Jr. Kelley et al., DIMINISHED VENOUS VASCULAR CAPACITANCE IN PATIENTS WITH UNIVENTRICULAR HEARTS AFTER THE FONTAN OPERATION, The American journal of cardiology, 76(3), 1995, pp. 158-163
Patients who have undergone Fontan's operation are known to have impai
red cardiac output response to dynamic exercise, This may be due to ei
ther poor cardiac function or a limited ability to mobilize blood from
capacitance vessels due to increased resting venous tone, We tested t
he latter hypothesis by determining venous vascular capacitance-at res
t and during orthostatic stress produced by lower body negative pressu
re (LBNP) in 6 subjects who had undergone the Fontan operation and 6 h
ealthy age-, sex-, height-, and weight-matched controls, Resting blood
volume was similar for Fontan and control subjects (79 +/- 6 vs 70 +/
- 3 ml/kg body weight, respectively), while central venous pressure (C
VP) was elevated in Fontan subjects (18.4 +/- 1.0 vs 3.5 +/- 0.9 mm Hg
, p <0.05). Forearm venous capacitance at a distending pressure of 40
mm Hg was less in Fontan subjects than in controls (2.6 +/- 0.1 vs 3.9
+/- 0.5 ml/100 ml), while resting plasma norepinephrine level was ele
vated in Fontan subjects (255 +/- 28 vs 144 +/- 9 pg/ml, p <0.05). The
increase in calf volume (1.6 +/- 0.2 vs 2.3 +/- 0.2 ml) and decrease
in CVP (-5,0 +/- 0.5 vs -6.7 +/- 1.1 mm Hg) during -30 mm Hg LBNP were
smaller for Fontan than control subjects (p <0.05). Reduced forearm v
enous capacitance and diminished pooling of blood into capacitance ves
sels of the leg during orthostatic stress indicated higher venous tone
in Fontan than control subjects, We propose that increased resting ve
nous tone in Fontan subjects may limit their ability to mobilize blood
from capacitance vessels during exercise and may contribute to impair
ed cardiac output response.