OFA Congenital Heart Disease Registry
General Procedures
- Purposes
- To gather data regarding congenital heart diseases in
dogs and to identify dogs which are phenotypically normal prior to use
in a breeding program. For the purposes of the registry, a
phenotypically normal dog is currently defined as:
1) one without a cardiac murmur, or as
2) one with an innocent heart murmur that is found to be otherwise
normal by virtue of an echocardiographic examination which includes
Doppler studies.
- Examination and Classification
- Each dog is to be examined and
classified by a veterinarian with expertise in the recognition of
canine congenital heart disease in accordance with procedures outlined
in the enclosed Application and General Instructions.
- Certification
- A certificate and breed registry number will be
issued for any dog found to be normal at 12 months of age or older.
The OFA fee is $15.00 and no charge will be made for recertification
at a later age. The breed registry number will indicate the age at
evaluation.
- Provisional Certification*
- Evaluation of dogs under 12 months of
age is possible if requested by the owner. OFA will enter the information
in a data bank at a fee of $10.00 for those found to be normal. Full
certification, however, requires subsequent examination at 12 months of
age or older.
- (* Such provisional certification may be of value to breeders prior to the sale of any dog or for assess-
ment of the breeding potential of a dog.)
- Dogs with congenital heart disease
- The veterinarian and owner are
encouraged to submit all evaluations, whether normal or abnormal, for
the purpose of completeness of data collection and to assist in the
analysis of inheritance of important canine congenital heart defects.
There is no OFA fee for entering an abnormal evaluation of the heart
into the data bank.
Identification, Classification, and Certification
DEFINITIONS AND GENERAL COMMENTS
A. Congenital heart disease (CHD) in dogs is a malformation of the heart
or great vessels. The lesions characterizing congenital heart defects
are present at birth and may develop more fully during the perinatal and
growth periods. Many congenital heart defects are thought to be
genetically transmitted from parents to offspring; however, the exact
modes of inheritance have not been precisely determined for all
cardiovascular malformations.
B. The most common congenital cardiovascular defects can be grouped into
several general anatomic categories. These anatomic diagnoses include:
- Malformation of the atrioventricular valves
- Malformations of ventricular outflow leading to obstruction of
blood flow
- Defects of the cardiac septa (shunting defects)
- Abnormal development of the great vessels or other vascular
structures
- Complex, multiple, or other congenilal disorders of the heart,
pericardium, or blood vessels
C. A careful clinical examination that emphasizes cardiac auscultation
is tbe most expedient and cost-effective method for identifying CHD in
dogs. While there are exceptions, virtually all common congenital heart
defects are associated with the presence of a cardiac murmur.
Consequently, it is recommended that cardiac auscultation be the
primary screening method for initial identification of CHD and the
initial classification of dogs.
D. Murmurs related to CHD may at times be difficult to distinguish from
normal, innocent (also called physiologic or functional) murmurs.
Innocent cardiac murmurs are believed to be related to normal blood
flow in the circulation. Innocent murmurs are most common in young,
growing animals. The prevalence of innocent heart murmurs in mature
dogs (and especially in athletic dogs) is undetermined. A common clinical
problem is the distinction between innocent murmurs and murmurs arising
from CHD.
E. Definitive diagnosis of CHD usually involves one or more of the
following methods: 1) Echocardiography with Doppler studies; 2) Cardiac
catheterization with angiocardiography; or 3) Post-mortem examination
of the heart (necropsy). Other methods of cardiac evaluation, including
electrocardiography and thoracic radiography, are useful in evaluating
individuals with CHD, but are not sufficiently sensitive nor specific
to reliably identify or exclude the presence of CHD.
- The noninvasive method of echocardiography with Doppler is the
preferred method for establishing a definitive diagnosis in dogs when
CHD is suspected from the clinical examination. Echocardiography is an
inappropriate screening tool for the identification of congenital heart
disease and should be performed only when the results of clinical
examination suggest a definite or potential cardiovascular abnormality.
- Two-dimensional echocardiography provides an anatomic image of the
heart and blood vessels. While moderate to severe cardiovascular
malformations can generally be recognized by two-dimensional
echocardiography, mild defects (which are often of great concern to
breeders of dogs) may not be identifiable by tbis method alone.
- Doppler studies, including pulsed-wave and continuous wave spectral
Doppler. and two-dimensional color Doppler demonstrate the direction
and velocity of blood flow in the heart and blood vessels. Abnormal
patterns of blood flow are best recognized by Doppler studies. Results
of Dopp]er studies can be combined with those of the two-dimensional
echocardiogram in assessing the severity of CHD. Color Doppler
echocardiography is used to evaluate relatively large areas of blood
flow and is beneficial in the overall assessment of the dog with
suspected CHD. Turbulence maps employed in color Doppler imaging are
useful for identifying high velocity or disturbed blood flow but
are not sufficiently specific (or uniform among manufacturers) to
quantify blood velocity. It is emphasized that quantitation of
suspected blood flow abnormalities is essential and can only be
accomplished with pulsed or continuous wave Doppler studies. Pulsed
wave and continuous wave Doppler examinations provide a display of
blood velocity spectra in a graphical format and are the methods of
choice for assessing blood flow patterns and blood velocity in
discrete anatomic areas.
