[2] Lecture 9: Cardiac Arrhythmias Flashcards
HR > 100bpm
And
Causes:
Tachycardia
Increased body temp.
Stimulation by sympathetic nerves
Toxic conditions of the heart
Endogenously mediated tachycardia:[exercise]
HR increase
CO increase
Filling time reduced but SV doesn’t decline
Sympathetic stimulation when exercising maintains SV how?
Increase contractility
Systolic interval reduced
Increase venous return
What are effects of pathologically mediated tachycardia?
HR increases
CO decreases
Why do the effects of pathological mediated tachycardia occur?
MAP decreases and activates sympathetic NS after the fact and is unable to compensate
No muscle pump to increase venous return
What is bradycardia and what causes it?
Respiratory type of sinus arrhythmia
Medullary resp. Center into vasomotor center during inspiratory /expiration cycles….increase/ decrease HR through sympathetic and vagus nerves to the heart
Sudden cessation of P waves- standstill of atria..ventricles pick up AV node rhythm. QRS pace is slower but not otherwise altered.
Sinoatrial block
Ischemia of AV node or AV bundles through coronary insufficiency
Compression of AV bundles by scar tissue
Inflammation of AV node/bundle
Extreme stimulation of the heart by the vagus nerve
Atrioventricular block
Extended PR interval:
Longer w/ slower HR
Shorter w/ faster HR
> .20s PR
1st degree AV block
Extended PR that results in dropped beats of the ventricle
2nd degree AV degree
No relation between the rate of the P waves and the rate of QRS-T complexes
Complete Atrioventricular block
Resumption of the ventricular beat may be due to parts of the purkinje system acting as ectopic pacemaker
Ventricular escape
Periodic fainting spells
Stokes-Adams syndrome
An alteration in the amplitude of P waves, QRS complexes, or T waves
Referred to as electrical alternans
Partial intraventricular block
These heart beats occur before they should
Most result from ectopic focus
Premature contractions
What causes ectopic foci:
Local ischemic areas
Calcified plaques
Irritation of the conduction system or nodes
HR becomes rapid suddenly in bursts that last sec’s, min, hr’s, or longer
Then, ends suddenly
Paroxysmal tachycardia
How can paroxysmal tachycardia resolve?
Pacemaker of heart instantly shifts back to the sinus node.
The twitching of individual muscle fibers in the atria or ventricles and also in recently denervated skeletal muscle fibers
Occurs as a result of circus movements
Fibrillation
3 different conditions that cause the impulse of heart to travel around the circle:
1-pathway around the circle is too long.
2-length of the pathway remains constant but the velocity of the conduction slows down.
3-refractory period of the muscle might become greatly shortened.
A contraction or excitation wave traveling continuously in circular fashion around a ring of uncle or through the wall of the heart
Circus movements
What condition generally causes circus movements d.t circle being too long
Enlarged/dilated heart
by the time the impulse returns to its starting point, the heart muscle will be in the refractory period.
When the length of the pathway remains normal, but the conduction velocity is slowed down in heart. What 3 things could cause this?
1-blockage of purkinje system
2- ischemia*
3-high potassium levels
What would cause the refractory period of the cardiac muscle to be shortened?
Rx: epinephrine
Or
Electrical stimulation
The atrial muscle fibers are separated from ventricular muscle fibers by the:
cardiac fibrous skeleton
Ventricular and atrial fibrillation can occur separate from each other
A fib
Causes of A fib [2]:
Enlargement of atria-d/t valve lesions
Inadequate emptying of the ventricles causing blood to back up into the atria
