pacing is better for young people

T wave inversion is standard in RBBB

Differential of irregular rhythms: 
- Irregularly irregular : afib, wap, mat, Afib + dig or afib + complete block
- Regularly irregular: grouped beats

Flutter
- Typically around tricuspid annulus. Most common and easiest to ablate.
- Can also go around septum, go around pulmonary veins

Old people, longstanding htn - will go into afib after surgery, and get flash pulmonary edema (diastolic heart failure)

Ivabradine for HFpEF- inhibits I-funny channels (slows rate without negative inotropy, like b-blockers) -- slow HR, more time to fill.  Increase VO2

	Increased automaticity	Re-entry	Notes
Sino atrial node	Sinoatrial tachycardia (ST) - can be physiologic (ie. exercise) or pathologic (inappropriate sinus atrial tachycardia, ca clock dysregulation	Sinoatrial node re-entry	differentiate the 2: they both appear as sinus rhythm, but ST starts and stops gradually, but re-entrant rhythms start and stops immediately
Atrial tissue	Atrial tachcardia (another focus in atria) - faster than sinus, necessarily, because if it were slower it’d be suppressed by sinus rhythm	Aflutter. Maybe a-fib - macro re-entrant rhythm, so there’s no electroneutral baseline, as something is always depolarizing - limb leads .The precordial leads will not show bc they show a small window of myocardium	Will not stop with AV nodal block - but if you apply adenosine the flutter will still go on, but there will be complete block
Av node	Junctional tach (more common in kids— adults due to dig toxicity) - P & QRS waves will be separated  - like complete block, but there will be more QRS than P	AVNRT	should break with AV nodal block (ie vagal maneurver, adenosine)
Pathways		AVRT (circuit involves ventricles)