Category Archives: Heart/Lungs

Heart Failure

Heart Failure
By Dr. Karen Burgess

What does heart failure mean?
The heart is a muscular organ that contains four separate blood holding chambers.  The heart muscle functions to push or pump blood held in these chambers through the body’s blood vessels.  When the heart is unable to push blood forward at a rate that keeps up with the body’s demand it is considered heart failure.  Heart failure typically leads to fluid backing up into the lungs.

What causes heart failure?
There are a variety of diseases that can lead to heart failure.  Pets with a heart murmur, or leaky heart valve account for 80% of heart failure cases in dogs.   In some cases the heart muscle is abnormal, either too thick or too thin.  Lung disease can also put added stress on heart muscle.

What is the significance of heart failure?
Heart failure can be chronic disease with symptoms waxing and waning or acute in nature leading to sudden death.  When blood flow to the body is affected energy level, organ function, and the ability to breathe can all be affected.  Owners may also notice an enlarged belly (from fluid buildup), gums that are blue or paler than usual, and weight loss.

What are symptoms of heart failure?
Pets experiencing heart failure are often first seen for coughing, in particular after exertion of first thing in the morning.  Other signs include exercise intolerance, reluctance to go for walks, and change in sleep pattern or position.

What tests are indicated if heart failure is suspected?
If a pet is experiencing collapse or severe breathing issue from heart failure it may be life-threatening within minutes to hours and immediate medical attention is necessary.   Hospitalization and oxygen support along with medications may be required in these situations.  Radiographs (x-rays) are often used to evaluate for heart failure which will often produce an enlarged heart shape of evidence of fluid buildup in the lungs.  Blood pressure, EKG evaluation, and blood tests are often recommended to further evaluate the impact of heart failure on the rest of the body.  Ultimately an echocardiogram (ultrasound of the heart) allows a veterinarian to understand the specific disease affecting the heart.

What is involved with treatment for heart failure?
Often pets with heart failure are able to be managed with oral medications for some time period after diagnosis allowing them to live a relatively normal quality of life.   It is helpful in managing heart failure patients to monitor their breathing rate while sleeping; changes in this number may indicate that a pet is having more troubles related to their heart function.

Is heart failure the same as a heart attack?
Heart attacks are common in humans and occur when blood flow to the heart muscle is interrupted thus leading to death of the heart muscle known as a myocardial infarct.  This is not a common cause of death or heart disease in cats and dogs.

Heartworm Disease

Heartworm Disease
By Dr. Karen Burgess

What is heartworm?
Heartworm disease is caused by Dirofilaria immitus, an up to foot long spaghetti-like worm that grows to maturity in the heart and pulmonary artery (blood vessel connecting the heart to the lungs).  Dogs become infected with heartworm disease when they are bitten by an infected mosquito that acts as an intermediary host.

What are symptoms of heartworm disease?
Dogs with heartworm disease range in showing no symptoms to experiencing heart failure.  More common symptoms include exercise intolerance or a cough.  The adult heartworm can clog blood vessels and cause dangerous inflammation within the lungs.  Symptoms often do not develop for several years after initial infection, but by this time extensive and permanent damage to the lungs has often already developed.

What is the life cycle of the heartworm?
Heartworms develop through five different life stages.  The adult heartworm resides in an infected dog’s pulmonary artery (blood vessel connecting the heart to the lungs).  After mating, adult female heartworms produce microfilaria, or microscopic larva that travels through the blood stream.  When a mosquito bites an infected dog, they ingest microfilaria along with blood.  The heartworm larva goes through two life stages in the mosquito over a several week timespan before being infectious to another dog via mosquito bite.   After a dog is infected, the heartworm must then go through three more lifestages before becoming an adult in the heart.  Ultimately it takes approximately four months from time of mosquito bite to when a mature heartworm is found in the heart.

How is heartworm disease diagnosed?
There are several blood tests readily available to screen for heartworm disease.  The biggest limitation being that most tests are only able to detect more than three adult female heartworms.  Since it takes four months from time of infection to having an adult heartworm, some dogs may test falsely negative for heartworm disease initially.

How is heartworm disease typically treated?
There are several components to successful treatment for heartworm disease.

