Fig. 11.4B ). The atrium-to-ventricle connections, however, are normal (concordant), with the right atrium joining the right ventricle and the left atrium emptying into the left ventricle.
The functional outcome is separation of the systemic and pulmonary circulations, a condition incompatible with postnatal life unless a shunt (such as a VSD) allows delivery of oxygenated blood to the aorta. Indeed, VSDs occur in one third of cases (see
Fig. 11.4, B ). There is marked right ventricular hypertrophy, since that chamber functions as the systemic ventricle; the left ventricle is hypoplastic, since it pumps only to the low-resistance pulmonary circulation. Some newborns with transposition of the great arteries have a patent foramen ovale or PDA that allows oxygenated blood to reach the aorta, but these tend to close; such infants typically require emergent surgical intervention within the first few days of life.
The dominant manifestation is cyanosis, with the prognosis depending on the magnitude of shunting, the degree of tissue hypoxia, and the ability of the right ventricle to maintain systemic pressures. Without surgery (even with stable shunting), most patients with uncorrected transposition of the great arteries die within the first months of life. However, improved surgical techniques now permit definitive repair, and such patients often survive into adulthood.
Congenital obstruction of blood flow can occur at the level of the heart valves or more distally within a great vessel. Obstruction can also occur proximal to the valve, as with subpulmonic stenosis in tetralogy of Fallot. Relatively common examples of congenital obstructions are pulmonic valve stenosis, aortic valve stenosis or atresia, and coarctation of the aorta.
Coarctation (narrowing, or constriction) of the aorta is a common form of obstructive congenital heart disease (see
Table 11.1 ). Males are affected twice as often as females, although females with Turner syndrome frequently have coarctation. There are two classic forms (Fig. 11.5
An “infantile” preductal form featuring hypoplasia of the aortic arch proximal to a PDA
An “adult” postductal form consisting of a discrete ridgelike infolding of the aorta, adjacent to the ligamentum arteriosum
Coarctation can occur as a solitary defect, but in more than half of the cases is accompanied by a bicuspid aortic valve. Aortic valve stenosis, ASD, VSD, or mitral regurgitation also can be present.
Coarctation of aorta
Fig. 11.5 Coarctationoftheaortawith(“infantile”orpreductalform)andwithoutapatentductusarteriosus(PDA)(“adult”orpostductalform);arrow indicatesdirectionofbloodflow.Ao, Aorta;LA, leftatrium;LV, leftventricle;PT, pulmonarytrunk;RA, rightatrium;RV, rightventricle.
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Fig. 11.6 Coarctationoftheaorta,postductaltype.Thecoarctationisasegmentalnarrowingoftheaorta(arrow).Suchlesionstypicallymanifestlaterinlifethanpreductalcoarctations.Thedilatedascendingaortaandmajorbranchvesselsaretotheleftofthecoarctation.Thelowerextremitiesareperfusedpredominantlybywayofdilated,tortuouscollateralchannels.(Courtesy of Sid Murphree, MD, Department of Pathology, University of Texas Southwestern Medical School, Dallas,Texas.)