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Systole
Ventricles are constricting. Valves between Atria and Ventricles are closed
Diastole
Atria are contracting. Mitral and Bicuspid valves open. Ventricles are filling.
Parietal Pericardium
Thick fibrous Protective sack around the heart.  Attached to thoracic cavity  Lower half of sternum, thoracic vertebrae, diaphragm
Visceral Pericardium
Thin layer of pericardium attached to the heart.
Pericardial Space
Space between Parietal and Visceral layers.  There is a little bit of fluid in the space 5-20 ml  up to 50.   Fluid in pericardial space keeps heart from completely filling.  Can handle gradual fluid increase, but not sudden fluid onset.
 
Atrioventricular Valves
b/w atria and ventricles Tricuspid valve - b/w right atria and right ventricle (3 leaflets) Mitral (bicuspid) valve - b/w left atria and left ventricle (2 leaflets)
Semilunar Valves
These valves consists of 3 cuplike cusps that preventblood from flowing back into ventricle during relaxation (diastole). Pulmonic semilunar valve - b/w right ventricle pulmonary artery Aortic semilunar valve - b/w left ventricle and aorta
How does the heart muscle get its blood supply?
75% of blood flow to heart muscle occurs during Diastole
Right Coronary Artery supplies:
Right Atrium, Right Ventricle, Inferior portion of LV, Posterior septal wall, Sinoatrial node (SA), Atrioventricular node (AV)
LAD (Left anterior descending coronary artery) supplies
Anterior wall Left Ventricle,
Anterior ventricular septum,
Apex of Left Ventricle
Circumflex supplies
-Left Atrium
-Lateral & posterior surface of Left Ventricle
-Occasionally post interventricular septum.
-SA & AV node
Excitability
Ability of heart muscle cells to depolarize (ie discharge) in response to a stimulus.  Once stimulated, the whole heart muscle contracts
Automaticity
- Unique ability of cardiac cells to initiate spontaneous impulses.  Pacemaker cells have the highest rate of automaticity of all cardiac cells.  The heart stimulates its own contraction.
Conductivity
Property of some cardiac cells that enables them to transmit electrical impulses
Refractory
State wherein electrical cells are unable to respond to electrical stimulation because they have not yet recovered from the previous discharge.
Polarized state
Refers to a "ready" state where the electrical charges are balanced and ready for discharge; no electrical current flows.
Depolarization
Electrical process of discharging polarized (ready) cells, usually resulting in muscle contraction.  Think of "discharge state".
Repolarization
The process of recharging depolarized cells back to their "ready" (polarized) state.  Think of the "recovery state".
Repolarization
After cell depolarizes, the positive and negative electrical charges will again return to original positions around the cell, and the cell will prepare for another discharge.   The process that follows depolarization, when cell charges are returning to their original state is called repolarization.
Absolute refractory period
occurs during depolarization and the first part of repolarization.  Cardiac cells will not respond to any stimuli, no matter what
Relative refractory period
Only a stronger-than-normal stimulus can excite the heart muscle to contract.  It occurs in the final stages of repolarization.
Purkinje's Fibers
rapidly spread the wave of depolarization through the ventricles.
Inherent rate of SA node
60 - 100 bpm
Inherent rate of AV node
40 - 60 Bpm
Inherent rate of Ventricles
20 - 40 bpm
Ventricular Systole
Aortic valve is open, allowing ejection of blood Mitral valve is closed, preventing regurgitation of blood into left atrium
Ventricular Diastole
Aortic valve is closed, preventing regurgitation of blood into ventricle Mitral valve is open, allowing blood to flow from left atrium into left ventricle.
During Diastole
Pressure in LA exceeds pressure in relaxed LV Blood flows from LA to LV across open mitral valve Just before the onset of ventricular systole, atrial contraction produces a slight pressure rise in both chambers (known as atrial kick).
S1     LUB
Closure of the Mitral valve.

Beginning of systole
S2   DUB
Closure of Aortic Valve

Beginning of Diastole
Contractility
ability of heart muscle to contract in response to electrical stimulation.
Cardiac output




adult cardiac output
amount of blood pumped by the LV in 1 minute.



between   3 - 8/L per minute
Cardiac index






Normal CI =
Cardiac output divided by the body surface area.  It describes the CO in terms of liters per minute per square meter of body surface area.


2.5 - 4/L/Min/M^2
S3
Rapid Ventricular filling.
Occurs during Diastole.
S4

marks atrial contraction and immediately precedes S1 of the next beat.  Ventricle us unable to take the last push of blood from atrium. Atrial has to work harder to get fluid into ventricle.      May indicate hypertrophy, disease or injury of the ventricular wall.
Atrial Kick
up to 30% of blood push
Stroke Volume
amount of blood ejected with each contraction of the LV (stroke volume) x (heart rate) = Cardiac output
Preload




Increased by:


Decreased by:
myocardial fiber length of the ventricle at end diastole

Increase: Fluid overload. Venous constrictor will initially increase preload.

Decrease: Folume loss, Necrotic tissue, Venous dialation
CVP
Pressure @ which blood is returned to the heart.  Higer CVP = > preload
Afterload
resistance to LV ejection or the amount of tension required by the LV to open the aortic valve during systole and to eject blood.
After load increased by
Narrowing of Pulmonary artery.  > peripheral Vascular Resistance
Afterload decreased by
Arterial Dialator.
Contractility increase
positive inotrope, inc. preload in a healthy heart
Decrease contractiliy
Death of muscle.  Negative Inatrope (beta blockers), Hypoxia, hypocapnia, hypocalemia, Hyponutremia.

Decrease contractility by increase preload in a sick heart
Digoxin  -- Indication
heart failure

Atrial fibrillation and atrial flutter (slows ventricular rate)

Paroxysmal atrial tachycardia
Digoxin -- Action
--Increases the force of myocardial contraction.
--Prolongs refractory period of the AV node
--Decreases conduction through SA and AV nodes
Digoxin Dosage

Digitalizing
--Digitizing affect -- larger initial loading dose over 12 - 24 hr.  0.5mg, 0.25mg @ 4hrs, 0.25mg @8hrs
--Maintenance 0.064 - 0.5
Digoxin Nursing implications
Assess heart for 1 full minute.  if pulse < 60 bpm (adult) <70(child) <90(infant) then notify DR.

--Know DIG levels
Antarrhythmics

PURPOSE:
Correct Cardiac arrythmias.  Achieve reduced symptomatology and increased hemodynamic performance.
Mean Arterial Pressure (MAP)
Average pressure throughout artery over the entire cardiac cycle

(diastolic bp)+(pulse pressure/3)
70-90 mmhg
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