Dr Nuala Summerfield
BSc BVM&S DipACVIM (Cardiology) DipECVIM CA(Cardiology) MRCVS
RCVS, American and European Specialist in Veterinary Cardiology
The great radiologist Merrill C. Sosman once said that “You see only what you look for. You recognize only what you know.” Now, while we’re always taught that if we hear hoofbeats, think horses, it’s important to remember that in some situations zebras might be more common than we think!
So, bearing this in mind, let’s take a look at our case.
George is a 9 year old, male neutered Staffie, apparently in good health until recently. His owners have noticed that he seems to get “out of breath” more often on walks and has had the occasional cough over the last few months, but they had put this down to his age. The reason for George’s visit to the practice today is that he “passed out” on a walk yesterday and although the episode was brief and he “recovered” fairly rapidly (within minutes), his owners are very concerned.
On clinical examination he is relaxed, not noticeably cyanotic or dyspnoeic at rest and no abnormalities are found on abdominal palpation. His neurological examination is also normal. His owner’s description of his “passing out episode” is not consistent with a seizure.
There is mild jugular distension present and he seems a little “pot-bellied”, but it isn’t immediately clear whether this is due to abdominal fat or ascites. Thoracic auscultation reveals diffuse crackles over both lung fields and some intermittent wheezes. His heart rate is 130 bpm. The rhythm is regular, there is no resting sinus arrhythmia and there is no audible heart murmur.
What are your immediate thoughts on this case? What do you think is the most likely cause? And what do you want to do next?
In a case like this, there are of course a range of different tests available to help us determine the underlying problem. Fortunately, in this case George is insured and a full work-up is possible.
Bloods
Routine biochemistry and haematology panel is normal.
Radiography
Obtaining radiographs is not always straightforward in patients with exercise intolerance and syncope, because these patients must always be considered high-risk for sedation or anaesthesia, especially if the underlying disease condition is not yet known. In George’s case, he is quiet and compliant (which given he is a typically excitable, enthusiastic Staffie, may be considered symptomatic of significant pathology in its own right!), and a good lateral and DV radiograph are obtained. They reveal significant right ventricular enlargement, as evidenced by an increased degree of sternal contact on the lateral view (yellow arrow) and a reverse D appearance of the cardiac silhouette on the DV view. There is also a diffuse interstitial pulmonary pattern.
5 minute ECG
Cardiac arrhythmias, especially paroxysmal ventricular tachycardia or intermittent bradycardias, are a potential cause of syncope in dogs. George’s resting ECG is normal, but this is not uncommon in patients with intermittent arrhythmias. In patients where we strongly suspect an intermittent arrhythmia, Holter monitoring may be indicated.
To summarise so far, George has been presented for exercise intolerance, collapse and coughing. No heart murmur or arrhythmia have been detected but he has crackles and wheezes on pulmonary auscultation. On thoracic radiographs, the right side of his heart appears enlarged and there is an interstitial pulmonary pattern evident.
Do you think George’s symptoms are due to primary heart disease or primary pulmonary disease?
Echocardiography
With any suspected heart disease, an echocardiogram (heart ultrasound) is the best way to confirm this suspicion and definitively diagnose the nature of the underlying problem. The left side of George’s heart appears normal. However, the right atrium (RA) and right ventricular chamber (RV) are visibly enlarged and the right ventricular walls appear thickened. Also the main pulmonary artery (MPA) and pulmonic valve (PV) annulus are dilated.
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General Ultrasound
Abdominal ultrasonography reveals that George has moderate amounts of anechoic free abdominal fluid (green arrow). There is also hepatic venous congestion evident (yellow arrow), which when considered in combination with the jugular venous distension detected on physical examination and the right heart enlargement on heart ultrasound, is suggestive of increased pressures in the right side of the heart and right-sided cardiac congestion.
So… what is your diagnosis? Are there any additional tests you feel George would benefit from?
George is not a straightforward case and it isn’t immediately clear from these findings whether we have primarily cardiac or pulmonary disease.
George’s ECG was normal, but in patients where we strongly suspect an intermittent arrhythmia, Holter monitoring may be indicated.
A more detailed heart ultrasound is required to assess the cardiac function more fully. Spectral Doppler can be used to assess blood-flow velocities across the pulmonic and tricuspid valves, to allow the right atrial, right ventricular and pulmonary artery pressures to be estimated.
This is, of course, where VVS comes into its own – rather than having to refer George, or wait for a cardiologist to visit your practice, you can have one of our cardiology specialists in on the case from the beginning. They’ll be able to help you to obtain the necessary echocardiographic images and to interpret these more advanced scanning techniques such as Spectral Doppler.
What was the diagnosis?
George is suffering from pulmonary hypertension (PHTN) and cor pulmonale, as a result of idiopathic pulmonary fibrosis (IPF).
Although we think of IPF as being a disease of West Highland White Terriers, it is well documented in Staffordshire Bull Terriers as well. This explains the interstitial pulmonary pattern on radiographs, as well as the wheezes and crackles audible on pulmonary auscultation.
IPF results in reduced compliance of the lungs and subsequent hypoxia, leading to chronic pulmonary arterial constriction and increased pressure in the pulmonary arteries. Therefore the right ventricle must pump against a higher resistance (afterload) in the pulmonary arteries in order to deliver blood to the lungs.
The term cor pulmonale refers to the enlargement of the right heart chambers and thickening of the right ventricular walls, as well as symptoms of right sided congestive heart failure (raised resting heart rate, jugular and hepatic venous distension and the ascites) that can occur in dogs with chronic significant PHTN. Dogs with PHTN and cor pulmonale frequently present with exercise intolerance and collapse.
Want to know more?
There’s a good article on Pulmonary Hypertension in dogs here at VetFolio, and a good summary from Clinician’s Brief here (needs login).