This study examines the hypothesis that nifedipine may increase splanc
hnic vascular capacitance and thus change the distribution of blood be
tween the splanchnic and pulmonary circulation in heart failure patien
ts. Relative regional blood volumes were determined by equilibrium blo
od pool scintigraphy during a 10 min baseline period and for 30 min af
ter nifedipine 20 mg sublingually, with simultaneous recordings of sys
temic and pulmonary arterial pressures, hepatic venous wedge pressure,
and cardiac output. Eight patients with ischaemic heart failure recei
ved nifedipine. Four patients served as controls. Nifedipine reduced m
ean arterial pressure and systemic vascular resistance in every patien
t. There were no significant changes in the relative blood volumes of
the intestinal, hepatic, or splenic regions or in hepatic venous wedge
pressure (reflecting portal venous pressure), suggesting unchanged sp
lanchnic vascular pressure-volume relationship. Nifedipine caused a 6.
3+/-1.0% increase in relative pulmonary blood volume and a slight incr
ease in pulmonary vascular distending pressure from 16.1+/-2.9 mmHg to
17.5+/-2.8 mmHg (P<0.05), suggesting that the increase in pulmonary b
lood volume was passively mediated. In conclusion, nifedipine did not
change splanchnic vascular capacitance, but caused a small increase in
pulmonary blood volume, which probably was a passive response to incr
eased distending pressure.