MMVD

Question 1

How do diuretics affect the (a) lungs and (b) heart?

Answer 1

(a) reduce cardiogenic pulmonary oedema

(b) reduce preload

Question 2

What stage heart disease do you start frusemide?

Answer 2

Stage C (Heart failure)

Question 3

What is a mid-moderate frusemide dose?

Answer 3

1-3mg/kg q8-12h

Question 4

What dose of frusemide would you use in severe/refractory heart failure?

Answer 4

4mg/kg q8h

Question 5

What is a potential serious side effect when starting frusemide therapy?

Answer 5

XS volume depletion and reduction in CO if circulating V decreases XS or if patient is dependent on high ventricular filling pressure to maintain CO (HCM, pericardial effusion) –> severe fall in CO –> Hypotension –> azotaemia

Question 6

What electrolyte abnormality can occur dt frusemide tx?

Answer 6

hypokalaemia

Question 7

How do venodilators effect the heart?

Answer 7

Cause relaxation in systemic and pulmonary veins –> increase capacity –> reducing preload

Question 8

How do arteriodilators effect the heart?

Answer 8

Reduce afterload - thus reduce workload

(dt reduction of SNS and peripheral vasoconstriction mediated by RAAS and SNA)

Question 9

What is a ‘balanced’ vasodilator?

Answer 9

it has both arterio and venodilator properties ie. Pimobendan

Question 10

When is pimobendan indicated?

Answer 10

Stage B2 onwards

Question 11

What is the IV dose of pimobendan in dogs?

Answer 11

0.15mg/kg IV (once then switch to PO)

Question 12

What is the oral dose of pimobendan in dogs?

Answer 12

0.1-0.3mg/kg PO q12h (one hour before food)

Question 13

When is pimobendan contraindicated?

Answer 13

hypertrophic cardiomyopathy or aortic stenosis

Question 14

Why is pimobendan known as an ‘inodilator’

Answer 14

i. Increases binding affinity of calcium to cardiac troponin C
ii. inhibits cardiac phosphodiesterase (PDE) III -> reduces breakdown of cAMP –> increases myocardial contraction (and subsequent relaxation)

Question 15

What vessels does Sildenafil act on?

Answer 15

predominantly veins (venodilator)

Question 16

When do you start ACE inhibitors?

Answer 16

Stages C onwards

Question 17

List 4 ACE inhibitors

Answer 17

1. Benazepril
2. Ramipril
3. Imidapril
4. Enalapril

Question 18

What is the MOA of ACE inhibitors?

Answer 18

1. Blocks conversion of angiotensin I –> angiotensin II
   - -> decreases plasma aldosterone –> mild arteriolar/venous dilation –> Less Na+/H2O retention
   - –> reduces pathologic remodelling/fibrosis

Question 19

Dose of benazepril

Answer 19

0.25-0.5mg/kg q24h

Question 20

What is the MOA of nitrates?

Answer 20

releases nitric oxide which causes vascular smooth muscle relaxation

Question 21

When are nitrates indicated?

Answer 21

In acute, severe heart failure

Question 22

Contrast administration of nitroprusside and nitroglycerin

Answer 22

Nitroprusside IV CRI (rapid acting, v. potent) in ECC

Nitroglycerin percutaneous ointment

Question 23

MOA of sildenafil

Answer 23

Phosphodiesterase V inhibitor –> acts predominantly on pulmonary arterial vasculature –> reduces pulmonary arteriolar resistance

Question 24

Indication of use of sildenafil

Answer 24

Treats pulmonary hypertension

i. Heartworm/severe lung disease
ii. Late stage MMVD

Question 25

What is the oral dose of sildenafil?

Answer 25

0.25mg/kg q12h to 2mg/kg q8h | Start at low end and titrate upwards

Question 26

Inotrope indications

Answer 26

i. Primary myocardial dysfunction (DCM) ii. Secondary myocardial dysfunction (eg. myocardial exhaustion) in late MMVD/ severe arrhythmia causing rapid and prolonged contraction

Question 27

What is the MOA of dobutamine?

