Managing Heart Disease in Bull Terriers: Symptoms and Treatments

"Heart disease in a Bull Terrier is due to structural defects within the heart which are present at birth. In Bull terriers these defects include leaky valves or narrowed valves. Both of these general defects will result in a heart murmur - an abnormal heart sound which is detected with a stethoscope by a veterinary cardiologist or a veterinary surgeon."

View Of The Normal Anatomy Of The Heart:

The heart has four chambers. The right atrium (RA) collects venous blood from the body, and it passes through the tricuspid valve to the right ventricle (RV) The right ventricle pumps the venous blood, though the pulmonic valve, into the pulmonary artery and so into the lungs, where the blood is oxygenated. The blood returns to the heart, into the left atrium (LA) Blood passes though the open mitral valve into the main pumping chamber of the heart, the left ventricle (LV) When this pumps, the mitral valve closes and blood is ejected out via the open aortic valve into the aorta which divides to every artery to all the organs of the body.

Mitral Dysplasia:

Mitral dysplasia is a malformation of the mitral valve apparatus. The normal mitral valve apparatus consists of two valve cusps. These are anchored by chordae tendinea to two papillary muscles in the left ventricle. The papillary muscles and the cow the valve to close when the ventricle contracts, but restrain the valve so it does not flap back into the left atrium. The closed valve should be a tight seal, allowing no blood into the left atrium. With mitral Dysplasia in Bull Terriers, the mitral valve apparatus is deformed. The valve cusps become thickened and nodular. The papillary muscles are very large and thick and only very short, thickened and chordae tendinea attach the papillary muscles to the valve leaflets. The most common consequence of mitral dysplasia is a leaky mitral valve. During ventricular contraction (systole) instead of the mitral valve sealing shut it allows a jet of blood to pass backwards into the left atrium, as well as pumping blood forward in the normal direction, into the aorta. This leak is known as mitral regurgitation The turbulent jet of blood flow due to mitral regurgitation can be heard with a stethoscope it is a systolic heart murmur, which is most intense over the mitral valve area of the dog’s chest. Loud murmurs can radiate to other parts of the dog’s chest as well. Occasionally, the mitral valve in mitral dysplasia can be narrowed as well, called mitral stenosis. It is difficult for the left atrium to empty into the left ventricle. Pressures can build up in the left atrium. The left atrium may become greatly enlarged.

Consequences Of Mitral Dysplasia:

Dogs with mitral dysplasia will have a heart murmur. If the valve is only slightly leaky, the murmur is only soft and the dog may not be affected at all. Where there is severe mitral regurgitation, a large volume of blood moves back and forwards across the mitral valve, overloading the left side of the heart. The left atrium and left ventricle can become very large indeed. Changes occur gradually, but eventually, pressures build up in the left atrium, and blood dams back into the lungs, and comes out of the circulation into the normally air-filled spaces of the lungs - this is called pulmonary oedema. Once this happens, the dog is in congestive heart failure. Dogs with pulmonary oedema will be breathless and will cough. With mitral stenosis also present, left atrial enlargement in massive and pulmonary oedema rapidly develops. Where the left atrium becomes very stretched, irregular or chaotic heart rhythms can develop, such as atrial fibrillation. The rhythm will worsen the symptoms of dogs with congestive heart failure, especially if they have mitral stenosis. Dogs with severe mitral dysplasia have poor heart output into their circulation they may faint on exertion or excitement or stress (syncope) as their brains can become short of oxygen.

Aortic Stenosis:

The aortic valve is positioned between the left ventricle and the aorta. It opens as the left ventricle contracts, allowing the left ventricle to eject blood into the aorta. It normally offers no restriction to blood flow. With aortic stenosis, the aortic valve itself or a fibrous band beneath the valve (Subaortic stenosis) restricts the outflow to blood from the left ventricle. The left ventricle has to work hard just to eject blood, and the heart muscle becomes thickened to compensate. Blood ejecting past the obstruction to outflow is very fast and turbulent. This turbulent flow causes a heart murmur which can be detected with a stethoscope over the aortic valve area of the chest wall. The louder the murmur, the more severe the aortic stenosis and the faster and more turbulent the blood flow passing the obstruction. This turbulent blood flow can affect the walls of the aorta, and it can stretch, called post- stenotic dilation. As the left ventricle muscle thickens, it exceeds the coronary artery blood supply to it. This means that areas of the heart can be deprived of oxygen. The muscle becomes irritable and may cause abnormal beats (called ventricular premature complexes or VPCs).

