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118 Cards in this Set

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Similarities b/w cardiac & skeletal muscle?
Both have striations. Banding arises from same arrangements of fibrils and filaments.
Differences b/w cardiac & skeletal muscle?
Cells differ greatly in shape & size. Cardiac muscle is NOT a syncytium. Only cardiac muscle has intercalated disks. Cardiac muscle has no NMJ's.
What kind of cells line the endocardium?
Simple squamous (entire CV system has this lining)
Histologically, what is the difference b/w atrial myocardium and ventricular myocardium?
Cells are more densely packed in the ventricular myocardium in order to overcome more resistance
What is the size of Purkinje fibers compared to myocytes?
Much bigger than myocytes
What is the role of intercalated disks?
They propagate wave of contraction after the terminus of Purkinje fibers. They transmit the impulse to the bulk of the myocardium.
What surrounds myocytes?
Collagen
What are valves composed of?
CT (elastic & collagen) covered with endocardium
What are the base of the flap in valves made of?
Muscle
What occurs in capillaries?
Site of gas, nutrient, and waste transfer.
What are transient heart sounds?
Cardio sounds of short duration, including the normally heart S1 & S2
What are heart murmurs?
Auditory vibrations of longer duration created when laminar flow is disrupted
What is S1 associated with?
Closure & tensing of the AV valves at the onset of systole coinciding with the QRS complex on the ECG
How does S1 compare to S2?
S1 is longer, louder, and lower pitched than S2
What are some causes of increased intensity of S1?
Thin chest wall, tachycrdia, high sympathetic tone, systemic arterial hypertension, and anemia
What can diminish the intensity of S1?
Obese animals, pleural or pericardial effusion, diaphragmatic hernia, DCM, hypovolemia, emphysema, or a prolonged P-R interval
What can cause splitting of S1?
Occasionally auscultated at the apex in large breed dogs or may result from electrical disturbances or mechanical factors (tricuspid or mitral stenosis)
What is S2 a/w?
Closure of the semilunar valves at the end of systole following the T wave on the ECG
Why is an audible split 2nd heart sound sometimes heard on healthy, large breed dogs during inspiration?
Due to a longer right ventricular ejection period, which causes the interval b/w pulmonic valve closing and aortic valve closing to be longer
What can pathologically cause the splitting of S2?
Delayed closure of pulmonic valve is most commonly auscultated in dogs w/pulmonary hypertension as occurs with heartworm dz & right to left patent ductus arteriosus. Also caused by pulmonic stenosis, right bundle branch block, ectopic beats, and ventricular pacing.
What can cause premature A2 closure?
On occasion can be noted with mitral insufficiency and mitral stenosis
When do the 3rd and 4th heart sounds occur? And what do they sound like?
Occur during diastole & are not normally audible. When heard, they sound like a gallop.
What makes the S3 sound?
Rapid ventricular filling generates the S3 sound, also known as S3 gallop, protodiastolic gallop, or ventricular gallop.
What causes the S3 sound to be audible?
Diastolic volume overloading as in DCM, patent ductus arteriosus, & mitral insufficiency
When is the S4 heart?
It is presystolic & is heard just b4 S1 & occurs just after the P wave on the ECG. Also called atrial gallop or presystolic gallop.
What generates the S4?
This low-frequency sound is generated by blood flow into the ventricles during atrial contraction
What is an audible S4 in dogs and cats a/w?
Usually a/w increased ventricular hypertrophy and stiffness and is sometimes audible in animals with third degree AV block
What can create a cardiac murmur?
High-velocity flow, flow from narrow restricted area into a larger area, or low blood viscosity
What does Reynold's number define?
The relationship of cardiac murmurs with flow velocity, vessel size, and blood viscosity
How is Reynold's number calculated?
(radius)(velocity)(density)/viscosity
What are the ways murmurs can be characterized and described?
By their timing within the cardiac cycle (systolic, diastolic, portions thereof), location (point of maximum intensity), radiation, intensity (loudness), shape, & frequency (pitch)
When do systolic murmurs occur?
Between S1 and S2
What are protosystolic, mesosystolic, and telesystolic?
Early, mid, and late systole
When do systolic murmurs occur?
After S2
What is the difference b/w protodiastolic and presystolic?
Protodiastolic occurs in early diastole. Presystolic is when it is audible only at the end of diastole.
How is the intensity of a murmur calculated?
Velocity x flow = force
How are murmurs graded?
1-6 with 1 being almost inaudible, 2 soft, 3 moderate, 4 loud but w/o thrill, 5 loud w/thrill, and 6 very loud w/thrill audible w/o stethoscope against skin
What are the 3 shapes of heart murmus?
