Table 1.

Lexicon of definitions

End point: end point is defined as a study outcome and how it is measured. End points can be primary, secondary, or exploratory; binary or continuous; and single or composite. All study end points should be determined a priori.

IDBD: the abbreviation IDBD refers to intervention, drug, biologic, or device.

Arteriovenous dialysis access circuit: the complete vascular circuit starting with the heart and including the complete feeding artery from its central origin, the arteriovenous dialysis access, and the complete venous drainage up to the superior vena cava-right atrial junction or the inferior vena cava-right atrial junction in the case of a lower extremity dialysis access.

Arteriovenous dialysis access patency: the status (yes/no) of an arteriovenous dialysis access with detectable blood flow through and beyond the anastomosis shown by either an imaging modality or physical examination (presence of a palpable thrill or audible bruit along some point of the arteriovenous dialysis access beyond the arteriovenous anastomosis).

Definitions of arteriovenous access patency durations: definitions of arteriovenous access patency durations are timeframes in which arteriovenous dialysis access is patent (defined above) and can be used for a variety of IDBD studies; thus, it may be necessary for patency to be defined from the time of initial arteriovenous dialysis access creation, the time of an index intervention, or both depending on the nature of the study (Figure 2).

Target lesion: a predefined area toward which the IDBD used in the trial was directed. This should be defined a priori in the study protocol.

Target zone: the area within the arteriovenous dialysis access circuit that encompasses the target lesion toward which the IDBD intervention is directed and the adjacent ± “X” portion of the access. This should be defined a priori in the study protocol. For example, target lesion ±2 cm.

Significant dialysis access stenosis: a reduction in the vessel luminal diameter (graft or draining venous system) that is ≥50% reduction in normal vessel diameter (see note below) accompanied by hemodynamic, functional, or clinical abnormalities not explained by reasons other than the dialysis vascular access lesion. In general, the hemodynamic, functional, or clinical abnormality should be present for two or more dialysis sessions.

Dialysis vascular access abandonment: the act of discontinuing the clinical use of a dialysis vascular access, because it is no longer functional and considered to not be salvageable. An abandoned dialysis access is one that can no longer be used for one- or two-needle prescribed dialysis, because it is unable to provide adequate blood flow and/or is deemed unsafe for the patient, and the associated problem cannot be corrected by any intervention: medical, endovascular, or surgical.

Intervention rate: the number of IDBD interventions performed (type to be specified in the protocol) on a dialysis vascular access within a defined time period. For example, the term “intervention rate, postintervention cumulative patency” would indicate the number of interventions performed during the postintervention period from index procedure to access abandonment. Additionally, the types of intervention and any complications incurred should be clearly indicated as per the study protocol.

Patency definitions

Patency from the time of dialysis access creation (figure 2 Upper panel):

Access primary patency: the time from arteriovenous dialysis access creation to the first of one of the following events: access thrombosis; any intervention designed to facilitate, maintain, or re-establish patency; the access reaches a censoring event as specified a priori in the study protocol; or study end.

Access assisted primary patency: term used to describe an access that needed assistance to maintain continued patency during the study period. It is calculated as the time from arteriovenous dialysis access creation to the first of one of the following events: access thrombosis, the access reaches a censoring event as specified a priori in the study protocol, or study end. This period includes all intervening interventions (surgical or endovascular) designed to maintain the functionality of the dialysis vascular access as long as patency is not lost.

Access cumulative patency: the time from arteriovenous dialysis access creation to access abandonment, when the access reaches a censoring event as specified a priori in the study protocol, or study end, including intervening manipulations (surgical or endovascular interventions) designed to maintain the functionality of the access. The term secondary patency has also been used in this context; however, this term has been misused in the literature, which makes it confusing. Hence, it is not used in this document.

Patency from the time of an index intervention: this may relate to the dialysis access circuit, the target zone, or both as defined a priori in the study protocol (figure 2 lower panel):

Postintervention primary patency: the time from the index IDBD to the first of one of the following events: access thrombosis; any intervention designed to facilitate, maintain, or re-establish patency; the access reaches a censoring event as specified a priori in the study protocol; or study end.

Postintervention assisted primary patency: term used to describe an access that needed assistance to maintain continued patency during the study period. It is calculated as the time from the index IDBD intervention to the first of one of the following events: access thrombosis, a surgical intervention that excludes the treated lesion from the dialysis access circuit, or the patient reaches a censored event as defined a priori in the study protocol. This period includes all intervening interventions (surgical or endovascular) designed to maintain the functionality of dialysis vascular access.

Postintervention cumulative patency: the time from the index IDBD intervention until the access is abandoned, including intervening manipulations (surgical or endovascular interventions) designed to maintain the functionality of a patent access, the patient reaches a censoring event as defined a priori in the study protocol, or study end. The term secondary patency has also been used in this context; however, this term has been misused in the literature, which makes it confusing. It is recommended that it not be used.

These definitions (including the full version described in Supplemental Material) should be used in the development of clinical trial end points for vascular access in the context of any new therapeutic product. IDBD, intervention, drug, biologic, or device.