MVD is a condition that has traditionally affected a large population of the Cavalier King Charles Spaniel. It is therefor of the utmost importance for all breeding dogs to be heart cleared by a Veterinarian Cardiologist. All of our cavaliers here at Countryside are tested and certified prior to breeding consideration.
Mitral Valve Insufficiency: A Cause of Heart Failure
Race Foster, DVM
Holly Nash, DVM, MS
Drs. Foster & Smith, Inc.
Circulatory patterns.
The heart is actually nothing more than a mechanical pump. It accepts blood on one side and forces it through the lungs, then its other half pumps the liquid on through the entire body. The heart does not change or alter the blood in any way. It has no glandular tissue and therefore secretes nothing into the blood nor does it extract anything. It is probably the simplest and most easily understood organ in the entire body.
As a quick review, blood returns from the body and enters the right upper chamber of the heart, called the right atrium. At this point, the blood is low in oxygen but high in carbon dioxide. It is then pumped from the atrium through the right atrioventricular valve into the right ventricle. From this larger chamber, it is then forced on into the lung field through the pulmonary artery. This is the only artery in the body that carries non-oxygenated blood. Carbon dioxide is a by-product of body metabolism and is attached to the red blood cells. In the lungs, carbon dioxide is replaced with
oxygen. The reoxygenated blood then moves through the pulmonary vein back into the heart and enters the left atrium. This chamber pumps the blood through the mitral valve into the left ventricle, which is the largest, most heavily muscled chamber of the heart. While other chambers only move the blood a short distance, the left ventricle has the responsibility of forcing blood throughout the entire body through the aorta. This completes the system, which allows blood to circulate throughout the body and then return to the heart.
Comparison of heart disease in people and dogs
In people, heart disease usually involves the arteries that supply blood to the heart muscle. In some cases they harden, losing their elasticity and the ability to respond to blood pressure differences as they distribute blood to the cardiac muscle. In other cases, possibly due to diet or genetics, the arteries may become obstructed with a plaque that builds up internally on the artery walls. This causes the muscles of the heart to receive less than adequate amounts of blood. Starved for oxygen, the result is usually a heart attack. In dogs, arteriosclerosis (the hardening of the arteries), plaque formation, and heart attacks are all very rare. However, heart disease is very, very common.
Canine heart failure simply means that the muscles 'give out.' This is usually caused by one chamber or side of the heart being required to do more than it is physically able to do. It may be that excessive force is required to pump the blood through an area, and over time, the muscles fail. Also, in some cases, the volume of blood that must be pumped to keep up with other areas of the heart is more than the particular chamber can adapt itself to move, again leading to muscle failure. Unlike a heart attack in humans, cardiac failure in the dog is a slow insidious process that occurs over months or years. In these cases, once symptoms are noted, they will worsen over time until the animal
is placed on treatment, dies, or is 'put to sleep.'
Mitral valve insufficiency
Heart failure in older dogs is usually due to problems with the mitral valve of the heart, and occurs most commonly in smaller breeds, such as Poodles, Yorkies, Pugs, Pomeranians, Lhasas, etc. As the dog ages, the mitral valve between the left atrium and left ventricle starts to fail. A heart valve is designed to prevent back flow. Blood can be easily pumped through the valve, but once the more forward chamber is filled, the valve closes to prevent blood from flowing backwards into the atrium. These valves greatly increase the efficiency of the heart as a pump, since the blood only has to be pumped once to keep it moving forward from one chamber to another chamber. No blood is spilling back, which would require additional effort to move it forward. In the case of a mitral valve disorder (referred to as mitral insufficiency), the valve ages and shrinks and thereby fails to completely close off the area on the left side
of the heart between the two chambers. The left ventricle is very strong, and with mitral insufficiency, it easily forces a portion of the blood backward into the left atrium with each heartbeat. The pressure of blood within a normally functioning heart is highest in the left ventricle, as it is required to move the blood throughout the entire body. When blood flows backwards into the atrium, it elevates the blood pressure in that chamber and even further back into the lung field. There are additional complications, which increase pressures in the right side of the heart as it attempts to correctly pump blood forward into the lungs for oxygenation. Confronted with this elevated pressure within the lung field, the right side of the heart must work harder in moving the blood into the area.
