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Heartworms and Heart Murmurs

Partnership for Environmental Education and Rural Health

Texas A&M University

http://peer.tamu.edu

An introduction to problems that can occur in the heart

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The Heart

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Basic Anatomy

• Arteries – Carry blood away from the heart

• Veins – Carry blood to the heart

• Capillaries – Site of gas exchange

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The Heart as a Pump

• The heart works as a pump, forcing blood forward into the arteries.

• Blood returns to the heart in veins. Veins have valves.

• Valves work to keep the blood from flowing backwards, even when the heart isn’t contracting.

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Blood Flow

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Heartworms

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What are they?

• Parasitic worms that live in the heart and blood vessels of animals.

• Heartworms (Dirofilaria immitis) affect dogs, coyotes, sea lions, ferrets and cats.

• They are transmitted by mosquitoes

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Life Cycle of a Heartworm

Microfilaria develop into larva (L3) in the mosquito

Larvae are transmitted to the dog when the mosquito takes a blood meal

Larvae continue to mature in the dog until they become adults

Adult heartworms live in the heart and mate to produce microfilaria

Microfilaria are released into the bloodstream

Microfilaria are transmitted to a new mosquito when it bites the infected dog

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Microfilaria

Seen at 400x magnification

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Adult Heartworms

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Clinical Signs

• Coughing

• Exercise intolerance

• Syncope (Fainting)

• Ascites (Fluid in the belly)

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Radiographs of Heartworm Disease

Enlarged Right Atrium

Widened Caudal Vena Cava (Caval Syndrome)

Lung Disease (Heartworm Pneumonitis)

Enlarged Pulmonary Arteries

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Prevention

•Prevention products make sure dogs don’t get heartworms in the first place

• Include: Heartgard, Interceptor, Sentinel, Revolution, Filaribits

•As long as the animal is medicated every month, it prevents any larvae from maturing and reaching the heart, thus stopping heartworm disease.

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Treatment

• Treatment products help cure the animal once it already has heartworms– Elimination of heartworms is a two step process– Must get rid of adult worms and larvae separately

• Consists of two shots in the muscle of Immiticide and 4 weeks of strict cage rest

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Surgical Removal

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Heart Murmurs

• What is a heart murmur?– A heart murmur is an extra or unusual sound heard

during a heartbeat. – There are many kinds of murmurs, some that are

insignificant and some that indicate a heart problem is present.

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Patent Ductus Arteriosus

• Special type of heart problem

• Breakdown the words:– Patent: to make open– Ductus: tube or canal– Arterio: relating to an artery

• Put the words together to see that it means there is an artery that is open (that should be closed!)

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PDA in canines

• Most common canine congenital (present at birth) heart problem

• Affects 5 out of 1000 dogs, in any size or breed

• 65% of dogs with this problem will die by 1 year of age if it is not fixed

• Most have the problem diagnosed between 1 month and 3 ½ years of age

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PDA in humans

• The estimated incidence is from 6 out of every 100,000 live births up to 2 out of every 10,000 live births.

• This incidence is increased in children who are born prematurely.

• The death rate is very low except in extremely premature infants.

• It occurs twice as often in girls as in boys.

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Return to Anatomy

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Normal versus PDA heart

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Symptoms

• Can a patient live normally?– Sometimes there are no symptoms– In large PDAs, symptoms can include:

• Exercise intolerance• Sweating• Dyspnea (difficulty breathing)• Poor weight gain

Audio of a normal heart Audio of a PDA murmur

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Management Options

• Observation and monitoring• Medical Management

– Medications may be prescribed to reduce blood pressure, maintain normal heart rhythm, and prevent fluid overload.

• Surgical– Surgical repair

• Ligating (suturing closed) the patent artery– Catheter based occlusion

• Placing a “coil” inside the artery to stimulate closure

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Surgical Ligation

Aorta

PulmonaryArtery

PDA

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Catheter Based Occlusion

• With a surgery called Transarterial Ductal Occlusion With Coils– Very safe procedure– Very successful procedure (95% need nothing else)

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Transarterial Ductal OcclusionAorta (with catheter inside)

Pulmonary Artery

PDA Coil within PDA

*Notice how no dye is visible in the pulmonary artery anymore!

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Any Questions?