Echocardiography reveals congestive heart failure and a heart base tumour in a bull-mastiff.

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canine cardiology

Subedited by Dr Phil Tucak

Lilly Rosewell is a nine-year-old female desexed bull-mastiff that presented to the Small Animal Specialist Hospital (SASH) on the Central Coast due to the owners’ concern about an enlarged abdomen, progressive dyspnea and coughing over the previous 48 hours. Lilly was also lethargic, according to the owners, and her appetite had declined over the last week. Prior to a week ago, Lilly was considered to be in good health. During transit to the referral hospital, Lilly had one episode of emesis.

On physical examination the following abnormalities were noted: 

  • Slight pallor of the mucus membranes with a prolonged capillary refill time of two seconds.
  • Tachycardia at a heart rate of 220bpm with a femoral pulse rate of 70bpm and hypokinetic pulses. 
  • The heart rhythm was irregularly irregular.
  • A respiratory rate of 70 breaths per minute with a moderate increase in inspiratory and expiratory effort. 
  • Thoracic auscultation revealed a possible grade 1 left apical cardiac murmur but due to the dyspnoea this was not definitive. No crackles were auscultated.
  • Lilly was lethargic and had a pendulous distended abdomen with a fluid wave on palpation. 

Given the patient signalment of a giant breed dog with an arrythmia and suspected congestive heart failure (CHF) causing the respiratory signs, dilated cardiomyopathy (DCM) was high on the differential diagnosis list for this patient. While an absolute cardiac murmur had not been auscultated—unlike patients with mitral valve disease who almost always present with a high-grade cardiac murmur when there is the presence of congestive heart failure—dogs with DCM may have a low-grade cardiac murmur or no murmur detected at all when in CHF.

Due to concern over the patient’s stability based on an SPO2 of 93% on room air and a systolic blood pressure of 80mmHg, prior to embarking on diagnostic tests, the patient was administered supplemental oxygen via a face mask, parenteral frusemide at 4mg/kg IV, butorphanol at 0.3mg/kg IV, and pimobendan at 0.15mg/kg IV.

Once it was deemed that the Lilly was more stable, the following diagnostic tests were performed in order of priority:

  • Packed cell volume and total protein to exclude anaemia as a cause for the pallor and respiratory signs.
  • Venous blood gas to assess ventilation.
  • 6 lead ECG to characterise the arrythmia and inform anti-arrhythmic therapy.
  • Complete echocardiography (left and right parasternal views with measurements of aortic and pulmonic velocities) to identify any structural cardiac disease and if present characterise it and gauge severity. The echocardiogram was performed by myself but the obtained images and measurements were submitted to IDEXX teleradiology (cardiology service) for a board-certified cardiologist to provide a STAT interpretation of any echocardiographic abnormalities and cardiac disease diagnosis if present.
  • TFAST and AFAST to investigate the presence of pleural effusion and ascites respectively.
  • 3 view thoracic radiographs to assess for evidence of pulmonary oedema and other causes for respiratory distress e.g. metastatic pulmonary neoplasia. 
  • Complete blood count and biochemistry to screen for extra-cardiac causes for an arrythmia e.g. metabolic disease and concomitant disease.
Right to Left: Lead 2 25mm/s ECG strip displaying ECG characteristic of atrial fibrillation; two of the thoracic X-rays taken; and echo still image showing the incidental heart base mass which was likely to be a chemodectoma based on location.

Results

The PCV/TP was in reference range. The blood gas was in reference range. The ECG confirmed an irregularly irregular arrythmia, with absent P waves, undulating baseline (F waves) and variable QR intervals. The characteristics of the ECG was consistent with atrial fibrillation.

The echocardiogram report from the cardiologist returned with the following findings:

“There is a normal LV lumen with discordant wall motion due to the irregular rhythm. Subjectively the myocardial function appears decreased but it measures normally. The LA is mildly to moderately enlarged.  Morphologically the MV is normal with mild mitral regurgitation. Subjectively the RV appears normal with a normal TV and mild TR. The RA appears normal. The aorta is slightly dilated with a slightly thickened aortic valve. There was no AR noted. The pulmonary artery is normal. There is a mass effect involving the heart base over the LA. The pericardium appears normal.”

