Canine Heart Health and Genetic Testing

The following article published by the AKC is the newest article on Heart Health and is essential for many purposes. Many companion owners need to be aware of the warnings and advice of a breed's Parent Club; in this case, it would be the Irish Wolfhound Club of America (IWCA.)

Unfortunately, the IWCA is noticeably absent from this article in providing valuable and critical guidance to Wolfhound owners, as cardiac disease is one of the leading causes of death in Wolfhounds. In my opinion, based on the number of emails and requests I receive, it is the leading cause of death as, sadly, countless breeders do not educate their IW owners about Atrial Fibrillation and Dilated Cardiomyopathy (DCM), as well, Ventricular Premature Complexes (VPC). Many wolfhounds die needless early deaths because they were not properly and annually tested.

My policy has always been to inform Wolfhound owners that heart testing is imperative and mandatory beginning at age two and annually after that. Any advanced cardiac testing MUST include Auscultation, EKG and Echocardiograms.

The IWCA website states: It is important to remember that testing is important for all Irish Wolfhounds, not just those who are used for breeding. Early detection of changes in health often leads to a better quality of life for your dog. All Irish Wolfhounds may benefit when your dog participates in a health study that increases our knowledge…Cardiac screening in IWs should always be performed by a Board-certified veterinary cardiologist.

Canine Heart Health and Genetic Testing

By Claire Wiley, VMD, DACVIM

Published: Feb 22, 2024

Canine genetic tests are important and must be interpreted together. Phenotype refers to a dog’s observable traits, whereas genotype refers to a dog’s genetic constitution. Phenotypic tests are typically performed by a veterinarian or board-certified cardiologist. DNA tests can be used to determine a dog’s genotype for specific genetic variants, but phenotype tests are required to obtain a diagnosis of heart disease.

The heart is a complex organ that can manifest disease in multiple ways. Some heart diseases are present at birth (congenital), whereas others develop as the dog ages. These conditions can lead to symptoms such as coughing, lethargy, exercise intolerance, fainting, and even sudden death if left untreated. Some common heart diseases seen in dogs include:

1. Degenerative Mitral Valve Disease (DMVD)

This middle to old age disease is the most common of all canine heart diseases. One of the heart valves, the mitral valve, becomes thickened and damaged as the dog ages. The valve can leak blood and cause heart enlargement that can progress to congestive heart failure (CHF). Although small breed dogs are more prone to developing this disease, any dog can be affected. At the time of writing this article, no genetic tests are available to help predict the occurrence of this disease.

2. Dilated Cardiomyopathy (DCM)

With DCM, the second most common form of heart disease in dogs, the heart chambers become enlarged (dilated) and the walls become thin. DCM can have multiple causes, including inherited and nutritional. Multiple genetic variants have been identified that are associated with DCM that are typically breed-specific tests. Although some of these variants are inherited in a simple Mendelian fashion, others are complex and represent risk factors. Age of onset can vary from breed to breed. For example, Portuguese Water Dogs can develop an inherited, juvenile form that typically manifests before 6 months of age, called Juvenile Dilated Cardiomyopathy.

Phenotypic tests are crucial for evaluating the current function of the heart. Some common tests include:

1. Auscultation: Auscultation involves listening to the heart sounds using a stethoscope. Abnormalities such as murmurs, irregular rhythms, or gallops can indicate underlying cardiac issues.

2. Echocardiography: Echocardiography, or cardiac ultrasound, provides detailed images of the heart’s structure and function. It helps assess chamber sizes, valve function, and overall cardiac performance.

3. Electrocardiography (ECG or EKG): ECG records the electrical activity of the heart, helping identify arrhythmias and conduction abnormalities.

4. Chest radiographs: Radiographs offer valuable insights into the size and shape of the heart, as well as detecting signs of congestive heart failure, such as pulmonary edema or pleural effusion.

5. Holter Monitoring: Holter monitoring involves continuous ECG recording over 24-48 hours, allowing for the detection of intermittent arrhythmias.

The American Boxer Club, Inc., for example, recommends routine Holter monitoring annually for breeding to help decrease the incidence of Boxer Cardiomyopathy.

Genetic testing related to canine cardiac health is most important for informing breeding practices when selecting breeding pairs. The AKC DNA Program is about to launch genetic testing in the coming months, and several genetic variants for heart health are included in this panel.

Parent Club Recommended DNA Cardiac Health Tests:

Dilated Cardiomyopathy (Schnauzer Type) This specific genetic variant investigates a deletion in the RBM20 gene.

Juvenile Dilated Cardiomyopathy in Portuguese Water Dogs (Available only through PennGen) This genetic variant investigates a locus on canine chromosome 8.

Other AKC DNA + Health Heart Tests:

Cardiomyopathy and Juvenile Mortality. This genetic variant is associated with severe heart disease that can cause death from heart failure by 8 weeks of age.

