APICAL MUSCULAR VENTRICULAR SEPTAL-DEFECTS BETWEEN THE LEFT-VENTRICLEAND THE RIGHT-VENTRICULAR INFUNDIBULUM - DIAGNOSTIC AND INTERVENTIONAL CONSIDERATIONS

Background Effective transcatheter or surgical closure of apical muscu lar ventricular septal defects (VSDs) requires accurate delineation of variable and often complex anatomy. These defects have generally been considered as communications between the apexes of both left and righ t ventricles. Methods and Results Among 50 consecutive patients with m ultiple muscular VSDs referred for transcatheter device closure betwee n October 1987 and April 1993, a subset of 10 patients (aged 7 days to 28 years) with apical muscular VSDs shared a unique set of anatomic c haracteristics: (1) large and often single opening in the left ventric le; (2) multiple right ventricular openings in the anterior aspect of the apical septum; and (3) separation of the right ventricular apical region into which the VSDs open from the rest of the right ventricular inflow and outflow by prominent muscle bundles. Additional analysis o f the anatomy by use of echocardiography and cineangiography showed th at these muscular defects were between the left ventricular apex and r ight ventricular infundibular apex. In 6 patients, the transcatheter d evices used to create a septum in these hearts were placed in the righ t ventricle, straddling muscle bundles that separated the apical VSD f rom the rest of the right ventricular inflow and outflow, resulting in incorporation of a portion of the right ventricular infundibular apex into the physiological left ventricle. Three patients had devices pla ced between the apexes of the left ventricle and the infundibulum. The defect closed spontaneously within the right ventricle in 1 patient. One patient died after surgery for tetralogy of Fallot in situs invers us. The remaining 9 patients were all clinically well at the time of t heir most recent follow-up visit (follow-up duration, 32+/-11 months). This distinct type of apical VSD was identified by echocardiography i n 20 of 274 patients who were followed up clinically for muscular VSDs . Conclusions Left ventricular-infundibular apical VSDs constitute a d istinct morphological type of muscular VSD that can be distinguished b y echocardiography and cineangiography. In selected cases, the infundi bular apex can be separated from the rest of the right ventricular inf low and outflow to eliminate flow across these defects.