Assessment of patent ductus arteriosus shunting using diastolic pressure analysis.

Ductal shunting significantly affected the time necessary for aortic diastolic pressure to fall to one-half an initially selected value (t1/2). Fourteen premature infants with clinical evidence of left-to-right ductal shunting had a mean t1/2 of 277 msec (range 133 to 383 msec) compared with a mean t1/2 of 455 msec (range 332 to 567 msec) in 14 neonates with no clinical evidence of ductal shunting (P less than 0.01). Seven older infants with ductal shunting confirmed at cardiac catheterization had a mean t1/2 of 360 msec (range 240 to 392 msec). Infant catheterization data and animal studies are suggestive of an inverse relationship between the magnitude of shunt and the t1/2. The t1/2 determined by diastolic pressure analysis is a useful method for serial evaluation of ductus arteriosus shunting.