The canine and feline hearts are essentially the same as the human heart (along with most all mammals). The basic pathway for blood to circulate in the body is a set of two loops. The heart has a left and right side, each responsible for one of those loops. The right loop takes blood back from other areas of the body through veins and pumps it to the lungs, where it is filled with oxygen and then returned to the heart. The left side of the heart takes blood from the lungs and pumps it out to the rest of the body through arteries.

Each side of the heart has 2 chambers: atrium and ventricle. There’s a valve between the atrium and ventricle on each side that prevents blood from flowing backwards through the circuit. The atria are smaller and have thinner walls. Their job is to push extra blood into the second chamber. The second (lower) chamber on each side is called the ventricle. The left and right ventricle are quite different from one another. The right ventricle doesn’t have to pump blood very far — just to the lungs — so it’s got thinner muscle walls and is a bit weaker. The left side is much stronger, with thicker muscle, because it pumps blood out to the whole body. We say that the left side of the heart is a high-pressure loop, while the right is a low-pressure loop. Each ventricle pumps blood out through another valve (aortic or pulmonic) that stops blood from flowing backwards. There is a single major blood vessel that takes blood from each ventricle and begins the pathway to the lungs or body.

The images below labels all of the parts of the heart and show the route of blood flow. You’re looking at the heart as if you were staring at the chest of someone facing you. Your left side is actually the right side of the heart, and your right side is actually the left side of the heart. Because the right side of the heart handles low-oxygen blood, it’s colored blue. The left side handles oxygen-rich blood, so it’s colored red. Arteries carry blood away from the heart and veins carry blood back to the heart. In general, arteries carry high-oxygen blood and veins carry low-oxygen blood. There are two exceptions to that rule that I’ll explain in a moment.

While nearly every artery and vein has a specific name, there are a few that attach to the heart that are really important. When blood is returning to the heart from the body, it arrives in the cranial(superior) and caudal(inferior) vena cava. The blood then goes into the right atrium. The atrium fills up, then contracts, which pushes blood through the tricuspid valve into the right ventricle. Once the right ventricle is full of blood, it contracts. The tricuspid valve closes, which stops blood from going back to the atrium and forces it to go through the semilunar (pulmonic) valve into the pulmonary arteries. These arteries are carrying low-oxygen blood out to the lungs. That’s the first exception to the above rule. In the lungs, the blood gives up carbon dioxide and picks up oxygen. High-xygen blood then returns to the heart in the pulmonary veins. That’s the second exception. The left atrium fills, then contracts. Blood is pushed through the mitral valve into the left ventricle. Once the left ventricle is full, it contracts. This closes the mitral valve and forces blood out of the aortic semilunar valve into the aorta. The aorta is that big arching red vessel that comes out of the top of the heart. It then runs down along the spine, giving off arteries all over the place to feed blood to all of the distant part of your body. Blood gives up oxygen to the body tissues, picks up carbon dioxide, and then makes its way back to the right side of the heart by way of the veins. The image below shows the flow of blood through the heart. If you start with the blue arrow going to the heart from upper or lower body, you’ll start the journey as I just described it.

Now that you’ve got an idea about how blood flows in the body, we can talk a little about how the heart does what it does. The heart is a big muscle made up of a special kind of muscle fiber. Cardiac muscle cells are all linked together in a special web that passes on the signals to contract from cell to cell. The heart has a special group of cells called the sinoatrial node. The SA node is also known as the pacemaker. It sets the rate at which the heart beats, and the signals it passes along to the rest of the heart are carried by a special network of fibers. The way the signals move from place to place in the heart causes the chambers of the heart to beat in a very specific order.

When the heart is beating as it’s supposed to, it generates some noise. The heartbeat sounds are from the atrioventricular (mitral and tricuspid) and semilunar (aortic and pulmonic) valves closing. They snap closed in a way that reminds me of shaking out a big towel or sheet.

We have a way to tell what order the heart chambers are contracting in, and whether the electrical signals are normal. It’s called an EKG (electrocardiogram. This is the little spike graph that everyone is familiar with – it tells us exactly what order the heart’s nerves are conducting impulses and how the heart muscle is responding.