Plateau or band-shaped, decrescendo, and crescendo decrescendo
How are plateau murmurs?
Equal intensity throughout their duration
How are decrescendo murmurs?
Murmurs that gradually taper off from an initial peak
How are crescendo decrescendo murmurs?
Diamond-shaped, ejection mumur that builds up to a peak intensity and then taper in intensity
What does a mitral insufficiency murmur sound like? And where is it located?
Best heard at left apex (mitral valve area) but radiates dorsally & to the right thorax. Characteristic murmur ir plateau & holosystolic. May be protosystolic at first.
What causes mitral valve insufficiency?
Chronic degenerative valvular dz (endocardiosis), endocarditis, hypertrophic obstructive cardiomyopathy, congenital malformations, & dz's that cause left heart enlargement & dilation of mitral annulus
Where is tricuspid insufficiency murmur heard? And what does it sound like?
Loudest over right apex (tricuspid valve area). Often difficult to distinguish from radiating mitral insufficiency murmur. Also plateau & holosystolic.
What can accompany a tricuspid murmur?
Jugular pulsations
What can cause tricuspid insufficiency?
Congenital malformations of valve, chronic degen. valve dz, or any disorder that causes marked right heart enlargement & valve annulus distention, such as pulmonary hypertension
Which of the 2 valve insufficiencies is more common in dogs & cats?
Mitral valve insufficiency.
Tricuspid valve endocarditis is extremely rare in dogs & cats.
What kind of murmur does aortic stenosis cause? Where is it best heard?
Systolic ejection murmur - crescendo-decrescendo. Best heard at left heard base. Sometimes radiates towards the right cranial thorax.
What kind of murmur does pulmonic stenosis cause? Where is it best heard?
High-frequency crescendo-decrescendo (ejection) holosystolic murmur. Best heard at the left heart base over the pulmonic valve.
What is the sound difference b/w pulmonic stenosis and aortic stenosis?
Pulmonic stenosis should not radiate along the carotid arteries and aortic stenosis does.
What kind of murmurs do ventricular septal defects cause?
They produce murmurs that vary tremendously in shape & quality. Most often the murmur is a harsh, mid-to-high frequency holosystolic murmur best heard on the right cranial thorax.
What does an atrial septal defect cause?
Increased flow across the pulmonic valve as a result of the left to right shunting
What causes functional (physiologic) murmurs?
Decreased blood viscosity or increased cardiac output. Most often noted in animals w/ anemia, fever, pregnancy, hyperthyroidism, and increased sympathetic tone.
How are most functional (physiologic) murmurs classified? And where are they loudest at?
Proto to mesosystolic, soft to moderate intensity (grade 1-3) and loudest at the left heart base
What kind of murmur does aortic insufficiency usually cause?
Decrescendo
Which is more common: aortic or pulmonic insufficiency?
Aortic insufficiency
What is the most common cause of a continuous murmur at the left heart base?
Patent ductus arteriosus (PDA)
What is atrial fibrillation?
Supraventricular tachyarrhythmia
Atrial fibrillation has a 50% incidence rate with which heart dz?
Dilated cardiomyopathy in dogs
What characterizes atrial fibrillation?
Characterized by electrical disorganization at the atrium leading to rapid & unorganized atrial depolarizations.
When does atrial fibrillation usually develop?
When atrial enlargement occurs secondary to an underlying cardio dz
How does atrial fibrillation show up on an ECG?
No visible P waves - replaced by fine undulations. Tall R waves and deep S waves.
The phrenicopericardial ligament is formed by a continuation of which layer of the heart?
Fibrous pericardium
What is the surface of the heart facing the left thorax called?
Auricular surface
What is the surface of the heart facing the right thorax called?
Atrial surface
What are the 4 openings into the sinus venarum of the right atrium?
Caudal vena cava, coronary sinus, cranial vena cava, and right atrioventricular orifice
What does the foramen ovale do?
Allows blood to pass from the right to the left atrium
Crista terminalis is at the entrance of the what?
Right auricle
Where is the trabeculae carnae more numerous?
More numerous in right ventricle than in left ventricle
What does the ligamentum arteriosum connect?
Pulmonary trunk to aorta
What is the ligamentum arteriosum called in a fetus?
(Patent) ductus arteriosus
Which nerve turns around the caudal surface of the ligamentum arteriosum?
Recurrent laryngeal nerve
Which coronary artery is larger?
Left coronary artery is about twice as large as the right
What is the coronary sinus?
The dilated terminal end of the great cardiac vein
Which nerve increases heart rate? And which one decreases heart rate?
Sympathetic nerve increases HR. Vagus nerve decreases HR.
How is duration of cardiac cycle calculated?
