Ventricular septal defect in infancy: a combined vectorgraphic and echocardiographic study.

Echocardiograms (echo) and vectorcardiograms (VCG) from 40 infants with ventricular septal defects (VSD) were compared with cardiac catheterization data to assess noninvasively the hemodynamics of VSD. The specific aim was to use VCG parameters of right ventricular hypertrophy and echo parameters which reflect pulmonary artery pressure to identify all patients with a nonrestrictive VSD. The configuration of the QRS vector in the horizontal plane was more reliable than individual voltages in assessing right ventricular systolic pressure. Among patients older than 2 months with a clockwise or anterior two-main-vector horizontal loop, 73% (eight of 11) had a nonrestrictive VSD. However, a counterclockwise or posterior two-main-vector loop was also frequently found (43%, six of 14) in infants with a nonrestrictive VSD. The most useful echo parameter was the ratio of right ventricular preejection period-to-right ventricular ejection time (RPEP/RVET), which closely (r = 0.74) reflected the pulmonary artery diastolic pressure. An elevated RPEP/RVET to greater than 0.30 was always associated with a nonrestrictive VSD, although many patients (36%, five of 14) with a nonrestrictive VSD had a normal ratio. By combining both echo and VCG parameters, a nonrestrictive VSD was correctly identified in all patients, while a restrictive VSD was correctly identified in 81% (21 of 26).