Cardiology COPY Flashcards
What disease accounts for 75% of cardiac cases in North America?
MMVD
What signalment of dog is more commonly affected with MMVD?
Males (1.5x), less than 20kg (85% show valve lesions by age 13)
What changes lead to progressive deformation of the valve structure in MMVD?
Dysregulation of the extracellular matrix
- Changes in collagen content and alignment of collagen fibrils
- Expansion of the spongiosa layer with changes in proteoglycans
Valvular interstitial cells aquire properties of activated myofibroblasts => increase in proteolytic enzymes (MMPs), which degrade collagen and elastin
What factors are moderately predictive of MMVD progression and can help identify dogs at risk for heart failure?
- Progressive enlargement of the LA and LV
- Increased transmitral E wave blood flow velocity
- Increased NT-proBNP
- Increased resting heart rate
What does the term heart failure refer to?
Clinical signs caused by heart dysfunction
What is “backward” heart failure?
- AKA congestive heart failure
- The heart fails to drain the veins adequately => increase in venous pressures => accumulation of fluid in the lungs or body cavities
What is “forward” heart failure?
- The heart’s pumping ability is compromised such that it cannot meet the body’s demands during exercise or at rest
- May or may not occur with backward heart failure
What is stage A MMVD?
Dogs at high risk for developing heart disease, but have no identifiable structural abnormalities (i.e. all Cavies without heart murmurs)
What is stage B MMVD?
Dogs with structural heart disease (murmur, etc) that have never developed clinical signs of heart failure
What is stage B1 MMVD?
Asymptomatic dogs with no radiographic or echocardiographic evidence of cardiac remodeling OR remodeling is present but mild (does not need criteria for treatment)
What is stage B2 MMVD?
- Asymptomatic dogs that have more advanced mitral regurgitation (hemodynamically severe) => radiographic and echocardiographic left atrial and ventricular enlargement
- Meet the criteria for treatment to delay the onset of CHF
What is stage C MMVD?
Dogs with current or past clinical signs of heart failure
What is stage D MMVD?
Dogs with end-stage MMVD - clinical signs of CHF are refractory to standard treatment and required advanced or specialized treatment strategies
How should patients with stage A MMVD be monitored?
Yearly physical examination with cardiac auscultation
If a murmur is identified during a routine examination, what diagnostics are always recommended?
- Thoracic radiographs - look for evidence of cardiac enlargement (use vertebral left atrial size) and establish a baseline for the patient’s appearance before CHF develops
- Blood pressure
- Echocardiogram, if possible
When should an echocardiogram be repeated in dogs with MMVD stage B1?
6-12 months (potentially more frequent in large breed dogs, as the disease progresses faster)
What are the criteria for meeting MMVD stage B2?
- Murmur greater than or equal to 3/6
- LA:Ao ratio in the right sided short axis view in early diastole >1.6
- Left ventricular internal diameter in diastole >1.7
- Breed adjusted VHS >10.5 (or greater than 11.5 if echo cannot be performed)
How is the vertebral left atrial score measured?
- Draw a line from the most ventral aspect of the carina to the the dorsal border of the caudal vena cava (the most caudal aspect of the LA)
- Transpose that line to the cranial edge of the 4th thoracic vertebral body
- > 3 likely = stage B2 MMVD
What are the treatment recommendations for MMVD stage B2?
- Pimobendan (0.25-0.3mg/kg PO q12)
- Mild dietary sodium restriction, highly palatable diet with adequate protein
- ACEi is recommended by 5/10 panelists
- Surgical valve repair can be considered
What two medications are currently not recommended for MMVD B2 patients?
Beta blockers, spironolactone - evidence is lacking
Name 3 potential complications of chronic mitral regurgitation
- Pulmonary hypertension
- Acquired atrial septal defect
- Pericardial effusion from an atrial tear
What dose of furosemide should be given to a hospitalized patient with CHF? When should it be repeated?
- 2mg/kg IV or IM
- Repeated doses of 2mg/kg hourly until the respiratory signs improve OR a total dose of 8mg/kg over 4 hours is reached
When should a furosemide CRI (1mg/kg/hr) be considered after the initial 2mg/kg bolus?
Life threatening pulmonary edema
- Expectoration of froth with severe dyspnea
- Radiographic “white out”
- Poor response to the initial furosemide bolus
Apart from furosemide, what other treatments are recommended for hospitalized patients with CHF?
- Pimobendan 0.25-0.3mg/kg q12
- Oxygen supplementation if needed
- Abdominocentesis or thoracocentesis, if needed
- Sedation to help with anxiety associated dyspnea (narcotics, anxiolytic agents)
- ACEi
In hospitalized CHF patients that are failing to respond to normal treatments, what drug may be considered? Why? What should be monitored during administration?
