 Assisted primary graft patency

Assisted primary graft patency credits maintenance of an open graft by interventions performed before it occludes. The distinction is temporal: assistance preserves uninterrupted patency, whereas successful reopening after an occlusion belongs to secondary graft patency. The 1997 reporting standard introduced this distinction explicitly when revising how preventive graft procedures were counted.^[ref]

A qualifying preventive intervention can end primary graft patency without ending assisted primary graft patency. Thus the two endpoints measure different aspects of durability: the former concerns performance without that assistance, while the latter also credits preservation work. They should share a stated time origin and compatible rules before their curves are compared.

Consider an original four-graft cohort. At month 2, one graft undergoes a preventive procedure while still open. At month 3, a different graft occludes, then is successfully reopened at month 4. The other two remain open without procedures. With complete follow-up to month 4, primary patency is $2/4$, assisted primary patency is $3/4$, and secondary patency is $4/4$, assuming the restoration qualifies for the original reconstruction’s secondary endpoint. The reopened graft does not regain an uninterrupted assisted-primary history.

Surveillance influences what is observed and when assistance is undertaken. A narrowing may be detected before occlusion, so reports need their detection and intervention rules. A high assisted-primary proportion can coexist with many preventive procedures; it is not a measure of low procedural burden. Conversely, two cohorts with different surveillance intensity are not made directly comparable merely by using the same endpoint name.

With incomplete follow-up, survival analysis uses a graft patency risk set rather than treating every graft as observed to the final study date. Clinical interpretation also requires the separately measured consequences for tissue function and the patient. Preserving a conduit is an important intermediate outcome, not a complete description of benefit.