Physio Ch 13 Flashcards
Enumerate the cause of Cardiac Arrhythmias
- abnormal rhythmicity of the pacemaker
- shift of the pacemaker from the sinus node to another place in the heart
- blocks at different points in the spread of the impulse through the heart
- abnormal pathways of impulse transmission through the heart
- spontaneous generation of spurious impulses in almost any part of the heart
Means fast heart rate, that usually defined in an adult person as faster than 100 beats/min
Tachycardia
Causes of Tachycardia
✓ increased body temperature
✓ stimulation of the heart by the sympathetic nerves
✓ toxic conditions of the heart
it causes tachycardia because increased temperature increases the rate of metabolism of the sinus node, which in turn directly increases its excitability and rate of rhythm
Fever
simple weakening of ___________ usually increases the heart rate because the weakened heart does not pump blood into the arterial tree to a normal extent
myocardium
Means a slow heart rate, usually defined as fewer than 60 beats/min
Bradycardia
the most striking example of any circulatory reflex that stimulates the vagus nerves causes release of acetylcholine at the vagal endings in the heart, thus giving a parasympathetic effect
carotid sinus syndrome
is an instrument that records by the height of successive spikes the duration of the interval between the successive QRS complexes in the electrocardiogram
cardiotachometer
during ______________, the heart rate increased and decreased with each respiratory cycle by as much as 30 percent
deep respiration
can result from any one of many circulatory conditions that alter the strengths of the sympathetic and parasympathetic nerve signals to the heart sinus node
sinus arrhythmia
cause alternate increase and decrease in the number of impulses transmitted through the sympathetic and vagus nerves to the heart
spillover signals
The only means by which impulses ordinarily can pass from the atria into the ventricles is through the?
A-V bundle
A-V bundle also known as?
bundle of His
Conditions that can either decrease the rate of impulse conduction in this bundle or block the impulse entirely are as follows;
- Ischemia of the A-V node or A-V bundle fibers
- Compress of the A-V bundle
- Inflammation of the A-V mode or A-V bundle
- Extreme stimulation of the heart by the vagus nerves
often delays or blocks conduction from the atria to the ventricles
Ischemia of the A-V node
by scar tissue or by calcified portions of the heart can depress or block conduction from the atria to the ventricles
Compression of the A-V bundle
can depress conductivity from the atria to the ventricles.
Inflammation of the A-V node
rare instances block impulse conduction through the A-V node.
Extreme stimulation of the heart by the vagus nerve
usually decreases in length with faster heartbeat and increases with slower heartbeat
P-R interval
In general, when the P-R interval increases to greater than 0.20 second, the P-R interval is said to be prolonged and the patient is said to have?
first-degree incomplete heart block
period fainting spells are known as?
Stokes-Adams syndrome
a small battery-operated electrical stimulator planted beneath the skin, with electrodes usually connected to the right ventricle
artificial pacemaker
this means that ventricular excitability is at first in a suppressed state because the ventricles have been driven by the atria at a rate greater than their natural rate of rhythm
overdrive suppression
results from partial intraventricular block every other heartbeat
electrical alternans
A premature contraction is a contraction of the heart before the time that normal contraction would have been expected. This condition is called?
extrasystole, premature beat or ectopic beat
Most premature contractions result from ___________ in the heart, which emit abnormal impulses at odd times during the cardiac rhythm
ectopic foci
Possible causes of ectopic foci;
- local areas of ischemia
- small calcified plaques
- toxic irritation of the A-V node, purkinje system or myocardium
the interval between the premature contraction and the next succeeding contraction is slightly prolonged
compensatory pause
disorders that delay depolarization of ventricular muscle following the action potentials and therefore excessively long Q-T intervals on the electrocardiogram
long Q-T syndrome (LQTS)
The major reason that the long QT syndrome is of concern is that delayed repolarization of ventricular muscle increases a person’s susceptibility to develop ventricular arrhythmias called?
torsades de pointes
literally means “twisting of the points”
torsades de pointes
What is the approximate increase in heart rate per degree Fahrenheit increase in body temperature?
10 beats/min
What is the approximate increase in heart rate per degree Celsius increase in body temperature?
18 beats per min
What is the physiological mechanism by which fever causes tachycardia?
Increase temperature increase the metabolic rate of sinus node, which in turn increase its excitability and rate of rhythm.
What is the typical range of heart rate increase due to sympathetic reflex stimulation in a patient experiencing blood loss and shock?
150-180 beats/min
They have larger and stronger heart than a normal person allowing it to pump large stroke volume output per beat even during periods of rest.