That should give us enough of a start on the structure function of the heart. Thanks for slogging through another long anatomy and physiology lesson! Next week, we’ll start talking about the things that go wrong in various types of cardiac disease. I intend to start with cats, then move on to dogs.

This is a link to the AVMA page that introduces the guidelines.

You can download a PDF of the whole set of recommendations here.

Have a good weekend! Be safe!

We should define the proper term for diseases that can be shared among species. Officially, “a zoonosis is any infectious disease that can be transmitted (in some instances, by a vector) from non-human animals to humans or from humans to non-human animals… In a study of 1415 pathogens known to affect humans, 61% were zoonotic.”

The most dangerous zoonotic disease out there is Rabies, in my opinion. We don’t hear a lot about it in Michigan, but it’s still a very real and very prevalent problem. Rabies is a virus. Any mammal can get rabies, but rodents (except for woodchucks) are less likely to have or transmit the disease. The virus is transmitted in saliva, and it infects the nervous system. No matter where the bite is, the virus makes its way toward the brain. The damage done to the brain is generally fatal. A recent case was treated by putting the brain into a medical coma, which allowed the patient to survive. This report didn’t say what degree of damage was done. Rabies is generally regarded as a uniformly fatal disease. Vaccination is available and highly effective. Vaccination is required by law in Michigan. Bats and skunks are the most common carriers in Michigan.

I’ve spoken and soapboxed about Leptospirosis many times already on the blog and in the hospital. It’s a prevalent disease in Michigan. Leptospira is a group of bacteria with a spiral shape. There are over 200 varieties worldwide. Four to six are the major cause of disease in Michigan. The bacteria is carried by wild animals such as raccoons, opossum, rats, and large domestic animals. It survives well in warm, wet conditions — soil and standing water both prolong lepto’s presence in the environment. If animals or people come into contact with lepto, liver and/or kidney damage can result. We have a vaccine against the 4 most common strains of lepto encountered by dogs. The blog post about lepto is here.

West Nile Virus makes a lot of headlines. This virus mainly infects birds. However, it can also infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic rabbits, crows, robins, crocodiles and alligators. This virus is transmitted by mosquitos and birds (crows and robins). The virus can cause an infection with no signs. It can also cause a high fever, or inflammation in the brain and spinal cord. This disease can be fatal, but some people recover after a long period of time. Horses have a vaccination, but we don’t have one for dogs/cats or people.

Lyme disease is a bacterial infection passed to pets and people by a bite from a specific kind of tick. Ixodes scapularis (the Deer Tick) will attach to an animal or person and drink blood. During that attachment/bite time, the lyme bacteria migrate into the dog or person. These bites usually create a very obvious and characteristic lesion called a Target Lesion (Erythema migrans). Lyme disease is treatable, but it’s not always easy to diagnose. The best way to avoid Lyme disease is to have your dog vaccinated and to wear protective clothing or tick repellant. Dogs and cats have topical tick prevention products that are also safe and effective.

Lastly, I want to mention intestinal parasites as a zoonotic disease. Hookworm and roundworm can cause infections in people. The eggs of these intestinal worms are passed in the feces of dogs and cats. Once in the environment, these eggs can contaminate the soil or even the interior of a house. Ingesting the eggs can infect a person. Hookworm can also burrow through the skin if a person comes into contact with contaminated soil. Bare feet in the yard is a common way exposure occurs. Hookworm larvae burrow through the skin, causing a nasty inflamed lesion on the skin surface. Roundworms get lost in the body and can migrate into the internal organs or the eye. Irreversible organ damage can occur. The best way to prevent these worms is to keep your pets clear of infections. Monthly heartworm prevention stops intestinal parasite infections. Fecal checks at least twice a year help verify that pets are not carrying parasites that could infect their families.

That’s a small selection of the more common zoonotic diseases. There’s a ton more information at the links below. Read on if you’re not looking to sleep for a night or two. There’s a lot of scary stuff out there!

http://www.cdc.gov/healthypets/browse_by_diseases.htm
http://www.cdc.gov/ncezid/
http://www.capcvet.org/

http://www.avma.org/public_health/default.asp

In 1918, a particularly nasty flu virus swept the globe. This vicious strain was thought to have come from a mixing of avian and human flu in pigs. In 2 years, between 50-100 million people died (3% of the world’s population). This flu pandemic killed more people in a year than the Black Plague killed in 100 years. The most deaths occurred in young, healthy people, which are normally the most resistant to disease. It’s believed that these people had such a violent immune reaction to the virus that their own body was damaged to the point of death.

