Boodu, a very fluffy 6 kg Pekingese, has been a regular at our practice for over 13 years. He is well known to all the staff for his extreme reluctance to have his nails clipped. However, his recent visit was under very different circumstances.

As with many older animals, Boodu’s mobility isn’t what it used to be. Combined with the heatwaves we’ve had this summer, a bit of slowing down and reduced exercise was to be expected. More recently though, he appeared to be struggling with getting around — particularly when going upstairs — and had collapsed three times within a 24-hour period. He would often pant before collapsing, then lie on his side for a few minutes before getting up and continuing as normal. He didn’t lose consciousness during these episodes, but they became more frequent over a couple of days.

He was initially seen on a Sunday, when a heart murmur and occasional missed beats were detected, raising suspicion of heart disease. As his breathing was still normal when resting, he was scheduled for further investigations the following Wednesday. However, he re-presented on both the Monday and Tuesday as his episodes worsened. By Tuesday, there was noticeable effort to his breathing, the heart murmur remained, and ‘crackles’ were audible when listening to his lungs. These findings were strongly suggestive of left-sided heart failure causing fluid build-up in the lungs, so he was given furosemide — a diuretic — to remove the presumed fluid.

Over the course of the day, however, there was no improvement. In fact, his breathing worsened, which should not have occurred if left-sided heart failure had been the cause.

We opted to perform chest x-rays, which showed no significant fluid build-up or masses. The next step was a heart scan (echocardiogram) to fully assess how the heart was functioning — and the findings were unexpected.

A snapshot of Boodu’s heart showing larger right sided chambers.

RA – right atrium, RV – right ventricle

LA – left atrium, LV – left ventricle

Most heart disease, especially in older small dogs (<20 kg), affects the left side of the heart, often leading to fluid in the lungs and breathing difficulties, as was initially suspected. However, Boodu’s heart showed right-sided changes, with the right-sided chambers larger than the left — a finding that should never occur. Using colour-flow Doppler imaging (see image below), we could see that the one-way valve on the right side of the heart (the tricuspid valve) was allowing blood to flow back in the wrong direction. This can occur due to valve degeneration, increased pressure in the lung’s blood vessels, or sometimes as an insignificant finding in older dogs.

The speed of this backward blood flow was measured using continuous wave spectral Doppler. The pressure was found to be elevated, leading to a diagnosis of pulmonary hypertension — high blood pressure within the lung vessels. Due to this increased pressure, blood from the right side of the heart was struggling to reach the lungs and return to the left side. A lack of blood reaching the left side of the heart means a lack of blood being pumped to the rest of the body, which explains Boodu’s weakness and episodes of collapse.

Colour Flow Doppler showing blood flowing back in the wrong direction across the tricuspid valve. Green colour indicates turbulence and is abnormal.

Continous wave spectral doppler measuring the speed of the blood flowing backwards.

The next question was: Why had Boodu developed pulmonary hypertension? There are many possible causes, including underlying lung diseases such as bronchitis, tumours, lungworm, or blood clots. The crackles heard earlier in the day were now thought not to be fluid-related, and since no tumours were visible on the chest x-rays, the crackles were likely due to underlying lung inflammation — such as undiagnosed bronchitis. This type of airway inflammation can affect the lung’s blood vessels and lead to pulmonary hypertension.

Treatment and Outcome

Boodu was started on two medications:

• Sildenafil – This is the active ingredient in Viagra. It dilates the lung blood vessels, allowing easier movement of blood from the right side of the heart through the lungs and back to the left side.
• Terbutaline – A bronchodilator that opens the airways, reducing resistance and increasing airflow to the lungs. This was prescribed due to the suspected bronchitis.

He responded very well to treatment. Within a few hours, the crackles previously heard had disappeared and his breathing had returned to normal. He was monitored overnight by our night nurses and discharged the next day, continuing both medications.

We’re pleased to report that Boodu has had no further collapsing episodes since.