Athlete’s heart
Which of the following is NOT a primary cause of cardiac arrhythmias?
a) Abnormal rhythmicity of the pacemaker
b) Abnormal heart muscle structure
c) Blocks in impulse transmission
d) Spontaneous impulse generation
Abnormal heart muscle structure
Tachycardia is defined as a heart rate exceeding:
100 beats/min
What is the approximate increase in heart rate per degree Celsius increase in body temperature?
18 beats/min
Sympathetic reflex stimulation of the heart in shock typically increases heart rate to:
150-180 beats/min
Bradycardia is defined as a heart rate below:
60 beats/min
Which of the following is a common cause of bradycardia?
a) Increased body temperature
b) Vagal stimulation
c) Sympathetic nerve stimulation
d) Toxic conditions of the heart
Vagal stimulation
Sinus arrhythmia is characterized by:
Heart rate variation with respiration
Sinoatrial (SA) block results in:
Cessation of P waves
Atrioventricular (A-V) block can be caused by:
a) Increased body temperature
b) Vagal inhibition
c) Ischemia of the A-V node
d) Increased sympathetic tone
Ischemia of the A-V node
A prolonged P-R interval (greater than 0.20 seconds) indicates:
First-degree A-V block
“Dropped beats” of the ventricles are characteristic of:
Second-degree A-V block
Complete dissociation of P waves and QRS-T complexes is seen in:
Third-degree A-V block
Stokes-Adams syndrome is associated with:
a) Sinus tachycardia
b) Complete A-V block
c) Premature atrial contractions
d) Electrical alternans
Complete A-V block
Ventricular escape occurs due to:
a) Increased sympathetic tone
b) Overdrive suppression
c) Vagal stimulation
d) Increased body temperature
Overdrive suppression
Electrical alternans is associated with:
Incomplete intraventricular block
Premature contractions result from:
a) Increased vagal tone
b) Ectopic foci in the heart
c) Decreased sympathetic tone
d) Hypothermia
Ectopic foci in the heart
A shortened P-R interval in a premature beat suggests:
Atrial origin near the A-V node
A pulse deficit occurs due to:
Decreased stroke volume in premature contractions
A-V nodal premature contractions are characterized by:
Absent P waves
Premature ventricular contractions (PVCs) typically show:
a) Shortened QRS complexes
b) High voltage QRS complexes
c) Normal T wave polarity
d) Absent P waves
High voltage QRS complexes
The QRS complex in PVCs is prolonged due to:
a) Rapid conduction through Purkinje system
b) Slow conduction through ventricular muscle
c) Atrial depolarization
d) Sinoatrial block
Slow conduction through ventricular muscle
The T wave polarity in PVCs is usually:
a) The same as the QRS complex
b) Opposite to the QRS complex
c) Absent
d) Variable
Opposite to the QRS complex
People with significant numbers of PVCs are at higher risk for:
Ventricular fibrillation
Long QT syndrome (LQTS) is characterized by:
a) Shortened Q-T interval
b) Prolonged Q-T interval
c) Absent T waves
d) Inverted P waves
Prolonged Q-T interval
LQTS increases susceptibility to:
Torsades de pointes
Acquired LQTS can be caused by:
- Plasma electolyte disturbances (Hypokalemia, hypomagnesemia, hypocalcemia)
- Antiarrhythmic drugs (quinidine)
- Antibiotics (fluoroquinolones, erythromycin)
Treatment for acute LQTS may include:
a) Beta-adrenergic blockers
b) Magnesium sulfate
c) Digitalis
d) Quinidine
Magnesium sulfate
Congenital forms of LQTS is caused by:
a) Electrolyte imbalances
b) Mutations of sodium or potassium channel genes
c) Drug toxicity
d) Myocardial ischemia
Mutations of sodium or potassium channel genes
Electrical alternans is associated with:
a) Rapid heart rate
b) Slow heart rate
c) Normal heart rate
d) Variable heart rate
Rapid heart rate
A cardiotachometer records:
Heart rate variability
What is the chemical produced by stimulation of vagus nerves after any circulatory reflex, giving a parasympathetic effect?
Acetylcholine
In this condition, the baroreceptors (pressure receptors) in the carotid sinus region of the carotid artery walls are sensitive.
Carotid sinus syndrome
How long can the heart stop in severe cases of carotid sinus syndrome following baroreceptor stimulation?
5-10 seconds
result from any one of many circulatory conditions that alter the strengths of the sympathetic and parasympathetic nerve signals to the heart sinus node
Sinus arrhythmia
What anatomical structure receives “spillover” signals from the medullary respiratory center during sinus arrhythmia?
