These have recently become the treatment of choice for treating congestive heart failure in people and dogs, since they have been shown fairly conclusively to prolong life.
Late congestive heart failure leads to vasoconstriction by a variety of mechanisms including increased sympathetic tone, renin - angiotensin system activation and increased ADH concentrations. Arterial vasodilatation reduces afterload, myocardial work, oxygen consumption, pressure across the mitral valve and thus increases cardiac output. Venous vasodilatation reduces preload and oedema.
congestive heart failure
mitral regurgitation
control of ABP during anaesthesia
navicular disease (isoxuprine)
(essential hypertension - not recognised in domestic animals)
hypotension
reflex tachycardia
plus effects specific to individual drugs
A very large number of drugs can cause vasodilatation; it is usually regarded as an undesirable side effect. The main group of vasodilators used for chronic heart failure is the angiotensin converting enzyme inhibitors. These are given orally for long term treatment. Nitrates and calcium channel blockers are less commonly used for both acute and chronic heart failure. They can be given by a variety of routes. Great care is needed if they are given iv in acute situations. A range of other drugs are used rarely, usually in a desparate attempt to find something that works!
Angiotensin converting enzyme inhibitors
Nitrates
Other vasodilators
