Background-Familial combined hyperlipidemia (FCHL) is a common hereditary d
isorder of lipoprotein metabolism estimated to cause 10% to 20% of prematur
e coronary heart disease. We investigated whether functional abnormalities
exist in coronary reactivity in asymptomatic patients with FCHL.
Methods and Results-We studied 21 male FCHL patients (age, 34.8+/-5.4 years
) and a matched group of 21 healthy control subjects. Myocardial blood flow
(MBF) was measured at baseline and during dipyridamole-induced hyperemia w
ith PET and O-15-labeled water. The baseline MBF was similar in patients an
d control subjects (0.79+/-0.19 versus 0.88+/-0.20 mL.g(-1).min(-1), P=NS).
An increase in MBF was seen in both groups after dipyridamole infusion, bu
t MBF at maximal vasodilation was lower in FCHL patients (3.54+/-1.59 versu
s 4.54+/-1.17 mL.g(-1).min(-1), P=0.025). The difference in coronary flow r
eserve (CFR) was not statistically significant (4.7+/-2.2 versus 5.3+/-1.6,
P=NS, patients versus control subjects). Considerable variability in CFR v
alues-was detected within the FCHL group. Patients with phenotype IIB (n=8)
bad lower now during hyperemia (2.5+/-1.2versus 4.2+/-1.5 mL.g(-1).min(-1)
, P<0.05) and lower CFR (3.4+/-2.1 versus 5.4+/-2.0, P<0.05) compared with
phenotype IIA (n=13).
Conclusions-Abnormalities in coronary flow regulation exist in young asympt
omatic FCHL patients expressing phenotype IIB (characterized by abnormaliti
es in both serum cholesterol and triglyceride concentrations). This is in l
ine with previous observations suggesting that the metabolic abnormalities
related to the pathophysiology of FCHL are associated with the phenotypes I