Cardio. MMVD. Chap 48 Flashcards
incidence
- approximately 10% of dogs presented to primary care veterinary practices have heart disease
- MMVD is the most common approximately 75% in NA
- small breed dogs, with up to 85% showing evidence of the valve lesion by 13 years of age
most commonly affects MV, ____% TV:
males vs females:
large vs small:
inheritied and genetic component in some breeds
30%
1.5X more common in males
large dogs have faster progression
Pathophys. disease consistently is characterized by:
- changes in collagen and alignment of collagen fibrils within the valve
- changes in the proteoglycan content = expansion of the spongiosa layer
- activated myofibroblasts & matrix metalloproteinases, which degrade collagen and elastin faster than they can be produced
- hypothesized that abnormal numbers or types of mitogen receptors (ie, any of the subtypes of serotonin, endothelin, or angiotensin receptors) on fibroblast cell membranes in the valves of affected dogs play a role in the pathophysiology of acquired valvular lesions
increased risk of sequelea?
no, no increased risk of PTE or infective endocarditis
Pathopys. leading to CHF
- progressive deformation of the valve structure
- prevents effective coaptation, allowing regurgitation
- valvular regurgitation increases cardiac work = ventricular remodeling (eccentric hypertrophy of both the atrium and ventricle, and intercellular matrix changes)
- eventually to ventricular dysfunction - volume overload and CHF
What factors are moderately predictive of the rate of progression of MMVD and can help identify dogs at risk for impending heart failure:
- progressive heart enlargement (of the left atrium [LA] and ventricle)
- increased transmitral E wave blood flow velocities
- increased serum NT‐proBNP
- increases in resting HR
Define “heart failure”:
“heart failure” refers to CS caused by heart dysfunction.
- such that either venous pressures increase so severely that fluid accumulates in the lungs or a body cavity (congestive heart failure [CHF]/ “backward” failure)
- pumping ability is compromised such that it cannot meet the body’s, in the face of either normal or increased venous pressures (sometimes called “forward heart failure”)
2009 consensus:
staging system for MMVD describes 4 basic stages
staging system, applied to dogs with MMVD, remains useful, although recent clinical trial results necessitate a more critical clinical evaluation of dogs in Stage B to facilitate sound therapeutic decision making
Stage A: identifies dogs at high risk but no identifiable structural disorder (eg, every Cavalier King Charles)
Stage B: identifies dogs with structural heart disease (eg, the typical murmur), never developed clinical signs
Stage B1
- asymptomatic dogs that have no radiographic or echocardiographic evidence of cardiac remodeling
- as well as those in which remodeling changes are present, but not severe enough to meet current clinical trial criteria that have been used to determine that initiating treatment is warranted
Stage B2
-asymptomatic dogs w more advanced mitral valve regurgitation caused radiographic and echo findings of left atrial and ventricular enlargement that meet clinical trial criteria that clearly should benefit from initiating pharmacologic treatment
Stage C denotes dogs with either current or past clinical signs of heart failure caused by MMVD.
Stage D end‐stage MMVD, clinical signs of heart failure are refractory to standard treatment (defined later in this consensus statement). Such patients require advanced or specialized treatment strategies to remain clinically comfortable
In a change from the 2009 recommendations:
strong evidence now supports initiating treatment to delay the onset of clinical signs of heart failure at stage B2 patients with more advanced cardiac morphologic changes
Diagnostic and theraputic guidelines/ stage:
Stage A:
unchanged from 2009 - 2019 consensus
- predisposed breeds (eg, Cavalier King Charles Spaniels, Dachshunds, Miniature, and Toy Poodles)
- yearly auscultation
Diagnostic and theraputic guidelines/ stage:
Stage B:
unchanged from 2009 - 2019 consensus
Dx: baseline radiographs, BP, echo
Diagnostic and theraputic guidelines/ stage:
Stage B1:
unchanged from 2009 - 2019 consensus
Dx: baseline radiographs, BP, echo
Tx: not recommended
Reeval: echo (or radiography) in 6‐12 months
Diagnostic and theraputic guidelines/ stage:
Stage B2:
Stage B2 criteria for treatment before the onset CHF: (Class I, LOE: Strong):
In the absence of echocardiographic measurements…
Stage B2 criteria for treatment before the onset CHF: (Class I, LOE: Strong):
- murmur intensity ≥3/6;
- echocardiographic LA : Ao ratio in the right‐sided short axis view in early diastole ≥1.6
- Left ventricular internal diameter in diastole, normalized for body weight (LVIDDN) ≥1.7
- vertebral heart score (VHS) >10.5.
..clear radiographic evidence of cardiomegaly (eg, a “general breed” VHS ≥11.5, or a comparable “breed‐adjusted” VHS in cases where breed‐specific VHS normal values are available) or evidence of accelerating (increasing) interval change in radiographic or echocardiographic cardiac enlargement patterns can substitute for quantitative echocardiography to identify Stage B2. (Class I, LOE: expert opinion)
newer index of radiographic left atrial enlargement:
explain how to perform it and what normal is:
VLAS (vertebral LA size) - quantitative method of estimating left atrial size
- right or left lateral radiograph
- line from the center/ventral carina
- to most caudal aspect of the LA
- intersects with the dorsal border of the caudal vena cava,
- line then is transposed to the cranial edge of the 4th thoracic vertebral body
-Studies are ongoing to determine a VLAS value that accurately predicts B2 remodeling, but in the absence of echocardiography, VLAS values of ≥3 likely identify Stage B2 MMVD. (Class 1, LOE: moderate)
Stage B2 treatment:
Pimobendan -0.25‐0.3 mg/kg PO q12h (Class I, LOE: strong)
Mild dietary sodium restriction and provision of a highly palatable diet with adequate protein and calories (Class IIa, LOE: weak)
ACEI on either initial examination, or in which the LA has increased markedly in size on successive monitoring examinations, 5 (of 10) panelists recommend treatment with ACEI (LOE: weak)
Clinical trials addressing the efficacy of ACEI for treatment of dogs in Stage B have shown mixed results
+/- cough suppressants - when their cough is thought to be the result of pressure from cardiac enlargement on adjacent bronchi. (Class IIa, LOE: expert opinion)