Shone Complex: An Under-recognized Congenital Heart Disease With Substantial Morbidity in Adulthood

Background: Shone complex consists of a constellation of left-sided, usually obstructive, cardiac lesions, including supravalvar mitral ring, parachute mitral valve, subaortic stenosis, and aortic coarctation. Incomplete Shone complex consists of a mitral valve anomaly associated with lesions involving the subaortic region, aortic valve, or thoracic aorta. There is a paucity of data regarding long-term outcomes in adults with Shone complex. Methods: We reviewed records of adults with complete or incomplete Shone complex followed at the Montreal Heart Institute between 1982 and 2014. Results: Among 4189 adults with congenital heart disease, 28 (0.67%) patients (mean age, 35 +/- 11 years; 50% women) had complete or incomplete Shone complex and were followed for a median of 8 years. Only 39% were previously diagnosed as having Shone complex. The most common defects were congenital mitral stenosis (93%), aortic coarctation (75%), and bicuspid aortic valve (71%). Heart transplantation was required in 2 patients (7.1%) at age 22 and 28 years, respectively. Overall, 48% had cardiovascular hospitalizations during adulthood, predominantly for arrhythmias or heart failure. Freedom from cardiovascular intervention was 55%, 18%, and 8% at 10, 20, and 30 years of age, respectively. Although aortic coarctation was the most common indication for initial intervention (61%), adult interventions occurred predominantly for aortic valve/left ventricular outflow tract (60%) and mitral valve (33%) lesions. Conclusions: Shone complex is an under-recognized entity associated with relatively low mortality in adulthood but substantial morbidity related to arrhythmias, heart failure, and interventions. Increased awareness of this condition and associated complications may allow for more tailored follow-up.