Page 988 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

CHAPTER 8

CARDIOVASCULAR SYSTEM
VetBooks.ir M Kim J McGurrin 963

In most instances the horse is first and foremost future use of the horse is critical in determining
a performance animal and the potential impact the significance of a finding and in planning future
of cardiovascular disease on performance and action. An abnormality that is unlikely to produce
re-sale value is important. Cardiovascular overt clinical signs in a pleasure animal may result
abnormalities of variable clinical significance in drastic performance limitations in a racehorse.
are frequently encountered in the horse. For example, atrial fibrillation (AF) may be unrec-
Heart murmurs and arrhythmias are common. ognised for an extended period of time in a pleasure
Congenital anomalies are infrequent in the horse but results in immediate inadequate perfor-
horse compared with small animal species. mance in a racehorse.
Performance data may be used to assess the
CARDIOVASCULAR EXAMINATION impact of an abnormality. This is of benefit in deter-
mining whether suboptimal performance has been
Evaluation of the cardiovascular system involves, at present and, if so, whether the animal has ever per-
minimum, acquiring a detailed history and perform- formed to expectations. Performance records can
ing a complete physical examination. Additional also be used to assess whether deterioration in per-
diagnostic modalities such as electrocardiography, formance has been sudden in onset or progressive.
echocardiography and radio telemetry may be nec- In racehorses they are used to assess what stage of
essary. More invasive diagnostic techniques such as the race was affected. Knowledge of the past use
cardiac catheterisation are infrequently performed in of a horse is an asset in assessing clinical findings.
the horse and are usually limited to referral facilities. For example, large cardiac size on echocardiography
would be considered as a normal finding in a horse
History that has undergone intensive training, but it may be
A detailed history is particularly important. Overt suggestive of disease in an animal with no perfor-
heart failure is uncommon, and horses are often pre- mance history. The proposed future use of the horse
sented with relatively mild disease when compared is essential in determining the potential impact of an
with small animal species. Frequently, an abnormal- abnormal finding.
ity is detected during either routine or pre-purchase It is important to determine the extent and nature
examinations. The veterinarian is often faced with of the clinical signs observed. An exact description of
the task of determining the significance of such the owner’s complaint is beneficial. The past medical
findings. In a high-level performance animal, even a history of the animal may help determine the role of
slight deterioration in performance may precipitate a current clinical findings. Documentation of a mur-
request for cardiovascular examination. mur over time and concurrent performance history
The signalment of the animal may aid in assess- may help elucidate the significance of the murmur.
ing cardiac disease. With the exception of con- Respiratory and musculoskeletal diseases are other
genital heart disease in the Arabian horse, breed potential causes of suboptimal performance. While
association with specific cardiac disease is uncom- respiratory signs may indicate underlying heart
mon. Aortic root rupture most commonly occurs failure, primary respiratory disease is considerably
in aged breeding stallions. The past, present and more common.