The following measurements were recorded:

IVSd 1.0 cm

LVIDd 4.0 cm weight normalised 1.27

PWd 1.0 cm

IVSs 1.25 cm

LVIDs 1.9 cm

PWs 2.0 cm

FS 52%

Ao 2.3 cm

LA 4.5 cm

LA/Ao 1.96

LAx 5.5 cm

Doppler LVOT 0.9 m/s

RVOT 0.5 m/s

TFAST and AFAST revealed a mild to moderate bicavitary effusion (which was worst in the abdomen than the pleural space). The composition of the fluid was not determined as centesis and was not pursued because of the suspected diagnosis of left and right congestive heart failure from biventricular failure causing a transudate pleural effusion and ascites.

The thoracic radiographs did not reveal radiographic signs of pulmonary oedema or other evidence of pulmonary parenchymal disease. There was marked cardiomegaly objectively and subjectively. The VHS measured 12. The cranial lobar arteries were normal. The caudal lobar arteries were normal. The caudal vena cava was severely distended consistent with the reported abdominal effusion (suspected ascites secondary to RCHF).

The complete blood test results revealed mild elevation of ALT and mild monocytosis but were otherwise unremarkable.

Diagnosis 

The echocardiogram revealed likely primary atrial fibrillation with secondary myocardial changes and resultant mitral regurgitation and tricuspid regurgitation. There was also a heart base tumour most consistent with a chemodectoma. The chemodectoma was most likely an incidental finding. The dyspnea was likely secondary to hypoxia from reduced cardiac output rather than left sided congestive heart failure.

Treatment and outcome

Regular diltiazem at 90 mg orally every 8 hours was administered for rate control of the atrial fibrillation. To treat the suspected ascites, benazepril at 0.5 mg/kg orally every 24 hours, spironolactone at 50 mg orally every 12 hours and frusemide 3mg/kg bid, were prescribed.

Lilly responded well to treatment—showing improved respiratory signs and demeanour but due to costs, a Holter monitor was not used to monitor heart rate. A recheck was scheduled for two weeks however the patient unfortunately did not return for follow-up. 

This case highlights that while pattern recognition is an important tool in veterinary medicine, a suite of appropriate diagnostics should always be performed to confirm the tentative diagnosis and investigative concurrent disease. In this case, Lilly was proven not to have DCM as suspected, and a heart base tumour was found which at the time of presentation the patient was asymptomatic for—but the owners were warned about the possible development of a pericardial effusion which could cause similar presenting signs to the primary atrial fibrillation.


Dr Tunbi Idowu

canine cardiology

Dr Tunbi Idowu is originally from Canberra and has always loved animals. She studied at Murdoch University and graduated as a veterinarian in 2010. After graduation, she gained a job as a small animal vet in Horsham, Victoria. However, in 2012 the opportunity to work in a small animal practice in Canberra arose and Dr Idowu moved back home and worked at that clinic for three years. 

In 2014, Dr Idowu gained Membership to the Australian and New Zealand College of Veterinary Scientists, in Small Animal Medicine. In 2015 she began a two-year small animal medicine residency training program at Melbourne Veterinary Specialist Centre, and following this worked as a medicine registrar at the Animal Referral Hospital in Canberra.

In 2019 Dr Idowu joined the Small Animal Specialist Hospital as a senior small animal medicine registrar. In 2020 she passed her Fellowship examination in Small Animal Medicine and became a specialist in 2021. Following this, she acted as a Fellowship examiner in Small Animal Medicine.

Dr Idowu is interested in all aspects of internal medicine but has an affinity for infectious diseases, endocrinology, haematology and immunology. She has gained much experience in echocardiography with cardiology being a special interest.

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