Congestive heart failure (CHF) is described by medical professionals as more of a syndrome than a disease. Yet, when pet owners are often attuned to ‘disease,’ how can veterinarians best convey what CHF really is to their clients?
“Congestive heart failure can result from a variety of different types of underlying heart disease,” says Emily Karlin, DVM, Dipl. (cardiology), clinical instructor at Cummings School of Veterinary Medicine at Tufts University. “When we say CHF, we generally are referring to fluid build up somewhere it should not be, as a result of heart dysfunction. We can see left-sided CHF (fluid build up in the lungs—pulmonary edema), resulting in cough or trouble breathing, or right-sided CHF (fluid buildup in the abdomen or around the lungs—ascites or pleural effusion), resulting in abdominal distension or trouble breathing. Basically, CHF is a potential outcome of having heart disease.”
Recognizing signs and symptoms
When it comes to differentiating CHF from heart disease, paying attention to clinical signs and symptoms is key.
“Asymptomatic, or occult, heart disease is often detected based on physical exam abnormalities—such as a heart murmur, cardiac gallop, or arrhythmia—or sometimes by echocardiographic screening, but the animal is feeling well at home with no clinical signs,” Dr. Karlin says. “CHF typically results in clinical signs, such as cough, trouble breathing, exercise intolerance, or collapse. Heart disease also can result in other clinical signs, such as weakness or collapse, which can either be related to CHF or other manifestations of heart disease like arrhythmia.”
The term ‘heart disease’ encompasses many congenital (structural), degenerative (structural), and electrical heart problems, according to Mark Kittleson, DVM, PhD, Dipl. ACVIM (cardiology), professor emeritus at the University of California, Davis School of Veterinary Medicine.
“Heart failure is caused by severe, overwhelming structural heart disease (e.g. a valvular leak or myocardial failure),” Dr. Kittleson says. “That’s important. Many veterinarians think mild to moderate heart disease can result in heart failure. It cannot.”
Veterinarians, however, need to be aware certain conditions may mask CHF or, on the opposite spectrum, may cause them to incorrectly believe symptoms point to CHF.
“Congestive heart failure and respiratory disease often mimic each other, making it difficult to differentiate the two in a patient with respiratory signs (elevated respiratory rate or difficulty breathing),” says Ashley Saunders, DVM, Dipl. ACVIM (cardiology), professor of cardiology at the College of Veterinary Medicine & Biomedical Sciences, Texas A&M University. “There are features that can help differentiate. For instance, a chronic, harsh cough; absence of a heart murmur; and history of a good appetite and activity level would be more consistent with a non-cardiac cause of respiratory signs. Congestive heart failure is more likely in patients with a murmur, arrhythmia, tachycardia, heart enlargement, and respiratory signs.”
Kittleson sees this type of mix-up on a regular basis.
“We commonly see dogs with chronic bronchitis misdiagnosed as being in heart failure,” Kittleson says. “Small, older dogs are prone to both mitral regurgitation due to myxomatous mitral valve disease and to chronic bronchitis. Both pulmonary edema and chronic bronchitis can produce a cough—actually chronic bronchitis always produces a cough. It’s common for a little old coughing dog to have a murmur and the veterinarian then to assume the cough is due to pulmonary edema (left-sided heart failure).”
While chronic bronchitis and pulmonary edema both cause a dog to cough, only pulmonary edema results in an increase in respiratory rate, according to Kittleson. It can also cause dyspnea.
“It takes severe, overwhelming heart disease to result in heart failure, and pulmonary edema causes tachypnea,” Kittleson says. “Severe overwhelming mitral regurgitation creates a severely enlarged left atrium, which can be seen on chest films.”
Kittleson sets up the next steps: First, take chest films to see if the left atrium is severely enlarged or not. If it is, have the owner count the dog’s respiratory rate when it is asleep. If the left atrium is severely enlarged and the sleeping respiratory rate is elevated, conduct a Lasix trial. If the sleeping respiratory rate comes down on Lasix, the dog is in left-sided heart failure. If not, the dog most likely has chronic bronchitis.
A pet’s age and breed also should be considered.
“Cavalier King Charles spaniels often get degenerative mitral valve disease, Doberman pinschers commonly get dilated cardiomyopathy (DCM), and cats are more likely to get hypertrophic cardiomyopathy,” Karlin says. “These are all heart diseases that can result in CHF. Many heart diseases are acquired with age and occur in middle-aged to older animals, but we also do see heart disease in young animals, and some congenital heart diseases can result in CHF in puppies or kittens.”
Primary care veterinarians don’t need to go about this on their own.
“Establishing a relationship with a specialist is beneficial to the client and pet,” Dr. Saunders says. “Partnering together can give them access to the most comprehensive care.”
Weighing the treatment options
While there is no cure for CHF, it can be managed with medical therapy to provide the patient a good quality of life, according to Saunders.
“Congestive heart failure is typically managed with medications, such as diuretics, pimobendan, and angiotensin-converting enzyme (ACE) inhibitors,” Karlin says. “Research is being done on other interventions, such as stem cell therapy and micro RNAs.”
Dogs with mitral regurgitation can be given pimobendan prior to the onset of CHF with the aim of delaying the progression, according to Kittleson. Pimobendan slows the progression of left-sided heart failure (pulmonary edema) in many, but not all, dogs with mitral regurgitation, he adds.
“I think the important thing to relay is [pimobendan] is indicated in dogs with moderate to severe mitral regurgitation, which means the left atrium needs to be moderately to severely enlarged before it should be started in a dog with subclinical mitral regurgitation,” he says.
Kittleson also points toward surgical mitral valve repair for mitral regurgitation in dogs. This rare (and expensive) surgery can be performed by its pioneer Masami Uechi, DVM, PhD, at the Japan Animal Specialty Medical Institute (JASMINE) Veterinary Cardiovascular Medical Center in Yokohama, Japan.
Tufts Cummings Veterinary Medical Center, among other universities, conducts CHF-related clinical trials to help propel research.
“There are ongoing trials for dogs with dilated cardiomyopathy and certain dogs with degenerative mitral valve disease, and new trials are on the horizon for Boxer dogs and for dogs taking medications that might negatively affect the heart, such as doxorubicin,” Karlin explains.
As for further down the road?
“New medications are continuously being developed in the field of human cardiology, and many of these become applicable to our veterinary patients,” she says. “The theoretical ideal treatment of CHF is to correct the underlying heart disease that has caused CHF.”
Kittleson would like to see a device that can be put in the heart of a small dog that stops or, at least, reduces the amount of mitral regurgitation.
“These devices exist in human medicine, but they are much too large to work in small dogs currently,” he says. “Investigators at Colorado State are working on this problem.”