Adjacent vasomotor center
Cause alternate increase and decrease in the number of impulses transmitted through sympathetic and vagus nerves to the heart
Spillover signals
Impulse from the sinus node is blocked before it enters the atrial muscle resulting to sudden cessation of P waves
Sinoatrial block
During sinoatrial block, this part of the heart picks up a new rhythm with the impulse originating in AV node, so the rate of the ventricular QRS-T complex is slowed but not altered.
Ventricles
The only means by which impulses ordinarily can pass from the atria into the ventricles is through?
A-V bundles (bundle of His)
Enumerate the conditions which can either decrease the rate of impulse conduction or block impulse in the AV bundle
- Ischemia of the A-V node or A-V bundle fibers
- Compression of A-V bundle by scar tissue or by calcified portions of the heart
- Inflammation of the A-V node or A-V bundle
- Extreme stimulation of the heart by the vagus nerves
Can cause ischemia of the A- V node and bundle in the same way that it can cause ischemia of the myocardium
Coronary insufficiency
Delays or blocks conduction from the atria to the ventricles
Ischemia of the A-V node or A-V bundle fibers
Can depress or block conduction from the atria to the ventricles.
Compression of A-V bundle by scar tissue or by calcified portions of the heart
Can depress conductivity from the atria to the ventricles
Inflammation of the A-V node or A-V bundle
Identify two causes of inflammation in the A-V node or A-V bundle
Diphtheria
Rheumatic fever
Is defined as a delay of conduction from the atria to the ventricles but not actual blockage of conduction
First-degree block
How many seconds of time lapse will a normal beating heart would have between the beginning of the P wave and the beginning of QRS?
0.16 seconds
Usually decreases in length with faster heartbeat and increases with slower heartbeat
P-R interval
When P-R interval increases to greater than 0.20 seconds, P-R interval is prolonged and patient is said to have?
First degree incomplete heart block
A heart disease in which severity can be measured through P-R interval
Acute rheumatic heart disease
Known to have atrial P wave but not QRS-T wave, characterized by “dropped beats” of the ventricles.
Second-degree heart block
A ratio of 2:1 rhythm which sometimes develop to 3:2 or 3:1, with the atria beating more than the ventricles.
Second-degree heart block
Complete block of the impulse from the atria into the ventricles occurs with the ventricles spontaneously establishing their own signal
Complete A-V Block (Third Degree Block)
Which A-V heart block is seen with P waves becomes dissociated from the QRS-T complex?
Third-degree block
Incomplete intraventricular block is also known as?
Electrical alternans
A contraction of the heart before the time that normal contraction would have been expected
Premature contractions
Other terms for Premature contractions
- Extrasystole
- Premature beat
- Ectopic beat
A cause of premature contractions which emit abnormal impulses at odd times during cardiac rhythm
Ectopic foci
What are the possible causes of ectopic foci? (3)
- local areas of ischemia
- small calcified plaques
- toxic irritation of the A-V node, Purkinje system, myocardium
A mechanical initiation of premature contractions is also frequent during?
Cardiac catheterization
Occurs frequently in otherwise healthy people and also to athletes whose hearts are in a very healthy condition
Premature atrial contractions
Refers to the depressed or almost absent stroke volume output when the heart contracts ahead of schedule that the ventricles are not filled with blood normally.
Pulse deficit
Treatment for long-term LQTS:
- Beta-adrenergic blockers
- Surgical implantation of a cardiac defibrillator
means that the heart rate becomes rapid in paroxysms
Paroxysmal
Beginning suddenly and lasting for a few seconds, a few minutes or much longer
Paroxysm
Paroxysmal tachycardia can often be stopped by pressing on the neck in the regions of the carotid sinuses to elicit?
Vagal reflex
Drugs used for Paroxysmal tachycardia which depresses the normal increase in Na+ permeability of the cardiac muscle membrane during generation of action potential, blocking the rhythmical discharge
- Quinidine
- Lidocaine
This type of tachycardia does not occur unless considerable ischemic damage is present in the ventricles
Ventricular paroxysmal tachycardia
It frequently initiates the lethal condition of ventricular fibrillation caused by rapid repeated stimulation of the ventricular muscle
Ventricular paroxysmal tachycardia
Heart drug treatment which could lead to irritable foci resulting in ventricular tachycardia
Digitalis
This drug increases the refractory period and maybe used to block irritable foci causing the ventricular tachycardia
Quinidine
A tachycardia resulting from an aberrant rhythm involving the A-V node.
Paroxysmal tachycardia
A tachycardia caused by almost normal QRS-T compexes but totally missing or obscured P waves.
Paroxysmal tachycardia
Also called as supraventricular tachycardia seen in young, otherwise healthy people
Atrial or A-V nodal paroxysmal tachycardia
Which tachycardia frightens a person tremendously and may cause weakness during the paroxysm
Supraventricular tachycardia
