Arrhythmias pt 1 Flashcards
tisdale pg 6 - 13 (background to sinus bradycardia)
what part of the heart starts the spark for cardiac conduction system?
SA (sinus) node
how does depolarization happen in the heart?
depolarization reaches the end of the cell which depolarizes the cell next to it and then so on
what is phase 0?
depolarization
right before the Q wave
up and down on the action potential wave
sodium current
what is phase 1?
rapid repolarization
potassium current (Ito)
Q interval
what is phase 2?
calcium current
plateau
QT interval
what is phase 3?
repolarization of K currents (Iks, Ikr)
T wave
what are the questions to ask if an ECG is a normal sinus rhythm?
is there a p wave in front of very QRS complex?
is there a QRS complex after every p wave?
Is the interval between the R waves equal?
Is the heart rate between 60-100 bpm?
what is the 300-150-100 method?
measures bpm
find a R wave on a box then count off starting at 300 then 150 then 100 then 75 then 60 for each big box passed
where ever the next R wave falls is the bpm
what is 5 big box method?
5 big boxes on an ECG is roughly 1 second so you can count the number of waves in each box will tell you the bpm
what is the normal value of the PR interval?
0.12 - 0.2 seconds
120-200 ms
what are example of drugs that change the PR interval?
BB
CCB
amiodarone
digoxin
what is the normal duration for QRS?
0.08-0.12 seconds
80-120 ms
what is normal value for QT interval?
0.38-0.46 seconds
380-460 ms
what is the normal time of the QTc interval for men?
0.36-0.45 seconds
360-450 ms
testosterone shortens it
what is the normal time for QTc interval for women?
0.36-0.45 seconds
360-460 ms
how would one find a corrected QT interval?
take the QT interval and divided by the square root of respiration rate
when does torsades de pointes occur?
when the QTc interval exceeds 500 ms there is an increased risk
what is torsades de pointes?
drug-induced arrhythmia due to lengthening of action potential too much
no p waves
what are the drug classes that can induce torsades de pointes when on long-term?
anti arrhythmic
antimicrobials
antidepressants
antipsychotics
anticancer
methadone
what anti-arrhythmics cause TdP?
procainamide
flecainide
amiodarone
dronedarone
ibutilide
dofetilide
sotalol
Phineas and Ferb Are Doing IDiot Stuff
what antimicrobials can induce TdP?
macrolides - azithromycin, clarithomycin, erythromycins
fluoroquinolones - levofloxacin, moxifloxican, ciprofloxacin
what antidepressants can induce TdP?
citalopram
escitalopram
clomipramine
desipramine
lithium
mirtazapine
venlafaxine
what antipsychotics can induce TdP?
chlorpromazine
haloperidol
pimozide
thioridazine
aripiprazole
clozapine
iloperidone
olanazapine
paloperidone
quetiapine
risperidone
sertindole
ziprasidone
what anticancer drugs can cause TdP?
arsenic trioxide
eribulin
vandentaib (and most drugs ending in nib)
what are examples of supraventricular arrhythmias?
sinus bradycardia
atrioventricular (AV) nodal block
sinus tachycardia
atrial fibrillation
supraventricular tachycardia
where do supraventricular arrhythmias occur?
above the ventricles
what are the types of ventricular arrhythmias?
premature ventricular complexes (PVCs)
ventricular tachycardia
ventricular fibrillaton
what are the features of sinus bradycardia?
HR under 60 bpm
impulse originates in sinoatrial (SA) node
what is the MOA of sinus bradycardia?
decreased automaticity of the SA node
what are etiologies of sinus bradycardia?
MI/ischemia
abnormal sympathetic/parasympathetic tone
electrolyte abnormalities (high K/Mg)
drugs
idiopathic (sick sinus syndrome)
what are examples of drugs that can induce sinus bradycardia?
digoxin
BB
diltiazem, verapamil
amiodarone
dronedarone
ivabradine
when a drug is suspected to cause sinus bradycardia, how should it be treated?
remove it and see if the HR returns to normal, need to know half-life though for this
for specifically diltiazem/verapamil, just stop it entirely
what are symptoms of sinus bradycardia?
hypotension - due to not generating enough CO
dizziness, fainting (syncope)
when is treatment necessary for sinus bradycardia?
only if pt is symptomatic
what is the first line treatment of sinus bradycardia?
atropine 0.5-1 mg IV, repeat as required every 3-5 minutes up to max dose of 3 mg
what is the AE of atropine?
tachycardia
urinary retention
blurred vision
dry mouth
mydriasis
how should sinus bradycardia be treated if pt is unresponsive to atropine?
transcutenous pacing OR
infusion of B-agonists with rate-accelerating effects
what is transcutaneous pacing?
electrical jolt to pt while figuring out next steps for sinus bradycardia
what are B-agonist used to tx sinus bradycardia?
dopamine 5-20 mcg/kg/min
epinephrine 2-10 mcg/min titrate to desired effect
isoproterenol 20-60 mcg IV bolus based on HR response
how should a person who recently had a heart transplant or spinal cord injury be treated for symptomatic or hemodynamically unstable sinus bradycardia?
amiophylline via IV over 20-30 minutes
theophylline via IV (transplant) or PO (spinal cord) titrated to effect
for patients who have sick sinus syndrome induced sinus bradycardia, how should they be treated?
long-term treatment of permanent pacemaker which titrated HR to 60-70 bpm
