B4.001 Tachycardia Big Case Flashcards
what is intermittent ventricular fibrillation?
doesn’t exist
you can’t spontaneously recover if you have ventricular fibrillation
what is tachycardia
rhythm with 3 consecutive beats > 100bpm
what are some mechanisms for tachycardia
enhanced automaticity
re-entry
triggered beats
what is atrial fibrillation?
most common form of sustained arrhythmia
atria out of coordination with ventricles
risk factors for a-fib
5% of people older than 65
2:1 M:F
lifetime risk for 40 yo is 1 in 4
different types of a-fib manifestations
paroxysmal
persistent
why can a-fib be deadly?
blood can pool in left atrium due to ineffective pumping and eddy formation
blood that is stagnant can develop clots, particularly in the L atrial appendage
induce a 4-5x increased risk of ischemic stroke
associations with a-fib
organic heart disease (electrical or mechanical)
disturbances of sympathetic-vagal balance (endocrine, physiological)
possible contributors to a-fib
anxiety anemia reactive hypoglycemia herbal supplement toxicity drugs alcohol abuse coronary disease
if you recognize a-fib in a patient, what do you do in response?
- call cardio for a consult, hopefully within 24 hrs
- CBC, TSH, electrolytes, LFTs and fax to cardio
- abstain from possible contributors
- begin anticoagulation therapy
- start rate control therapy
what are the 4 big parts of managing a-fib
- ECG in all pts
- anticoag unless contraindicated
- initial rate control with beta-blocker or Ca channel blocker (digoxin only as adjunct)
- transthoracic echo in most (transesophageal only when it changes management)
why would you want a transesophageal echo?
left atrial appendage visualization
what is cardioversion
administering a shock to regulate sinus rhythm
atria receive smaller shock than ventricles
what is ablation?
a procedure that can correct heart rhythm problems (arrhythmias)
works by scarring or destroying tissue in your heart that triggers or sustains an abnormal heart rhythm
in some cases, ablation prevents abnormal electrical signals from entering your heart and, thus, stops the arrhythmia
3 ways to increase cardiac output
increase HR (electrical adjustment)
increase power behind beats (muscle power adjustment)
fix “sloppy” valves, streamline efficiency
how does HR respond to exercise?
increases consistently with level of activity
how does SV respond to exercise?
lowest when standing
slight increase with activity, but much less than HR
increase with sitting and laying down as well
describe the conduction velocities at different locations in the heart
vary greatly between areas AV node = 0.05 m/sec atrial muscle = 0.5 ventricular muscle = 0.5 bundle of His = 2 left and right bundles = 2 Purkinje fibers = 4
where is conduction velocity the lowest
AV node
what is the direction of conduction through the heart
SA atrial muscle AV bundle of HIs left and right bundle branches Perkinje fibers ventricular muscle
what creates the P wave on an EKG
atrial depolarization
what creates the QRS complex
heart contraction due to opening of voltage gates Na channels
which ions are depolarizing
Na
Ca
which ions are repolarizing
K
difference between SA/AV vs atrial/ventricular action potentials
SA/AV
-no resting potential
-funny sodium currents responsible for phase 0 depolarization (open during repol)
atrial/ventricular
-resting potential present
-voltage gated sodium currents responsible for phase 0 depolarization
CO =
HR * SV (l.ventricle)
PBF =
HR * SV (r.ventricle)
in general, how do left and right ventricular stroke volumes compare?
generally the same since HR is the same on each side and CO = PBF
MAP =
CO * TPR