- Dobutamine - increased LV function
- Monitor ECG, decrease dose if tachycardia or ectopic beats occur
In hospitalized CHF patients with life threatening pulmonary edema that is not responding to standard treatments, what drug may be considered?
Sodium nitroprusside CRI for up to 48 hours
What is the dose of torsemide compared to furosemide?
5% to 10%
- For example, if at home furosemide is 2mg/kg q12, may give 0.1-0.3mg/kg torsemide q24
A patient is considered stage D if what dose of furosemide is needed to control clinical signs?
> 8mg/kg q24 (or torsemide equivalent) with appropriate doses of pimobendan, ACEi, and spironolactone
When should a chemistry panel be performed after starting furosemide or ACEi therapy?
3-14 days
What clinical sign has the best predictive value for impending clinical decompensation in a controlled CHF patient?
Increased resting respiratory rate above normal baseline
In patients with atrial fibrillation, what drugs are used to control ventricular rate? What is the goal heart rate?
- Diltiazem +/- digoxin
- <125 BPM
What should the maintenance calorie intake be in patients with stage C MMVD?
60kcal/kg (~RER x2)
What drugs may be used to reduce afterload in patients with stage D MMVD?
Hydralazine or amlodipine
What clinical signs should raise concern for pulmonary hypertension in dogs with primary left sided heart disease?
Ascites, jugular distension
In the EPIC trial, dogs treated with pimobendan developed CHF in how many days compared to placebo?
Pimo 1228 days, Placebo 766 days
So essentially prolonged the preclinical period by 15 months
Hazard ratio 0.64
What is the definition of a cardiomyopathy?
A myocardial disorder in which the heart muscle is structurally and functionally abnormal WITHOUT other cardiovascular disease capable of causing these changes (MMVD, etc)
What is hypertrophic cardiomyopathy?
Diffuse or regional increased LV wall thickness without LV chamber dilation
What characterizes the endomyocardial form of restrictive cardiomyopathy?
- Prominent endocardial scar that bridges the interventricular septum and LV free wall
- May cause fixed, mid-LV obstruction, LV apical thinning or aneurysm
- LA or biatrial enlargement common
What characterizes the myocardial form of restrictive cardiomyopathy?
- Normal LV dimensions (including wall thickness) with LA or biatrial enlargement
- Increased wall rigidity leads to diastolic dysfunction
What characterizes arrhythmogenic cardiomyopathy?
- Severe RA and RV dilatation, RV systolic dysfunction, RV wall thinning
- Left heart can be affected
- Arrhythmias and right sided CHF common
What mutation causes HCM in Maine Coons?
A31P mutation in the myosin binding protein C (MyBPC3 gene)
What mutation causes HCM in Ragdoll cats?
R820W mutation in the myosin binding protein C (MyBPC3 gene)
What is the 5 year cumulative incidence of cardiac mortality in cats with HCM?
23% - so most cats are subclinical
What factors are associated with longer survival times in HCM cats with CHF?
- Cause of CHF: iatrogenic (IV fluids, general anesthesia, corticosteroids) do better than cats that develop CHF naturally
- Greater decrease in NT-proBNP concentrations during hospitalization
- Resolution of CHF at reexamination
How should the results of genetic testing influence breeding in Maine Coon or Ragdoll cats?
- Cats homozygous for mutations should not be bred
- Cats that are heterozygous but have other outstanding characteristics may be bred to genotype negative cats
A palpable thrill (grade 5-6/6 murmur) in cats is most likely to be associated with what?
Congenial malformations - rarely appreciated in HCM
What point of care test has reasonable diagnostic accuracy for differentiating between cardiac and non cardiac causes of respiratory distress in cats?
NT-proBNP
What cardiac biomarker is prognostic in cats with HCM, independent of left atrial size?
Cardiac troponin I - increases are associated with increased risk of cardiovascular death
For most normal sized cats, what is a normal end diastolic LV wall thickness?
<5mm
>6 mm = hypertrophy
When echocardiography is not available, what test can be used to screen cats for HCM? How do you interpret the results?
- NT-proBNP: increased = clinically significant heart disease is likely and an echocardiogram is recommended
- May be normal in early HCM (without LA enlargement), so it does not tell you that a cat is free of the disease
In older cats with heart murmurs, gallop sounds or arrhythmias, what tests should be performed?
- Serum T4
- Blood pressure
- Echo
What are the radiographic findings of CHF in cats?
- Pulmonary infiltrates
- Cardiomegaly
- LA enlargement and distended pulmonary vessels are inconsistently identified in cats!
For cats with stage B1 cardiomyopathy, how frequently is monitoring recommended?
Annual echocardiogram