Lecture 9: Cardiac Arrhythmias Flashcards
What is tachycardia?
fast heart rate
What are the causes of tachycardia?
increased body temperature
stimulation of the heart by sympathetic nerves
toxic conditions of the heart
What happens during endogenously mediated tachycardia?
heart rate increases
cardiac output increases
filling time is deducted but stroke volume does not fall
What happens during pathologically mediated tachycardia?
heart rate increases
cardiac output decreases
What is bradycardia?
slow heart rate
What are the causes of bradycardia?
athletic heart
vagal stimulation
extremely sensitive carotid baroreceptors in carotid sinus syndrome
What is spillover signals?
signals that alternatively increase and decrease number of impulses transmitted through sympathetic and vagus nerves to the heart
What are the characteristics of a sinoatrial block?
sudden cessation of P waves
resultant standstill of atria
ventricles pick up new rhythm, usually originating in AV node
rate of QRS is slowed but not otherwise altered
Conditions of atrioventricular block?
ischemia of AV node or AV fibers through coronary insufficiency
compression of AV bundle by scar tissue or calcified portions of the heart
inflammation of the AV node or bundle
extreme stimulation of the heart by the vagus nerves
What is first degree incomplete atrioventricular block?
normal PR time interval (0.16 sec)
increases in length with slower heartbeat and decreases with faster heartbeat
When PR interval increases to greater than 0.20 seconds, the PR interval is ________ and the pathetic has ______ heart block
prolonged; first degree incomplete
What is second degree incomplete atrioventricular block?
PR time interval increases to 0.25 to 0.45
Atrial P wave is present but QRS-T wave may be missing, resulting in dropped beats of the ventricle
What type of rhythm is present in second degree incomplete atrioventricular block?
2:1 rhythm
In a complete atrioventricular block, ventricles establish their _______
own signal
How long is the duration of a complete atrioventricular block?
highly variable: seconds to weeks
If a complete atrioventricular block occurs, what may resumption of the ventricular beat be due to?
parts of the Purkinje system acting as an ectopic pacemaker
Stokes-Adams syndrome
periodic fainting spells due to complete Glock from lack of blood to the brain
What is a partial intraventricular block?
electrical alternans
alternation in the amplitude of P waves, QRS complexes or T waves
When do premature contractions occur?
before they should
Premature contractions are the result of what?
ectopic foci:
local ischemic areas
calcified plaques
irritation of the conduction system or nodes
What is paroxysmal tachycardia?
heart becomes rapid
begins and ends suddenly
pacemaker of the heart instantly shifts back to sinus node
What is fibrillation?
twitching of individual muscle fibers in the atria or ventricles and also in recently denervated skeletal muscle fibers
Fibrillation occurs as a result of ___________
circus movements
What are the three conditions that causes the impulse to travel around the circle?
pathway around circle is too long
length of the pathway remains constant but conduction velocity slows down
refractory period of the muscle might become greatly shortened
What are the causes of atrial fibrillation?
enlargement of the atria
inadequate emptying of the ventricles causing blood to back up into the atria
Ventricular and atrial fibrillation may occur ________ from one another
separate
Circus movements are the basis of heart fibrillation. Which of the following statements is NOT true?
A. Fibrillation may occur when the refractory period of the muscle is greatly shortened.
B. Fibrillation may occur when the pathway around the circle is too short.
C. Fibrillation may occur when the conduction velocity slows down.
D. Fibrillation may occur when the heart becomes dilated.
B. Fibrillation may occur when the pathway around the circle is too short.
Which of the following conditions may result in tachycardia? A. Toxic conditions of the heart B. Increased body temperature C. Sympathetic nerve stimulation D. All the above E. BandConly
D. All the above
