The Congenital Cardiac Exam
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.
Board certification 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. Other veterinarians may be able to perform these
examinations, provided they have received advanced training in the subspecialty
of congenital heart disease.
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
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 be 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 be right craniodorsal cardiac border.
- Any cardiac murmurs or abnormal sounds should be noted. Murmurs should
be described as indicated below.
A full description of the cardiac murmur should made and recorded in the
medical record.
- 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
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.
At this time the OFA does not require a post exercise examination in
the assessment of heart murmurs in dogs; however, this practice may be
modified should definitive information become available
