April is Heartworm Awareness Month

What is Heartworm?

Chico Gilgulin_heartworm3Heartworm disease is caused by a parasite called Dirofilaria immitis that is spread to dogs through mosquito bites.  Cats can also get heartworm disease but they are more resistant to the infection.  Heartworms cause the blood pressure in the pulmonary arteries to increase. This increased pressure, called pulmonary hypertension, increases the workload on the right side of the heart which pumps blood to the lungs which can lead to right sided heart failure.

Heartworm symptoms include coughing, exercise intolerance, increased breathing rate or effort, abdominal distension with fluid, discolored urine as well as many other symptoms, depending on the severity of the disease process. Dogs with severe infection can be at risk for what is called caval syndrome – this is a life threatening condition where the adult heartworms back into the right heart, obstructing blood flow as it enters the right ventricle. Once there are mature adult heartworms living in the pulmonary arteries, Immiticide therapy needs to be administered after assessing the overall health of the pet. Immiticide, also known as melarsomine, is administered through injections given over a several month period.  During this time, all activity is restricted to short leash walks and when not supervised, dogs should be crated to prevent any excursion.  This helps to limit the risk of pulmonary thromboembolism and associated complications as the heartworms die off.  For those dogs with caval syndrome, immediate heartworm extraction is the best method of treatment.

How can Heartworm be prevented?

Administering a monthly heartworm preventative such as Heartgard easily prevents heartworm disease.  While we don’t see a lot of Heartworm in Colorado, dogs that come from other parts of the country can bring the disease here, and because it is spread through mosquitos, every dog is at risk of acquiring this disease.

A Real Life Story.

Heartworm disease is generally diagnosed and treated by a veterinary cardiologist through the course of an exam that includes an echocardiogram.  An echocardiogram is a non-invasive diagnostic tool that shows real time images of the  heart beating, blood flow, valve activity, etc. Rocky Mountain Veterinary Cardiology recently diagnosed and treated a patient with Heartworm disease. Here is Chico’s story.

 

Chico is a 12 year old Chihuahua who was adopted by his family in 2012. About a year later, he developed several concerning symptoms, including fainting, coughing, abdominal distension, and swelling in his legs.  In July, he was referred to Dr. Jeremy Orr, a board certified cardiologist at RMVC.  During the course of Chico’s exam, he was diagnosed with Heartworm disease and pulmonary hypertension, which was a result of the Heartworm disease.  Several adult heartworms were visualized during Chico’s echocardiogram in his pulmonary arteries as well as several worms within his right atrium which were not causing obstruction to blood flow.  As a result of his heartworm infestation and pulmonary hypertension, he was also in right sided congestive heart failure.

 

The first step was getting Chico’s congestive heart failure under control. After several weeks of medication, he was ready for his first series of Immiticide therapy which included a single injection followed by one month of strict cage rest. One month later, he received another two injections, twenty-four hours apart. He tolerated the treatment well, remained inactive as directed by Dr. Orr, and by February of this year, his heartworms were gone and his pulmonary hypertension symptoms were almost completely resolved with resolution of his right sided heart failure.  Chico is now very active and loves to play soccer!  He no longer is fainting and having labored breathing with activity.  His family is thrilled with his progress and his second lease on life.

 

Left untreated, Heartworm disease can be much more difficult to treat and with time, there can be irreparable damage to both the heart and pulmonary arteries leaving some animals with severe pulmonary hypertension and heart failure.  Therefore, prevention is key and for those animals who are infected, prompt and early diagnosis and treatment improves prognosis and outcome. Chico’s parents were on top of his symptoms and got him the care he needed and as a result, his long term prognosis is excellent!

 

 

 

 

Monitor Your Pet’s Respiratory Rate at Home

One of the concerns for dogs and cats with heart disease is the development of congestive heart failure – this refers to fluid build-up (congestion) within the lungs, which generally causes signs of coughing (dogs), restlessness, labored breathing and lethargy.  Therefore we recommend that many clients begin monitoring their pets resting respiratory rate at home to not only determine their baseline, but also determine if fluid is beginning to congest in their lungs.  A resting study revealed that monitoring of the resting respiratory rate at home was both sensitive and specific for the development of pulmonary edema (heart failure).  In our modern age of technology and smart phones, it shouldn’t be a surprise that an app is presently available to help clients not only count the respiratory rate but also trend the values.  The app also gives the user the ability to email their respiratory rates to their doctor!  The app is available for both the iPhone and for android phones using the links below:

 

https://play.google.com/store/apps/details?id=com.bivi.restingrate

https://itunes.apple.com/us/app/your-dogs-heart-resting-respiratory/id593676501?mt=8

http://www.yourdogsheart.com/tools-resources/Resting-Respiratory-Rate-App.html

 

Update on Treatment for Feline Arterial Thromboembolism (FAT): Clopidogrel vs. Aspirin Trial

by Geri Lake-Bakaar, DVM, Residency Trained in Cardiology

Feline arterial thromboembolism (ATE) is a serious complication typically associated with cardiac disease in cats. A 5-17% incidence has been reported in cats with cardiac disease. It is believed that an enlarged left atrium is a risk factor for ATE, however the disease has also been reported in cats without cardiac disease.

