W. E. Siegenthaler

W. E. Siegenthaler coauthored the 1979 primary evaluation of coronary angioplasty with A. R. Grüntzig and A. Senning. The published byline records these initials. The report combined a clinical case series with measurements of the narrowed vessel and its pressure drop, and explicitly called for a prospective randomized comparison with surgical and medical management.^[ref]

This contribution illustrates a distinction between demonstrating that an intervention can change a physical obstruction and establishing how its outcomes compare with alternatives. A selected series can document feasibility and observed complications. It does not automatically supply the outcomes that the same patients would have had under another treatment.

The report's 32 technical successes among 50 treated patients give the observed fraction $32/50=0.64$.^[ref] That denominator is the treated series, not every person with coronary artery disease or everyone considered for an intervention. Eligibility, selection and the definition of success determine what the fraction describes.

An original case mix example shows why a comparison can change even if subgroup responses do not. Suppose a hypothetical endpoint occurs with probabilities $0.9$ and $0.5$ in two patient groups. A series containing $80\%$ from the first group has modeled ratewhereas a series containing only $20\%$ from that group has rate $0.58$. The difference $0.24$ was created entirely by group composition in this model. It is not a treatment-effect estimate or a result attributed to Siegenthaler.

A clinical trial with a justified comparison addresses a different question from a selected feasibility series. Randomized experiment design helps control treatment assignment; follow-up and endpoint definitions still need scrutiny. Siegenthaler's jointly authored report is scientifically notable for presenting the initial clinical evidence while recognizing the further comparative evidence required.