Sonrisas Havanese
The Normal Heart



drawing by Willard Thomas

  • In a normal heart blood comes from the body(1)
  • and flows through the right atrium (2)
  • to the right ventricle (3).
  • From there the blood continues to flow to the lungs (4).
  • Once the blood is oxygenated it returns to the left atrium (5)
  • and flows through the left ventricle (6)
  • to exit the heart (7)
  • through the aorta to the rest of the body.
Dogs differ from humans in that they do not have heart attacks as such but develop what is called congestive heart failure. There are different causes of heart failure but the overall effect is to interfere with the blood supply to the rest of the body thus slowly causing damage to the various organs which depend on the nutrients carried by the blood. There may be a resultant accumulation of fluid in the lungs and abdominal cavity which can cause coughing and a swollen abdomen, two common signs of heart problems. Other symptoms of heart damage include difficulty breathing, tiring easily, reluctance to exercise, poor appetite, weight loss, and fainting. Just as with humans, there are medications and treatments available for dogs, so early detection is important.

While many heart conditions are a part of the aging process and are a result of life style, nutrition, medication, and weight gain, there are breeds of dogs that seem to be predisposed to certain heart problems and in these cases heredity plays an important part.

Heart Murmurs
My dog has a heart murmur, so what does that mean? Many breeders and pet people are terrified when they hear these words but, in fact, it may be meaningless. Many dogs and people are born with a heart murmur which goes away or diminishes with time. If the murmur continues past the age of four or five months then it is important to find out what may be causing the heart murmur and to determine to what extent the condition impacts the dog and whether, in the case of a breeding dog, the condition is thought to be hereditary.

This article divides the most frequent heart conditions into two parts, congenital or conditions that dogs are born with, and acquired heart abnormalities. A dog can be born with a heart condition but that condition is not necessarily a result of a genetic problem. Poor nutrition and other environmental conditions can interfere with the normal development of the fetal heart just as diet, lack of exercise and excessive weight can cause or contribute to acquired heart problems.


Congenital Heart Conditions
While congenital conditions are not common, those that do occur most frequently are patent ductus arteriosus, pulmonic stenosis, aortic stenosis and hole in the heart.


Patent Ductus Arteriosus
Similar to the liver, the heart has a special blood vessel which allows the blood to by-pass the fetal heart. As with the liver, if this blood vessel does not seal after birth, all the arterial blood does not go through the heart and thus is not re-oxygenated. This vessel usually closes or seals when the pup takes it first breath. It is found to occur most frequently in females, and certain breeds such as the Bichon Frise, Maltese, Cavalier, German Shepherd, Toy and Miniature Poodles, Border Collie, Keeshound, Pomeranians and Shetland Sheep Dogs.


Pulmonic Stenosis
Stenosis means narrowing, and in this case it is a narrowing of one of the vessels in the right side of the heart which impedes the flow of blood to the lungs causing the heart to work harder to pump the blood through the heart. The narrowing may have various causes, but no matter the cause, the heart is affected by the extra work load. This condition is commonly found in the English Bulldogs, Mastiffs, Terriers, Spaniels, Boxers and Miniature Schnauzers.


Aortic Stenosis
Again, the flow of blood is impeded by an obstruction but in this case it is found on the left side of the heart thus interfering with the flow of blood to the body.


Hole in the Heart
A malformation of the heart leads to a hole between the right and left ventricles. Again, this causes the heart to have to work harder to pump the blood through the heart and body. This type of defect is most commonly found in Terriers, especially Border Terriers and West Highland Whites, Sprinter Spaniels, Basset Hounds and Border Collies.
Acquired Heart Disease
Those heart conditions that are most frequently seen in the older dog are chronic valvular disease, myocardial disease, pericardial disease and arrhythmias.


Chronic Valvular Disease
As a dog ages the heart valves may thicken and harden which results in poor circulation. This may result in restricted blood flow or may allow blood to leak back through the valve. Unfortunately this is being seen more and more in the Havanese.

All dogs can be affected by this condition but smaller dogs tend to be more prone to developing valvular problems. These breeds include Cavalier, Chihuahua, Miniature Schnauzer, Maltese, Pekingese and Whippet.


Myocardial Disease
The form of this disease most frequently seen is dilated cardiomyopathy which a condition where the walls of the heart are not able to expand and contract correctly. This is thought to be caused by poor nutrition, viral infections and some medications but there seems to be some genetic predisposition to it. Males are affected more often than females.

The larger breeds seem to suffer from this more often than the smaller breeds but those most affected are Dobermans, Irish Wolfhounds, Great Danes, St. Bernards and Newfoundlands.


Pericardial Disease
Pericardial differs from myocardial in that the protective sac surrounding the heart fills with fluid or hardens thus interfering with the normal expansion and contraction of the heart. This condition is more easily treated than the myocardial disease and is most frequently seen in the larger dogs especially Golden Retrievers.


Arrhythmias
When there is an interruption to the signal from the brain to the heart this may result in irregular heart beat or arrhythmias. This results in poor circulation and insufficient volume of blood circulating in the body. The interruption may be severe enough that it causes the heart to stop beating completely but this is not common. Just as with humans, dogs can and have received pacemakers to regulate the beating of their hearts.

The breeds most affected by this condition are the Cavalier, Pugs, Miniature Schnauzers, Boxers, German Shepherds, Dobermans and Irish Wolfhounds.

While breeders need to be fully aware of the genetic components of heart disease, the owner also must be aware of the importance of diet, weight, life style and its influence on the dog’s heart. Hopefully we will all work together to ensure long, healthy lives for our Havanese.