Diagnosis Of Congenital Heart Disease By Clinical Examination:

1. The clinical cardiac examination should be conducted in a systematic manner. The arterial and venous pulses, mucous membranes, and precordium should be evaluated. Heart rate should be obtained. The clinical examination should be performed by an individual with advanced training in cardiac diagnosis. In the USA, Board certification in by the American College of Veterinary Internal Medicine, Specialty of Cardiology is considered by the American Veterinary Medical Association as the benchmark of clinical proficiency for veterinarians in clinical cardiology, and examination by a Diplomate of this specialty board is recommended. However, any licensed veterinarian may be able to perform this examination by auscultation.
2. Cardiac auscultation should be performed in a quiet, distraction-free environment. The animal should be standing and restrained, but sedative drugs should be avoided. Panting must be controlled, and if necessary, the dog should be given time to rest and acclimate to the environment. The clinician should be able to identify the cardiac valve areas for auscultation. The examiner should gradually move the stethoscope across all valve areas and also should auscultate over the subaortic area, ascending aorta, pulmonary artery, and the left craniodorsal cardiac base. Following examination of the left precordium, the right precordium should be examined.

• The mitral valve area is located over and immediately dorsal to the palpable left apical impulse and is identified by palpation with the tips of the fingers. The stethoscope is then placed over the mitral area and the heart sounds identified.
• The aortic valve area is dorsal and 1 or 2 intercostal spaces cranial to the left apical impulse. The second heart sound will become most intense when the stethoscope is centered over the aortic valve area. Murmurs originating from or radiating to the subaortic area of auscultation are evident immediately caudoventral to the aortic valve area. Murmurs originating from or radiating into the ascending aorta will be evident craniodorsal to the aortic valve and may also project to the right cranial thorax and to the carotid arteries in the neck.
• The pulmonic valve area is ventral and one intercostal space cranial to the aortic valve area. Murmurs originating from or radiating into the main pulmonary artery will be evident dorsal to the pulmonic valve over the left hemithorax.
• The tricuspid valve area is a relatively large area located on the right hemithorax, opposite and slightly cranial to the mitral valve area.
• The clinician should also auscultate along the ventral right precordium (right sternal border) and over the right craniodorsal cardiac border.
• Any cardiac murmurs or abnormal sounds should be noted. Murmurs should be described as indicated below.

• Murmurs should be designated as systolic, diastolic, or continuous.
• The point of maximal murmur intensity should be indicated as described above. When a precordial thrill is palpable, the murmur will generally be most intense over this vibration.
• Murmurs that are only detected intermittently or are variable should be so indicated.
• The radiation of the murmur should be indicated.

Grading of heart murmurs is as follows:
Grade 1— a very soft murmur only detected after very careful auscultation
Grade 2— a soft murmur that is readily evident
Grade 3— a moderately intense murmur not associated with a palpable precordial thrill (vibration)
Grade 4— a loud murmur; a palpable precordial thrill is not present or is intermittent
Grade 5— a loud cardiac murmur associated with a palpable precordial thrill and not audible when the stethoscope is lifted from the thoracic wall
Grade 6— a loud cardiac murmur associated with a palpable precordial thrill and audible even when the stethoscope is lifted from the thoracic wall

• Other descriptive terms may be indicated at the discretion of the examiner; these include such timing descriptors as: proto(early)-systolic, ejection or crescendo-decrescendo, holo-systolic or pan-systolic, decrescendo, and tele(late)- systolic and descriptions of subjective characteristics such as: musical, vibratory, harsh, and machinery.

• Some heart murmurs become evident or louder with changes in autonomic activity, heart rate, or cardiac cycle length. Such changes may be induced by exercise or other stresses. The importance of evaluating heart murmurs after exercise is currently unresolved. It appears that some dogs with congenital subaortic stenosis or with dynamic outflow tract obstruction may have murmurs that only become evident with increased sympathetic activity or after prolonged cardiac filling periods during marked sinus arrhythmia. It also should be noted that some normal, innocent heart murmurs may increase in intensity after exercise. Furthermore, panting artifact may be a problem after exercise.
• It is most likely that examining dogs after exercise will result in increased sensitivity to diagnosis of soft murmurs but probably decreased specificity as well. Auscultation of the heart following exercise is at the discretion of the examining veterinarian.

Conclusion:

An internist and/or cardiologist should auscultate all breeding animals. Optimally all breeding animals should have a color Doppler/echo cardiogram and all murmurs should be followed by a color Doppler/echocardiogram evaluation.