Dilated Cardiomyopathy (Doberman Pinscher Type Risk Factor, Variant 1)

This specific genetic variant investigates a deletion in the PDK4 gene and is associated with disease in Doberman Pinschers, and its association with DCM in other breeds is not clear. This genetic variant is inherited in an autosomal dominant manner with incomplete penetrance. In other words, not every dog with this genetic variant goes on to develop the disease DCM.

Dilated Cardiomyopathy (Doberman Pinscher Type Risk Factor, Variant 2)

This specific genetic variant investigates a single nucleotide polymorphism (SNP) in the TTN gene and is associated with disease in Doberman Pinschers.

Canine genetic testing for heart disease represents a valuable tool in the arsenal against decreasing the risk of producing cardiac conditions in dogs. By leveraging the power of genetics, veterinarians and dog owners can work together to identify at-risk individuals, implement preventive measures, and provide personalized care to improve the overall cardiac health and well-being of our beloved canine companions. Each known genetic variant for DCM will be discussed in more detail in the coming months. As research continues to advance, genetic testing holds the promise of further enhancing our understanding and management of canine heart disease.

Citations:

1. Werner P, Raducha MG, Prociuk U, Sleeper MM, Van Winkle TJ, Henthorn PS. A novel

locus for dilated cardiomyopathy maps to canine chromosome 8. Genomics. 2008

Jun;91(6):517-21.

1. Harmon MW, Leach SB, Lamb KE. Dilated Cardiomyopathy in Standard Schnauzers:

Retrospective Study of 15 Cases. J Am Anim Hosp Assoc. 2017 Jan/Feb;53(1):38-44.

3. Gurtner C, Hug P, Kleiter M, Köhler K, Dietschi E, Jagannathan V, Leeb

T. YARS2 Missense Variant in Belgian Shepherd Dogs with Cardiomyopathy and

Juvenile Mortality. Genes (Basel). 2020 Mar 14;11(3):313. PubMed: 32183361

4. Meurs KM, Lahmers S, Keene BW, White SN, Oyama MA, Mauceli E, Lindblad-Toh K. A

splice site mutation in a gene encoding for PDK4, a mitochondrial protein, is associated

with the development of dilated cardiomyopathy in the Doberman pinscher. Hum

Genet. 2012 Aug; 131(8):1319-25.

5. Owczarek-Lipska M, Mausberg TB, Stephenson H, Dukes-McEwan J, Wess G, Leeb T. A

16-bp deletion in the canine PDK4 gene is not associated with dilated cardiomyopathy

in a European cohort of Doberman Pinschers. Anim Genet. 2013 Apr;44(2):239.

6. Meurs KM, Friedenberg SG, Kolb J, Saripalli C, Tonino P, Woodruff K, Olby NJ, Keene

BW, Adin DB, Yost OL, DeFrancesco TC, Lahmers S, Tou S, Shelton GD, Granzier HG. A

missense variant in the titin gene in Doberman pinscher dogs with familial dilated

cardiomyopathy and sudden cardiac death. Hum Genet. 2019 May;138(5):515-524.

Irish Wolfhound Heart Health

In the Irish Wolfhound breed, regular annual heart evaluations or workups consisting of electrocardiography (ECG or EKG), echocardiograms, and an ambulatory heart monitor (ECG), e.g., Holter Monitor are essential and indispensable. In layman's terms, an ECG provides heart rate and rhythm information. An Echocardiogram is an ultrasound of the heart muscle measuring the heart's chambers size, the thickness of the heart walls, its valves, and blood flow. The Holter Monitor is a mobile ECG device that is strapped to the wolfhound's chest with electrodes for a minimum of 24 hours.

I advise all wolfhound owners to begin undergoing routine yearly heart workups, with all three of the procedures above, at approximately two years of age, and then annually from there on out for the remainder of the Wolfhounds' life. I urge doing so despite that an owner or breeder believes their wolfhound is in good health because Veterinary Board Certified Cardiologists are the only qualified individuals to determine the heart health of your Irish Wolfhound. Sadly and frustratingly, I have received one too many puppy inquiry calls from deeply saddened owners who lost their beloved wolfhound, and when I inquire as to the cause of death, more often than not I am told heart disease. After I delve deeper into the time span between when the wolfhound was diagnosed and when they died, it usually was within one year or as soon as six months between diagnosis and prognosis.

What a terrible, unfortunate pity as many of these early deaths could have been avoided. Today, there exists many pharmaceuticals that have proven to be life-savers, extending the hound's quality lifespan after being diagnosed with a cardiac disease. Often it is no longer a terminal prognosis but a manageable chronic illness. One of my dearest friends' Irish Wolfhound male lived to 12 years of age with managed cardiac disease, and I too had a wolfhound male residing in a companion home who lived to 11.5 years before he died and whose heart disease was controlled with medications.

