Читать книгу Manual of Equine Anesthesia and Analgesia - Группа авторов - Страница 144

 Initially assessed by auscultation.

 Further definition with echocardiography is indicated.

 Murmurs are generated by turbulent blood flow often due to back flow through a heart valve or flow through an abnormal or persistent anatomic opening (e.g. a ventricular septal defect (VSD), patent foramen ovale).

 Left‐sided systolic murmursLeft AV (mitral) valve regurgitationUsually occurs as a holosystolic, soft blowing murmur.May be focal or radiate mildly to widely. PMI at the left heart base.Ventricular septal defect (VSD)Murmurs are pansystolic, sound quality may be anywhere from soft‐blowing to a coarse, rumbling murmur.May be focal or they may radiate widely.Usually loudest on right side but may be heard on the left; may be louder on the left if there is right to left shunting.Less commonly, a VSD may be located such that there is shunting from the left ventricle to the right ventricular outflow tract. The PMI with this type of defect is at the left‐third ICS, under the triceps muscle.Valvular endocarditisCan occur at any or a combination of heart valves.Left‐sided lesions are more common in the horse than right‐sided lesions.Murmurs are due to both altered blood flow passing by the lesion (anterograde) as well as regurgitant flow through the valve.The quality generally depends on the size and location of the valvular lesion(s).

 Left‐sided diastolic murmursAortic valve regurgitation (AVR)A very common condition in older horses, usually over 15‐years‐of‐age.This is classically a decrescendo murmur which may be soft to coarse in quality.The sound may be quite profound and has been termed a “dive bomber” murmur.Aortic valve endocarditis – similar to AVR.

 Right‐sided systolic murmursRight AV (tricuspid) valve regurgitationThe PMI is usually at the fourth ICS due to flow from the right ventricle to the right atrium.Typically, a holosystolic, soft, blowing murmur.Aortic valve regurgitationThe PMI is usually left‐sided, but the murmur is often heard to a lesser degree on the right side (see above).Ventricular septal defectThe murmur is usually loudest on the right side of the chest as there is shunting from the left‐to‐right side of the heart.The common defects are located high in the interventricular septum.Occurs most commonly in Arabian or Arabian cross‐breed horses, indicating that this breed is genetically predisposed to the condition.

 Continuous (systolic and diastolic) murmursPatent (persistent) ductus arteriosus (PDA)This type of murmur may be heard in the newborn foal but usually resolves in the first days‐to‐weeks of life.It may persist beyond this period; however, this condition is very uncommon to rare in horses.