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Cough! Gasp! 'Is it my heart or my lungs, doc?'
When a veterinary patient presents with coughing, you know you must distinguish between a cardiac or respiratory cause. Which is it? This veterinary cardiologist helps you sort through your differentials.
Small dog, big problem. (Mindy Valcarcel)If you've spent any time in small animal private practice, then you've dealt with coughing, geriatric small-breed dogs and understand that these cases can be diagnostic conundrums. There's a murmur. There are crackles, but the dog is also wheezing. Is it cardiac? Is it respiratory? Is it both? If both, which do you treat? Fetch dvm360 speaker Nicole Culwell, DVM, MS, DACVIM, a veterinary cardiologist at MedVet Dallas, is on hand with practical tips to help you sort out heart versus lung problems in both cats and dogs.
Be a breedist and an ageist
Even before you enter the room, the patient's chart will give you clues, Dr. Culwell says. Don't pigeonhole yourself, but know which heart and lung diseases are common in the breed or species you are treating. Age can also give you a hint as to whether the condition is congenital or acquired.
Has history repeated itself?
That all-important patient history. You need to know if the problem is acute or chronic, what therapies have been tried, and the patient's response to that therapy. In dogs, Dr. Culwell says, respiratory disease is usually chronic and episodic, and cardiac disease is usually associated with an acute onset of coughing unless there's chronic compression of the left mainstem bronchus. Intermittent and transient cyanosis is associated with respiratory disease, while cyanosis in congestive heart failure is present only with severe pulmonary edema.
In cats, cardiac and respiratory disease are almost always of acute onset because our feline friends don't follow any textbook rules. Cats confound pet owners because they hide disease, and coughing can look like retching or be followed by vomiting. The most common causes of coughing in cats are asthma, bronchitis, and parasitic disease, says Dr. Culwell. Cats almost never cough with cardiac disease unless they have a chylous pleural effusion.
When to try a therapeutic trial with furosemide
Per Dr. Culwell, a furosemide trial might be just what you, the doctor, ordered in these cases:
Fragile patients-if you suspect cardiac disease but can't get a cat to the radiograph table without it decompensating, then it's time to try furosemide and an oxygen cage.
While waiting on a radiography consultation
Client financial constraints-however, if you go this route, your client needs to know that furosemide dries out respiratory secretions, and it may improve a cough that needs different treatment, so they may be back in a couple of days to get radiographs anyway.
Examine all the things
A physical examination will give you clues or it may give you the answer. Even if you can't touch the pet (e.g. the cat that's close to death anytime you take it out of the oxygen cage) and can only get a visual examination, that can still help you. Here's what to look for:
Sort out stertor versus stridor. Remember, stertor indicates the nasal cavity-anything above the larynx-while stridor indicates a problem in the laryngeal area, neck, or cervical trachea. Dr. Culwell says inspiratory issues without stridor are usually due to intrathoracic causes such as pneumonia or congestive heart failure, while an expiratory push means lower airway such as asthma (cats) or collapsing airway disease (dogs).
Weigh in on weight. The body condition score can also help point you in the right direction, says Dr. Culwell. Most normal to obese patients present with respiratory disease. Thin or emaciated canine patients should cause you to consider late-stage cardiac disease because of cardiac cachexia.
Meditate on the membranes. With cardiac disease, mucous membranes can be normal or demonstrate prolonged capillary refill time or pallor. With respiratory disease, mucous membranes can be normal or intermittently cyanotic.
Catch the patient's breath. Thoracic auscultation can give you all sorts of clues. Remember that wheezes indicate lower airway disease, while focal crackles can be secondary to pneumonia, pneumonitis from heartworm disease or congestive heart failure. If your patient has a murmur and crackles, don't immediately assume cardiac disease is the culprit. If a small-breed geriatric dog presents with dyspnea and you're going to blame it on cardiac disease, then Dr. Culwell says that dog must have a loud murmur. If it ain't loud, look for another cause. She says that if a patient presents with crackles in the lungs and a sinus arrhythmia, then think respiratory disease with high vagal tone.
To make things more difficult, large breeds, such as Dobermans, often don't have crackles despite severe dyspnea secondary to pulmonary edema. And, once again, cats don't follow any rules. A third of cats with hypertrophic cardiomyopathy will not have a murmur, and it's not uncommon for older cats to present with nonpathologic gallop cardiac rhythms, Dr. Culwell says.
Other physical exam hints. Looking for more clues? Dr. Culwell says pulse derangements, abdominal ascites or jugular distention all point to the heart.
‘Your pet needs radiographs'
Thoracic radiographs are essential for the diagnosis or exclusion of congestive heart failure. Left atrial enlargement, pulmonary venous congestion and pulmonary perihilar infiltrates (caudal dorsal in dogs, patchy or ventral in cats) are the hallmark signs of cardiac disease.
Dr. Culwell's tips:
You can't call it off of a lateral view, so don't even think about saving your client some money by scrimping on radiographs. Two views are the standard of care.
Be a stickler for inspiratory films, which are necessary for accurate diagnosis. If you have a panting dog that's not dyspneic, try putting a muzzle on it to get it to slow down its breathing so you can take a picture.
Butorphanol is very helpful in facilitating radiographs in fractious or fearful animals. Alfaxalone is a good choice for fractious cats.
Are your radiographs inconclusive? Try again after furosemide therapy (see the sidebar, “When to try a therapeutic trial with furosemide”).
Lateral views are not helpful to see left atrial enlargement in cats.
A valentine-shaped heart is seen with left-side enlargement in cats.
A ruptured cordae tendinae will fake you out! It presents acutely. On radiographs, the heart size can be normal without left atrial enlargement. These patients may need an echocardiogram for definitive diagnosis.
The ultimate goal-achieving a sigh of relief
Hopefully, these insights into coughing patients from Dr. Culwell will help you face these cases with a little more heartfelt hope while breathing a little easier.
Fetch dvm360 educator Dr. Sarah Wooten graduated from UC Davis School of Veterinary Medicine in 2002. A member of the American Society of Veterinary Journalists, Dr. Wooten divides her professional time between small animal practice in Greeley, Colorado, public speaking on associate issues, leadership, and client communication, and writing. She enjoys camping with her family, skiing, scuba and participating in triathlons.