Doberman Dilated Cardiomyopathy
Cardiomyopathy is a non-specific term meaning diseased heart muscle. There are several different types of cardiomyopathy; for example, one type is hypertrophic cardiomyopathy where the muscle of the heart thickens and the internal chambers of the heart are small due to encroachment of the excess muscle. In contrast, with dilated cardiomyopathy the muscular heart is actually thinned from stretching to accommodate abnormally large, dilated heart chambers. While in other species and in other breeds of dogs there are many
causes of dilated cardiomyopathy (DCM), in the Doberman the disease is primary, a genetic predisposition, not caused by other medical problems. The primary problem in Doberman DCM is within the heart muscle cell, an inability to contract normally which leads to abnormal function of the heart. To compensate for the poor contractile ability the heart dilates increasing the chamber size which in the early stages of disease will improve output of the heart (stroke volume). At this time the disease is in the asymptomatic or occult stage. However, with further progression of disease, there comes a time when further dilation of the heart no longer improves stroke volume but in fact leads to increasing pressure within the heart (heart failure). This in turn causes a back up of blood in the blood vessels in the lungs and in turn causes fluid to leak out into the lungs leading to difficulty breathing, and eventually death. Another potential cause of death with Doberman DCM is arrhythmias. With the abnormal stretching of the heart electrical abnormalities can occur, some are of a benign nature but may aid in early detection of disease, but malignant forms can occur leading to sudden death.
Diagnosis of DCM
Overt disease: When the disease is in the symptomatic or overt stage, diagnosis is not difficult. Symptoms may include shortness of breath, coughing, poor appetite and weight loss, fainting episodes. Physical examination will reveal a heart murmur, a gallop (an extra heart sound which indicates heart failure) and often irregular beats. Chest X-ray will show an enlarged heart and fluid in the lungs. Echocardiogram (ultrasound of the heart) will show a dilated left ventricle and atrium, with poor function and mitral valve insufficiency (leaking of the valve).
Occult disease: When the disease is in an asymptomatic or occult stage, the diagnosis maybe suspected by testing, but at this date these criteria are not uniform from center to center. Echocardiography of healthy Dobermans recently studied at the UDC nationals and it was found that the average fractional shortening of these healthy dogs was 26% using a short axis view, and 22.5% using a long axis view. In other breeds a fractional shortening of 25% or less in the short axis view is considered abnormal. This either indicates that a large percentage of healthy Dobermans have occult DCM or that the Doberman heart at baseline is not comparable to that of most breeds. As such, to diagnose occult DCM, most centers now require not only a depressed fractional shortening, but some evidence of functional impairment such as dilated heart chambers or frequent ventricular arrhythmias. While diagnostic criteria may vary from center to center, the largest ongoing study is being performed by Dr. Michael O'Grady at the University of Guelph, and his criteria are the best defined and studied to date. To diagnose occult DCM, Dr. O'Grady requires the following echocardiographic findings, measured in the parasternal long axis view/ A fractional shortening of less than 20% with the following left ventricular chamber measurements: greater than 49 mm at the end of diastole (when the ventricle is completely filled), greater than 42 mm at the end of systole (when the ventricle has completed emptying). This diagnosis is collaborated by a progression of 3-5 mm since a prior examination. Alternatively, the diagnosis can be suspected by frequent ventricular arrhythmia – the criteria currently in use by Dr. O'Grady is greater than 50 PVCs (premature ventricular contractions) per hour, however this study is on-going. This is measured by a Holter monitor, which is and ECG running continuously for a 24 hour period.