Answer 27

Sympathomimetic direct acting on B1 receptors. --> increases force of ventricular contraction + rate of myocardial relaxation

Question 28

When do you use dobutamine in heart disease?

Answer 28

IV by CRI (ECC) as rescue drug in acute heart failure.

Question 29

Describe the pathology of MMVD

Answer 29

i. Affects mitral and tricuspid valve leaflets and chordae tendinae: pathology alters valve motion and closure ii. Valve thickening, prolapse, annular dilation, mitral (and tricuspid) regurgitation

Question 30

Compare the typical onset of MMVD in a toy poodle vs. a dalmation

Answer 30

typically smaller breeds have a slow progression through stages A--> D where in larger sized dogs they have a more rapid progression and onset of CHF.

Question 31

List 5 more serious, later stage complications of chronic MMVD

Answer 31

i. chordae tendinae may rupture ii. arrhythmias esp. supraventricular: atrial premature contractions, atrial fibrillation, syncope may become freq. w/ these arrhythmias iii. cardiac cachexia develops in some cases iv. atrium may rupture --> haemopericardium (sudden deterioration) v. myocardial exhaustion

Question 32

Actions taken at Stage A

Answer 32

simple recognise that some dogs such as CKCS/small breeds have a high risk of MMVD No treatment

Question 33

Actions taken at Stage B1

Answer 33

``` - thoracic rads +/or refer for echo: VHS<10.5 follow up rads q12m 10.5-11.4 q6-12m - measure BP for baseline - advise O to observe for disease progression (RR>30bpm sleeping) ``` No medications

Question 34

Actions taken at B2

Answer 34

Pimobendan 0.25mg/kg q12h PO | + all B1 actions if not already done

Question 35

Actions taken at stable Stage C

Answer 35

Full cardiac evaluation (Echo) Pimobendan 0.25mg/kg POq12h + frusemide 1-3mg/kg PO q12h (+/- anti-arrhythmic if indicated)

Question 36

List 3 anti-arrhythmics

Answer 36

Digoxin Sotalol Beta-blockers

Question 37

Actions taken at acute Stage C presenting as an emergency

Answer 37

i. Oxygen ii. Frusemide 2mg/kg IV --> then 2mg/kg IM/IV q1h until RR/RE good iii. Pimobendan 0.15mg/kg IV iv. Absolute rest v. Anxiolytics (butorphanol, buprenorphine) vi. Stabilise before rads.

Question 38

Actions taken at progressing Stage C

Answer 38

Pimobendan + frusemide (as w/ C) + ACE inhibtor - Benazepril 0.25-0.5mg/kg PO q24h + Diet: low salt, prevent cachexia

Question 39

Actions taken at Stage D

Answer 39

``` Meds (4) Pimobendan 0.25-0.3mg/kg PO q12h Frusemide >4mg/kg PO q12h Benazpril 0.25-0.5mg/kg PO q24h Spironolactone 1mg/kg q12h PO Diet: low salt +/- anti-arrythmics +/- drain effusions (pleural +/-ascites) ```

Question 40

Actions taken at acute stage D CHF

Answer 40

i. O2 ii. Frusemide 2mg/kg IV q1h OR 0.66-1mg/kg/h CRI iii. Pimobendan 0.25mg/kg PO or IV iv. Drain effusions (pleural/ascites) v. Buprenorphine 0.0075-0.01mg/kg + ACP 0.01-0.03mg/kg IV/IM (anxiolytic) vi. Dobutamine 2.5-10ug/kg CRI (myocardial failure) vii. Nitroprusside CRI (poorly responsive oedema) viii. allow free access to water

Question 41

3 signs of MMVD cardiac remodelling on rads

Answer 41

i. Straight cd. border (enlarged LV) ii. Increased sternal contact (enlarged RV) iii. Large left atrial wedge