 |
LACK OF A COORDINATED CONTRACTION
arrhythmia
dyskinesia
|
|
|
PRESSURE OVERLOAD
tenotic semilunar valve
hypertension
|
| |
VOLUME OVERLOAD
A-V valve insufficiency
semilunar valve insufficiency
fluid overload
congenital heart disease
chronic increased cardiac output
(thyrotoxicosis, anemia, fistula)
|
|
|
LACK OF A COORDINATED DEPOLIRIZATION
The inability of the heart to generate an effective pace and coordinated contraction due to an electrical abnormality is called an
"arrhythmia" or "dysrhythmia". The two basic villians that are the cause for these arrhythmias are abnormal automaticity and abnormal conduction.
|
|
ABNORMAL AUTOMATICITY
Abnormal automaticity means that the SA node either is not creating the pace, is doing so at too high or too low of a rate or at
an irregular rate. If an area of the heart other than the SA node is creating the pace an EKG can usually show this.
|
|
ABNORMAL CONDUCTION
Abnormal conduction prevents the well-organized depolarization that allows the atria to contract followed by a coordinated
contraction of the apex toward the base of the heart. Normal conduction allows the action potential developed in the SA node
to be conducted through the atria into the AV node, then through the bundle of His, bundle branches and the Purkinje cells
which are specialized to conduct an action potential to several surrounding myocytes.
A slow rate (bradycardia) allows arterial pressure to fall so low between beats that the stroke volume is inadequate to maintain
arterial pressure to support a normal cardiac output. A rapid rate (tachycardia) allows arterial pressure to fall because of
inadequate ventricular filling before each contraction. An uncoordinated contraction of the heart decreases the force that the
ventricle can produce to move blood through the semilunar valve against the arterial pressure.
Arrhythmias are caused by factors that will alter the automaticity or conduction through the heart, because of alterations in the
ionic bases of automaticity and conduction: ischemia, electrolyte imbalances, drugs, inflammation of the heart or metabolic
abnormalities (thyrotoxicosis).
In the end, it is these arrhythmias that are our demon...they are what turnour hearts black. Now, let us view the "MANIFESTO"...the
map through the CHAMBER OF HORRORS, and look at the diseases
man faces that brings on these villianous arrhythmias.
|
|
