cardiac arrhithmias ( chapter 13) Flashcards
Common causes of abnormalities in rhythmicity
abnormal pacemaker, shift of pacemaker to different spot, blocks at different points of impulse spread, abnormal pathways of impulse, spontaneous generation of spurious impulses in any part of heart.
Tachycardia
Fast heart beat.( more than 100/ min.), Sympathetic stimulation causes it
how many beats does heart rate rise per degree fahrenheit with a fever?
10 beats per degree
Bradycardia
slow heart rate ( less than 60 beats/min.) Common in athletes, Vagus nerve slows heart down.
what is carotid sinus syndrome?
pressure receptors in carotid sinus are excessively sensative. Causes bradychardia
sinus arrhythmia
Results from conditions that alter strengths of the sympathetic and parasympathetic nerve signals. ( not a constistant beat, its all over the place)
sinoatrial block
impulse from sinus node is blocked before entering the atrial muscle. ( ECG shows sudden cessation of p waves with standstill of atria)
Atrioventricular block
problem with the transition from the a-V node to the ventricles
name some causes of the atrioventricular block problems
ischemia of AV node or AV budle fibers, compression of AV bundle by scar tissue or calcified spots on heart, inflammation of AV node or AV bundle, extreme stimulation of heart by vagus nerve
first degree AV block
when P-R interval increases to greater than .2 second. Its a delay of conduction from the atria to the ventricles but not actual blockage. ( acute rheumatic heart disease causes this)
second degree
P-R interval increases to .25-.45 second. Action potential sometimes is not strong enough to get passed to ventricles. So you see P waves but no QRS-T complex. This develops a 2:1, 3:2, 3:1 rhythm
Third degree
( complete block)- impulse is not passed to ventricles. Ventricles create its own new pacemaker. P waves are now dissociated with QRS-T complex
Stokes adams syndrome
When AV conduction ceases and ventricles stop beating for 5-30 seconds. Eventually they start ( ventricular escape) but sometimes brain damage occurs.
incomplete intraventricular block
partial intraventricular block every other heart beat
premature contractions
also called extrasystole, premature beat, or ectopic beat
what causes premature contractions?
ischemia, calcified plaques at different points of heart, toxic irritation of AV node/ purkinje fibers by caffeine or other drugs
pulse deficit
heart contracts before ventricles fill up all the way. This results in a low stroke volume
ECG of A-V bundle premature contractions
P wave is missing. It is superimposed onto the QRS-T complex
ECG of premature ventricular contractions
QRS complex is usually considerably prolonged. This is cause the implulse is conducted through slowly conducted muscle rather than purkinje fibers. QRS also has a high voltage because it passes through both ventricles simultaneously. The T wave also has an electrical potential polarity exactly opposite to that of QRS
what causes disorders of cardiac repolarization?
inherited- mutations of sodium or potassium channel gates.
acquired- associated with plasma electrolyte disturbances like hypomagnesemia, hypokalemia, or hypocalcemia
parazymal tachycardia
Heart rate becomes rapid in paraxysms( lasting small period of time). It can be stopped by a vagal reflex( pressing on neck) or by quinidine or lidocaine.
atrial paraxysmal tachycardia
??
AV nodal paraxysmal tachycardia
??
Ventricular paraxysmal tachycardia
is serious for 2 reasons. First, it only occurs if there is damage in the ventricles. Second, this condition usually initiates ventricular fibrilation