The microfiliaria (baby heartworms, L1) and recently injected and developing heartworms (L3 and L4) are killed by ivermectin based heartworm preventatives (Heartgard Plus).  This prevents other dogs from being infected and recently injected larva from growing into adult heartworms in an exposed dog.  Injected heartworms (L3) remain in the skin for three months developing to the larval stage that ultimately migrates to the heart (L5).  Developing larval heartworms (L3, L4) are killed by ivermectin based (Heartgard Plus) heartworm preventatives.

Treatment for the adult heartworm (L5) involves a very specific medication called immiticide, a derivative of arsenic.  Prior to treatment, dogs should have their overall health and stage of disease determined.  Blood tests and thoracic (chest) radiographs are recommended at a minimum.  If there is evidence of lung or heart disease on radiographs, a modified treatment regimen or further testing may be necessary in an effort to prevent complications.  Current recommendations for treatment involve an initial one month course of doxycycline.  Research has shown that doxycycline kills a specific bacteria associated with the adult heartworm thus making it more susceptible to immiticide and potentially decreasing side effects of treatment.  After the course of doxycycline, there is a month delay prior to treatment with immiticide.  This allows time for immature heartworms to either be killed by preventative or mature to adulthood allowing immiticide to kill them.  A confirmatory heartworm test should be performed after this eight week delay and prior to immiticide therapy.

Immiticide is administered as an injection in the back muscle.  One month after this first injection, the same injection is given again twice over a two day period.  Each injection of immiticide kills a certain percentage of heartworms.  By dividing the treatment over a two month period, the total number of dead worms a dog is exposed to at any one time is limited.

What is follow-up care after treatment for heartworms?
Dying adult heartworms and the ensuing inflammation they cause in the lungs is a potentially life-threatening problem for dogs undergoing heartworm treatment.  There is no way to completely prevent complications secondary to heartworm treatment.  Anti-inflammatories are often administered immediately after treatment to assist with any local pain at the injection site which can be severe enough to cause a dog to bite.  An estimated 30% of dogs will experience some sort of reaction secondary to the injection.  Strict rest is required for four weeks after each injection; this means short leash walk to go to the bathroom in the yard, no running, walks, playing, or excessive excitement.  The dying adult heartworm can be very dangerous and the more the heart is rested the safer it is for the dog.  It is better to error on the side of caution (crating a pet) than risk a possible complication.  A heartworm test should be performed again six months after treatment.

What are signs of complications from treatment?
Cough (often closely resembling vomiting but with no food present), lethargy, vomiting, difficulty breathing, loss of appetite, or collapse are all possible complications and warrant immediate medical attention.

Can heartworm be prevented?
There are several different products available to prevent heartworm disease.  These are typically a pill that is administered once monthly year round.  Care should be taken to purchase a reliable product from a trusted brand as several product lines have experienced recalls over the years.

Can a dog get heartworm disease while on preventative?
Heartworm treatment is nearly 100% effective.  Reasons for breakthrough include failure of pet to ingest pill, poor owner compliance in giving pill monthly, resistant strains of heartworm (not a current problem in this region), and an animal that had immature worms that were not detected on a previous heartworm test.

Why do dogs need to be tested for heartworm disease prior to giving preventative?
Heartworm preventatives quickly kill off microfilaria.  In rare instances this can lead to a potentially fatal anaphylactic reaction in a dog.  Heartworm positive dogs with microfilaria should be monitored in a hospital setting when first being given preventative.


Heart Mumur

Heart Murmurs
By Dr. Karen Burgess

What is a heart murmur?
The heart is a muscular organ that contains four separate blood holding chambers.  The heart muscle functions to push or pump blood held in these chambers through the body’s blood vessels.  Between the four chambers of the heart or valves that help compartmentalize the blood within the heart.  When a heart murmur is heard by your doctor via a stethoscope it is actually the sound of blood flowing inappropriately through what should be a tightly sealed valve.  If the heart chambers are rooms and the valves are doors, this would be similar to wind rushing through a partially closed door.  There are six grades that qualify how loud a heart murmur sounds with grade one being the quietest.

