Acquired Canine Cardiac Diseases

Question 1

2 most common acquired canine cardiac diseases.

Answer 1

• Myxomatous mitral valve disease (MMVD).
• Dilated cardiomyopathy (DCM).

Question 2

1. Predispositions for MMVD?
2. MMVD onset and progression.
3. Predispositions for DCM?
4. DCM onset.
5. DCM produces…

Answer 2

1. Small breed dogs up 20kg e.g. CKCS.
2. Adult onset, slow progression.
3. Large breed dogs.
4. Adult onset.
5. Ventricular arrhythmias.

Question 3

What would be heard on auscultation from a dog with MMVD?

Answer 3

Increased RR, normal lung sounds.
Increased HR, murmur, extra beats which do not have a pulse associated with them.
Murmur.

Question 4

Blood pressure.

Answer 4

Lower pressure in the left atrium and higher pressure in the aorta so blood goes to path of least resistance which is back into the atrium due to regurgitation.
Regurgitation causes pressure in the atrium to increase, NOT WANTED!
If systemic hypertension, then need to treat to try and reduce mitral regurgitation.
If forward failure is the issue, looking for hypotension due to reduced forward stroke volume.

Question 5

3 features looking for on echocardiography?

Answer 5

• Valve prolapse.
• Valve thickening.
• Regurgitation of blood through the valve, into the atrium.

Question 6

Blood tests.

Answer 6

• Electrolytes.
• Renal values.
• Cardiac biomarkers.
  – N-terminal pro-B-type natriuretic peptide (NT-proBNP).
  –> cardiac filling pressures (myocardial stretch).
  – Cardiac troponin I (cTnI).
  –> myocardial injury.

Question 7

MMVD staging.

Answer 7

A = at risk.
B1 = preclinical disease (murmur) (no cardiomegaly).
B2 = preclinical disease (murmur) (cardiomegaly).
C = CHF.
D = CHF refractory to standard therapy.

Question 8

Treating MMVD (stage C).

Answer 8

Pulmonary oedema: furosemide.
Contractility: Pimobendan.
RAAS: ACE-inhibitor (and spironolactone). Diuresis (and remodelling?): spironolactone.

Question 9

MMVD stages and action.

Answer 9

Stage A: monitoring for murmurs, no treatment.
Stage B1: no treatment, no evidence anything works at this stage, monitor heart size w/ echo (ideally).
Stage B2: Pimobendan.
Stage C: Furosemide, Pimobendan, ACE-inhibitors (Benazepril), Spironolactone.

Question 10

Post-diagnosis of MMVD?

Answer 10

Discharge home, monitor sleeping RR at home:
- should be <30brpm (call if increasing or >40brpm.
In 1 week:
- repeat bloods.
- measure BP.
Re-examine in 3m, or earlier if concerns.

Question 11

1. DCM MMs.
2. Heart sounds DCM.
3. Pulses.
4. RR?
5. Lung sounds.
6. Extremities.

Answer 11

1. Pale, CRT 3secs.
2. Soft systolic murmur (due to dilation causing annulus on mitral valve to stretch), chaotic rhythm.
3. Peripheral pulses weak w/ deficits.
4. Dyspnoea and tachypnoea.
5. Crackles.
6. Cold.

Question 12

1. Why thoracic radiographs?
2. Why ECG?
3. Why BP?
4. Why echo?
5. Why blood tests.

Answer 12

1. CHF?
2. Chaotic rhythm, pulse deficits.
3. Heart failure, weak pulses, cold extremities.
4. Dx, severity.
5. Biochemistry, biomarkers.

Question 13

Thoracic radiograph DCM.

Answer 13

Cardiomegaly.
V large left atrium.
Severe elevation of trachea towards spine.
Large pulmonary veins
Pulmonary oedema (increased opacity in caudodorsal lung lobes).

Question 14

DCM ECG.

Answer 14

Irregular.
R interval variation.
R wave height variation (some shorter R-R intervals meaning less time for the ventricles to fill, so smaller at point of depolarisation, so QRS also smaller).
No clear P waves.
Atrial fibrillation.

Question 15

1. DCM BP.
2. Biochemistry and other bloods.

Answer 15

1. Hypotension (80mmHg).
2. Biochemistry: electrolytes normal, mild azotaemia.
   Cardiac troponin I: >0.07ng/ml.

Question 16

DCM echo.

Answer 16

Dilated and rounded ventricle.
Poor systolic function (contraction poor).

Question 17

Case Dx of DCM.

Answer 17

DCM.
L sided CHF.
Cardiogenic shock from forward failure due to reduced CO caused by poor systolic function.
Atrial fibrillation.

Question 18

Case DCM treatment and routes.

Answer 18

Furosemide IV.
Pimobendan PO/IV.
Diltiazem PO/IV (antiarrhythmic drug for supraventricular tachycardias).
Minimise stress.

Question 19

Further monitoring for DCM case.

Answer 19

Monitor RR.
Monitor HR.
Repeat BP.
Repeat bloods for azotaemia.

Question 20

Evidence for preclinical DCM?

Answer 20

Benazepril.
Pimobendan more effective – helps the systolic function.

Question 21

DCM treatment evidence once in CHF.

Answer 21

No evidence for Furosemide but used anyway.
Pimobendan for systolic function.
ACE-inhibitors effective.
Spironolactone evidence not strong but rational to use.

Question 22

DCM case after care.

Answer 22

Discharge home.
Monitor sleeping RR at home:
- should be <30brpm (call if increasing or <40brpm).
In 1 week:
- repeat bloods.
- measure BP.
Re-examine in 3m, or earlier if concerns.

Question 23

1. Lifetime prevalence of MMVD in CKCS.
2. Lifetime prevalence of DCM in Dobermans.

Answer 23

1.100% if live longer than ~10yrs old.
2. 45%.