Cardiomyopathy
There are many diseases of the heart and as (sic) all heart problems seem to be getting tagged as “cardio”. Dilated cardiomyopathy is when the heart muscle becomes weak. Since the heart muscle tries to compensate for the weakness it becomes larger.(Picture a over-stretched balloon).
People have been known to contract cardiomyopathy from certain viral illnesses. This usually results in a heart transplant.
Left congestive heart failure is a disease caused by the left side of heart not being the heart being unable to pump blood well- it BACKS UP in the lungs because the right side of the heart still works fine and pumps more blood into the lungs. Right congestive heart failure is when the right side of the heart doesn’t work well, and blood will back up in the liver and spleen. The term ‘congestive heart failure’ can refer to either right or left sided failure.
Heart rhythm disturbances are electrical conduction disturbances not necessarily related to cardiomyopathy. There can be many types of cardiac conduction disturbances depending on where the conduction disturbance is. Atrial disturbances are generally pretty benign unless they cause extremely rapid heart rates. The electrical conduction system may be functioning poorly but the heart may not show any deformity on echo or x-ray. The problem may not appear on a EKG as the rhythm disturbance may be intermittent. A Holter monitor can be used to monitor the heart for a 24 hour period.
Lethal arrhythmia may appear as P.V.C.’s (premature ventricular contractions).The more PVC’s that appear the higher chance that the dog will develop ventricular tachycardia. Rhythum disturbances may be noted in the dogs pulse by a pause as the blood isn’t effectively pumped through the arteries without a the whole electrical conduction sequence, but all pauses don’t mean PVC’s.
Ventricular tachycardia is when the heart beats so fast, sometime 250 per hour, that it can’t effectively pump blood. The symptoms may be fainting or seizures due to lack of blood supply to the brain. If this is sustained for more then a few minutes the heart itself runs out of oxygen and stops. This is a common cause of sudden death. It is possible that even on autopsy no cause of death will be determined. There are many conduction rhythm disturbances, this is only one.
Murmurs are commonly caused from problems with the cardiac valves. The murmur can be heard because the blood is more turbulent going through a poorly closing valve. Murmurs may be totally benign or, depending on the condition of the valve, be very problematic. Congestive heart failure is a disease caused by the heart not adequately pumping blood through the lungs. This would be a common symptom of advanced cardiomyopathy. The lungs fill with fluid causing coughing and shortness of breath. These are pretty simplistic definitions but thought it might help those who are not medically inclined.
Dilated Cardiomyopathy (DCM) is a fatal heart condition that affects many breeds of dogs, including Doberman Pinschers. Dogs with DCM may suffer from exercise intolerance, shortness of breath, a pendulous abdomen (ascites) and coughing. Affected animals may have a very rapid heart rate, greater than 180 beats per minute. Chest radiographs of the dog may reveal a grossly enlarged heart resembling a basketball in the chest cavity. An echocardiogram, or ultrasound of the heart, will demonstrate a large, flabby heart that has lost much of its ability to pump blood through the body. The inefficiency of the heart’s pumping action causes the clinical symptoms of the disease. Exercise intolerance, pale mucous membranes, fainting and lethargy result from poor circulation to distal body parts. Excessive panting, ascites, and reluctance to lie down result from a backup of blood in the lungs and abdominal organs that causes fluid to leak out of the blood vessels (due to increased hydrostatic pressure). As the disease progresses, the heart loses more contractility and dilates due to pooling of blood in the chambers.
Another name for Dilated Cardiomyopathy is congestive heart failure, so named for the congestion, or pooling, of blood in the heart, lungs and liver. (Please keep in mind that some dogs are asymptomatic and can die acutely from sudden cardiac arrrhythmias).
There is no cure for this disease. Once diagnosed, an affected Doberman usually lives for 3-6 months before its heart fails completely. although the condition can be managed medically with cardiac drugs, vasodilators, and diuretics, theses simply alleviate the symptoms of coughing, dyspnea (difficulty breathing) and fluid retention. The dog’s quality of life will improve with drug therapy, but eventually the heart becomes too damaged to respond to the medications.
The disease appears to be genetic in nature since many affected dogs are related. DCM in the Doberman was first noted in the 1950’s when 3 of the founding sires of the breed in the US appeared to have died acutely form “heart attacks”. In the 1970’s veterinarians noted a high incidence of congestive heart failure in male Dobermans.
Although the disease predominantly affects males, females contract the disease as well. A survey of the Vet Med Data Base revealed that 75% of the affected dogs were male, and 25% were female. The ratios in my database are approximately 60-40. There is a penetrance problem for the disease, meaning that not all dogs who carry the diseased allele will demonstrate the trait. We have created age penetrance curves that can estimate how likely a dog of a certain age is to develop cardio.For example, a female 10 years old has a 25% chance of getting the disease. These numbers will change to become more accurate as more and more affected and unaffected dog samples are collected. (My plug to get involved!!:))
The Vet Med Data Base also revealed that Dobes have 3X the incidence of DCM that is present in the general canine population. From what little I can get from this, cardiomyopathy will NOT be able to be determined by this particular registry. They are looking primarily for congenital heart murmurs. Here’s what they list:
- Malformation of the atrioventricular valves
- Malformations of ventricular outflow leading to obstruction of blood flow
- Defects of the cardiac septa (shunting defects)
- Abnormal development of the great vessels or other vascular structures
- Complex, multiple, or other congenital disorders of the heart, pericardium, or blood vessels.
The specific congenital defects listed are:
- Patent ductus arteriosus
- Ventricular septal defect
- Arterial septal defect
- Pulmonic stenosis
- Valvular and subvalvular aortic stenosis
- Mitral valve dysplasia
- Tricuspid valve dysplasia
- Right-to-left cardiac shunt.
Dogs must be 12 months of age or older to get a congenital heart certification. There is some opinion that all Dobes are predisposed to DCM since normal echo values are decreased in Dobes than in other breeds. This research has been published by Clay Calvert, Georgia and Mike O’Grady, Guelph.
Please let me know if I can fill in any gaps that I probably left in this dialog. Thanks!!!
Tracy Hammer