William D. Tyrrell, Jr., DVM, DACVIM (Cardiology), presented a seminar sponsored by the Irish Wolfhound Foundation (IWF) as part of the Irish Wolfhound Club of America’s 2013 national specialty show’s educational events. This article will cover some of the highlights of that presentation for those who were unable to attend.
Atrial fibrillation (known colloquially as A-fib) can occur spontaneously in large and giant breed dogs, but not in small ones, for the simple reason that there has to be a certain amount of surface area for the heart’s electrical signals to be misdirected within the atria. It is not, by itself, a fatal condition in dogs. A-fib can be detected during an electrocardiogram (EKG) screening, which is non-invasive and painless to the dog. A large screening in 1992 showed that about 30% of Irish Wolfhounds have abnormal EKGs, and that figure still stands for today’s IWs.
Wolfhounds with A-fib often have no or very subtle symptoms, such as a slowdown in normal activity, anxiety/clinginess, or the general assessment owners refer to as ADR (Ain’t Doin’ Right). As in so many other diseases, your IW will tell you when something is wrong if you know your dog and pay close attention.
The IWF Lifetime Cardiac Study (LCS)
The IWF is currently trying to conduct the final follow up for IWs entered in the IWF Lifetime Cardiac Study (note: please contact Frances Abrams of the Foundation via email at Frances.firstname.lastname@example.org, or Dr. Tyrrell at Chesapeake Cardiologists via http://www.cvcavets.com/ if you have data to submit for a hound in the study). Thus far the LCS has revealed no change in the average lifespan of Irish Wolfhounds. A-fib has been consistently found in 12-13% of the IWs in the study over the years.
Dr. Gina Pasieka and Dr. Kacie Schmitt, colleagues of Dr. Tyrrell, have been conducting a study, sponsored by the IWF, using a subset of the LCS participants that were diagnosed with ventricular premature contractions (VPCs) to try and determine if this rhythm disturbance is actually an indicator of underlying heart disease such as dilated cardiomyopathy (DCM) or may be representative of an underlying life threatening arrhythmia. Ventricular premature beats are often quite concerning in Doberman Pinschers, but may not be in Irish Wolfhounds. There is very little overlap between IWs with VPCs and those with A-fib. While VPCs are not always fatal, they may not be as benign as once thought. A history of VPCs or sudden unexplained deaths in a family of IWs should be taken as a cautionary sign when making breeding decisions.
We have found that AV block (a delay in conducting the heart’s electrical signals from top to bottom) is not significant in Irish Wolfhounds. Atrial premature contractions (APCs), however, usually progress to A-fib. The LCS questionnaires are also providing us with non-heart related data. Osteosarcoma, for instance, has been found to account for 75% of all the cancer deaths in LCS dogs.
The LCS study differs from the heart study published in Europe by Dr. Andrea Vollmar in 2000 in several significant ways. The Vollmar population consisted of dogs who had been brought in to veterinary hospitals due to illness, while the LCS population consists largely of IWs brought to specialty shows. The Vollmar data showed that 10% of IWs with DCM showed no clinical symptoms of DCM, but 73% of those with DCM did have A-fib. Our data does not show nearly that rate of illness, but it could be because American IWs have less heart disease, or that we generally see younger dogs at shows. Testing more veteran IWs might help clarify the trends we have seen.
A-Fib and DCM
A-fib is actually quite common in humans and does not correlate to heart disease, per se. How closely does A-fib correlate with DCM in dogs? A-fib in conjunction with a rapid heart rate is likely to be associated with DCM, but A-fib with a normal heart rate may never develop into DCM. Nonetheless, A-fib should always be treated to keep the dog’s heart rate in a normal range.
In humans, A-fib is sometimes treated with electric shocks, but that treatment does not routinely work in dogs. However, since dogs don’t tend to form blood clots the way people do in response to underlying atrial fibrillation, we do not get too concerned about the arrhythmia itself other than simply controlling the fast heart rates that can be associated with A-fib through drug therapy. The aim of most of these drugs is to slow down the electrical impulses from the atria (top chambers) to the ventricles (bottom chambers) area of the heart.
A Cornell University study has shown that sustained release calcium channel blockers, given 2 times daily, may be as effective as beta blockers in controlling heart rate. Thankfully, most drugs used to control heart rate are generic and therefore quite affordable, even for IWs. The degree of abnormality of the heart rate determines the intensity of the required treatment.
In addition to annual heart tests, owner-monitoring of heart rate at home can reduce the need for costly hospitalizations for heart problems, as an adjustment in medication can often correct an abnormal rhythm before it progresses too severely. Just behind the left elbow of the dog is the best place to find a pulse and measure heart rate (count pulse beats using a stopwatch for a full minute, or count for 6 seconds and then multiply by 10 to get an approximate rate). Knowing what is normal for your dog will help you spot problems quickly.
Congestive Heart Failure
Once a dog has actually progressed to congestive heart failure (CHF), then different medications are needed. Pimobendan is an expensive drug but it can improve survivability in dogs with DCM. Compounding pharmacies are usually the most cost-effective source for this drug. Patients in Dr. Tyrell’s practice have gotten years of quality life because of treatment with Pimobendan, and one study suggests its use in the IWH prior to the onset of congestive heart failure.
Certain supplements may also prolong survivability in dogs with heart disease. These include taurine, l-carnitine and fish oils. Therapeutic dosing of fish oil may be as high as 8 capsules per day (40 mg/kg of EPA and 25 mg/kg of DHA). L-carnitine is dosed at 50mg/kg of body weight, 2 times daily. Taurine should be given at the rate of 500mg, 2 times daily. Caution should be used in patients taking fish oil who require surgery, as it may negatively affect clotting. It would be safest to discontinue supplementation with fish oil prior to any scheduled surgery.
Heart Disease, Testing and Breeding
Heart disease in IWs is not sex-linked. It appears to be autosomal-dominant with varying penetration. Late onset A-fib in an IW with long-lived ancestors should not mandate removing the dog or its offspring from the breeding pool. Breeding dogs should have an annual echocardiogram, since we don’t know yet if an EKG is sufficient as a screening tool for heart disease in IWs. Breeders should not only test breeding stock annually and remove affected dogs from the breeding program, but track the heart health of all littermates throughout their lives to get a complete picture of heart health in the line. DNA screening would permit genetic screening of breeding stock for heart disease markers, but such a tool does not yet exist in Irish Wolfhounds.
The Orthopedic Foundation for Animals (OFA) certifies heart test results for congenital heart disease (physical malformations of the heart present from birth), but does not yet completely address adult-onset congenital diseases (such as DCM). However, much work is being done with the American College of Veterinary Internal Medicine (ACVIM) and OFA to rectify this deficiency.
Cardiac biomarkers are increasingly being utilized in both human and veterinary medicine to possibly help screen for early heart disease or to discern between congestive heart failure and primary lung disease as the cause of breathing difficulties. Dr. Tyrrell and his CVCA partner, Dr. Steven Rosenthal, DVM, Diplomate, ACVIM (Cardiology), will be collecting blood from the IWH they perform echocardiograms on at the 2014 Potomac Valley specialty show and IWCA Nationals in St. Louis. This blood will be analyzed at IDEXX Laboratories in Maine and will help determine normals for NT-proBNP (a cardiac biomarker) levels in the IWH breed. Much research is still required to determine if cardiac biomarkers will aid in the diagnosis and treatment of heart disease in the canine, however, this is a first step for our breed as only a few breeds have had normal values established for them. We are thankful for IDEXX and the IWF in helping to sponsor this study. Results will be presented at the ACVIM Forum in 2015.