 What is the significance of a heart murmur?
A heart murmur alone is only a symptom.  It may be innocent, meaning of no harm to the patient, or an indicator of extensive heart disease.  Neither presence of nor the grade of a heart murmur are reliable indicators of whether relative heart disease is present in a pet.  What it signals is that more information should be obtained to ensure overall heart health.

What tests are indicated when a heart murmur is diagnosed?
In some cases the first recommendation may be to simply reauscult the heart in several weeks.  Some medical conditions that may be temporary (ex. change in hydration status, fever, infection) can lead to transient murmurs that will self-resolve.  Further evaluation of the heart typically involves imaging.  Radiographs or x-rays of the chest can help define the size and shape of the heart, the density of the lungs, and look for other anatomical issues.  Radiographs do not determine how the heart is functioning.  An ultrasound or echocardiogram of the heart allows direct visualization of the heart size, shape, and real time views of the valves and heart muscle.  While a more expensive test, and echo is the gold standard for evaluating overall heart health.  Laboratory tests, EKG (evaluates the electrical impulses that cause the heart to contract), and blood pressure measurement are also typical diagnostics when evaluating a heart murmur.

Can a heart murmur be harmless?
Yes, in some cases a heart murmur is innocent.  This means that there is no corresponding or detectable heart disease. These are most commonly seen in young puppies less than fifteen weeks old.  It is important to ensure these murmurs resolve as puppies can also be born with congenital heart defects which are far more problematic.

What if my pet is found to have heart disease?
There are a variety of specific diseases and treatments that affect the heart.  Without an echocardiogram it is impossible to treat a pet for a specific problem and therefore improve chances of success.  Treatment may involve medication, diet change, or in some rare cases surgery.

Asthma, Feline

Feline Asthma
By Dr. Karen Burgess

What is feline asthma?
Feline Asthma is an airway condition in cats that in its worst forms can be life-threatening.  Also known as allergic or obstructive lung disease, feline asthma has symptoms that closely resemble those of human bronchitis.

What causes feline asthma?
There is not one exclusive cause for asthma in cats.  It is typically an abnormal response or sensitivity to an airborne agent, bacteria/virus, or parasites.  This then sets off a cascade of inflammation in the lungs which ultimately leads to constriction or narrowing of the small airways, buildup of mucous in the airways, cough, and difficulty breathing.  Asthmatic cats can then become more susceptible to secondary bacterial lung infections or even emphysema (air trapped in the lungs/overinflated lungs).

What are risk factors for developing asthma in cats?
Siamese, middle aged (two to eight years of age), and overweight cats may have a higher incidence.

What are symptoms of asthma?
Coughing or difficulty breathing are the primary symptoms associated with asthma.  Often owners may mistake vomiting for coughing as they can look very similar.  A good way to differentiate is that a cough will typically not have food or bile expelled.  It may however appear as though a pet is swallowing after a cough.  Youtube is another good resource for seeing examples of cats coughing (search for “cat cough”).  Other signs or asthma include inappetance, vomiting, sneezing, and a squatting/neck extended stance while coughing.  If a cat is open mouth breathing for any reason it is considered a medical emergency.

How does asthma get diagnosed?
Radiographs or x-rays of the lungs are typically taken to diagnose asthma.  Evidence of inflammation on films along with consistent clinical signs is even more convincing.  Additional diagnostics may include blood work, heartworm testing, feline leukemia/AIDS testing, and fecal parasite exam.  A lavage or wash of the airways can also be used to identify specific cells in the airway.

What is the treatment for feline asthma?
Corticosteroids (steroids) are the common treatment modality for asthma.  Available orally and via an inhaler, steroids reduce inflammation.  While it can take time and patience to desensitize a cat to an inhaler device (similar to ones used for children), this form of steroid has less systemic side effects and is preferred for long term use.  In some cases bronchodilators (oral or inhaled) can also be of benefit.  In emergency situations sedation and oxygen may be necessary to stabilize a cat in crisis.

What is the prognosis with feline asthma?
While there is no cure, asthma can typically be managed and not affect quality or quantity of life.  For cats that are in a crisis the condition can however be life-threatening within minutes to hours.

What other resources are available?
The website provides a wealth of knowledge on feline asthma.  Yahoo also has several groups dedicated to this condition.