BISFERIENS PEAKS IN THE RADIAL ARTERY PRESSURE WAVE DURING PATENT DUCTUS-ARTERIOSUS IN NEWBORN-INFANTS - RELATIONSHIP WITH ASCENDING AORTICFLOW

Previously, we found evidence that bisferiens peaks in the radial arte ry pressure wave in the newborn infant may suggest the presence of a l eft-to-right shunt through a patent ductus arteriosus (PDA). The purpo se of the present study was to analyze the origin of this pulsus bisfe riens. Starting from the assumption that the radial artery pressure wa ve form is similar to the aortic pressure wave form, as described prev iously, we attempted to explain the bisferiens peaks on the basis of e cho-cardiographically obtained ascending aortic flow. We studied 11 pr eterm mechanically ventilated infants with a left-to-right shunt throu gh a PDA and 7 without. Aortic volume flow was established echocardiog raphically, and radial artery blood pressure measurement was performed with a high fidelity catheter-manometer system. Ascending aortic peak flow during PDA was significantly higher in the case of PDA, compared with the case without PDA. An augmented peak flow with an abrupt decl ine after the high peak in PDA, resulting in a sharp pressure peak wit h a steep decline after the peak, was thought to explain the first sha rp peak of pulsus bisferiens. An abrupt decline of flow after peak flo w is thought to be due to the fast runoff of blood through the ductus. According to the pulsatile pressure dynamics theories, which state th at pressure wave forms consist of forward and backward wave forms, the second peak of the pulsus bisferiens can be explained by the return o f the reflected (backward) wave form when the forward wave form has al ready considerably decreased. We conclude that the bisferiens peaks fo und in PDA result from a combination of large stroke volume (augmented first peak) and large runoff (quick decline of the forward wave) befo re the return of the reflected wave.