- Cardiac catheterization is an invasive method for identification
of CHD that is considered very reliable for the diagnosis of CHD.
Cardiac catheterization should be performed by a cardiologist,
usually requires general anesthesia, carries a small but definite
procedural risk, and is generally more costly than noninvasive
studies. While cardiac catheterization with angiocardiography is
considered one of the standards for the diagnosis of CHD, this
method has been supplanted by echocardiography with Doppler for
routine evaluation of suspected CHD.
- Necropsy examination of the heart should be done in any breeding
dog that dies or is euthanatized. The hearts of puppies and dogs
known to have cardiac murmurs should always be examined following the
death of the animal. A post-mortem examination of the heart is best
done by a cardiologist or pathologist with experience in evaluating
CHD. While it is obvious that necropsy cannot be used as a screening
method, the information provided by this examination can be useful
in guiding breeders and in establishing the modes of inheritance of CHD.
F. Each of the methods of evaluation indicated above may be associated
with false positive and false negative diagnoses. It must be recognized
that some cases of CHD fall below the threshold of diagnosis. In other
cases, a definitive diagnosis may not be possible with currently
available technology and knowledge. These limitations can be minimized
by considering the following general guidelines:
- The results of the examinations described above are most reliable
when performed by an experienced individual with advanced training
and experience in cardiovascular diagnosis. Echocardiography with
Doppler, cardiac catheterization, and post-mortem examination of the
heart for CHD requires advanced training in cardiovascular diagnostic
methods and the pathology and pathophysiology of CHD.
- Examinations performed in mature dogs are most likely to be
definitive. This is especially true when considering mild congenital
heart defects. Innocent heart murmurs are less common in mature
animals than in puppies and are less likely to be a source of
confusion. Furthermore, the murmurs associated with some mild
congenital malformations become more obvious after a dog has
reached maturity. While it is quite reasonable to perform
preliminary evaluations and provide provisional certification
to puppies and young dogs between 8 weeks and 1 year of age,
final certification, prior to breeding, should be obtained in
mature dogs at 12 months of age or older.
- Examination conditions must be appropriate for recognition of
subtle cardiac malformations. The identification of soft cardiac
murmurs is impeded by extraneous noise or by poorly restrained,
anxious, or panting dogs.
- A standardized cardiac clinical examination must be performed
according to a predetermined and clearly communicated protocol.
Physical examination and cardiac auscultation should be used as
the initial method of cardiac evaluation. If the clinical
examination is normal, no further diagnostic studies are
recommended. If the clinical examination is abnormal, a tentative
diagnosis may be made, but the definitive diagnosis generally
requires other diagnostic studies (as indicated above).
- Examiners who perform echocardiography with Doppler must use
appropriate ultrasound equipment, transducers. and techniques. Such
individuals should have advanced training in noninvasive cardiac
diagnosis and should follow diagnostic standards established by
their hospital and by the veterinary scientific community, including
standards published by the American College of Veterinary Internal
Medicine, specialty of Cardiology (J Vet Internal Med 1993; 7:247-252).
G. Examination of dogs for CHD is aimed at the identification and
classification of phenotypic abnormalities. Heritable aspects of
CHD cannot be addressed unless suitable genetic studies have been
conducted.
METHODS OF EXAMINATION
Clinical Examination
- 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 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 be
become most intense when the stethoscope is centered over the
aortic valve nrea. 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.
- Description of cardiac murmurs - A full description of the cardiac
murmur should be 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.
- Grading of heart murmurs is as follows:
- Grade 1 - a very soft murmur only detected after very carefull
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 - loud murmur: a palpable precordial thrill is not
present or is intermittent
- Grade 5 - a loud cardiac murmur associated with a palpable
precordial thrill; the murmur is 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.
- Effects of heart rate, heart rhythm, and exercise
- 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 munnurs 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. Furthenore,
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
Echocardiography
- The echocardiographic examination should be conducted in a
systematic manner. The examiner must be able to perform two-
dimensional, pulsed-wave Doppler, and continuous wave Doppler
examinations of the heart. The availability of color Doppler is
valuable but not essential for most examinations. The
echocardiographic examination should be performed and interpreted
by individuals with advanced training in cardiac diagnosis. Board
certification by American College of Veterinary Internal Medicine,
Specialty of Cardiology is considered by the American Veterinary
Medical Assaciation 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 appropriate
equipment and have received advanced training in echocardiography.
