L9: Cardiac Arrhythmias Flashcards
fast heart rate >100bpm
tachycardia
causes of tachycardia
increased body temp.
sympathetic stimulation
toxic heart conditions (weakened myocardium)
tachycardia: increased body temperature
HR increases by 10 bpm per 1F
or
increases by 18 per 1C
tachycardia: sympathetic stimulation
severe blood loss or shock
slow heart rate <60bpm
bradycardia
causes of bradycardia
athletic heart
vagal stimulation
extremely sensitive carotid baroreceptors in carotid sinus syndrome
respiratory sinus arrhythmia
ability to change heart rate thru inspiration/expiration cycles
thus increases/decreases number of impulses sent via the sympathetic/vagal
exercise induced tachycardia
endogenously mediated tachycardia
increased HR,CO
decreased filling time but SV does not drop
pathologically mediated tachycardia
increased HR
decreased CO
what factor drops in pathological tachycardia and why?
cardiac output
mean arterial pressure decreases
sympathetic activated after thus not able to compensate
thus no muscles stimulated to increase venous return
sudden cessation of P waves
sinoatrial block
atria standstill
sinoatrial block
ventricles pick up new rhythm
QRS is slowed but not altered
P wave is missing
causes of atrioventricular block
ischemia of AV/bundles
compression of AV by scar tissue
inflammation of AV
extreme stimulation of heart by vagus
PR interval increases greater than 0.2 seconds
1st degree incomplete atrioventricular heart block
PR interval increases 0.25 to 0.45 seconds
2nd degree incomplete atrioventricular heart block
results of 2nd degree atrioventricular block
missing beats of ventricles
2:1 rhythms develop
P wave and QRS complex are no longer related
complete atrioventricular block
in atrioventricular blocks the AV node may cease conduction
ventricles may not beat again for 5 to 30 seconds
ventricular escape
resuming of ventricular beats due to purkinje fibers acting as ectopic pacemaker
in a complete atrioventricular block patients may…..
faint due to lack of blood to brain
stokes-adams syndrome
fainting spells caused by complete atrioventricular blocks
electrical alternans
partial intraventricular block
an alternation in amplitude of P, QRS, or T
no missing waves
contraction occurring before it should
premature contraction caused by: an ectopic focus local ischemia calcified plaques irritation of conduction system or nodes
heart suddenly beats rapidly, ranging from seconds to hours or even days
paroxysmal tachycardia
begins and ends suddenly
returning to normal at conclusion
the slow-twitching of individual muscle fibers in a heart chamber
fibrillation
occur when the length of the pathway remains normal but the conduction velocity of the impulse is slowed
circus mvt
causes of circus mvts
blockage of purkinje system ischemia high K+ levels response to epinephrine response to repetitive electrical stimulation
basis for fibrillation
occurs as a result of circus mvts
why does normal ventricle depolarization die out in circus mvts and fibrillation?
because a portion of the heart is already in refractory period and cannot respond to a second stimulus
3 different conditions resulting in circus mvts
the pathway is too long – dilated heart
length of pathway is constant but velocity has slowed
refractory period has become greatly shortened
cardiac fibrous skeleton
ventricle and atria fibers are separated by this
allows each chamber to exhibit fibrillation independently of each other
causes of atrial fibrillation
enlargement of atria – How?
- -valve lesions
- -inadequate emptying of ventricles
how does inadequate emptying of ventricles enlarge the atria?
causes blood to back up into the atria