Needless to say, we need to take Influenza viruses very seriously.

In 2004, a large number of racing Greyhounds at a track in Florida got sick with respiratory signs. The disease resembled kennel cough, but some of the dogs were far sicker than is usually seen with ‘regular’ kennel cough. Extensive testing eventually revealed that an equine influenza virus had changed just enough to allow it to infect dogs. Currently, this virus has not infected any people.

Canine influenza has the official “name” of H3N8. These letter-number combinations describe the viruses based on their structure. The “H” stands for hemagglutinin protein; “N” for neuraminidase protein.


Signs and symptoms in dogs include cough, runny nose, fever, and in some patients, severe respiratory distress. While most dogs don’t get severely sick, about 8% do develop severe or life-threatening illness.

Spread and infection in dogs happens by aerosol transmission. Dogs that cough and sneeze send little droplets of moisture into the air that contain the virus. Normal breathing can also spread the virus in the air. People and inanimate objects that are contaminated by respiratory fluids from a dog can pass the infection on to other dogs. Once a dog is infected, it will actually be able to spread the virus for a few days before it shows any signs of being sick. Places that have lots of dogs in an enclosed area are massive risks for transmission of Canine Influenza: boarding facilities, daycare, groomers, veterinary hospitals, kennels. This is a completely new virus for dogs, so 80% of those exposed to the virus will get sick.

Testing and treatment are both available. Samples of respiratory secretions or blood testing can be done to determine if a dog with respiratory illness is suffering from the H3N8 virus. Treatment is generally just supportive care. IV fluids, antibiotics to prevent a bacterial pneumonia from happening, and time. The severely affected dogs may need oxygen therapy or intensive care. Most patients will survive H3N8 infection.

A vaccine is available for Canine Influenza. Dogs have to be vaccinated twice, about 3-4 weeks apart, to be protected. The vaccine has to be boostered once a year. While the vaccine does greatly reduce the chances of a dog becoming gravely sick from H3N8, it does NOT completely stop the infection from occurring. It’s the only vaccine on the market at this time.


Do dogs in Michigan need to be protected? That’s a good question. Better than half of the states in the US have had canine influenza outbreaks, but Michigan is not currently one of them. Ohio and Illinois have had outbreaks. Somehow, we’ve dodged the bullet so far.

There are two choices: vaccinate BEFORE the outbreak, or vaccinate after. I certainly can identify with not vaccinating dogs for something that’s not even present in the state yet. However…The first choice is preferable because of the ease with which H3N8 is transmitted. Once it gets into the population here in Michigan, it is going to rapidly spread. Because it takes 6 weeks for the vaccine to reach peak effect, it may be difficult to protect dogs in an area where the virus has already shown up. A giant rush to get vaccinated will also cause high numbers of dogs to visit the hospital, which is just asking for trouble because of the way influenza is transmitted.

I prefer to give as few vaccines as possible, so we are recommending the influenza vaccine for any patients that are ‘social’ dogs at this time. If your dog goes to the groomer, boards anywhere, goes to daycare, goes to a dog park, travels to other states, goes to dog shows, or is social with other dogs in the family or neighborhood, you should strongly consider the vaccination. (These recommendations are the same for the Bordetella vaccine.) The vaccine is safe and we’ve been using it since 2009 when it was approved for use in dogs.

You can read more about the H3N8 virus and vaccination at the vaccine manufacturer’s website.

More information about Canine Influenza can be found here.

The AVMA’s page about Canine Influenza is a very detailed look at the virus.

The AVMA’s Pet Dental Health Month Page has links there for a Facebook event, Flickr gallery of pet smiles, a podcast, a video on brushing teeth, and more.

I closed voting on the poll that I put up at the beginning of the year. The most popular topics were news, heart disease, canine influenza, chronic renal failure, and osteoarthritis. I’ll probably come up with a few more as time goes along.