Symptoms: The result of mitral insufficiency is elevated blood pressure within both the lung field and right side of the heart. The symptoms caused by this condition are very predictable . When hypertension (higher than normal blood pressure) occurs within the lungs, fluid actually leaves the blood vessels and leaks into the tissues. The medical term used to describe 'fluid in the lungs' is 'pulmonary edema.' This causes the affected individual to cough in an attempt to clear the lungs of the fluid, just as you would do with a chest cold. The cough that typically occurs after exercise, excitement, or when the animal has first gotten up after sleeping is the first clinical symptom noted with mitral insufficiency. In most cases, this is controlled with diuretics that cause the animal to urinate more and thereby remove excess fluids from his lungs.
As the condition progresses, the right side of the heart starts to fail because of its increased work and elevated pressures. At first the muscles strengthen, thereby increasing the mass and thickness of its walls. Over time, however, even these 'athletic' muscles cannot keep up with the ever-increasing pressures and they start to fail. During this latter stage of the disorder, the animal will be weaker and tire more easily, maybe even faint.
Treatment: Medications are used to strengthen and coordinate the muscles' contractions and they will help (and possibly eliminate) the clinical signs. These medications include digoxin and angiotensin-converting-enzyme (ACE) inhibitor such as enalapril. Diuretics (water pills) such as Lasix can help remove the excess fluid that can accumulate in the lungs. Diets lower in sodium may assist in decreasing the fluid build-up. Limited exercise may be beneficial, however, consult with your veterinarian before starting your dog on an exercise program. Regardless of treatment, anatomical changes continue to occur internally so the medications will only slow down the progression of the disease. Even with therapy, the condition usually worsens over time, and in many cases, finally results in the death of the animal.
Prevention: There are few things that can be done to prevent mitral valve insufficiency. Diagnosing the disease earlier in its course is very helpful in slowing the progression. Notify your veterinarian of any signs of heart failure in your dog. Keeping your dog healthy and at his ideal weight can lessen the severity of symptoms if mitral insufficiency does occur. Valves of the heart can be injured by infection; this infection can result from severe dental problems, which allow bacteria from the mouth to enter the bloodstream. Good oral health then, is also important.
Mitral Valve Insufficiency: A Cause of Heart Failure
Race Foster, DVM
Holly Nash, DVM, MS
Drs. Foster & Smith, Inc.
Circulatory patterns.
The heart is actually nothing more than a mechanical pump. It accepts blood on one side and forces it through the lungs, then its other half pumps the liquid on through the entire body. The heart does not change or alter the blood in any way. It has no glandular tissue and therefore secretes nothing into the blood nor does it extract anything. It is probably the simplest and most easily understood organ in the entire body.
As a quick review, blood returns from the body and enters the right upper chamber of the heart, called the right atrium. At this point, the blood is low in oxygen but high in carbon dioxide. It is then pumped from the atrium through the right atrioventricular valve into the right ventricle. From this larger chamber, it is then forced on into the lung field through the pulmonary artery. This is the only artery in the body that carries non-oxygenated blood. Carbon dioxide is a by-product of body metabolism and is attached to the red blood cells. In the lungs, carbon dioxide is replaced with
oxygen. The reoxygenated blood then moves through the pulmonary vein back into the heart and enters the left atrium. This chamber pumps the blood through the mitral valve into the left ventricle, which is the largest, most heavily muscled chamber of the heart. While other chambers only move the blood a short distance, the left ventricle has the responsibility of forcing blood throughout the entire body through the aorta. This completes the system, which allows blood to circulate throughout the body and then return to the heart.
Comparison of heart disease in people and dogs
In people, heart disease usually involves the arteries that supply blood to the heart muscle. In some cases they harden, losing their elasticity and the ability to respond to blood pressure differences as they distribute blood to the cardiac muscle. In other cases, possibly due to diet or genetics, the arteries may become obstructed with a plaque that builds up internally on the artery walls. This causes the muscles of the heart to receive less than adequate amounts of blood. Starved for oxygen, the result is usually a heart attack. In dogs, arteriosclerosis (the hardening of the arteries), plaque formation, and heart attacks are all very rare. However, heart disease is very, very common.
