Eq & Ruminant Cardiology

Is mitral valve regurg performance limiting?

Not usually

When to recommend an echo in a horse with suspected mitral valve regurg

-prepurchase

-grade >3

-pansystolic

-exercise intolerance, inc HR/RR, AFIB

Prognosis of mitral valve regurg

Good with no structural change

ALL LEFT SIDED SYSTOLIC MURMURS IN HORSE ARE

Mitral regurg until proven otherwise

Is grade in mitral valve regurg correlated with severity of dz?

No

Ruptured chordae tendinae

-systolic murmur over mitral valve

-musical/honking

->3 grade

-poor prognosis (got to go to CSU now)

Ejection/Flow Murmur

-heart base

-normal valves

-grade <3

-VARIABLE causes (A2, excitement, hemodynamic compromise/change)

Tricuspid regurgitation breed predilection

Standardbreds

ALL R SIDED SYSTOLIC MURMURS IN HORE ARE

Tricuspid regurg until proven otherwise

When to do echo for tricuspid regurg

->3 grade

-pansystolic

-musical

-evidence of heart dz

PDA

-continuous murmur

-normal in neonates <96hr

Most common congenital defect in horse

VSD

VSD murmur for shunt

4-6 pansystolic, band shaped murmur with PMI over tricuspid valve

VSD murmur for relative pulmonic stenosis

Lower grade holosystolic-pansystolic crescendo-decrescendo over L pulmonic valve

If you hear a systolic R sided murmur over the tricuspid valve, make sure you

Can't hear one over the pulmonic valve too

Aortic regurg

-diastolic dive bomber sound

-incidental finding on PP

-sometimes associated with poor performance

Aortocardiac fistulas

-R sided continuous murmur

-poor prognosis, always echo

-DO NOT RIDE THIS HORSE

Vegetative endocarditis

-bacterial infection of valve leaflets

-aortic and mitral are most common

Myocarditis causes

-monensin toxicity

-strongylus vulgaris

-rattle snakes

-cantharidin (blister beetle)

Myocarditis is associated with

Ventricular arrhythmias

Diagnosis of myocarditis

-echo

-troponin

-history

Second degree AV block should stop with

Atropine/exercise

How to know if AV block is not benign?

-more than 2 consecutive blocked beats

-does not resolve w exercise

Horse with second degree AVB that disappears w exercise should

Only be ridden by consenting adult

Horse with second degree AVB that does not disappear with exercise or atropine should

Be rested/reevulated and are not AS safe to ride

Horse with symptomatic bradyarrythmias should

Not be ridden, have poor prognosis

What heart sound might you hear in 2nd degree AVB?

S4

Most important arrhythmia in horses leading to poor performance

A Fib

What do you see with A fib?

F wave, no p wave, irregular R-R

A fib predisposing factors

-standardbreds

-age

-mitral valve regurg

-concurrent cardiac dz

-APCs

Methods for conversion to sinus rhythm

-quinidine

-transvenous electrical conversion

Consider conversion if

-horse expected to perform at max capacity

-horse ridden by child

-no structural cardiac dz

-going on for <4mos or first occurrence

If the owner does not convert, the horse can be used if

-by informed consenting adult

-HR < 220bpm during max exercise

-no concurrent ventricular arrhythmias via exercising ecg

APCs look like

-normal QRS

-irregular R-R

-occ P waves

-sometimes buried by previous T

Causes of APCs

-changes in autonomic tone

-hypokalemia

-drugs (catecholamines, anesthetics)

-systemic dz (colic, fever, hemorrhage)

-structural cardiac dz

When are APCs relevant?

-poor performance w no other cause

-freuent at rest

-associated w runs of atrial tachy

-in conjunction with structural change

-after AFIB conversion

What should I tell the client with a horse with APCs?

APCs overdriven with exercise or are occassional are as safe as any other horse. There is possibility for A fib.

What can be done for horse with APCs?

-assess systemic wellness, electrolytes

-echo to ck for structural dz

-assess for myocarditis

VPCs look like

-early beat

-no P waves

-QRS does not match

-abnormal T wave repolarization

-compensatory pause

When are VPCs reklevant?

-frequent

-sustained V tach

-rapid ventricular rate (>120bpm)

What can be done for horse with VPCs?

Same as APC recommendations

Contributing factors to cattle developing BHMD or pulmonary hypertension

-genetics

-pneumonia

-migrating parasite larva

-high altitude

-poisonous plants

-nutrition

-age

-illness

-body condition

-breed

-gender

-anything that may affect respiratory tract

Pathophy of BHMD

1. Altitude induced pulmonary hypoxia

2. Pulmonary shunting and vasoconstriction

3. Pulmonary artery hypertrophy

4. Pulmonary hypertension, right ventricular hypertrophy, right ventricular failure, death

How to identify animals at risk for BHMD

PAP measurement, cull those with high score >50mmHg

Economical effect of BHMD on the cattle industry

Can cause losses of >5% on calf crop = thousands of dollars lost per year. It is most likely the major concern and most costly for high altitude ranchers

What is the use of PAP by high altitude ranchers?

Developing genetically resistant herd to effects of high altitude through using low PAP testing bulls and females

Pathophys hardware disease

1. Metal object falls to lower portion of reticulum

2. Penetrates stomach wall and often chest cavity

3. Stomach contents leak in and overwhelm

Where is endocarditis commonly found in cattle?

Right side of heart — pulmonary or tricuspid

Why?

Periodical bacteremia starting in the rumen. In other species, the source is the lungs so is on the left side

Most common location of VSD in ruminants

Ventral to the tricuspid valve but can be located at the apex

Murmur for VSD

Best intensity noted on right side over tricuspid valve as pansystolic murmur

ECG

Base-apex lead

What Afib caused by in ruminants?

Electrolyte imbalances/toxemias

Treatment for Afib

Correct electrolyte imbalances and pain control

If a cow presents not doing well and just had a baby a month ago, what should your first differential be?

Hardware dz

Most common neoplasia rum

-juvenile melanoma

-bovine lymphosarcoma (sp column)

Vit E deficiency

-very painful

-high CK

-diaphragmatic paralysis

-bone pain = vit D problem, hypophosphatemia

Ionophore toxicity

-looks like high mountain disease

-influx of Na into cell followed by Ca = mitochondrial death

-pale areas and streaks in myocardium

Why are ionophores used?

Increase rumen proprionate from streptomyces cinnamonensins. Also coccidiostatic.