However, each time I questioned these grieving wolfhound owners, I was informed that he or she never had annual heart evaluations performed on their wolfhounds. It was ONLY after the hound was symptomatic presenting multiple characteristics of progressive heart disease or even congestive heart failure did they seek medical care. What is more, ALL of these dog owners reported that their breeders had not shared any measurable amount of health advice, but most certainly no recommendations for heart monitoring. Eventually, as is usually the case with the general dog owning population, these dog owners believed that their wolfhound's annual check up with their local veterinarian was an adequate health provision with many meekly and bleakly offering the excuse that their vet listened to their dog's heart with a stethoscope.

This is NOT adequate heart healthcare for a breed predisposed to congestive heart disease.

Most Wolfhound owners, as well as many breeders, are not aware that many affected dogs can have a normal health examination. Even more, on occasion, an astute local doctor may pick up on a premature beat and listen for others. During this snapshot in time, however, there may not be others detected and no further follow through is prescribed. They would be wrong, especially involving the Irish Wolfhound breed and requires further evaluation by a Veterinary Board Certified Cardiologist, DACVIM. Importantly, in my considered opinion and experience, your general practice veterinarian should NOT prescribe any heart medications.

Single ventricular premature complexes (VPC's) warrants and requires further investigation by a specialist where a proper diagnosis is achieved not only by a EKG and Echocardiogram, but more importantly, by an ambulatory heart ECG Holter Monitor. A Holter monitor verifies the frequency of VPC's occurrence and duration, and if any dangerous couplets, triplets, and ventricular tachycardia occur. These are serious arrhythmic complexities which can result in sudden cardiac arrest. Sadly, twelve years past I had a veteran wolfhound collapse and who died in front of me, in my home, from sudden cardiac arrest. He had been diagnosed and was receiving treatment for VPC's, and it was heartbreaking as I could not save him. In the early stages, the average pet owner would not be able to recognize symptoms unless the wolfhound collapsed and lost consciousness (syncope), and, left undiagnosed, often these arrhythmias develop and grow more severe, though it is not always definitive that the disease will progress. Nonetheless, it bears reiterating; affected Wolfhounds can be asymptomatic.

Typically, if any abnormalities are detected by an in-office ECG and Echocardiogram, the Board Certified Cardiologist will urge that a Holter Monitor is attached to the wolfhound and worn for a minimum of 24-hours. It is a vital tool for analyzing arrhythmias, identifying and counting premature ventricular complexes, and characterizing heart rates (tachycardia). Then and only then can a proper diagnosis be given on the state of your wolfhound's heart health. Additionally, any prescribed drug protocols are determined by the Veterinary Board Certified Cardiologist, DACVIM, and NOT by your general practice veterinarian. Repeat follow-up Holter monitoring, typically within several weeks after the commencement of medications, is entirely necessary until such time that a 24-hour recording establishes that the Irish Wolfhound is responding well to the drug therapy. Even then, a wolfhound's owner must continue with recurrent follow-up visits with the specialist, as frequent as every 3-6 months or as directed by the cardiologist once the drug therapy has been determined successful in suppressing the arrhythmias.

Unfortunately for us, we had a veteran wolfhound diagnosed with malignant arrhythmias (couplets and triplets) via a Holter monitor evaluation, and she was receiving antiarrhythmic medications. We were planning for her annual echocardiogram recheck and repeated Holter evaluation when suddenly she failed, and we discovered that she was in congestive heart and subsequent renal failure. Just prior, she was asymptomatic, there was no syncope, yet she developed congestive heart failure. I can only stress that you must adhere to a strict follow-up Holter monitoring schedule while managing Irish Wolfhound heart disease as serious heart developments can occur over a short period. I must bear the burden thinking that if I had gotten her in earlier, we could have discovered the progression and treated it with additional medications.

Prudently and importantly, many Cardiologists recommend conducting an annual 24-hour ECG Holter monitor on a regular, yearly basis throughout a healthy wolfhound's life -- even if there are no electrical issues initially detected. I believe this is a very sensible and wise course of action, and one I wholeheartedly concur with as twelve months can mean the difference between life and premature death.

Why use a Holter monitor if an ECG and Echocardiogram detect no ventricular arrhythmias (abnormal heart rhythms)? Well, for one, the in-office ECG and subsequent echocardiogram are for brief periods and are not representative of what may be occurring over the course of 24 hours. Therefore, the Holter monitor will provide comprehensive real-time data over a twenty-four-hour-clock. Parenthetically, there are one or more cardiologists who believe that VPC's can be inconsistent, varying in numbers or frequency from day-to-day and if cardiac disorder is suspected then another Holter monitor assessment is recommended. However, most importantly for the healthy, unaffected Wolfhound; annual Holter recordings create a baseline for future heart monitoring in which the data obtained from this spotlight in time will be valuable in creating an archival recording. The ability to have this vital information for the doctor to review and compare to future recordings will be instrumental to your wolfhound's longevity and quality of life. In a breed that has prevalent congestive heart failure, Holter monitoring is a necessity, though expensive, and that is the price we have to pay for loving Irish Wolfhounds.