Page 1004 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Cardiovascular system 979

VetBooks.ir Table 8.4 (Continued) Common drugs used in the management of cardiovascular disease

ATROPINE AND GLYCOPYRROLATE
• Main application. Used for the treatment of bradycardia, most commonly during anaesthesia. Have been used as a diagnostic
tool in heart block and sinus arrhythmia (removal of parasympathetic tone should remove these arrhythmias)
• Toxic effects. Mydriasis and decreased intestinal secretions and motility are possible even at therapeutic levels. Ileus and colic
may develop. Tachycardia without increased contractility and arrhythmias may also occur
• Dose (therapeutic). 0.005–0.01 mg/kg for bradycardia (both agents)
ENALAPRIL
• Main application. Inhibits angiotensin convering enzyme, decreasing afterload. May be beneficial in management of horses with
aortic regurgitation or aortic root rupture/aneurism. Considered potentially to slow progression of disease in aortic regurgitation.
Must be withdrawn prior to competition
• Toxic effects. Hypotension, diarrhoea and anorexia may develop
• Dose. 0.25–0.5 mg/kg p/o q24 h
OTHER AGENTS
• A number of other medications have reportedly been used in the management of equine cardiac arrhythmias, but much of the
information available on these is anecdotal.
• Hydralazine (0.5 mg/kg i/v q12 h) has been used as a vasodilator to reduce afterload
• The use of flecainide in the management of limited cases of equine AF has been reported. Anecdotal reports and one published
report on the use of this medication in clinical cases have not been favourable
• The use of amiodarone in equine AF has been limited both in scope and efficacy

8.16

Fig. 8.16 Sinus arrhythmia. Base–apex lead recorded from a clinically normal Standardbred gelding presented
for evaluation of arrhythmia detected at routine physical examination. Normal P, QRS and T complexes with
normal temporal relationship (sinus rhythm) occurring at irregular intervals. An association with respiration
was not detected and the arrhythmia abated with exercise.

8.17

Fig. 8.17 Sinus arrest/block. Base–apex lead recorded from the same horse as in 8.14. A 6-second interval
between complexes is present in this recording and pauses of up to 8 seconds were detected. No clinical
abnormalities were detected, the cardiac rhythm was normal at exercise and the horse was performing to
expectations. The cause of the arrhythmia in this horse was unknown.