Heart Week 1b: Rhythmns, etc. Flashcards
PSVT
Paroxysmal Supraventricular Tachy:
a. sudden onset and termination
b. atrial rates between 140 and 250 bpm
c. normal QRS
d. often causes by reentry
Tachycardia
Heart rate > 100bpm
Sinus Bradycardia
P and QRS is normal, but rate is < 60bpm
Escape Rhythm
a. normal QRS but no P
b. wide QRS, maybe no P (Ventricular)
Tell me about the three AV blocks.
a. 1st Degree: PR interval > 5 small boxes (0.2 secs)
b1. 2nd Degree, Mobitz: P is constant, but QRS gets closer and closer until a P happens with no QRS
b2. Mobitz II: all looks normal, then QRS drops out, sometimes the QRS is wide
c. 3rd degree: aka- complete block, QRS and P are completely independent
What is normal sinus rhythm?
60-100 bpm
What is sinus tacky?
100-180 bpm
What is Reentrant SVT?
a. 140-250 bpm
b. P wave is hidden or retrograde
c. may abruptly terminate
Focal Atrial Tachy
a. 130-250 bpm
b. P wave is not normal, but presentation may vary
c. AV block may increases, but rarely reverts
Atrial Flutter
a. 180-350 bpm
b. “saw-toothed” (different from atrial fibrillation)
c. AV block may increase
Atrial Fibrillation
no distinct P waves (different than atrial flutter)
Give me the M/E (mechanism/Example) for decreased automaticity
M: decrease in phase 4 depolarization, eg- parasympathetic stimulation
E: sinus bradycardia
give me the M/E for conduction block.
M: ischemia, anatomics or drug-induced impaired conduction
E: 1st, 2nd, and 3rd degree AV block
Give me the M/E for sinus node enhanced automaticity.
M: increased phase 4 depolarization, e.g.- sympathetic stimulation.
E: sinus tachycardia
Give me the M/E for enhanced automaticity of the AV node, ectopic focus
M: acquires phase 4 depolarization
E1: AV junctional tachy
E2: ectopic atrial tachy and some forms of VT
Gimme the M/E of DAD (delayed afterdepolarization).
M: high intracellular Ca++ (e.g.- digitalis toxicity)
E: premature atrial/ventricular beats, idiopathic VT and digitalis
Gimme the M/E of EAD.
M: prolonged AP duration
E: Torsades de Pointe
Compare DAD and EAD.
DAD: has p wave very soon after QRS
EAD: has p wave while QRS is still happening, ends up with a P wave that can look like an M.
What channels can cause the EAD?
a. during phase 2, it is most likely Ca++
b. during phase 3, it is most likely a recovery of some inactivated Na+ channels
What causes a DAD?
high intracellular Ca++ concentration, can be caused by digitalis toxicity.
What is the difference between ionotropic and metabotropic receptors?
Ionotropic: becomes a channel, ion flows right in, acts more quickly
Metabotropic: uses a second messenger like G-protein, acts slower, ion does not enter the cell.
During what part of the EKG are the K+ channels maximally open?
Q-T Interval.
Most K+ channels are opened when the cell depolarizes and stay open until repolarization.
Why is the done by the left ventricle greater than the work done by the right ventricle?
Work is proportional to output. Since the R/L ventricles have equal output, then you consider the resistance against which it moves, AFTERLOAD. Aortic pressure is greater than the pulmonary pressure, so the L ventricle does more work.
What area of the heart does the LAD supply?
apex, ant wall of LV and ant 2/3 of septum
What area of the hear does the LCX supply?
lateral wall of LV.
What area of the heart does the RCA supply?
RV free wall, post 1/3 of sept, posterior wall of LV.
How big are arterioles? What surrounds them?
10-60 microns with 1-5 layers of smooth muscle.
How big are capillaries? What surrounds them?
5-10 microns in diameter (aout 0.5 to 1.0 mm in length). No smooth muscle.
How big are venules? What surrounds them?
~10-60 microns in diameter. No smooth muscle.
