Vasopressin and angiotensin II contribute equally to the increased afterload in rabbits with heart failure
Study objective - Vasopressin, like angiotensin, has both vasoconstrictor and fluid retaining properties and therefore may make an important contribution to the pathogenesis of low output congestive heart failure. The study aimed to examine the relative importance of the renin-angiotensin system and vasopressin in an animal model of heart failure.Design - The acute haemodynamic effects of vasopressin receptor blockade with a selective antagonist, d(CH2)5 DAVP (AVPA) (30 μg·kg-1) and angiotensin converting enzyme inhibition with captopril (1 mg·kg-1) were compared. The effect of combined blockade (ie, vasopressin receptor antagonist + angiotensin converting enzyme inhibitor) was also examined.Experimental material - Rabbits, 2.5-3.5 kg, with doxorubicin induced cardiomyopathy and heart failure (n = 20) were used. There were 15 controls.Measurements and main results - Both AVPA and captopril produced significant increases in cardiac output (11% and 13% respectively) and falls in peripheral vascular resistance (21% and 17% respectively). Inhibition of the two vasoconstrictor systems was additive and resulted in a fall in peripheral vascular resistance to levels found in normal animals.Conclusions - Vasopressin and angiotensin II make equal contributions to the raised peripheral vascular resistance observed in this model of heart failure. Vasopressin inhibition may be useful in the treatment of heart failure either alone or as an adjunct to angiotensin converting inhibition.