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what are the chambers of the heart
- right and left atria
- right and left ventricle
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what are the valves of the heart
- atrioventricular valves which are the papillary muscles and chordae tendinae
- pulmonic valve
- aortic valve
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myocardium
- specialized muscle tissue
- heart muscle
- cats- 1 billon beats/avg
- dogs-600 million beats/avg
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what are the conduction fibers
- sinoatrial node-LA (pacemaker)
- atrioventricular node-between A and V (gathering tissues)
- purkinje fibers/bundle of his-IV septum (spread out the muscles
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what are the major vessels
- cranial and caudal venae cavae-RA (veins leaves)
- pulmonary vessel- RV, LA
- aorta- LV
- coronary vessels
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systolic function
- cardio output
- amount of blood going out to body
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diastolic function
relaxation and filling
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heart rate
speed of the beats
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heart rhythm
regularity of the beats
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cardiac hypertrophy
- concentric-pressure overload/wall thickening (gets to stiff to pump, cats)
- eccentric-volume overload/end diastolic enlargement (making walls thinner losing strength, weak)
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systolic function
- four closely interrelated determinants
- three determine how much blood is pumped with each beat-stoke volume which is preload, afterload, and contractility
- cardiac output-SV x HR= L/min
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determinants of cardiac output
- heart rate
- preload
- afterload
- contractility
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preload
- volume of blood in the veins returning to the heart
- measure of how much the ventricle is stretched at the end of diastole
- monitoring the central venous pressure, pulmonary capillary wedge pressure, and LV end diastolic diameter
- increasing any of these parameters causes increased preload and increased stroke volume
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increased preload
- one of the ways the body compensated for reduced CO from heart disease is by small increases in ventricular filling pressure and fluids retention and venoconstriction
- continued increases in preload due to progressive disease cause CHF
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afterload
- force that resists the flow of blood from the heart- increased afterload-decreased stroke volume
- monitoring arterial blood pressure and systemic vascular resistance
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afterload and compensation
- hypotension stimulates vasoconstriction-improved BP, increased afterload and decreased CO
- poor myocardial function=sensitivity to change in afterload
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contractility
- change in stroke volume independent of changes in preload or afterload
- affected by calcium levels in myocardial cells-increases calcium causes increased contractility, drugs like digoxin or dobutamine, chemicals like epinephrine
- monitoring more difficult- shortening fraction which is how much change in wall movement and cardiac output
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heart rate and rhythm
- more of an effect on duration of diastole than duration of systole-alters the normal sequence and duration of atrial and ventricular contraction (dyssynergy)
- increases in heart rate usually increase CO- tachycardia prevents adequate filling during diastole and bradycardia passes the point where output takes advantage of the increased preload
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diastolic function
- diastolic dysfunction interferes with relaxation and filling
- diastolic dysfunction alone can cause CHF-important in the heart disease of cats, HCM RCM Hyper T4, ventricles are noncompliant and cannot fill
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normal heart rhythm
- depolarization- P, Q, R, S waves
- SA node, atrial muscle, AV node, purkinje fibers/IV septum to apex, ventricular muscle back to base
- repolarization- T wave (getting ready for next beat)
- normal sinus rhythm-basic normal heart rhythm
- respiratory sinus arrhythmia- normal variation in dogs, consistent ebb and flow of rate with breathing, changes in vagal tone and thoracic pressures
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what are the common symptoms of normal heart rhythm
- strong possibilities-tachypnea and dyspnea, syncope, weakness and collapse
- moderate possibilities-coughing dogs, exercise intolerance, abdominal distension
- at least keep it in mind-weight loss
- sudden death
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physical exam findings
- heart murmur-disturbed blood flow
- heart rate abnormality- tachycardia(fast), bradycardia(slow)
- heart rhythm abnormality
- dropped pulses
- respiratory abnormals- change in rate effort and sound
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heart murmurs
- location M,A,P/5,4,3
- mitral-dogs left 5th IC space, CC junction, cats left 5-6th IC space 1.4 from sternum
- aortic-dog left 4th IC space above CC junction, cats left 2-3rd space 1/2 to 3/4 from sternum
- pulmonic-dog left 2-4th IC space sternal border, cats left 2-3rd IC space 1/3 to 1/2 from sternal border
- tricuspid-dog right 3-4th IC space CC junction, cats right 4-5th IC space 1/4 from the sternum
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