Treatment of DCM
Overt disease: Once heart failure has occurred, treatment is symptomatic and palliative. Life expectancy is limited, generally less than six months. Treatment usually consists of diuretics to rid the lungs of fluid and an angiotensin converting exzyme (ACE) inhibitor to decrease the workload of the failing heart. Some veterinary cardiologists also use digoxin to attempt to increase the contractility of the heart muscle, others do not believe it is helpful in this setting. If the dog has an arrhythmia than a drug will be used specifically for this purpose, there are several different types of drugs which may be chosen. A newer medication, Pimobendan (increases contractility of the heart and decreases workload) is currently undergoing trials. While nutritional supplements such as L-carnitine, co-enzyme Q are sometimes recommended, there is no scientific evidence that these are helpful in treatment of Doberman DCM.
Occult disease: There is some evidence that treatment with ACE inhibitors in the asymptomatic or occult stage will slow progression of the disease, prolonging life and time until the onset of symptomatic disease.
Prevention of DCM
The cause of this disease is unknown. Many theories (such as carnitine or taurine deficiency) have been tested with no positive results. It is likely a heritable disease but the mode of genetic transmission is still unknown. There is not known preventative strategy for Doberman DCM. The best strategy for an individual Doberman is to have annual cardiac screening to diagnose the disease in its early occult stage. With diagnosis treatment with ACE inhibitors will not only prolong life but improve the quality of life.
More info:
Links to articles on Dr O'Gradys healthy heart study
Dr O'Gradys have a heart study
Dr. Meurs review of canine dilated cardiopathy
submitted by
Helayne Silver MD
DPCA Public Education Committee
Second Article From Dr.O'Grady, DVM,MS,From:The University of Guelph, Ontario Canada!Written by Larralyn McKay...May, 1997!
CARDIOMYOPATHY UPDATE...5/97
In May of 1997 Dr. Michael O'Grady, Cardiologist at Ontario Veterinary College, University of Guelph, Ontario, presented a Seminar to the Greater Metro Doberman Fanciers in Toronto, outlining some of the history, research and findings, of the "Doberman Heart Studies taking place at OVC. I have pulled my notes from this seminar to give you and overview of what has been going on. This seminar covered only a small part of Dr. O'Grady's work and touched lightly on several areas. As Dr. O'Grady was responding to questions from the audience, this overview may tend to wander a bit, but I hope some of the "facts and figures" as well as some of the "suppositions, possibilities, and thoughts" will be of interest to you.
I believe Dr. O'Grady's work in this area began in the spring of 1989, in response to the persistence of Rhonie Horne who had lost two beloved Dobes to Cardio. Rhonie continues to work with Dr. O'Grady today and is a driving force behind this study, a shoulder to cry on when we need it, a prick in the conscience if we aren't doing enough, and a very special person.
Since then over 600 Dobermans have been involved in his studies. Many have been examined several times over a period of years. Some of the data on each Dobe include:
Blood samples (and heart muscle biopsy on euthanized Dobes)
Ultrasound studying fractional shortening and heart chamber size plus valve assessment.
Routine ECG including about 30 minutes of rhythm strip.
Physical Exam for Chest sounds, heart murmurs.
X-ray when indicated.
In 1991 a leading drug company asked for dogs of all breeds who had Cardiomyopathy, which is the 2nd most common heart problem in both dogs and people. This study included 1 Canadian Vet College (Guelph) and 17 U.S. Veterinary Colleges. The Following statistic showed up. Of the TOTAL numbers of dogs seen:
55.5% were Doberman Pinschers
7.1% were Great Danes
5.7% German Shepherds
5.7% Labs
4.3% Irish Wolfhounds
It would appear that our breed has the market on this disease and Dr. O'Grady did feel that this would indicate that the cause is genetic.
In June of 1994 a study was done using a select group of 103 Dobermans who initially were presented as normal healthy Dobermans according to their owners. These were dogs who presented NO outward signs or symptoms of heart disease. 50 were male, 53 were female, age ranged from 4 months to 124 months (10+years).
Of these otherwise healthy dogs, 15 were found to have one or more abnormal beats (electrical instability) on the initial examination. (This a symptom not a cause of the disease.) In follow up, all 15 of these dogs went on to develop DCM. In the two year follow up study a total of 29 dogs developed the disease.
