Heart disease may be either ‘congenital’ (the dog was born with it) or ‘acquired’ (a problem occurring later in life).
Congenital heart disease usually results in a heart murmur which can be heard by listening to the heart sounds with a stethoscope. This is because an abnormal opening (like a hole in the heart) or abnormal narrowing of a valve at the great vessels exiting the heart causes turbulence of blood within the heart itself or the great vessels and the turbulent flow is detected as a cardiac murmur. In many cases, the loudness of the murmur (which is graded out of 6 on a scale 1 – 6), is correlated with the severity of the heart disease.
Many puppies have murmurs which they grow out of called innocent murmurs – these tend to be very low grade. If these are still present when the puppy is over 12 – 15 weeks old, many veterinary surgeons will want to rule out heart disease. Many athletic dogs also have innocent murmurs called flow murmurs, resulting from the turbulence of blood leaving the heart. Obviously, there can be a problem distinguishing mild congenital heart disease (which may be significant if the animal is bred) and these innocent murmurs.
A number of Bull Terriers have been identified with a congenital condition known as mitral dysplasia. The mitral valve is leaky in this condition and when the main pumping chamber – the left ventricle – contracts, instead of all the blood leaving into the aorta, some leaks backwards into the left atrium causing a murmur. This is known as mitral regurgitation. Very rarely, the mitral valve can be narrowed as well as being leaky in some cases – this means it is difficult to let the blood pass from the left atrium (the collecting chamber) to the left ventricle (the pumping chamber). This is called mitral stenosis. Other Bull Terriers can be born with a narrowed aortic valve, making it difficult for blood to leave the left ventricle. This is called aortic stenosis. In some cases, both mitral dysplasia and aortic stenosis occur together.
Bull Terriers with mitral dysplasia may be affected very mildly to very severely. Many dogs will lead normal lifestyles and be very active. Some may have problems as they get older, possibly because of concurrent acquired valvular disease called valvular endocardiosis. A few dogs will develop heart failure manifested as coughing, breathlessness, tiring easily on exercise and occasionally, fainting. However if there is any degree of heart disease present, it is possible this will be passed on to offspring if the dog is bred from.
If a heart murmur is detected in your dog, you must discuss it with your own veterinary surgeon. He/she may decide to investigate the problem further or decide to refer your dog to a veterinary cardiologist.
Information Supplied By Joanna Dukes-McEwan
BVMS, MVM, PhD, DVC, Dip ECVIM-CA (Cardiology), MRCVS
RCVS & European recognised Specialist in Veterinary Cardiology