It is the reciprocal of HR so just divide 1 by the HR to get sec/beat
Atria increases the ventricular pumping effectiveness by ___%
20%
When atria fail to function, the difference is not noticed unless _____________
Exercise-induced
How is stroke volume calculated?
End diastolic volume - end systolic volume
How is ejection fraction calculated?
Ejection fraction = stroke volume/end diastolic volume
What is pulse pressure? And how is it calculated?
Pulse pressure is the amplitude of the pressure pulsations in an artery. It is calculated by subtracting the arterial diastolic pressure from the arterial systolic pressure.
How does the pressure compare b/w systemic, aorta, pulmonary artery, and pulmonary veins?
Aorta > systemic > pulmonary artery > pulmonary veins
How does gravity affect the pressure below and above the heart?
Gravity increases the actual pressure that is below the heart, but decreases the actual pressure that's above the heart level.
Where does most of the resistance to blood flow happen?
Arterioles and capillaries
Diff. organ capillary beds are in parallel from each other so that the blood passing thru one will not pass to the other. What is the exception to this?
Splanchnic circulation: portal veins carry splanchnic venous blood to the liver
Are there more mechanoreceptors or chemoreceptors in the terminal bronchioles and alveoli?
More chemoreceptors
Where is the cough center located? And which nerve takes the impulses there?
Afferent impulses pass via the vagus nerves to the cough center located in the medulla oblongata of the brain
What are the 3 anatomical regions a cough can originate from?
Upper airway, lower airway, and cardiovascular
What is nonproductive (dry) cough usually a/w?
Dz of upper airways
What does a productive cough suggest?
Dz of lower airways
What is a "goose honk" cough in toy breeds typical of?
Collapsing trachea
At what time of day is cough secondary to cardio dz more severe? And why?
Evening hours when blood flow is redistributed to the heart, resulting in increased pulmonary venous pressures & interstitial or alveolar edema
At what time of day is cough a/w bronchial dz more severe? And why?
More severe in the morning b/c pooled bronchial secretions in the terminal airways are moved by increased airflow a/w activity & more forceful breathing.
What characterized DCM?
Poor myocardial contractility, with or w/o arrhythmias
Which breeds of dogs have a genetic predisposition to DCM?
Doberman Pinschers, Boxers, and Cocker Spaniels
DCM has been a/w deficiency of which nutrient?
1-carnitine
What is 1-carnitine essential for?
Essential component of the mitochondrial membrane transport system for fatty acids, which are the heart's most important energy source
What is the major functional defect in DCM?
Decreased ventricular contractility (systolic dysfunction)
Is DCM chronic or acute?
Probably develops slowly but onset of clinical signs may appear acute
What kind of arrhythmias commonly develop in association with atrial enlargement?
Atrial tachycardia and atrial fibrillation
What chambers typically dilate in dogs with DCM?
Left atrium and ventricle
What are some clinical signs of DCM?
Weakness, lethargy, tachypnea or dyspnea, exercise intolerance, cough, anorexia, ascites, and syncope
What type of dogs are more likely to have subclinical DCM?
Some giant-breed dogs
What is a classic heart sound finding in DCM dogs?
S3 gallop
What ECG abnormality is consistent with left ventricular dilation?
Tall QRS complexes
What clinical pathology is seen with DCM?
Prerenal azotemia, increased liver enzyme, hypoproteinemia, dilutional hyponatremia
What is the goal of tx. for DCM?
Controlling the signs of CHF, optimizing CO, managing arrhythmias, improving quality of life, and prolonging survival
What is the prognosis for DCM?
Guarded to poor. Most don't live longer than 3 months after showing signs of heart failure.
What drug class is Digoxin in?
Cardiac glycoside
What is Digoxin's function?
Increases myocardial contractility (inotropism) with increased cardiac output, increases diuresis
When is Digoxin used?
To treat CHF, atrial fibrillation/flutter, supraventricular tachycardias
What is digoxin's most probable MOA?
Inhibition of membrane-bound Na+/K+ -ATPase pump. When this occurs, Na+ increases in the cell, the exchange of Na+ for Ca2+ is augmented, and calcium influx is increased
How can digoxin be toxic?
It can directly slow sinus nodal activity due to increased sensitivity to AcH, which can lead to atrial arrhythmias.
Which species is more sensitive to digoxin tox.?
Cats
What are the signs of digotoxin tox.?
Cardiac arrhythmia, diarrhea, anorexia, nausea, and vomiting
What drug class is Enalapril in?
ACE inhibitor
What is Enalapril's MOA?
Prevents formation of angiotensin II by competing with angiotensin I for the enzyme ACE
What does enalapril do?
Vasodilator in tx. of heart failure