Common signs resulting from ATE include acute onset paralysis and pain.  Most commonly the hind limbs are affected, however thrombembolism can also affect the forelimbs, and in some cases, result in neurological signs.

The prognosis for cats with ATE is guarded, with a mortality rate of 61-67%. Prognosis is largely dependent on the severity of signs at presentation and at least 50% of patients are euthanized. Typically ATE is associated with a high rate of recurrence of 35-50% within one year.  Long term survival has been reported to be between 51 to 471 days.

Recently, a study conducted by veterinary cardiologists at Purdue University evaluated the efficacy of two medications, clopidogrel (Plavix) and aspirin, in preventing the recurrence of ATE.  Clopidogrel is an antithrombotic drug that specifically targets platelets.  Cats previously diagnosed with a thromboembolic event were administered 18.75mg of clopidogrel once daily, or 81mg of aspirin every 3 days. The study evaluated whether a thromboembolic event had occurred within one year and whether the patient had any adverse effects from the medication. The study found that there was a significant improvement in survival in patients receiving clopidogrel, with these cats surviving 8 months longer than cats receiving aspirin.  Elevated liver enzymes were appreciated in one cat receiving clopidogrel, otherwise the medication was well tolerated.

Overall, this study is strongly supportive of the use of clopidogrel over aspirin for prevention of recurrence of feline ATE.  However, the study did not evaluate the use of clopidogrel with other medications such as low molecular weight heparin, and whether this treatment modality may provide further improved benefits without complications from excessive anticoagulation.  These studies are currently ongoing.

 

References:

The following update was a summary from the ACVIM 2013 proceedings.  All statistical data reported was obtained from the proceedings report and oral presentation.

Hogan, D et al. Analysis of the Feline Arterial Thromboembolism: Clopidogrel vs Aspirin Trial (Fat Cat). Proceedings, ACVIM 2013.

Medical Therapy for Dogs with Asymptomatic Heart Disease

by Dr. Jeremy Orr, DVM, DVSc, Diplomate ACVIM, Cardiology

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One of the most common questions veterinary cardiologists receive from both their clients and referring veterinarians are the options for medical therapy for those patients with asymptomatic heart disease. At the present time, we estimate that as much as 10% of the canine population is affected by heart disease. Many of us are comfortable with therapy once clinical signs develop (congestive heart failure) but admittedly there are many differing opinions on how to manage those patients in their occult phase of their disease. Unfortunately, evidence based medicine for therapeutic options for asymptomatic patients is largely lacking. However, there have been some recent exciting new options for Dobermans with occult dilated cardiomyopathy (DCM) and I wanted to take the opportunity to not only present this information, but summarize what we know about therapies for other forms of heart disease in our canine patients.

Dilated Cardiomyopathy (DCM)

DCM is a devastating myocardial disease which most commonly afflicts larger breed dogs, with the Doberman Pinscher being over-represented. In the Doberman, we know the disease is characterized by a prolonged occult phase (2-3 years) before overt clinical signs of heart failure (dyspnea, exercise intolerance, syncope) develop. Once heart failure develops, the prognosis is grave with average survival times reported at 2-4 months, with a 90% fatality rate by 1 year post diagnosis. Given the prevalence of DCM in the Doberman breed (estimated at 25-50% of adult dogs affected), the current recommendation is to screen Dobermans (especially those with familial history of disease, or those with recently acquired murmurs or arrhythmias) with echocardiography annually after the age of 5 years. New advances in echocardiography such as Tissue Doppler imaging (which assesses the speed of wall motion) have allowed earlier detection of dogs with occult disease. The utility of this screening is that we may identify those patients with early evidence of disease in an effort to delay their progression, especially given the grave prognosis even with supportive therapy once symptoms develop. A retrospective study in 2009 demonstrated that therapy with benazepril (0.5 mg/kg dose once daily) in the occult phase of disease significantly delayed the onset to overt disease compared to those dogs who did not receive benazepril (454 versus 356 days)1. These results are similar to the human literature where ACE inhibitors are an important therapeutic option for those patients with asymptomatic ventricular dysfunction. Recently, the multi-center prospective, placebo controlled and blinded study PROTECT revealed a significant delay to heart failure or sudden death (718 days versus 441 days) for Dobermans receiving pimobendan at standard dosages (0.25 mg/kg dose twice daily) versus those receiving placebo2. Furthermore, the study also showed that the median survival time was significantly longer in the pimobendan versus the placebo group (623 versus 466 days). These two studies demonstrate the importance of early detection of occult disease as it provides an opportunity to prolong the lives of affected Dobermans. This extra time is significant, especially given the poor prognosis once symptoms develop.

