chronic Degenerative valve disease

Question 1

synonyms

Answer 1

endocardiosis

valve disease

myxomatous valve diseasee

mitral valve disease

Question 2

prevalence

Answer 2

most common canine heart disease

breed predisposition

rare in cats

Question 3

what is degenerative valve disease?

Answer 3

unknown etiology

abnormally thickening

develop nodules

cannot form tight seal

leading to blood regurgitation

Question 4

what happens histologically?

Answer 4

collagen is lost

replaced by protoglycans

Question 5

pathophysiology of mitral regurgitation

Answer 5

decreased forward LV stroke volume

diminished tissue perfusion

tissue perfusion maintained by increasing HR, stroke volume and vasoconstriction.

increased left atrial pressures

Question 6

how can total stroke volume increased in mitral regurgitation

Answer 6

increasing contractility

increasing blood volume (renal retention of salt and water)

Question 7

what is the mediator behind renal retention of sodium and water?

Answer 7

angiotensin 2

leads to release of aldosterone

Question 8

how is the left atrium affected by mitral regurgitation?

Answer 8

increased pressures

LV volume overload

mitral regurgitation

left atrial chamber dilation

impedes pulmonary venous drainage __>increased capillary hydrostatic pressure and pulmonary edema

atrial myocardial necrosis and fibrosis

atrial perforation

Question 9

how does mitral regurgitation promote atrial fibrillation?

Answer 9

increased sympathetic signaling

results in atrial dilation and fibrosis

Question 10

how is ventricular contractility affected by mitral regurgitation in small dog breeds? large dog breeds?

Answer 10

small dogs: preservation of contractility, pure volume overload

large breeds: diminished contractility, systolic dysfunction contributes to volume overload, DDx: DCM

Question 11

epidemiology

Answer 11

middle age to older dogs

smaller breed dogs

males

breeds: Cavalier, Dachshunds, Mini and toy poodles, whippets, terriers

1 in 7 dogs

Question 12

Clinical signs

Answer 12

systolic murmurs with its point of maximal intensity over left apex-radiates craniodorsal on L side

systolic click-high frequency, heard midsystole

asymptomatic

left sided CHF

coughing, restlessness, tachypnea, dyspnea, reduced exercise tolerance, weight loss, inappetance

synocope (associated with coughing)

bronchovesicular sounds

if dysnpic, crackles and wheezes will be heard

Question 13

what is the click sound?

Answer 13

mid systole

caused by mitral valve prolapse associated with elongation and/or tearing of chordae with DVD

transient and replaced by murmur

Question 14

mechanisms for cough syncope

Answer 14

acutely increased intrathoracic and intra-abdominal pressure associated with couging –>venous compression, decreased venous return, decreased cardiac output

acutely increased intrathoracic and intra-abdominal venous pressure associated with coughing is transmitted to spinal and intracranial veins–>acute increase in intracranial presure–>decreased cerebral perfusion

Question 15

what dx tests can be used to differentiate mitral insufficency from pulmonary disease?

Answer 15

thoracic rads

therapeutic trial of diuretics

Question 16

other than pulmonary edema, what is another cause of cough in a dog with mitral regurgitation?

Answer 16

left atrial enlargement causes left mainstem bronchus to collapse

Question 19

radiographic findings in mitral insufficiency

Answer 19

increase in size of cardiac silhouette

left atrial and ventricular enlargement

pulmonary edema-interstital to alveolar pulmoary infiltrate; usually found dorsocaudal lund fields

if right sided CHF, pleural effusion, distended caudal vena cava, hepatomegaly and/or ascites

Question 20

ECG

Answer 20

normal in beginning

p wave changes (left atrial enlargement)

tall R waves (ventricular enlargement)

mainly supraventricular arrhythmias (APCs, atrial tachycardia, atrial fibrillation)

Question 21

ECHO findings

Answer 21

chamber enlargement on either side of affected valves

prolapse, flail, irregular, knobby thickening of affected valve leafs

M-mode: exuberant inteventricular septal and left ventricular posterior wall motion (increased preload)

doppler: high velocity, retrograde flow from ventricles to atria during systole

Question 22

treatment

Answer 22

surgical replacement or repair of valves

frequent evaluations and medications adjustments needed

depends on functional class of patient

Question 23

treatment of an asympomatic patient

Answer 23

no indication for drug therapy

client education-early signs of CHF, monitor RR and cough

reduce weight if obese

eliminate high salt snacks from diet

omega 3 fatty acids

+/- ace inhibitor

get good baseline data on patient

some dogs will never develop signs of CHF

Question 24

treatment of mild to moderate CHF due to mitral valve regurgitation

Answer 24

diuretics (furosemide)

ace inhibitor

+/- pimobendan (inodilator)

evulate every 3 months (do PE, renal panel, thoracic rads)

Question 25

advanced CHF treatment

Answer 25

emergency! cage rest, oxygen therapy, high doses of diuretics IV, vasodilator therapy, anti-anxiety meds, thoracocentesis

Question 26

prognosis

Answer 26

unpredictable median survival time when in CHF: 9 months progressive disease