COMPUTER-ASSISTED MODELING OF BLOOD-FLOW - THEORETICAL EVIDENCE FOR THE EXISTENCE OF OPTIMAL FLOW WAVE PATTERNS

The purpose of this study was to model blood-flow waveforms in order t o examine the relationship between various waveform shapes and input i mpedance spectra. Twenty distinct single cardiac cycle flow waveforms having the same mean flow and heart rate were created based on clinica l and published observations. The ''best'' waveform was one with a ste ep flow upstroke, a high peak flow value, swift deceleration following peak flow, and flow reversal during diastole. Each flow waveform was paired with 20 computer-generated pressure waveforms to calculate inpu t impedance spectra by discrete Fourier transformation. ''Favorable'' flow waveforms were associated consistently with a lower characteristi c impedance (average of 4th-10th harmonics, Z(av)) irrespective of the shape or magnitude of the input pressure wave. Z(av) corresponds to t he degree of compliance of the vascular bed and could be expected to b e lower under favorable outflow conditions and in non-diseased vessels . In conclusion, this study provides theoretical evidence for the exis tence of optimal flow wave patterns and supports the notion of flow wa veform assessment for diagnostic purposes.