atrial rhythms Flashcards
what are atrial arrhythmias also referred as?
supra ventricular bc they occur above the ventricles
what does supra ventricular mean?
refers to arrhythmias originating outside the sinus node but above the branching portion of the Bundle of Hist
the electrophysiologic mechanism responsible for atrial arrhythmias are? caused by?
increased automaticity, re-entry, or triggered activity (after depolarizations) caused by myocardial schema, electrolyte imbalances inc sympathetic tone (catecholamines), stretch of the chambers, dig toxicity, and pro-arhythmic effects of anti arrhythmic drugs
when would ventricular depolarization be wide?
if there is an underlying bundle branch block (BBB) or if beats are aberrantly conducted (one of the bundle branches has not depolarized and is unable to conduct normally)
what are the 3 basic mechanisms that cause abnormal electrical impulses ?
enhanced automaticity, re-entry, and triggered activity
what is enhanced automaticity?
abnormal condition in which the firing rate of latent pacemaker cells is increased beyond their inherent rate. when the cell membrane becomes permeable to Na during phase 4 which results in leakage Na into the cell and a sharp rise cells that do not ordinarily possess the property of automaticity can acquire enhanced automaticity under certain conditions and depolarize spont
enhanced automaticity can cause what kinds of beats and rhythms?
atrial, junctional and ventricular ectopic beats and rhythms
what are common causes of enhanced automaticity?
common causes are an increase in symp tone (circulating catecholamines), digitalis toxicity, hypoxia hypercapnia myocardial ischemia or infarction, stretching of the heart, hypokalemia, heating or cooling of the heart and certain drugs
what is re-entry?
is the condition in which the progression of an electrical impulse is delayed or blocked (or both) in one or more sections of the conduction system while the electrical impulse is conducted normally through the rest of the conduction system
what does re-entry result in?
delayed impulse entering cardiac cells which have just been depolarized by the normally conducted impulse and if they are depolarized sufficiently, deploring them prematurely and producing ectopic beats and rhythms
re-entry can result in the abnormal generation of what?
a single or repetitive electrical impulse in the SA node, atria, AV junction,bundle branches and purkinje system. this can produce ectopic beats and rhythms originating in any of these areas
what are the most common causes of re-entry?
ischemia and hyperkalemia
what is triggered activity?
an abnormal condition of the latent pacemaker and non pacemaker cells in which these myocardial cells can depolarize more than once following stimulation by a single electrical impulse
what occurs in triggered activity in re: phases?
the level of phase 4 sponta and rhythmically inc after the first depolarization until it reaches threshold potential causing the ells to depolarize. referred to as after-depolarization and can occur immediately following depose (early after depolarization) or late in phase 4 (delayed after depolarization
what does triggered activity cause?
atrial or ventricular ectopic beats occurring singly, in pairs, or in bursts of three or more beats
what are some common causes of triggered activity?
increase in catecholamines, digitalis toxicity, hypoxia, myocardial schema or injury and stretching or cooling of the heart
what are premature atrial contractions?
extra atrial contractions originating from a focus other than the sinus node that occur before the next expected p wave.
is there a pause in premature atrial contractions?
bc the SA node is interrupted by the premature beat, the timing is re-set resulting in incomplete compensatory pause
