AUTHORS' SYNOPSIS: In animal experiments regurgitant flow through competent and incompetent pulmonary valves was evaluated with electromagnetic flow velocity catheters by using the ratio of the separately integrated backward and forward flow velocity signals. This ratio was obtained with a special purpose analog computing circuit set by an in-vitro zero flow reference signal, which was in good agreement with in-vivo zero flow signals.,
Cardiovascular Research

Van Der Mark, F. (F.), Rohmer, J. (J.), & Zijlstra, W. (1976). Pulmonary valve incompetence: I. Evaluation using electromagnetic flow velocity catheters and a new valve insufficiency analyser. Cardiovascular Research (Vol. 10, pp. 37–45). doi:10.1093/cvr/10.1.37