- The pericardial space, both atria, both ventricles, the great
vessels, and the four cardiac valves should be imaged using long
axis, short axis, apical, and angled image planes as necessary to
perform a comp]ete examination of the heart. Nomenclature should
follow that recommended by the American College of Veterinary
Internal Medicine Specialty of Cardiology. An anatomic diagnosis
may be possible based on two-dimensional imaging; however, the
origin of cardiac murmurs should also be evaluated using Doppler
methods.
- Doppler examination of all cardiac valves should be performed
and recorded. Abnormal flow should be quantified using pulsed or
continuous wave Doppler techniques. Values obtained should be
compared to reference values. The depressant effects of any
tranquilizers or sedatives must be considered when measuring peak
flow velocities. Color Doppler echocardiography should be employed
if available to assess normal and abnormal blood flow patterns.
Identification of abnormal flow across the cardiac septa or shunts
at the ]evel of the great vessels is best done by a combination
of color and pulsed wave Doppler techniques. Typical echocardiographic
features of common congenital heart defects are indicated in Table 1.
- Special attention should be directed to the assessment of flow
patterns and velocities in the left ventricular outlet and ascending
aorta. Optimal alignment with blood flow should be sought for accurate
velocities to be recorded. This may require the use of subxiphoid
(subcostal) transducer positions as well as left apical (caudal
parasternal) transducer placements. In addition to measurement of
peak velocity using pulsed or CW Doppler, the pulsed wave sample
volume should be gradually advanced from the subaortic area into the
ascending aorta to order to identify sudden accelerations in flow
velocity, turbulence. or aortic regurgitation.
- Echocardiographic studies should be recorded on videotape for
subsequent analysis and a written record of abnormal findings should
be entered into the medical record.
TABLE 1. SALIENT AUSCULTATORY AND ECHOCARDIOGRAPHIC FINDINGS
IN CANINE CONGENITAL HEART DISEASE
CONGENITAL TYPICAL AUSCULTATORY DIAGNOSTIC ECHOCARDIOGRAPHIC and DOPPLER
DEFECT FEATURES* ECHOCARDIOGRAPHIC FEATURES
Patent ductus Continuous heart murmur with maximal intensity Continuous retrograde flow from the patent
arteriosus over the left, craniodorsal cardiac base. ductus arteriosus into the pulmonary artery.
Ventricular Systolic murmur with maximal intensity over the The septal defect can ofen be imaged in
septal right ventral precordium: less often maximal multiple imaging planes. Ahnormal, generally
defect intensity is over the pulmonic valve area and high velocity, systolic flow across the septal
pulmonary artery. defect is evident.
Atrial septal Systolic murmur with maximal intensity over the The septal defect can generally be imaged in
defect pulmonic valve area and pulmonary artery. The multiple imaging planes. Abnormal blood flow
second heart sound may be widely split. may be identified crossing the septal defect
into the right atrium.
Pulmonic Systolic murmur with maximal intensity over the Abnormal pulmonary valve and/or subvalvular
stenosis pulmonic valve area and pulmonary artery. anatomy. Sudden acceleration or blood flow in
the right ventricular oullet with turbulent,
high velocity systolic flow across the pulmonary
valve and into the main pulmonary artery.
Valvular and Systolic murmur with maximal intensity over the Abnormal subvalvular or aortic valvular anatomy
subvalvular subaortic or aortic valve area and radiating may be evident. Sudden acceleration of blood flow
aortic into Ihe ascending aorta. The murmur may also in the left ventricular outflow tract with
stenosis be prominent over the right cranial thorax. turbulent, high velocity systolic flow across the
aortic valve and into the ascending aorta.
Concurrent aortic regurgitation is usually present.
Mitral valve Systolic murmur with maximal intensity over the Abnormal anatomy of the mitral valve apparatus.
dysplasia left apex and mitral area. High velocity retrograde systolic flow across the
mitral valve into the left atrium. Concurrent mitral
valve stenosis may be present.
Tricuspid Systolic murmur wirh maximal intensity over the Abnormal anatomy of the tricuspid valve apparatus.
valve tricuspid valve area. High velocity retrograde systolic flow across the
dysplasia tricuspid valve into the right atrium. Concurrent
tricuspid valve stenosis may be present.
Right-to-left Variable - a systolic murmur at the left base Abnormal anatomy related to the cardiac malformations;
cardiac shunt is ofen detected: cyanosis is an important examples include: tetralogy of Fallot, patent ductus
clinical sign. arteriosus with pulmonary hypertension; pulmonary or
tricuspid valve stenosis with atrial septal defect.
Right to left shunting may be documented by Doppler
techniques and/or by contrast echocardiography.
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