CHAPTER 28: CARDIAC DISEASE
Introduction
Cardiac disease is rare in the horse. The horse’s lifestyle of continual exercise, low fat and low sugar diet and relatively little stress promotes the well being of the heart. The cardiac diseases that do occur in horses are most often related to congenital defects or ________________ damage. The diagnosis of cardiac disease in the horse may be more difficult than in people, as the types of disease occurring in the equine heart are not related to hypertension or high cholesterol levels, both of which are easily tested. The most common tool used in the diagnosis of veterinary cardiac disease is the ______________________ . This allows the veterinarian to listen to the contraction of the atria and the ventricles, and to assess the flow of blood through the heart valves. Auscultation can indicate the presence of disease but is often not able to pinpoint the exact location or nature of the pathology. ________________________ are ultrasonic pictures of the structures of the heart. These can be used to detect structural abnormalities of the heart chambers or of the valves. Congenital defects or areas of damage may be detected by ultrasound imaging. (EKG/ECG) are devices that detect and record the electrical activity of the heart over a set period of time. Electrodes are placed over various locations on the thorax that correspond to particular regions of the heart. The electrodes then monitor the electrical activity and send the readings to a machine which integrates the information and presents it as a series of waves on a graph. The duration, amplitude, deflection and shape of each wave indicates the functionality of particular parts of the heart. __________________________ The P-wave denotes the depolarization, or contraction, of the _____________ . This normally occurs first in the right atrium, followed closely by the left. The atrial depolarization creates the sinus rhythm of the heart. The QRS-complex denotes the depolarization, or contraction, of the _________________ , with the Q-wave indicating the depolarization of the intraventricular septum. The QRS-complex is usually positive and has a sharply spiking appearance. The T-wave denotes the repolarization, or relaxation, of the ventricles. The U-wave is often not present or is very small. It denotes the repolarization, or relaxation, of the papillary muscles or Purkinje fibres. By combining clinical presentation, auscultation, EKG and ECG the veterinarian is generally able to evaluate the structure of the heart, the function of the heart and the flow of blood through the heart chambers and valves.
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