INCIDENCE AND PROGNOSIS OF OBSTRUCTION OF THE LEFT-VENTRICULAR OUTFLOW TRACT IN LIVERPOOL (1960-91) - A STUDY OF 313 PATIENTS

Objective-To determine the incidence of the various types of obstructi on of the left ventricular outflow tract in patients born in the five health districts of Liverpool and to compare their prognosis into earl y adult life. Design-Notes of all patients with obstruction of the lef t ventricular outflow tract born in the study area between 1960 and 19 91 were reviewed. Patients with hypoplastic left ventricle, mitral val ve atresia, and those with discordant atrioventricular or ventriculoar terial connections were excluded. Survivors were traced and assessed c linically; eight were lost to follow up. Results-Obstruction of the le ft ventricular outflow tract occurred in 313 patients (67% male), givi ng an incidence of 6.1/10 000 live births. The median (range) age at p resentation was 13.9 months (0-20 yr). Aortic valve stenosis occurred in 71.2%: subvalve in 13.7%, supravalve in 7.7%, and multilevel in 7.4 %. The median (range) duration of follow up was 10.0 (1-29) yr. Aortic regurgitation at presentation occurred more often (p < 0.001) in pati ents with subvalve stenosis than in those with other types of obstruct ion, but there was an increased incidence (p < 0.001) at follow up in patients with valve stenosis. Ninety eight patients (31.3%) underwent operation. The reoperation rate was 27% for valve stenosis and 9% for subvalve obstruction. No patients with supravalve stenosis underwent r eoperation. The median duration from first operation to aortic valve r eplacement (17 patients) was 12.3 years. Hazard analysis confirmed tha t the risk of death was higher in patients presenting at a younger age , with more severe stenosis, and those with subaortic, multilevel obst ruction or a syndrome. Hazard analysis also showed that the risk of a clinical event (surgery, balloon dilatation, or endocarditis) was grea ter in patients who presented at a younger age, with more severe steno sis or aortic regurgitation, and in those with subvalve or multilevel obstruction. Conclusions-Aortic valve stenosis was the most common typ e of obstruction. Hazard analysis indicates that the age and severity of obstruction at presentation have a significant effect on survival a nd freedom from a clinical event. The risk of premature death in patie nts presenting with moderately severe stenosis is reasonably small, in creases considerably in those with subvalve, supravalve, and multileve l obstruction. Patients who present with mild valve stenosis have a go od prognosis. The risk of sudden death is less than previous predictio ns. Patients with subvalve and multilevel obstruction, even when mild at presentation, are more likely to undergo intervention or develop en docarditis than those with valve or supravalve stenosis. Follow up int o adult life is essential.