Canine heart failure simply means that the muscles 'give out.' This is usually caused by one chamber or side of the heart being required to do more than it is physically able to do. It may be that excessive force is required to pump the blood through an area, and over time, the muscles fail. Also, in some cases, the volume of blood that must be pumped to keep up with other areas of the heart is more than the particular chamber can adapt itself to move, again leading to muscle failure. Unlike a heart attack in humans, cardiac failure in the dog is a slow insidious process that occurs over months or years. In these cases, once symptoms are noted, they will worsen over time until the animal
is placed on treatment, dies, or is 'put to sleep.'
Mitral valve insufficiency
Heart failure in older dogs is usually due to problems with the mitral valve of the heart, and occurs most commonly in smaller breeds, such as Poodles, Yorkies, Pugs, Pomeranians, Lhasas, etc. As the dog ages, the mitral valve between the left atrium and left ventricle starts to fail. A heart valve is designed to prevent back flow. Blood can be easily pumped through the valve, but once the more forward chamber is filled, the valve closes to prevent blood from flowing backwards into the atrium. These valves greatly increase the efficiency of the heart as a pump, since the blood only has to be pumped once to keep it moving forward from one chamber to another chamber. No blood is spilling back, which would require additional effort to move it forward. In the case of a mitral valve disorder (referred to as mitral insufficiency), the valve ages and shrinks and thereby fails to completely close off the area on the left side
of the heart between the two chambers. The left ventricle is very strong, and with mitral insufficiency, it easily forces a portion of the blood backward into the left atrium with each heartbeat. The pressure of blood within a normally functioning heart is highest in the left ventricle, as it is required to move the blood throughout the entire body. When blood flows backwards into the atrium, it elevates the blood pressure in that chamber and even further back into the lung field. There are additional complications, which increase pressures in the right side of the heart as it attempts to correctly pump blood forward into the lungs for oxygenation. Confronted with this elevated pressure within the lung field, the right side of the heart must work harder in moving the blood into the area.
Symptoms: The result of mitral insufficiency is elevated blood pressure within both the lung field and right side of the heart. The symptoms caused by this condition are very predictable . When hypertension (higher than normal blood pressure) occurs within the lungs, fluid actually leaves the blood vessels and leaks into the tissues. The medical term used to describe 'fluid in the lungs' is 'pulmonary edema.' This causes the affected individual to cough in an attempt to clear the lungs of the fluid, just as you would do with a chest cold. The cough that typically occurs after exercise, excitement, or when the animal has first gotten up after sleeping is the first clinical symptom noted with mitral insufficiency. In most cases, this is controlled with diuretics that cause the animal to urinate more and thereby remove excess fluids from his lungs.
As the condition progresses, the right side of the heart starts to fail because of its increased work and elevated pressures. At first the muscles strengthen, thereby increasing the mass and thickness of its walls. Over time, however, even these 'athletic' muscles cannot keep up with the ever-increasing pressures and they start to fail. During this latter stage of the disorder, the animal will be weaker and tire more easily, maybe even faint.
Treatment: Medications are used to strengthen and coordinate the muscles' contractions and they will help (and possibly eliminate) the clinical signs. These medications include digoxin and angiotensin-converting-enzyme (ACE) inhibitor such as enalapril. Diuretics (water pills) such as Lasix can help remove the excess fluid that can accumulate in the lungs. Diets lower in sodium may assist in decreasing the fluid build-up. Limited exercise may be beneficial, however, consult with your veterinarian before starting your dog on an exercise program. Regardless of treatment, anatomical changes continue to occur internally so the medications will only slow down the progression of the disease. Even with therapy, the condition usually worsens over time, and in many cases, finally results in the death of the animal.
Prevention: There are few things that can be done to prevent mitral valve insufficiency. Diagnosing the disease earlier in its course is very helpful in slowing the progression. Notify your veterinarian of any signs of heart failure in your dog. Keeping your dog healthy and at his ideal weight can lessen the severity of symptoms if mitral insufficiency does occur. Valves of the heart can be injured by infection; this infection can result from severe dental problems, which allow bacteria from the mouth to enter the bloodstream. Good oral health then, is also important.