There are several different heart defects which Bull Terriers may have. The commonest is mitral displasia, in which the valve between two of the heart chambers does not close properly, so when the heart tries to send blood into the arterial system, some of it leaks back. In an attempt to send enough blood round the body the heart overworks and as a result may become enlarged. If the mitral valve leaks badly this may lead to heart failure even in young dogs. The other frequent problem is sub-aortic stenosis. In this condition the main artery from the heart, the aorta, is narrowed just where it leaves the heart. To push enough blood past this constriction the heart has to work harder, again possibly leading to heart failure. In a normal heart the valves opening and closing and the blood flows produce characteristic sounds. If a valve is faulty or a blood vessel constricted, the abnormal sounds produced are called heart murmurs. The severity of these is graded from 1 (mild) to 6 (very serious). The detection and grading of heart murmurs should be entrusted to a veterinary cardiologist - a veterinary surgeon with special training leading to the Diploma or Certificate in Veterinary Cardiology. Although an ordinary veterinary surgeon can detect heart murmurs from grade 3 upwards, they cannot reliably find lower grade heart murmurs. Obviously such murmurs are undesirable in breeding stock because heart problems are inherited (the mode of inheritance is as yet unknown). Veterinary cardiologists have held screening sessions in recent years at the shows of four Bull Terrier Clubs, finding that between 25% and 40% of Bull Terriers have heart murmurs.
Cardiologists check dog’s hearts using ausculation (listening for murmurs with a special stethoscope). However, sometimes the cardiologist may be uncertain if the sounds heard are completely normal, and a doppler ultrasound scan may be necessary to make sure. This uses extremely expensive equipment to actually ‘look’ inside a beating heart (it is non invasive and may be likened to the use of scans on pregnant women). Needless to say doppler scans are expensive! Cardiologists issue certificates for the dogs they examine, which state that the heart was murmur free at the time of examination or state what grade of murmur was detected. As ‘innocent’ murmurs often occur in puppies, at least one test should be conducted after the dog has enjoyed its first birthday. Your vet will be able to refer you to your nearest cardiologist.