These results may apply to Dobermans only and future studies evaluating these claims in non-Doberman breeds will likely be lacking. Presently there is a study evaluating pimobendan in Irish Wolfhounds with occult DCM and results thus far have been encouraging with a survival benefit for dogs receiving pimobendan. For this reason, I still consider these therapeutic options in non-Doberman breeds with occult DCM.

References:

1. O’Grady MR, O’Sullivan ML, Minor SL, Horne R. Efficacy of benazepril hydrochloride to delay the progression of occult dilated cardiomyopathy in Doberman Pinchers. J Vet Intern Med 2009; 23: 977-983.

2. Summerfield NJ, Boswood A, O’Grady MR, et al. Efficacy of Pimobendan in the prevention of congestive heart failure or sudden death in Doberman Pinschers with preclinical dilated cardiomyopathy (the PROTECT study). J Vet Intern Med 2012; 26:1337-1349.

Puppy as a holiday gift?

Holiday shopping is in full gear and some people are planning on a puppy to join their family or that of a loved one as an extra special holiday gift and celebration this year.

What most people don’t realize is that their new holiday puppy may have one of several common heart conditions.  Puppy owners should consider having their new pet screened for a heart murmur which could indicate that a PDA (patent ductus arteriosus), Subaortic Stenosis (SAS), Pulmonic Stenosis (PS) or a VSD (ventricular septal defect) are present.  Of course there are less common congenital heart defects that could be detected as well, but these are the most common conditions found in puppies.

PDAs are common in many breeds (such as Newfoundland, Miniature Poodle, English Springer Spaniel, Cavalier King Charles Spaniel, and German Shepherd).  This defect can be devastating if left undetected. Thankfully, its correctable with non-invasive techniques.

SAS is another common congenital heart condition in dogs and when severe, carries a heartbreaking diagnosis.  Karen Sanderson, DVM, MS, Diplomate ACVIM (Cardiology) says it’s a complex genetic problem most often seen in German Shepherds, Boxers, Newfoundlands, Rottweilers, and Golden Retrievers.  It’s an inherited heart condition that causes the heart to develop abnormally. As the puppy grows, its heart works harder due to narrowing of the walls within. Eventually, when the disease is severe, the heart begins to fail.  Dogs that are mildly or moderately affected have a good prognosis.

Pulmonary Stenosis (PS) is a defect of the pulmonic valve where it opens incompletely when the heart beats.  This disease is seen commonly in small breed dogs but also occasionally in Boxers and Samoyeds.  When severe, non-invasive catheterization is recommended to alleviate the stenosis.  The prognosis is typically excellent if the defect is mild or treated.

Finally, VSDs are commonly seen but are typically quite small and do not cause any problems.  A VSD is a hole in the septum (the wall that divides the right ventricle from the left ventricle in the heart).

If purchase or receive a puppy this holiday season, Dr. Sanderson recommends that you bring it it in for an exam to see if it has any of these heart conditions. A veterinary cardiologist can listen for a heart murmur, which can be one of the signs of a heart defect. If a puppy still has a murmur at the age of 6 months, a more serious condition may be present.  A specialist can distinguish between a murmur that sounds like a PDA, SAS, PS or VSD versus other common heart defects that may be present.

If a murmur is heard, Dr. Sanderson says that there are tests that a veterinary cardiologist may perform to evaluate your puppy, including:

  • Ultrasound/Echocardiography
  • X-ray
  • EKG

Treatment choices vary but can include medications, surgery or a balloon can be inserted into the heart; similar to what is done with people and angioplasties. Like any other serious condition, early detection is important and can have a significant impact on your puppy’s health and prognosis.

Finally, the most important reason it’s critical for you to be aware of SAS and take action with your new puppy is that most dogs with the condition do not live more than three years without some kind of treatment.  For more information on Dr. Sanderson and veterinary cardiology, go to www.RMVCcolorado.com.