Isolated, non-reoperative congenital mitral valve abnormalities in adults are rare.1,2 Mitral pathology concurrent with other cardiac anomalies is less rare. Atrial septal defect is the third commonest congenital cardiac lesion presenting in adulthood, occurring in an estimated 1/5700 persons, nearly 10% are ostium primum defects, and almost all primum defects have an associated mitral valve cleft.3 Congenital mitral valve pathology such as arcade or parachute mitral valve very rarely present in adulthood, though the patients surviving unrepaired to adulthood may be milder forms, amenable to repair.
In contrast to the rarity of non-reoperative mitral pathology presenting in adulthood, patients needing reoperation for formerly corrected mitral pathology represent an expanding adult population. Survivors of corrective surgery in infancy and childhood add an estimated 8960 new adults cases annually to the adult congenital population in the US and there are over 1,000,000 adults living in the US today with congenital heart disease.4 The prevalence of atrioventricular septal defect (AVSD) is 5.3 per 10,000 live births.5 Mitral insufficiency is the principal reason for reoperation in the AVSD population. For patients undergoing an anatomic repair for complete or partial AVSD in infancy, freedom from reoperation for mitral regurgitation (MR) is 81 to 83% at 15 years, so the number of adults presenting with the need for reoperative mitral valve surgery is steadily increasing as successful infant repairs continue to accrue.6
Consideration of the normal mitral apparatus is important to the success of any repair for congenital mitral valve abnormalities. Congenital mitral valve pathology is widely variable between patients, demanding an individualized approach to each. A systematic analysis of the annular, leaflet, and subvalvar support structures informs a surgical strategy that can be tailored to the individual.
The normal mitral valve is attached to a dynamic, saddle-shaped fibrous annulus with the horn of the saddle at the anterior annulus, and the low points of the saddle at the commissures—a shape that minimizes leaflet stress through the cardiac cycle (Fig. 39-1).7 The annulus is dynamic through the cardiac cycle, with apical to basilar displacement of the entire annulus, annular “folding” that changes the planar versus saddle configuration of the annulus, and a 23 to 40% contraction in annular circumference between systole and diastole.8
Descriptive anatomy of the mitral valve. The annulus is saddle-shaped, with commissures at the low points. Anterior and posterior leaflets and their subvalvar support structures are described as anterior and posterior components of 3 segments.
The anterior, or aortic leaflet, occupies one-third of the annular circumference, is broader than the posterior leaflet, and is anchored in its continuity with the aortic annulus. ...