Sunday will remain the main posting day for ‘big’ topics. I will try to post news/interest stories at least once per week in addition to the Sunday post.

Some of you are new to the blog and may not have looked all the way back through the last year of posts. I’m going to make links down below for some of the more popular and/or better posts so you know what’s been covered. I will still get any comments you leave on any of the posts, so don’t hesitate to speak your mind about anything at all. I try to respond within 24 hours of a comment. Comments have to be approved before they will show up on the post. That’s how I filter out spam comments for drugs and illicit services — no kidding, they happen!

Thank you again for your interest and participation in the blog! I really enjoy writing and conversing through comments. I’m looking forward to the next year!

Selecting a Good Pet Food Part 1.

Selecting a Good Pet Food Part 2.

Stool Samples & Heartworm Tests

Canine Vaccines

Feline Vaccines

Pet Authority Calendar

You can read about the Foundation here. I believe in the work they’re doing, and I wholeheartedly approve of the excellent medical care and basic care the Foundation provides these animals. Many of them are special needs – seizures, permanent damage from human interaction, wildlife rehab, etc. The sheer amount of community outreach the Foundation takes part in is wonderful, too.

I’ll post a couple of pictures showing some of the things I was up to last week. In the first, I’m holding a python. In the second, that lion cub needed to have her claws trimmed. She wasn’t happy about it at all. I learned that to soothe a cranky lion cub, you should hold them up in the air from behind and under the arms and gently rock them forward and back. It mimics having the lioness pick the cub up to move it. It worked like a charm and I was able to get all of the nails trimmed without incident.

Next week, I’ll be tackling the survey results and catching up some of our new readers.

I will try to make up for it with the next post, however. I don’t wan to ruin a good surprise so I’m not going to elaborate.

I hope everyone has had a good weekend!

What does that mean, exactly?

Last Thursday we voluntarily underwent an intense evaluation by an AAHA representative. She spent over 5 hours speaking with us, inspecting the facility, and reviewing our records. She looked over our patient files, communication logs, computer system, and phone system. She inspected each area of the hospital to ensure that it was clean, neat, and equipped to provide safe, high-quality care for pets. She examined the educational materials we provide to clients. She checked our surgery equipment to make sure everything was sterile, clean, and organized. She checked over the pharmacy to ensure that we are handling our medications safely. She even checked over each doctor’s office to see what reference books, equipment, and computer systems we utilize.

In each area, points are awarded if the AAHA standard is met. Some specific areas require a certain number of points to achieve a passing mark. I’m proud to say that we met the standards required to become accredited, which means that we have been recognized as upholding a very high level of care and practice at Pet Authority.

Why is that a big deal?

AAHA is the only organization that accredits animal hospitals throughout the U.S. and Canada. AAHA-accredited hospitals voluntarily choose to be evaluated on 900 standards in the following areas: quality of care; diagnostic & pharmacy; management; medical records; and facility.
The Standards developed by AAHA are widely accepted as the components of veterinary practice that represent high quality care. The Standards are updated to ensure that they remain consistent with evolving knowledge and technology.
Accreditation helps veterinary hospitals stay on the leading edge of veterinary medicine and provide the quality and range of services you and your pet deserve.

How does our accreditation help you and your pet?

Your pet will benefit from up-to-date knowledge of medical procedures, treatments, and preventive healthcare.
You can be confident that our staff is required to undergo a set amount of continuing education to make sure that they improve their knowledge and skills to keep pace with current medical practice.
We can provide you the peace of mind from knowing that our hospital provides care that meets the guidelines set by a nationwide network of specialist and expert veterinary professionals.

Where can you find out more information about AAHA?

AAHA’s website is an excellent place to start. Here are a few select links that lead to more in-depth information:
Information about AAHA as an organization.

AAHA Guidelines for anesthesia, preventive healthcare, pain management, and more.
AAHA’s Client-oriented website, HealthyPet.com.

I’d like to take this opportunity to thank the staff of Pet Authority, as well. Without their dedication to their professions, we would never have been able to pass the accreditation inspection. Every employee has demonstrated a commitment to the hospital, but more importantly, to the pets and clients that trust us to care for their family. Well done!