Background Few studies have investigated the clinical advantages of surgica
l correction with the morphologic left ventricle (MLV) instead of the morph
ologic right ventricle as a systemic ventricle (SV) in patients with congen
ital heart disease.
Methods Twenty-four healthy control subjects (group A1), 6 patients with is
olated congenitally corrected transposition of the greet arteries (TGA) (gr
oup A2), 16 patients with TGA who had undergone an arterial switch operatio
n (group B1), 18 patients with TGA who had undergone a venous switch operat
ion (group B2), 9 patients with atrioventricular and ventriculoarterial dis
cordance who had undergone a double switch operation (group C1), and 6 pati
ents with atrioventricular and ventriculoarterial discordance who had under
gone a conventional external conduit operation From the MLV to the pulmonar
y artery (group C2), performed treadmill exercise testing. Their heart rate
(HR), oxygen uptake ((V)over dotO(2)), and oxygen pulse (O-2 pulse), which
reflects individual stroke volume, were measured, and contractile function
was assessed by echocardiography.
Results The peak HR for the patients after a definitive operation were sign
ificantly lower than that in group Al and was correlated with peak(V)over d
otO(2) (r = .67 P < .0001). The peak(V)over dotO(2) and peak O-2 pulse for
the groups A2 and B2 were significantly lower than those for the groups Al
and B1, respectively. The peak O-2 pulse data were strongly correlated with
those of peak(V)over dotO(2) (r = 0.91, P < .0001). The left ventricular e
jection fraction was significantly lower in groups B1 and C1 than in group
Al and was correlated with peak(V)over dotO(2) (r = .50, P < .01). No signi
ficant differences in (V)over dotO(2), HR, and O-2 pulse at peak exercise w
ere observed between groups C1 and C2.
Conclusions Chronotropic incompetence and an impaired response of the strok
e volume of the MRV during exercise are partly responsible for the reduced
exercise capacity in groups A2 and B2 compared with groups with the MLV as
an SV, and the SV function at rest is also related to exercise capacity. Su
periority of the double-switch operation compared with the conventional con
duit operation was not observed. A longer-term Follow-up is necessary befor
e the advantages of these 2 operations can be compared.