Adam’s owners were upset that as he was getting older he was losing his va va voom! He had become worryingly lethargic and weak, seemed depressed and at times barely had the energy to hold up his head. Going for a walk was out of the question and his quality of life was disappearing fast.
The stand-out finding at Adam’s clinical examination was that he had a very low heart rate. When we examine dogs of around Adam’s size, we would expect to register a heart rate of between 80-120 beats per minute (bpm). Adam’s was only 50-60 bpm – practically half this!
After a chest x-ray was unremarkable and blood tests ruled out common problems, we ran an electrocardiogram (ECG) to record the rate and rhythm of Adam’s heart through a series of electric traces.
Adam’s chest radiograph shows no abnormalities
What we discovered was that Adam had 3rd degree heart block – also known as complete heart block. This condition is so rare that Hamish had never seen it before in 16 years as a vet!
With complete heart block, the normal pacemaker in the heart works efficiently (Adam’s was running at 165 bpm). However, these electrical impulses are blocked from reaching the main muscular part of the heart, hence the term ‘heart block.’Without this electrical stimulation, the main muscular part of the heart must generate its own impulses or else the heart stops beating entirely!
To keep beating, the heart naturally creates a second pacemaker in its lower chamber which generates a default ‘escape rhythm.’
In Adam’s case the second pacemaker has occurred in a favourable place, leading to relatively normal electrical impulses (the ‘escape rhythm’), and therefore relatively normal heart beats beating at an acceptable rate.
Adam’s ECG: The small peaks are the normal pacemaker impulses, and the large, the ‘escape rhythm’
Although we cannot ‘unblock’ his heart, with appropriate medication, we have restored Adam’s va va voom! Now he can look forward to his summer walks!