Of the original 15 dogs to display abnormal beats:
7 died of "sudden death"
6 were euthanized
2 died before euthanasia.
All of this took place within 11 months.
13 of the dogs showed abnormal size of the heart when empty (some of these dogs were also in the group that showed abnormal beats) Of these 13:
5 died of sudden death
5 were euthanized when their symptoms became untenable for the owners &/or the dog
2 died of cardio before euthanasia
1 was still alive after 2 years
15 of the dogs displayed abnormally large heart size when measured full(again a dog may be in one or more groups here)> Of the 15, 13 went on to develop DCM in the 2 year period studied.
So it would appear that there are markers to tell us if our dog is developing DCM, i.e.:
Abnormal beats
Abnormal (large) heart size (as compared to other Dobes)
However lack of these markers does NOT mean your Dobe will not get DCM! There appears to be a possible 2 year predictability window.
This was only for a two yar period, of the remaining 74 dogs, followed for another 2 year period 17 more dogs developed markers and presumably went on to develop DCM. This brings to a total of 44.7% of the original 103 Dobes who had Dilated Cardiomyopathy. Given more time this number could go higher!
Dr.O'Grady warns that saying it is acceptable for a 12 to 14 year old dog to get the disease is not an acceptable premise. An old or aging heart does not lead to DCM. While it is easier to accept the death at this age it is not okay in terms of Breeding Stock!
On autopsy these dogs are found to have a heart two times as heavy as a normal heart, holding a volume of 4 times as much blood.
Can we avoid or delay this disease? At this point, avoid, no. A search is on for a genetic marker, which Dr. O'Grady feels may well be found in the next 2 to 3 years.
In the meantime, work with Angiotensin Carrying Enzymes (Ace Inibitors) indicate that if they are given before the symptoms appear they may help in some instances.
In 72 Dobes free of symptoms according to the owners, but found to have markers (big heart, aberrant beats) 41 Dobes were given the drug, (29 males, 12 females). 31 Dobes were not put on medications (18 Males, 13 Females). The ages of these dogs ranged from 2.6 to 7 years of age.
Those dogs who received NO medication lived 288 days on the average (240 days for females -325 days for males):
2 dogs were still alive at the end of the 2 years
5 dogs were euthanized for reasons other than DCM, IE: cancer, accident, etc.
42% died of sudden death
Those dogs put on Ace inhibitors lived 414 days average (250 days for females - 480 days for males)
12 dogs were still alive at the end of the study
3 dogs were euthanized for other illness
15% died of sudden death
This study pointed up some perplexing facts, mainly that Males do better with or without the drug than Females. It is not known why at this time or whether there is a corresponding event in humans. However the drug does help protect against sudden death in both males and females and delays the onset of death in the disease.
Further studies are anticipated, IE: neutered vs unneutered males. Also a search for earlier markers to get the dogs on medication even earlier.
Dr. O'Grady is looking at the effects of Beta Blockers which look interesting, however very expensive, and Antiarrythmics which will not prevent the disease from progressing however, may cut down sudden death episodes.
Over the years Dr.O'Grady has looked at such things as:
Taurine Deficiency: This was not studied at Guelph however, many studies in this area have been done (the largest in California) which indicated that while Taurine Deficiency was a factor in heart disease in Cocker Spaniels and Goldens it is not indicated as a factor in Dobermans.
Pedigrees: While a great many pedigrees have been gathered on the dogs studied at Guelph, No information has been correlated from them at this time. A great many were forwarded to Texas A&M for the study taking place there. The Comment from that area was "It is Everywhere".
Viruses: While parvo can cause heart disease in puppies (of all breeds) there is no evidence at this time to suggest it has any bearing in DCM in Dobes.
Immunologic Causes: The early answer is NO. A large study done in England concurs with this.
Studies are also taking place in the area of Batista procedure, and implanting pacemakers.